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2001 Spectra Blue MR2 2ZZ/C60 swapped
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Discussion Starter · #1 ·
Hello. I recently picked up a 2zz swapped spyder. ~88k on motor and trans. Lately the car has been idling high on cold starts around 2k rpm with no fluctuation. Once the car is warm if I am driving and clutch in the revs will bounce between about 900-1500 rpm before eventually settling around 900 rpm within about 10 seconds.

I think I may have pinpointed the idle air control valve as the issue but I wanted to run it by the forum before buying a new one to replace. What I did to diagnose was disconnect the throttle cable and the connector to the IACV. On cold start with this done the car is not supposed to idle, however my car idled smoothly at about 1200 rpm. Next, I reconnected the throttle cable, leaving the IACV connector unplugged to rule out an overly tight cable. This time on cold start, same result. The car idled smooth at 1200. Lastly, I reconnected the IACV and sure enough the car is back to idling at 2k rpm. So is this a case of a stuck open IACV? If so should I try to clean it or just go ahead and replace?

Perhaps I should add that I got a PO420 code the other day. Not sure if this is related but thought I'd mention in case. I did just resolve a misfiring issue last week so this may be for another thread.
 

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I took mine apart and cleaned the rotating valve. Solved my problem. I had tried dumping lots of carb cleaner into the intake but no help there. Toyota doesn't make it easy. Found out you need 5 point Torx bits and a good fitting phillips bit. I was able to get my powered screw driver up there to break away the phillips screws.
 

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2001 Spectra Blue MR2 2ZZ/C60 swapped
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Discussion Starter · #5 · (Edited)
Alright guys, update: Today I took off the throttle body and then the IACV. On inspection the iacv looked pretty dirty. I basically let throttle bottle cleaner pool inside of it for about 2 hours. Then when at it with some paper towel. I didn't bother taking off those 5 point torx screws so not sure how thorough a job I did.

Anyways threw everything back together and the problem is still there. I went for a drive and took a video to better show the behavior: Bouncing + high idle. This is after the car has been warmed up. So you can see it bounces and eventually settles at about 1400 rpm when coasting in neutral.

Can we be sure this is the iacv and I'm safe to just replace it? I recently had a misfire issue due to an over-oiled K&N filter and this problem started alongside that one. I now have a new dryflow filter on, cleaned the MAF and no more misfires. Thought I'd mention.
 

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2001 Spectra Blue MR2 2ZZ/C60 swapped
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Discussion Starter · #8 ·
I've cleaned up the IAC valve thoroughly following the video above. The bearing was definitely a bit crunchy when I took it out. Unfortunately the problem has persisted after reinstalling so I am going to go ahead and replace it with a brand new oem unit.

Will update when the new IACV arrives and I install.
 

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2003 Toyota MR2 Spyder 2.0L Stroker
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The IACV should rotate freely. Sometimes taking out the 5 point torx is the only way to really clean it properly. That's the only way I got mine to idle correctly.
 

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2001 Spectra Blue MR2 2ZZ/C60 swapped
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Discussion Starter · #10 ·
The IACV should rotate freely. Sometimes taking out the 5 point torx is the only way to really clean it properly. That's the only way I got mine to idle correctly.
Yeah I took those torx screws out. Even after cleaning, the bearing still felt a little rough turning it slowly, and turning it fast it would stop spinning very shortly after releasing my fingers.

I also electrically tested it outside the car. The valve seemed to not want to stay open when powering it. It would open momentarily and quickly close again.

I should update on the new part this weekend
 

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2001 Spectra Blue MR2 2ZZ/C60 swapped
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Discussion Starter · #11 ·
@triz @MerryFrankster @rmeller
Update: installed a brand new OEM IACV and the problem still persists.

After testing the new IACV, I performed another test. I took off my intake and ran the car. Then I covered my hand over the throttle body. The car stalled out. Correct me if I am wrong, but this indicates that there are no vacuum leaks (significant ones anyways) past the throttle body, right? If there were, the car should have kept idling.

One thing I noticed when I was replacing the IACV is that when I hold the T-body up to the sky, I can see light around the edges. Not a ton but a little. And I also notice that the butterly valve does not sit vertically, but rather rests at a small but noticeable angle as if it is stuck open by the throttle set screw. Is it worth trying to adjust the set screw to close up the valve better?

Other than that, my only other guess would be an air bubble in the coolant system?

What do yall suggest I try next?
 

