'97 Previa RWD VERY HIGH IDLE Warm Engine

Greetings Forum,
Just bought a '97 Previa RWD, 101K miles. On cold start idle seems normal (slightly fast idle). One warm, in neutral, idle is VERY HIGH. Van does not have guage but I would over 2000 RPM. When I try to blip the accelerator, it idles even faster. I see no obvious leaks or cracks in any hoses under the hood or at driver's seat access panel. The throttle cables move very freely. If I put it Neutral while coasting the idle goes up and down until van comes to a stop, then high idle is back. Any ideas on possible causes would be very appreciated.
Thanks,
Steve
CT/USA

Forgot to mention...other than high idle, van performs very well.

remove the throttle body and then remove the idle air controller... clean both parts.... carbon buildup will prevent them from working properly
check the A/C idle up valve also.... it is connected to a 5/8" rubber hose that runs a few inches away from the throttle body, closer to the starter... those things tend to get sticky also from carbon build up

some brute forcing is necessary to take out the throttle body... it took me about 2 hours to do it because of little room and so much crap in the way
https://lh6.googleusercontent.com/-1...0/DSC_3795.jpg

you will need a JIS crosshead screwdriver to remove the IAC screws frustration free, if you mistakenly use a phillips screwdriver on them, you will damage the screw head and it will not come out
https://lh4.googleusercontent.com/-_...0/DSC_3787.jpg

https://lh5.googleusercontent.com/-m...0/DSC_3785.jpg
https://lh3.googleusercontent.com/-D...0/DSC_3786.jpg
https://lh3.googleusercontent.com/-G...0/DSC_3794.jpg

Thanks TM, I haven't experienced this problem yet so I'm glad you posted. Nice pics. Tim

Thanks so much for the very detailed info and photos! I will try this and report.

My 92 previa is suffering that same very high idle after doing head gasket. I decided to do the throttle thingy before hitting the road seriously..and well ran into a rubber o/ring type gasket butting up to idle air controller and so..does the o- ring gasket for the idle air controller need to be replaced? any part numbers out there? just finished throttle body and made gasket from felpro material but leary about rubber gasket stuck in throttle body... i havent damaged it-did best to steer away from it till i figure that out..,yea a good 2 hours to remove throttle body is right...taking off with drop light to boot! the screws were hard to get off allright. I filed down PHILLIPS to mimic JIS. Worked great. Really wicked build up in there is right. I used a toothbrush and fingers for a good hour cleaning but i found one hole near intake on right side really clogged with a chunk of black carbon plugging it up.. letting spot soak so i can chip it out. seems the more i clean more the more comes out? not sure where it leads but its there, looked for the thread on it but WOW its evading me. i recall someome saying the used a allen wrench? yea you right theres a ton of hoses all in good shape though. waiting for some info before reinstalling.

you will need to buy the proper gaskets for the throttle body and idle air controller from the dealer
I went ahead and replaced the screws in mine and good thing I got them ahead of them because I knew one of them would strip! That was back before I knew anything about JIS screws lol

thanks TheMan,
i found number on previous posting
here at this terrific forum.
toyopartmotors had them cheap enough
needed a few other small hard to find plastic parts
to make the $11 shipping worth while.
still wondering about that upper roller part (68310) of side door
but i think ill use tims trick later after tackling this throttle/idle thingy
any advice on plugged up hole on intake?
thinking recirculating line? havent traced it
i m still cleaning on the spot. its quite a build up...
tough spot... has me wanting to investigate further.

The port hole seems it leads to EGR VALVE...to
recirculate exhaust gases to intake manifold
to lower max combustion temperature.
wonder if buildup contributed to my HG failure...humm?
cleaning of EGR MODULATOR is part of inspection.pretty simple...
i finished cleaning port hole.. got best results using an old meat hook
i used years ago in meat business.
It has the perfect angle to "hook" around and reach into hole.
Carb cleaner melted it eventually...patience.

it could be EGR, but it could very much also be oil due to faulty PCV valve or bad piston rings... my EGR valve was shot and the oil made a mess in the throttle body

thanks, well i finished cleaning up throttle body and
dug out lump of build up in intake, found several threads
on it...cleaned up and tested ISC valve. it was crusty with rusty
I felt so good about it that i installed it and well the previa still
has that high idle.:pissed:
guess i be takings off the throttle body again (pretty simple
especially after I cleaned up the area that really needed cleaning) to test TPS
(and BVSV) and reset it on throttle. i found Tims video on photobucket...
I'm hoping its not the EGR...ITS IN A TOUGH SPOT! and rather costly to just take a chance
on. Not too many used/parts previas this part of LA. not to mention one pick your parts.
i replaced PCV valve just cause, cleaned EGR Vacuum modulator, it was easy considering
the postion on previa.
Following the FSM flow chart for high idle, just not getting lucky?
..no codes popping up either.
I had van since new and I just can't wait to get back on the road again. Time
for a ROAD TRIP!

on the S/C, the throttle body is under the hood... did you actually remove that one and clean it?

