Rough Hot Idle - 1992 2TZ-FE - The Saga of Njordi

[Boerderij_Kabouter]

Hi Everyone, first task with my new Previa is to figure out why I am having bad idle once hot. I started by taking out the throttle body, EGR, and EGR modulator. Two culprits found.

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All the vacuum hoses to the modulator were cracked and/or fully blocked. When taking apart the modulator the filter was completely solid and caked with carbon. I tried cleaning it out but I think it is a total loss. I just ordered a new one (https://www.ebay.com/itm/226251347230) (Toyota part number 25870-76010).

The other problem I found was that the intake tube to the throttle body is falling apart and was fully cranked off at what I believe is the crank case vent that connects between the intake hose and the oil fill. It is cracked almost completely off where shown here:
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So I ordered a new Dorman intake hose (https://www.amazon.com/dp/B07HPPY5N3?ref=ppx_yo2ov_dt_b_fed_asin_title) and hopefully that will be sorted (Toyota part number 17881-76050).

The throttle body was really quite clean and the IAC was also smooth and clean. I gave both a thorough cleaning anyway, but I very much doubt either of those are my problem.

Njordi goes into my mechanic on Wednesday for a block test.

[Boerderij_Kabouter]

I found this great thread detailing the EGR modulator: https://www.toyotavantech.com/forum/showthread.php?5558-Vacuum-Modulator-Exhaust-Gas-Recirculation-Previa

All the symptoms of a stuck open EGR align with Njordi 's symptoms (bad gas mileage, stalling at idle). Fingers crossed this fixes my issue this weekend.

[Boerderij_Kabouter]

The stoke is high!!!! Block test came back negative! No blown head gasket (for now). List of things after taking a close look up on the lift and running diagnostics:


bad mass air flow sensor
bad coolant temp sensor
leaking valve cover
leaking front main seal
leaking seal on the manual transmission
super small seeping on the front brake calipers


And that is about it!!! So once I get the idle figured out, I have a few projects, but nothing urgent.

[Boerderij_Kabouter]

Installed the new intake hose and new EGR modulator. Rechecked all vacuum hoses. And fired up Njordi...

Complete victory. Runs smooth as butter and idles at 800 (or whatever that mark is on the tach). Dead even, easy power, feels WAY better to drive.

Feeling very happy.

[timsrv]

Awesome! :dance2:

[John Kaufmann]

I second Tim's assessment; I liked your troubleshooting (and Jonny's, on the EGR operation).
So to summarize: you think the running problems were due to the EGR modulator and a leaky intake hose?

[Boerderij_Kabouter]

That is correct. If the EGR modulator diaphragm is ruptured, the EGR valve will always be open, leading to a super lean air/fuel mixture and make it impossible for the engine to idle smoothly. The lean mixture causes a very low and inconsistent idle. Similarly, vacuum blockages or leaks cause the EGR system to function inconsistently. Here is the EGR function diagram from the factory manual:

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Similarly, the broken intake hose was allowing air to enter the throttle body after the mass airflow meter on the airbox. So the computer has an inaccurate indication of how much air is entering and therefore the air/fuel mixture will again be lean and inconsistent.

[John Kaufmann]

Nice.

[Jonny]

When the modulator diaphragm is ruptured, the modulator unit is unable to create the necessary pressure differential between lower and upper halves for the modulator to function, so it is unable to effect change on the position of the EGR valve diaphragm. A functioning EGR valve is closed by default and most EGR valves work even at our vans' old ages. A faulty EGR valve might stick open, but this doesn't seem like it would happen very often, and a non-functional modulator would not be the cause.

[Boerderij_Kabouter]

I see that I was wrong there. So maybe my hot idle issue was more related to the leak in my intake hose and not really the EGR modulator. Either way, I am glad to have the EGR system working again and my hot idle is still going great. At least this is one thing off my project list! Thanks @Jonny !

