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

[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



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/previalege...l/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

[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]

PXL_20250508_131717416.jpg

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. 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 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 have 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-Reth...C8N-&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-2564...20&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 . 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.