Might be a long shot, but I'd check the coolant temperature sensor.

thanks TheMan, and yes I'm still tackling that high idle after HG replacement... followed your threads and Timsrv's, even searched out toyotanation, Zen and a few others and i tell you...you two are legends! anywho, i found that big lump in intake and took care of it and felt that was the problem, so i cleaned throttle and replaced, boy was i mistaken :doh: DOH!!! I just didn't listen!!!:wall: so i dug out the old FSM and following the troubleshooting chart for high idle. it could be exhaust system (EGR etc. ) but im going to finish EFI SYSTEM check. then move on to EGR even if I get to bottom of problem (TPS etc. ) i have the PB Blaster working on EGR connections and I'm wondering if the crowfoot needed is 15/16 or 1" to remove the nut since its in a very difficult spot as engine is in car... ive read two different threads and each differs. i think they were for S/C or 80's toy van..I found both sizes (and theyre not cheap)on EBAY but have not ordered for that reason....i did do modulator just cuz it was EZ. it was okay. seems everything I test with multimeter so far is good... guess its blockage? (but I 've yet to test TPS OR BVSV). Is the passage from intake to EGR able to be cleaned? ( in picture) thats where the build up i found in intake came through after all these years..i can remove other end of recirculation tube by exhaust manifold and clear it out pretty EZ. I had to remove it to do HG.

thanks pdgizwiz,
had time tonight and checked into coolant temp sensor. I found 3 sensors on water outlet. removed top one and tested it hot and cold, passed resistance as per FSM... middle one just goes to temp guage. The lower one escapes me, couldnt find wrench to fit (bigger than 19mm)....and i could not find the sensor mentioned in FSM. so I started prev and disconnected upper one. It triggered code. Havent had any codes (so I was relieved to see one). I reset CU to see if it comes up again.. at least I know the upper Sensor works...:cnfsd:
lower one does nothing that i can tell...so far. any way to test the lower one you know of? its a water temp sensor for sure just not sure what it sends temp to...i may remove it to get toyota numbers off it and look on rockauto or Toyotaparts.com.
I'll let car heat up thoroughly tomorrow and disconnect it to see if any effect on prev.
again thanks for chiming in.
Did you have a HIGH IDLE problem...?

maybe it's for the transmission?

yea you could be right...trany does wait till prev warms up to shift to high most mornings less I let it really warm up before driving it. Ill check in transmission section of FSM.. :thmbup:
looks like weather warming and drying for a spell, so I can get back to TPS/BVSV...
any clue what size crowfoot i need to remove EGR?

I just found what third sensor is. I ran across it in FSM today. Its a START TEMPERATURE TIME SWITCHAttachment 2233

Well, at least you've ruled it out!
I've no experience with the SC engine, and I gather that few of us on this list do. So you're a pioneer in diagnosing problems like you're describing.
My experience with the coolant temperature sensor was one where I had no idle, rather than a fast one. But I learned that the CPU looks to it to control the ISC, and I suppose that the sensor might fail in different ways. Anyway, I figured it was a long shot.
Keep at it! We all stand to gain from your experience!

I've cleaned out throttle body
of my 92 previa NA also
replaced TPS,
checked BVSV,
replaced EGR modulator,
and cleaned ISC valve
and still have the high idle...
Prev just doesn't idle down...after warming up (I think).
next on the list in FSM is to check the A/C VSV and power steering air valve for leaks.
Then the fuel pressure regulator and
then off to cold start injector and injectors
maybe I set injectors in wrong after doing HG?
Seems I would've solved issue by now?:no:
Think I'll just retrace vacuum hoses, never had
the FAST IDLE before Head Gasket repair:cnfsd:

:dance2:COULD IT BE?My 92 previa finally calmed down!
I was waiting to persue checking A/C and POWER STEERING
IDLE UP VALVES when I decided to fix a leaky EXHAUST LEAK
that magically appeared after doing the HG. (I guess I pushed too hard on exhaust
in attempt to move out of my way). I found pieces of aged and cracked up
gasket fragments leftover in MANIFOLD to CAT connection. Replaced gaskets and
fired her up and she just PURRS!! GO FIGURE? well she got a good thorough much needed
work over. Its definitey time for a ROAD TRIP...! Sure feels GREAT.:roflmao:
P.S.
I never did get EGR VALVE off... I purchased 15/16 and 1" crowfoot wrenches
on Ebay and the first one was too small, and the latter was too big..Go figure!:doh:
Its probably a 25 mm .. but hey I'll let it be...
not broke, not tinker with...

