WTF is wrong with my idle? - 3SGTE

[Boosted_162]

Ok, now ive had idle problems on and off with the MR2 for the last wee while, and now its really starting to bug me.

If i start from cold, it idles about 2krpm (which i dont mind) and then goes down to normal (around 900). But, if i turn it off, and restart it while still warm, the idle instantly goes up to 2k, and wont come down unless i rev it to around 3k, then it goes to normal. Wierd i know...

..And the wierdest bit of all.. If i turn my headlights on, the idle goes up to 2krpm, if i rev it to stop it, the idle comes back down then starts to hunt really bad between 1k and 1500, and wont stop until i turn the headlights off.

Car is a 1993 MR2 turbo. Gen 3 engine. Is completely standard bar turbo upgrade, exhaust, and powerfc which is still on basemap. Also, aircon has been removed.

Cheers

[RS13]

Pretty sure theres' an idle-up wire on the aircon pump somewhere that needs to be grounded, would possibly explain the high idle?

[cat007]

Faulty ISC valve?

[Adoom]

Do you have an airflow meter? Checked for airleaks or split air hoses?

[Boosted_162]

Do you have an airflow meter? Checked for airleaks or split air hoses?

Nah gen 3 is MAP. The idle used to hunt (but not as bad) before the aircon was removed.

[thegreatestben]

Check your ISCV.

[Boosted_162]

In regards to the ISCV - what part do i check/how do i determine if thats causing my problem??

Cheers

[fivebob]

Easiest way to see if it's faulty is to disconnect it when it's warmed up and idling correctly and see if the problem goes away.

Failing that, IIRC, the checking procedure is quite complicated. I'll see if I can find the appropriate pages from the workshop manual.

[Boosted_162]

Easiest way to see if it's faulty is to disconnect it when it's warmed up and idling correctly and see if the problem goes away.

Failing that, IIRC, the checking procedure is quite complicated. I'll see if I can find the appropriate pages from the workshop manual.

Cheers Fivebob. Ill try that tomorrow. Would be great if you can find the pages!

[CelicaGT8]

Its a 3sgte, get use to it haha they are so dam annoying that you just want to pull over and kick the shet out of it...

Do you have the water lines to your throdle body around the right way?

If you unplug the idle control valve does it make any difference?


Ow yea and if its my car if you unplug it, the engine will die!

[thegreatestben]

I find that if you unplug the ISCV the idle goes up, engine check light comes on. I gave it a damn good clean which bought my high idle (3000rpm) down to 1500, which is still too high. So I did a rangi and am currently using a pair of vice grips to change the idle speed

[Boosted_162]

If im correct and disconnected the right plug (its the little white box underneath the tb? with the 2 coolant pipes going in), the idle starts hunting permanently with it disconnected.

I didnt get a CEL because im using a PowerFC, i know the diagnostic port doesnt work so i assume it doesnt log error codes.

[fivebob]

It's probably hunting because the PowerFC is trying to do idle control using ignition timing.

Have you got access to the PowerFC settings for idle speed control and ignition vs engine temp corrections?

[Boosted_162]

It's probably hunting because the PowerFC is trying to do idle control using ignition timing.

Have you got access to the PowerFC settings for idle speed control and ignition vs engine temp corrections?

Im not sure, where are the settings? I have the hand controller for it.

And just out of interest, i put the standard ecu back in, and it wanted to idle at 2k no matter if the ISCV was plugged in or not, and the headlights were on or not.

[fivebob]

It's probably hunting because the PowerFC is trying to do idle control using ignition timing.

Have you got access to the PowerFC settings for idle speed control and ignition vs engine temp corrections?

Im not sure, where are the settings? I have the hand controller for it.

Sorry I don't know. I only have the DataLogit for tuning, so those settings may not even be accessible on the handcontroller.

And just out of interest, i put the standard ecu back in, and it wanted to idle at 2k no matter if the ISCV was plugged in or not, and the headlights were on or not.

I don't think the stock ECU uses ignition timing to control idle so it sounds like either;

• Faulty ISCV
• Faulty TPS
• An airleak (possibly in the A/C idle up system),
• The base ignition timing is to far advanced,
• A faulty engine temp sensor.

Check out the "EFI -> Troubleshooting w/ Volt, Ohmmeter" section at http://www.celicatech.com/imagearchive/bgbonline/94_205_engine/EG/EG.htm

[Boosted_162]

Thanks for that Fivebob, ill have a read through that and start checking things tomorrow.

[Akane]

It's probably hunting because the PowerFC is trying to do idle control using ignition timing.

sweet.

[Anth_555]

it wont be A faulty engine temp sensor. if it was the car wont start my celica is doing this but its becose ive got a big vacum leak. but my water temp senor wasnt working and it wouldnt start.

[Boosted_162]

I think ive narrowed it down. Was checking everything was sweet, cos i thought it might be vsv (forgot to block it, whoops) but wasnt that. While i was looking, i discovered that there is a vaccum line that gets plumbed into the air intake, which i suspect is the one that comes from the ISCV. Now, if i block this pipe the idle goes back to normal when the lights are on.

Does this means my ISCV is stuffed?

[fivebob]

While i was looking, i discovered that there is a vaccum line that gets plumbed into the air intake, which i suspect is the one that comes from the ISCV. Now, if i block this pipe the idle goes back to normal when the lights are on.

Does this means my ISCV is stuffed?

No, the ISCV should not have anything to do with A/C or electrical load idle up. There is the A/C & electrical load idle up solenoid that is located on the rear firewall which has a vacuum line like you describe. This is only an on/off solenoid VSV and AFAIK all the ECU does when it gets load signal is to open the VSV.

There is an allen key adjuster on the front of the valve that controls the amount of air flow.