[Boerderij_Kabouter]

The rough hot idle has returned. Makes me think it is actually to IAC. I cleaned it and it worked for a bit, but has regummed up??? Seems plausible. I think I will try cleaning it again and see if that does it. Then if the issue returns I bite the bullet and but the new one for $260. Oddly, the idle flattens out at 700 rpm if you let it idle for about 3-5 minutes. I posted up a YouTube video of the tach during the issue. I would love to hear any ideas about diagnosing the issue.


https://youtu.be/sc-aJ20YnjM

[Jonny]

I watched the video. Are you regulating the idle with the throttle to stop it stalling or do the revs oscillate like that on their own? Your note on the video makes it sound like it does that all by itself, but just wanted to clarify.

FWIW, I had a low idle when hot (~ 300 rpm - practically stalling), bought a used IAC (or ISC if you have one of the early year previa repair manuals) from the scrap yard... it solved the problem and has worked fine since. However, my problem was a constant low idle which never came back up, and my hunch is that your problem is different. A scrap yard IAC might be a cheaper way of testing whether it's the IAC, but of course the scrap yard one could be bad too (but my guess is that the chances are fairly low).

The idle oscillation seems like it might be the ECU compensating for some problem it is detecting. Maybe? Any codes?
I have a friend who has an old Toyota truck which does the oscillating idle rev thing. I don't know much about it other than he has a major exhaust leak.

[man_btc]

Did you make any measurements of the IAC ("ISC" in Toyota-speak) as in the shop manual? Here's a write up that's sort of a rework of the same info - can't remember where I sourced it from.

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[Boerderij_Kabouter]

I am not touching the gas pedal or throttle at all in the video. That is the Previa all on its own hunting for a steady idle. I did not take the measurements when I first took the IAC off and cleaned it. I will be under the van again shortly to replace the front end seal, oil pump seal, and filter housing seal. When I am under there I will remove the IAC and give it a thorough going over and testing. Thanks for the tips!!!

[Boerderij_Kabouter]

It has been really busy lately, but I just took a minute to go check codes and I am storing a 41 code for open circuit at the throttle position sensor (TPS). None of the other codes that I used to be getting. I checked the wires going to the TPS sensor and the sensor itself and everything was in spec. so I really doubt that is my problem. Also, those who report the wire failure at the TPS connector have issues with throttle under load; that is not my issue. I think I will clean out the IAC valve first and see if that fixes it. Then, if that fails, I think I will take the EGR valve apart again. I never really tested the EGR valve itself after cleaning it. The EGR loop is the primary thing that changes between cold engine and hot engine, so this seems like a likely problem point.

[John Kaufmann]

It has been really busy lately, but I just took a minute to go check codes and I am storing a 41 code for open circuit at the throttle position sensor (TPS). None of the other codes that I used to be getting. I checked the wires going to the TPS sensor and the sensor itself and everything was in spec. so I really doubt that is my problem. Also, those who report the wire failure at the TPS connector have issues with throttle under load; that is not my issue. ...
Maybe, but I would not just discount an open-circuit code as spurious: the whole aggravation of the TPS harness problem is its intermittence, characteristic of fraying wires. If there is a correlation with engine load, that probably reflects mechanical stress on the harness as the engine rocks (vibrates) around its crankshaft axis. With frayed wire, it might not take much mechanical displacement to make a measurable electrical difference. FWIW, when I checked mine, I pulled the harness to see the problem, using an analog meter.

[Boerderij_Kabouter]

Well... my rough hot idle issue rapidly deteriorated into a dead van. No longer starts. I am suspecting the distributor. The previous owner appears to have not done very good work and the state and quality of the spark plug cables makes me think they probably screwed up the whole spark assembly. Ordered a new distributor cap, new rotor, dust packing (gasket) and oring. Time to push it into the garage and get after it. Really hoping this is the problem and not a blown head gasket or something bigger. Dang it.

[Jonny]

I'm really sorry your Previa is giving you so much grief.

That code 41 is there for a reason and should probably be fixed. A properly functioning TPS/fuel/air delivery system would seem essential to effective diagnosis of other problems which may exist on your van, and just maybe fixing this will solve a few things. And yes I think you're right that the IAC system might still be suspect.

If you decide to dive deeper it could be a good time to do some basic stuff from scratch if you haven't already.
Are you getting spark at each plug? Does each injector give a good spray pattern? What is the compression of each cylinder? At least this might put your fears of a head gasket problem to rest, (or not, depending on compression readings!)