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Your hand over the intake just proves that you don't have a large intake leak. Look in the shop manual about how to set the throttle stop and you will see that the throttle isn't supposed to completely shut or it would tend to stick. Don't mess with the stop screw unless the setting doesn't agree with the manual.
Hello. I recently picked up a 2zz swapped spyder. ~88k on motor and trans. Lately the car has been idling high on cold starts around 2k rpm with no fluctuation. Once the car is warm if I am driving and clutch in the revs will bounce between about 900-1500 rpm before eventually settling around 900 rpm within about 10 seconds.

I think I may have pinpointed the idle air control valve as the issue but I wanted to run it by the forum before buying a new one to replace. What I did to diagnose was disconnect the throttle cable and the connector to the IACV. On cold start with this done the car is not supposed to idle, however my car idled smoothly at about 1200 rpm. Next, I reconnected the throttle cable, leaving the IACV connector unplugged to rule out an overly tight cable. This time on cold start, same result. The car idled smooth at 1200. Lastly, I reconnected the IACV and sure enough the car is back to idling at 2k rpm. So is this a case of a stuck open IACV? If so should I try to clean it or just go ahead and replace?

Perhaps I should add that I got a PO420 code the other day. Not sure if this is related but thought I'd mention in case. I did just resolve a misfiring issue last week so this may be for another thread.
It is normal for the IACV to open up to fast idle when it is cold. When the coolant loop to the throttle warms it up, the IACV should try to control the idle speed to the lower setpoint

I would also re-check for fault codes.
 

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The IAC slows the idle when the ECM commands it to do so based on measurements from the coolant temp sensor in the cylinder head. Has nothing to do with the coolant loop through it and the TB, that's just for icing protection in the winter. Mine is bypassed and the engine idles just fine once warm.

I am suspicious of the MAF since it sounds like a lot of this started after it was cleaned.
 

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2001 Spectra Blue MR2 2ZZ/C60 swapped
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Discussion Starter · #14 ·
The IAC slows the idle when the ECM commands it to do so based on measurements from the coolant temp sensor in the cylinder head. Has nothing to do with the coolant loop through it and the TB, that's just for icing protection in the winter. Mine is bypassed and the engine idles just fine once warm.

I am suspicious of the MAF since it sounds like a lot of this started after it was cleaned.
Hmm. I would agree about the MAF but I also suspect my problem could be a vacuum leak.

I did a kinda basic test of the MAF using live data. At idle the MAF reads 3gps which I think is normal. At 2500 it reads 6.8gps, also normal. Maybe I can pickup a new cheapo MAF to test?

My TPS looked good on live data as well. 11% off throttle and 78% at WOT.

Today was the first day driving it with the new IACV. It still idles high cold and all, and surges in neutral, but with the new valve when fully warm it seems to surge less and once fully warm idle does drop to 900 or so. Btw, I realized the surging doesn't occur for a set period of time. The surging is continuous when coasting and stops when the car is maybe going 5mph or less.

Only code that was pending after today's drive was a P0420. The car has a full exhaust and I think this code is pretty benign.

I think the next thing I might do is check the fuel trims to see if I have a vacuum leak but I'll have to read into that.

I appreciate everyone contributing to the thread! Hope to have this sorted soon
 

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2001 Spectra Blue MR2 2ZZ/C60 swapped
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Discussion Starter · #19 · (Edited)
I bled the coolant and am happy to report good progress. First off, when I cracked the bleed valve up front tons of air rushed out and suddenly my overfilled coolant reservoir was below the low mark.

On cold start I'm now idling closer to 1900 and will idle down to 900 much faster now. The surging when coasting in neutral is also way improved. Now it will only surge once to about 1500 and then once more to about 1100 before settling at 900 or so.

I think I am gonna do another bleeding for good measure. Btw, I was not able to bleed from the valve on the radiator because when I opened the valve coolant would just leak out of the valve and not into my bleeder hose. Anyone know a way around this? I ended up just using the valve by the windshield.
 

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MR-2 ZZW30 2001 RHD
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I think I am gonna do another bleeding for good measure. Btw, I was not able to bleed from the valve on the radiator because when I opened the valve coolant would just leak out of the valve and not into my bleeder hose. Anyone know a way around this? I ended up just using the valve by the windshield.
You probably unwinded the bleeder too far. If you unscrew it a few turns the O-ring should seal the shaft, but open up the channel to the bleeder hose.
If it does not work out I would suggest removing the bleeder screw completely and check the condition of the O-ring.
 
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