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Discussion Starter · #1 ·
Sorry - this one requires a bit of background info.
A while back, I saw a number of posts discussing cleaning the throttle body (I was having issues with the car lagging intermittently when cold). When I checked mine (2002 Celica GT-S, about 196,000 km at the time), it was very dirty, so I hosed it down with TB cleaner (had also cleaned the MAF). I reset the ECU as suggested, but then had issues with high / hunting idle. The hunting seemed better after driving for a bit, but the the high idle (12-1300) never went away.
I did a bunch of research on the forums again, and found a number of threads indicating the IACV. This made sense, as I believe the issue may have been caused by a bunch of the crap I cleaned off the throttle body making its way down through the hole in the TB to the IACV. I confirmed this by removing the electrical connector to the front of the IACV - the idle speed dropped from 16-1800 rpm cold, to about 1200.
So I used Rhace GTS's excellent guide for newbies: http://www.newcelica.org/forums/showthread.php?t=359406 to remove the throttle body and IACV, and followed Deniance's suggestion to take apart the IACV and clean it thoroughly (this really does help confirm the condition of it, as it should spin freely, which mine did not). I will spare you the story of the grief along the way :>)
So here is where the current issue starts; after putting everything back together, it is idling even higher (1800-2000 rpm cold, down to about 1200 rpm warm). I have reset the ECU, and completed a full drive cycle so that all monitors are ready. What really throws me, is that when I unplugged the IACV again to test when I discovered the idle speed issue was still there, it didn't make a difference - the idle speed was still high. I had thought I had a solid diagnosis, which was confirmed when I took the IACV apart, and it was pretty much seized (I was able to clean it and get it to spin freely again). I have checked the vacuum hoses to ensure I didn't forget to connect anything, or connect something improperly. The ECU does not show any codes (new or pending).
So before I pull everything apart again, does anyone have any suggestions? Is there a way to test the IACV? I have also checked the throttle cable, and and added Seafoam to the gas and oil (first time I have tried it).
 

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Electromagnetic Wave :-h
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1200 is too high. Check that the throttle stop screw or the throttle cable haven't been messed with. BTW, you probably should pop a code when the IACV is disconnected.

Testing the IACV can probably be done by applying +12V. Normally, it is PWM.

Don't run too long w/SeaFoam in the crankcase oil. It thins it out.
 

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Discussion Starter · #3 ·
2way,
Thanks for the suggestions. I checked the throttle cable and stop screw - both of these are fine, as far as I can tell. As I said before, it seemed to be working OK before when I unplugged the IACV. I know 1200 is high (I would expect 800-850), but that was on a cold start - the idle speed typically drops once it has warmed up (assuming that is normal behaviour).
Sorry, it did throw an IACV code when I unplugged it previously to test - I think it may have been a pending code, and I reset it when I was trying to get all the ECU monitors to a ready state. I checked it again today - no codes, monitors all OK (for at least a couple of weeks).
Thanks for the tip on the Seafoam in the crankcase.
Any other suggestions? So frustrating, when it seemed like a solid diagnosis / fix.
 

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Electromagnetic Wave :-h
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Idle speed is strictly controlled by the IACV. IF no: vacuum leak, overtightened throttle cable, or mis-adjusted stop screw; THEN: IACV=bad....... usually.
 

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Discussion Starter · #6 ·
Looks like it's still an IACV issue...

So I pulled the IACV connector again, just to verify from when I had tested it earlier, and...now the idle drops. So don't know what happened when I had initially tried this after cleaning the IACV - perhaps it makes a difference whether all the ECU monitors are ready.

I did a bunch of research, and I am trying to test the IACV on the vehicle, so I can determine if it needs to be replaced (see this post for testing info: http://www.newcelica.org/forums/showthread.php?p=6059601#post6059601). The part is well over $600 at the local dealer (Calgary, AB, Canada), so I would like to be certain that it is faulty before I replace it. I know I can order it one much cheaper from the US, and even cheaper than that from overseas, but it's an expensive part regardless, and will involve waiting a while for the part to get here. And I don't want to go through all that and find out that I still have the same issue :furious:.
 

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I suggest that you source a different throttle body from a local JY for $30 and swap them to see if it cures your issue. There are plenty of them available right now.
Dentman
 

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Discussion Starter · #8 · (Edited)
Used parts

I suggest that you source a different throttle body from a local JY for $30 and swap them to see if it cures your issue. There are plenty of them available right now.
Dentman
Dentman,
Not sure what you guys have there for wreckers, but out here, I am getting $125-175 from the places that do have it. And the place I just called won't warranty the IACV or TPS on the throttle body assembly. Also looked online - cheapest price I saw used was $100 USD.
 

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Discussion Starter · #9 · (Edited)
IACV is off the vehicle (again) - see my testing post: http://www.newcelica.org/forums/show...01#post6059601
I am still not 100% sure if it is good or not, without another unit to compare to. The service manual says it should be half open - it is partway open, less than half (hard to tell because of how the light reflects, and my old eyes :>). You can adjust it slightly by using the screws that attach the electrical bit. The valve moves when you use a 9V battery, and when you turn the ignition key on when it's connected to the vehicle (as per the service manual, although I didn't disconnect the ECT). It rotates freely if you take it apart. But none of this is conclusive without another unit to compare against. Local Toyota dealer won't test it off the vehicle and wants $650, 25% restocking fee and no returns on installed parts. Still looking at the wreckers, but for what they have been quoting, it is almost as cheap to order one in from the US. I'm almost ready to put it back together and take it to the dealer, but last time I took it there, it cost me $2300 for a new clutch and a serpentine belt.
 