If you have the injectors out, get ready for this...
https://www.toyotavantech.com/forum/showthread.php?8478-Fuel-injector-insulators&highlight=injector

[Boerderij_Kabouter]

I double checked all my wiring a second time and I really do not think I have a wiring failure in the EFI system. I can wrench around all the wire looms I can see with no loss of conductivity.

I also spent some more time reading in the FSM and find that there are NO CODES for the spark system. That seems crazy to me. What a world. But all the trouble shooting sections around failure to start when it cranks smoothly note the distributor as a likely culprit. My OEM stuff gets delivered tomorrow, so I can hopefully get that stuff put in sometime over the next week or so.

Njordi is still only sitting at $3553 all in, so I am doing pretty well I think. Fingers crossed that the distro is my main issue. I really want this thing 100% functional soon.

[Boerderij_Kabouter]

Distro was not the issue. Swapped it out this weekend, and no change in my issues.

My issue is clearly an air/fuel issue at this point. Sometimes it runs totally fine. But more often than not now, I get massive power loss and stuttering while trying to drive. Just feels like a total cutout. So my thought is that either the ECU is not detecting airflow and therefore not injecting fuel, or the fuel system is physically not working and therefore simply not delivery fuel as called for.

I guess the first thing to do is a deeper dive on the EFI wiring harness. I have not been able to find any issues, but maybe I need to do a more in depth tear down. My other thought is to redo the fuel delivery system and replace the fuel pressure regulator, injectors, and seals. But that is kind of a pricey project.

[13ozLatte]

Have you checked fuel pressure? When mine had a bad fuel pump, it would often idle rough when warm, and sometimes would take lots of cranking to start, or simply not start at all.

[Boerderij_Kabouter]

Good thought, I have not checked fuel pressure. I am hoping the weather next weekend is good and I can do some wrenching.

[Boerderij_Kabouter]

Scorched earth mission to renovate Njordi continues. I just order all new OEM injectors and seals, found an OEM fuel pressure vsv, and a Delphi brand fuel pressure regulator. An expensive bill for sure, but it feels like all these things are good to refresh even if they are not the primary problem.

[timsrv]

Have you verified spark yet? When you turn the key to "Run" position, do you see the little engine icon/light on your instrument cluster?

[Boerderij_Kabouter]

I do not have the special fuel pressure checking tool, but the pump runs and the squeeze test on the fuel lines seems like the fuel pump is working. Also found that the injectors are actually discontinued, so I guess I will visually inspect them when I pull them out and can replaced with reman injectors from RockAuto if needed.

I have not checked spark yet, but I can once I get the passenger seat out. The only piece of the spark circuit that isn't new OEM is the coil. Maybe I should just swap that out anyway...

[timsrv]

Verifying the CEL light on your dash is the 1st and easiest thing to check. Does it illuminate when the key is in the run position? Codes should be next, then spark and fuel pressure. When activated, if the fuel pump runs, you will be able to hear it flowing through the system.

[Boerderij_Kabouter]

Yes, I am still getting the CEL and the full compliment of codes 22/24/32/41 which is all the signals that run through the connected circuit of the MAF/water temp/TPS/Air temp. I am not saying these are definitely not the problem, but I am saying that all those sensors/devices pass the tests shown in the factory manual. They are all within spec and I can find no shorts or weak connectivity in the wiring.

Also just confirmed that I can indeed here fuel returning the to the tank when running the fuel pump by jumping FP and +B in the Diagnostic port. So I think I can at least skip the fuel pump for now, which is nice because they are pricey.

[Boerderij_Kabouter]

Fuel rail is out. All the injectors look OK to me and they all test out fine for resistance (all at 13.9 ohms). I don't know how to test if the old pressure regulator is good or bad. I don't have the tools to do the fuel test described int he factory manual. Anyway, this all seems like good stuff to replace. Still waiting on all the seals and the new injectors to arrive on Saturday.

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I haven't checked the spark yet, but I will check that once I get a coupled minutes.

I did strip one of the bolts that hold on the injector retainers. I can't find a part number anywhere, what is the best way to find correct replacements?