hi, I'm not sure if this might help. But I remember seeing an article a while ago, possibly on the yahoo group of the supercharged previa's getting black flakes in the coolant and blocking up one of the pipes where it t's off. I'll try finding the article, but here's a pic showing the pipe I believe it is. I used to have a 95 le s/c and the dealership could never figure out it's high idle in the cold.
Attachment 2242

It was toyotanation actually. I asked the question a while ago. Attachment 2243

http://www.toyotanation.com/forum/85...le-previa.html

I hope it helps.

yea, i found the source of some black flakes in my coolant by the way ... while I replaced the big water hoses, I noticed that the black paint around the pipes ( guess TOY wanted them to look good?) that connect the hoses is just "Flaking" off. I rubbed all paint off pipe ends and connected hoses... Flushed the system real good afterword..thanks for info...." its what we do"

OKAY! I had thought the fast idle had gone away miraculously but I was mistaken! So I replaceded fuel filter, replaced fuel pressure regulator, and even swapped out fuel rail with injectors (mine tested 17.2 each and FSM wants them around 14.2). So all in all I ended working EFI system over real good. Ended up replacing cold start injector, cold start time valve, coolant temp sensor, Egr modulator, hoses, PCV, TPS, and list goes on...(found 2 previa at U pull it and worked them over real good too, Yea used parts I know but they worked just the same...didnt remedy or worsen the symptom!) Anywho, after scratching my head over it I decided to check ISC again. I might have to replace ISC? and I was hoping the Previa were still at the bone yard. After removing throttle body for 3rd time, I ran across a sticking valve!! I dont know how I missed it the first time:wall:
but I caught the buggar this time... cleaned it really good till valve moved freely!! Reinstalled on 92 PREV and she definitely purrs. :dance2:
So now its up the coast I go! Heading up Atlantic coast!:fshn::sfr:
Its definitely BEER-THIRTY HERE!:drunk:
thank you everybody that chimed in.:wrthy:

Yeah, I think these 2 issues are MUST DO if you have a previa.

The black flakes and EGR clean out. I was so angry that the shop that did my motor ignored the manifold. It could have easily been cleaned out and taken cared of.

Glad to see it helped. :wave1:

I feel this is a must do for the Previa.

Clean out the IAC valve and put in the "flake filter".


IAC valve and "flake filter"
- Fram G15 inline filter - this for the flakes going into the ventilation tube.
- 2 small hose clamps for the filter.
- Throttle body gasket - 22271-76020
- IAC valve rubber gasket - 22215-76010 - gasket between the IACV and Throttle body
- IAC valve screws (set of 4) - 21821-25180 - holds the IACV to the throttle body

I believe the lowest one is the "Start Injector Time Switch"

Quote:

---

Originally Posted by tbkilb01

thanks pdgizwiz,
had time tonight and checked into coolant temp sensor. I found 3 sensors on water outlet. removed top one and tested it hot and cold, passed resistance as per FSM... middle one just goes to temp guage. The lower one escapes me, couldnt find wrench to fit (bigger than 19mm)....and i could not find the sensor mentioned in FSM. so I started prev and disconnected upper one. It triggered code. Havent had any codes (so I was relieved to see one). I reset CU to see if it comes up again.. at least I know the upper Sensor works...:cnfsd:
lower one does nothing that i can tell...so far. any way to test the lower one you know of? its a water temp sensor for sure just not sure what it sends temp to...i may remove it to get toyota numbers off it and look on rockauto or Toyotaparts.com.
I'll let car heat up thoroughly tomorrow and disconnect it to see if any effect on prev.
again thanks for chiming in.
Did you have a HIGH IDLE problem...?

---

Quote:

---

Originally Posted by Jwsmsmith

I believe the lowest one is the "Start Injector Time Switch"

---

I believe your right, thanks...
However, my speedometer just stopped working and I'm thinking/hoping speed sensor?:cnfsd:
found picture:
Attachment 4994

hopefully it was the sensor that has gone bad
otherwise, the capacitors in the speedometer itself has gone bad.... that's relatively easy to fix for less than $10 (search for my thread)

Quote:

---

Originally Posted by TheMAN

hopefully it was the sensor that has gone bad

---

I've replaced speedometer cluster, VSS and wiring to VSS. Speed still does not register. Computer problems?