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Electromagnetic Wave :-h
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Can you read IAC DUTY RATIO with a scanner? Intake Air Control Valve Duty Ratio (Opening ratio rotary solenoid type IAC valve) is normally 22.5-43 % @ idle. This ratio would be affected by a vacuum leak or the throttle stop screw.
 

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I assume you don't have a u-pull yard in Calgary. Too bad. We have several in Ottawa. I bought a whole u-pull intake with TB off a parts Celica for $40 last fall. There usually is no warranty from a JY on used parts, just an offer to swap it for another one if it is defective.
Good luck with your project!
Dentman
 

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Discussion Starter · #12 ·
Can you read IAC DUTY RATIO with a scanner? Intake Air Control Valve Duty Ratio (Opening ratio rotary solenoid type IAC valve) is normally 22.5-43 % @ idle. This ratio would be affected by a vacuum leak or the throttle stop screw.
The reader I have doesn't have the IAC duty cycle (just a cheap reader, enough to read and clear codes and freeze frame data). Any suggestions? How are the cheap Bluetooth dongle + software kits on ebay?
I assume you don't have a u-pull yard in Calgary. Too bad. We have several in Ottawa. I bought a whole u-pull intake with TB off a parts Celica for $40 last fall. There usually is no warranty from a JY on used parts, just an offer to swap it for another one if it is defective.
Good luck with your project!
Dentman
We have at least one u-pull yard here, but they have no Celica stock newer than 1990's. Will have to do some more research - I believe they may have had one newer Celica when I checked a few weeks ago, but it's gone now. They seem to be pretty scarce around here.

Everything is back together at this point, still the same issue. As far as I can tell, the IACV is functioning as it should, but that's still not conclusive. I took it apart again, tested it with a battery and connected to the IACV connector and it does move (see the link above to my testing thread), and tested it with a meter. The idle speed drops when I pull the IACV connector (when cold), although I believe the IACV monitors have to be ready, based on my experiences above.

I also checked all the vacuum hoses, and made sure the blue and black VSV connectors were not reversed (as seen in another post). When I pull the MAF connector off, the car stalls, which I believe is normal. I can also pull off other vacuum hoses and get a strong suction, and a drop in RPM going to a stall until I plug the hose (assuming it's a source hose from the intake manifold). I will drive it again now until all the monitors are reset, and will have to decide if I am ready to give up and take it to a mechanic (I am a bit loathe to do that, being unemployed and after reading many of the stories of unsuccessful / bungled diagnosis in the forums), or whether I keep chasing it. I'm an IT guy, not a car guy, so I am already over my head :>)
 

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Electromagnetic Wave :-h
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What is the warm idle at?
Spec is:
2way said:
Auto: 750 rpm 1ZZ or 2ZZ
Man: 700 rpm 1ZZ, 800 rpm 2ZZ
+/- 50 RPM
 

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Discussion Starter · #14 ·
2way,
As per my first post, it eventually drops to about 1200 (haven't checked it again specifically since I put everything back together, but nothing seems to have changed).
Thanks for the idle rpm specs - I have been figuring it should sit at 800, and I think it was before all of this started.
 

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What does it drop to with IACV disconnected? It should drop below spec idle. If it doesn't, you probably have a leak, an over-tight throttle cable, or the throttle stop screw is mis-adjusted.
 

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Discussion Starter · #16 ·
What does it drop to with IACV disconnected? It should drop below spec idle. If it doesn't, you probably have a leak, an over-tight throttle cable, or the throttle stop screw is mis-adjusted.
Don't know if I have it documented when warm, but as per my original post, it drops to about 1200 when cold when the IACV is disconnected.
You mentioned the throttle cable and stop screw in an earlier post - throttle cable is fine, a touch of slack and sitting against the stop screw. The stop screw also seems to be fine, from what I have seen in earlier posts - it is sitting right at about the middle, and it still has the yellow paint on it. Also, the idle speed was fine before all this started (when I cleaned the throttle body), and I have never touched the stop screw.
I can do research and look for a vacuum leak. Thought that it was the IACV because I had cleaned the throttle body without removing it, and that's when the issues started. I can also test it warm - what should I get for idle speed if I disconnect the IACV when it's warm? Same result (drop below stock idle)?
 

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Electromagnetic Wave :-h
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Idle is always measured warm. It should drop below spec when disconnected. It is an air valve. It lets more air in to raise the idle. Check vacuum hose routing & make sure you didn't mistakenly connect the Blue electrical connector to the EVAP Purge VSV.
 

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Discussion Starter · #18 · (Edited)
Was out for the day today, drove about 1/2 hr. home (50-80 km/hr.), outside temperature is about 25C, so definitely well-warmed :>) Idle speed was about 1250. Shut it off and unplugged the IACV, then restarted it. Idle went to about 2000, then after a second or so, started to surge back and forth between about 1200-2200.
2way - yes, I did see in another post about the VSV connectors being swapped, and I did check those (see my post from 5/29).
 

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Sounds like a vacuum leak in the intake somewhere or the throttle body plate is not sealing tight when closed. You may have bent the plate a little bit or there is some debris left in the TB from cleaning it.
Hope this helps.
Dentman
 

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Discussion Starter · #20 ·
Throttle body has been thoroughly cleaned multiple times now. I checked it again when I had it out the last time - there is enough of a gap between the plate and the throttle body to see light between when I hold it up in front of a fluorescent light, but for a metal-to-metal contact between the plate and the body, the gap seemed like it would be normal (don't know enough to say how big the gap is, but didn't seem much more than would be needed to ensure the plate didn't bind to the body). I don't believe the plate is bent, so I am thinking the next step will be to look for a vaccuum leak.
Any comments on the "surging" when I disconnected the IACV when warm? Is that normal behaviour?
 
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