[13ozLatte]

The little 10mm drive bolt? I'd find a replacement from an Ace Hardware, or small hardware store. It just holds down that metal retainer

[John Kaufmann]

... I did strip one of the bolts that hold on the injector retainers. I can't find a part number anywhere, what is the best way to find correct replacements?
As just suggested, it's probably just M6 (probably the most common size in my hardware bins), and in your shoes I'd probably just find a match (because that's why we save these bits :wnk:). However, if you would like a p/n, are you working with ToyoDIY? If not, you probably should be, so I'm sending a PM about it.

[Boerderij_Kabouter]

New injectors and fuel pressure reg are in!

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Fired right up and was running nicely!!!

https://www.youtube.com/watch?v=1sXS8667ULg

I think it sounds relatively smooth. So let's take a test drive!!! ...

Died when I sat int he driver seat. Uh oh.

So I start poking around under the seat and find this:

https://www.youtube.com/watch?v=jTo5hePVUWQ

A little more poking showed me that the bad connection is the center connector that holds all the air:fuel stuff. So there is the source of my error codes and CEL. It appears it is not the wires, but rather right at the connector. So you all get to say "TOLD YOU SO" but not in the spots I was checking as closely.

[man_btc]

So you all get to say "TOLD YOU SO" but not in the spots I was checking as closely.

What I'll bet most want to say is CONGRATS on the perseverance fixing your problem! And probably preventing some others from cropping up by the inevitable NTF side-trips (No Trouble Found). Plus think of everything you've learned! A lot of "proper" troubleshooting plus how to "DIY by the seat of your pants."

[John Kaufmann]

... https://www.youtube.com/watch?v=jTo5hePVUWQ

A little more poking showed me that the bad connection is the center connector that holds all the air:fuel stuff. So there is the source of my error codes and CEL. It appears it is not the wires, but rather right at the connector. So you all get to say "TOLD YOU SO" but not in the spots I was checking as closely.
Anyone who might be tempted to say "TOLD YOU SO" would have to appreciate the lesson of your troubleshooting: a stressed wire has connectors at two ends. Nice work.

[timsrv]

What I'll bet most want to say is CONGRATS on the perseverance fixing your problem! And probably preventing some others from cropping up by the inevitable NTF side-trips (No Trouble Found). Plus think of everything you've learned! A lot of "proper" troubleshooting plus how to "DIY by the seat of your pants."

:whs: :wave2:

[Boerderij_Kabouter]

I called Toyota parts department, stopped at Autozone and Advance Autos, and looked online including Rock Auto and no one has any idea what pins are in these connectors. The connectors themselves are discontinued and I cannot seem to find any on eBay or elsewhere. It seems I found a pretty uncommon problem. I suppose my only option is to very carefully try to remove a couple pins and see what they look like. I might have to start calling salvage yards.

[Boerderij_Kabouter]

Victory! Njordi is officially running in excellent condition!!!! Idles rock steady, acceleration is WAY different than it was before, and is sounds smooth.

The ECU pins are very easy ones to pull, and I went through every pin on the center connector. I popped each out, and used a pin tipped tweezers to access the clamp lever arm fromt he back side and bend it down. Each of them was clearly worn and bent up to a loose position. I think the ECU pins should all get replaced, but this should work for a good long while.

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Feels very good to have this thing purring and running like a normal car. Now onto more fun projects!

[13ozLatte]

I have most of a harness I kept after doing the JDM swap on my van. Which connector is it? I can send you some with wire on them if you're fine splicing the wires together

[John Kaufmann]

Victory! Njordi is officially running in excellent condition!!!! Idles rock steady, acceleration is WAY different than it was before, and is sounds smooth.
Congratulations!

But i don't understand something:

The ECU pins are very easy ones to pull, and I went through every pin on the center connector. I popped each out, and used a pin tipped tweezers to access the clamp lever arm fromt he back side and bend it down. Each of them was clearly worn and bent up to a loose position. I think the ECU pins should all get replaced, but this should work for a good long while. ...
So the problem was not wire frayed at the pin, but male-to-female mating?

[Boerderij_Kabouter]

Correct, all the wires and crimps are in good shape. It is the female pins themselves that have worn out. And only on the middle connector. Very odd. But who knows what the previous owner was doing, maybe they did something weird.