Regarding the original problem posted in this thread I had exactly the same issue in my 97 AWD Previa: slightly high idle on cold start, increasingly fast idle as it warms up. Surging idle in Neutral, very fast idle in drive or park (or stopped in neutral). Undriveable.

I first tried the coolant temp sensor. Didn't change anything.

I next assumed it was the Idle Air Control, so I ordered a new one (off eBay! Huge mistake). I changed it, but got no improvement.

Digging further in, I took out the new IAC and bench tested both the old and new IAC valves. The old one was all gummed up with sticky carbon crap so it couldn't move freely, which I cleaned out with lots of carb spray and manual movement of the valve. Got it moving very freely. Then it bench tested properly.

The new one I ordered for cheap failed the bench test. One side of the circuit didn't work at all. It would open but not close, which is a recipe for a high idle! So it's going back for a refund.

Here's a GREAT article on how to test the valve so you KNOW whether it's the problem:

https://www.toyotanation.com/threads...valve.1676205/

Meanwhile, I re-installed the cleaned OE IAC. I also cleaned out the "T" junction clog with Qtips (very crapped up--see further up in this thread for details about this procedure) and then opened the other end (under the van) and blew out the coolant line with compressed air. While I had the throttle body out, I cleaned it thoroughly with carb spray as well.

Reassembled everything, and the idle is perfect. In the end, the issue was the gummed-up IAC, which is partially dependent on the T-junction flow to function. So if you're having this problem, I would go straight to testing and cleaning the IAC, and cleaning the T junction.

Quote:

---

Originally Posted by aplarsen22

Reassembled everything, and the idle is perfect. In the end, the issue was the gummed-up IAC, which is partially dependent on the T-junction flow to function. So if you're having this problem, I would go straight to testing and cleaning the IAC, and cleaning the T junction.

---

Personally, I would start with the T-Junction. It's easier to get at and 9.8 times out of 10 will solve the problem.

On my left hand drive van, it had the high idle issue; cleaned the T-junction and it went away immediately. Not even 6 months later, the high idle came back. Second time around I not only cleaned the T-junction but also installed a filter between the junction and the IAC. The filter should collect any black flakes and prevent the junction from clogging in the future.
I am currently overseas, but I am going to do the filter mod to my right hand drive as soon as I get back!

If cleaning the T-junction does not solve the problem, then the IAC is obviously the next suspect.

I know this is an old thread but it helped me fix my van so I thought I'd chime in.

A few years ago I had a shop replace the headgasket and after getting the van back I've had nothing but problems. So much so that my friends and I had labeled it the "worlds most unreliable Toyota".

I've taken it to several different mechanics and they couldn't figure it out either. Symptoms were inconsistent but generally hard to start, would misfire/load up and the idle was all over the place.

You could start the van cold and let it idle, it would seem fine and then die for no reason. So I replaced the ICV. No luck.

Replaced the EGR valve and vacuum modulator, no change, engine temp sensor, plugs, new vacuum lines, fuel pressure regulator, removed and cleaned the throttle body and EGR/Vacuum ports, etc. I chased theories and replaced parts all over the van, even the charcoal cannister. For two years I toiled and could not solve the issue. Some things would make it better and some worse (like the new EGR Valve).

About two weeks ago I decided to mess with it again. I started reading forums and finding similar issues but none of the solutions solved it.

I had previously ordered a throttle body off of eBay which had a new ICV and TPS sensor on it. I found the guide in this thread to test the ICV and thought, well, might as well. So I removed it, tested the new one and it was good. I took the old one off the van (which I had replaced), tested it, and it failed. So I had been chasing the symptoms of a problem I thought I had solved two years ago.

I was both elated and frustrated at the same time.

So as I go to reassemble the van, I'm putting the spark plug cover back on the valve cover and the engine starts to stumble. I reach down and touch one of the wires and got a big shock! Turns out, there were tiny slits in the spark plug wires that was making it short out against the valve cover! You couldn't see them at a glance but upon closer inspection you could. So I replaced the plugs and wires and then discovered the distributor cap was LOOSE. At some point, someone had sheered off one of the three bolts holding it on and didn't bother to tighten the remaining two.

So I replaced the cap and rotor and snugged it down really good.

Now the van runs like its brand new. Its been such an oddessy for me over the last few years and I'm so relieved its fixed. It was this thread that lead me to the solution so I thank all of you who contributed.

There is a lesson in here that I should be learning as well, maybe check the obvious stuff first, put your hands on the parts, visually inspect, dont over complicate things... etc... One day I'll figure that one out too, lol.