@Latte thanks for the offer, but I think I am good. I may repin the connectors but I will just use new pins if I go that route.

[Boerderij_Kabouter]

A few days of driving Njordi under the belt and I have some success and some lingering affects. Once running and warmed up, I now have great stable idle, even power, and everything drives like you would expect. I am very happy with that. I would say this would meet most peoples' expectations of an old car.

That said, it starts a bit uneven. It fires right up, but the idle is a tad uneven for 2-5 seconds before it climbs to the 1200 or whatever high idle it maintains until operating temp is reached. It is not a big deal, but it is one of those things that is clearly not perfect.

My theory is that due to the misfires and general bad condition of all the systems I have now replaced or fixed, this thing was experiencing poor combustion for who knows how long. I know from peeking in through the injector ports that there is a lot of carbon built up in the intake chamber and on the back sides of the intake valves. SO my thought is that with good clean fuel, regular driving, and complete combustion now that may partially clear itself up. I am running through a can of 505-CRF (https://www.atschemicals.com/505-pour-ins/) right now, and plan to use some kind of cleaning additive every other tank of gas for a while to hopefully burn/clean off some of that build up. No real clue if the snake oil will be effective, but seems worth a try.

My second issue is a tailpipe smoke on start up. It is not every time, and feels fairly weather dependent, but again, a sign that we are not truly at 100% yet. My thought is again general past maintenance of previous owners. I changed the oil which is a good start. But my plan is to do a fuel cleaner 505-CRO and then change oil to the Valvoline Restore&Protect and hope I can get those oil side rings to clean themselves up and function better.

Physical systems I have not gone over or replaced at this point include the ignition coil (looks like it was recently replaced) and the cold start injector. It seems like the cold start injector may be worth replacing, but I want to give the snake oil a few tanks of gas first and see how it works into shape.

The Saga continues, but I am making progress.

[Jonny]

Yay! Way to persevere. Let's hope this particular issue is fixed for good, eh?

Some related info on the unreliability of very old connectors, for other people who may read in the future...

When I bought my '93 it had an intermittent non-starting problem. About once every 10 starts. Turn the key and no turn the starter. Very annoying. Starter worked fine, so problem was in that low current circuit to the starter solenoid. Whenever it intermittently failed to turn over I'd hold the clutch pedal down with a stick, crawl underneath and jump the connections at the starter to get it running. Eventually I went through the methodical process of checking every junction in the solenoid circuit by unplugging the connectors in sequence and testing for voltage. I got to the point where the only remaining connection to test was the final frame ground. I wasn't sure where this ground point was so I never tested it, but I never had the problem again. I believe that unplugging and plugging back in one of the connectors cured a bad connection in there.

Ditto with the windshield washer fluid motor. Motor worked, column switch did not. Voltage getting to all connectors when disconnected and tested. Has worked fine ever since.

[Previologist]

Let it sit for several days and see what the tailpipe smoke looks like.

[Boerderij_Kabouter]

https://youtu.be/DjmZNlrpFzM


https://youtu.be/DjmZNlrpFzM

It makes a lot more smoke than this sometimes, but it is the same color always.

New gremlin surfaced last night... when I was stopped at a light or stop sign, the engine would bog down if I was applying brakes. Feels like a brake booster issue with a vacuum line or the booster itself. Need to look into it.

[Previologist]

Video was a little short. If head gasket, it would keep getting worse for a couple minutes and then stop smoking after a couple more. I posted a video of mine when the HG was bad, I'll try and find it.

[Previologist]

No luck finding mine but here is Samay's https://www.instagram.com/previalegend/reel/CqUAaggA5iV/

His is more intense than mine was but you get the idea. The longer it sits before cold start, the more coolant collects in the cylinder and the more white smoke, but it takes a minute to really start blowing. If you start it every day you might not even notice the smoke because not much has collected and it burns off quickly.

[Previologist]

Found mine


https://www.youtube.com/watch?v=P27JZmrwWuM

[Boerderij_Kabouter]

Well, that looks quite a bit like mine... Not encouraging. I will get a longer video uploaded today.

Did you replace head gasket and find it was actually blown?

[Previologist]

I did not, because: I had purchased the van from a repair shop owner only 6 months earlier and soon discovered they had done dubious work on multiple systems. They replaced the SADS couplers at my request before I bought it, and didn't tighten them. I had to have them retightened only a month or two later when there were only 1 or two bolts still holding the shaft on. They had rebuilt the engine a year or two earlier but hadn't put any miles on it to speak of (or so they said), but neither he nor the shop that rebuilt it could produce a receipt for what they had done. And they had "rebuilt" the transmission, which I found out from the tranny shop involved replacing one seal. So by the time this happened I had zero faith in any of their work. I was not equipped to do HG work myself and It would have been costly to have a shop drop the engine and tear it apart just to find out there were other problems, and it had 250,000 miles on it, so I just spent the extra money and replaced the engine with a JDM. But you can see the coolant being spit out the exhaust and landing on the garage floor in the video, so there wasn't much room for doubt in my mind.

You can get a kit that tests for exhaust gases in coolant that might take some guesswork out of it. I don't know if they are 100% reliable or not, but that and a compression test might help. Previas rarely seem to mix oil and coolant when they blow, which would be a dead giveaway.

[Boerderij_Kabouter]

Interesting. Your feedback is helpful. I had my shop run an exhaust gas test and it came back negative (no coolant). But that was when I first got the van. Definitely a chance that the gasket was going and then went from me driving it and opening it up a bit with the Italian turn up.

[Previologist]

If the previous owner knew it was going they may have thrown some stop leak in it. Stop leak bought me many miles and several cross country trips on my previous Previa before she finally blew sky high.

[Boerderij_Kabouter]

Well my current plan is to drive Njordi a bit more and see if this issue miraculously irons itself out. I think the chances of poor maintenance in the past feel likely and that the head gasket is toast. That said, I think if that is the case I will be going with a reman crate engine and send this unit back for the core exchange instead of rebuilding myself. Looks like I will be able to get a reman for under $4k. Rebuilding the engine I have looks like it will be over $2k in parts plus a ton of time I do not have. Seems like the reman makes sense to me and makes me a whole lot less worried about being gentle to my current engine.

Fingers crossed that it is just some oil/carbon/crap burning off, but I am not really feeling very hopeful. The oil looks clean, so at least that is something, and I will watch the coolant level as I drive it a bit more.

[Boerderij_Kabouter]

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With all my other projects going on, I figured I would check the spark plugs again and see if my Hail Mary threaded insert actually held. No joy. SO it is time to actually fix this thread correctly. Very unfortunate. No engine shops in the area are willing to do the job with the engine in the car, so I am going to have to buy a Big-Sert tool set (https://time-serts.com/store/big-sert-m14x125-spark-plug-kit-extended-pn-5141e-407/). I have a few buddies I am asking, but hope is low. Pretty bummed as these are very expensive, but it needs to be done at this point.

[Boerderij_Kabouter]

Talked to two shops in my area about my head and fixing the damaged spark plug hole and none of them wanted to take on the fix. The tooling to overbore and fix the spark plug hole is like $500 for the Big-Sert kit and inserts. That cost seems really high for a "fix" that might cause more damage.

And so... I am joining the ranks of the Previa owners who have redone their head gaskets...

I ordered a reman head from Cylinder Heads International (https://www.headsonly.com/) for $425 shipped. I don't think I am going to change out the timing chain though.

[timsrv]

I haven't tried this on a Previa, but I have installed inexpensive "spark plug thread repair kits" on several aluminum heads during my career with minimal efforts and great results. There are different brands with slightly different methods. Most kits come with a tap & a thin bushing that has threads on the outside and inside. You make sure the piston isn't near the top of it's travel, then run the tap down inside the stripped hole. After the hole is tapped install the bushing with some permanent thread locker on the outside threads. Some kits might also come with drill bits and special insert tool(s). For reference only, here is one such kit on Amazon: https://www.amazon.com/Cylinder-Rethreaded-Gasoline-M14x1-25-M16x1-25/dp/B0B2X6LC8N/ref=asc_df_B0B2X6LC8N?mcid=7d1f396d76f1348f95bc2e3 82f6991ed&tag=hyprod-20&linkCode=df0&hvadid=693675076548&hvpos=&hvnetw=g&hvrand=11682316265295364541&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9033612&hvtargid=pla-1951094768068&psc=1&hvocijid=11682316265295364541-B0B2X6LC8N-&hvexpln=0

Disclaimer: I have not used this particular kit, it's just the 1st one that popped up when I searched. Also, it's inevitable that some aluminum shavings will enter your cylinder and although damage is possible, but it's been my experience that shavings tend to get blasted out through the exhaust without any notable damage to the engine. I had one instance when the engine "missed" upon 1st start-up but cleared itself during the test drive. I assumed it was a shaving that got stuck in between the exhaust valve and it's seat for a bit but eventually cleared itself. Tim

PS: On the Previa there are spark plug tubes, so you would want to remove the valve cover and the tubes before installation. Also, extra care should be taken to avoid getting shavings in the "oiled" part of the head. Also, I'd want to be sure the surface where the spark plug tube seats is the same height as before. Due to this, I may be inclined to use one that installs flush then gets "swaged" https://www.amazon.com/OEMTOOLS-25647-Spark-Plug-Saver/dp/B000CMHL1C/ref=sr_1_3?dib=eyJ2IjoiMSJ9.VFxF4--QdN-Kph97VwD6NWLNcPzADw6yWSzVZv1Rwj34rz6hmTQ68Bo7HH0Og 8UH9Xt5LG1mknsU-o9Pq5uD5A-F-uvHaVkPgaJnb38Ipi9ybrl7fhwZXlsxCIsSb5_Ul57sXaPS3Dz 6H_mcKBr2f83cdYifnkRLULpyKYhDeBPU-xGonOakfetQzw28yIXxnnbb9taQVNST5gO96FyUtA0PY9yFiPL iO1TSpMmJEhs.bkIQn6gID9hT6rX-CnMzeAkidTRlHeS343nuMf1292k&dib_tag=se&keywords=spark%2Bplug%2Bhole%2Brepair%2Bkit&qid=1746858720&sr=8-3&th=1. If installed correctly this should prevent interference with the spark plug tube.

[13ozLatte]

I've had luck with those inserts as well on other cars. I always cover the tap in bearing grease, and remove, clean and regrease it often during the process. Metal shavings will stick to the grease, and very few will fall into the cylinder. Then, if that cylinder is in a position where the valves are closed when you start, you can put a shop vac on it and possibly get any shavings that did fall in, if the vacuum can get close enough.

[John Kaufmann]

I've had luck with those inserts as well on other cars.
Aren't these (which Tim also mentioned) the insert type that failed (and might be replaced by the Big-Serts)?


I always cover the tap in bearing grease, and remove, clean and regrease it often during the process. Metal shavings will stick to the grease, and very few will fall into the cylinder. Then, if that cylinder is in a position where the valves are closed when you start, you can put a shop vac on it and possibly get any shavings that did fall in, if the vacuum can get close enough.
FWIW, I've found Harbor Freight's vacuum accessories find a way to get you close enough in almost any situation.

[Boerderij_Kabouter]

Those and the inserts that the previous owner attempted to install. They either used cheapo inserts, or did it wrong because the hole is fouled. So to fix this, it needs to be drilled out over size and an oversized insert used. Like the Big-Sert.

The reman head was cheaper than the Big-Sert kit, so that is why I am going that direction. Currently trying to gather all the new gaskets I need for the swap.

[timsrv]

Okay, I missed the part where this repair had already been done and failed :doh:. In this case I agree that a new head is your best bet. Probably also a good idea to get a selection of valve shims so you can properly check/set up the valve lash on the new head. Tim

Latte, that's a good idea to use grease to collect shavings. Thanks for the suggestion. Tim

[John Kaufmann]

... The reman head was cheaper than the Big-Sert kit, so that is why I am going that direction. ...
FWIW: cost aside, I'm more comfortable with that.

[Boerderij_Kabouter]

Njordi is now idling like new. So the simple fix for idle issues is clearly to rebuild the throttle body, rebuild the IAC valve, replace the EGR modulator, rebuild the EGR valve, replace all vacuum lines, replace the intake boot, rebuild the entire fuel system, re-pin the ECU, and replace the head and all associated gaskets. Easy!