Is my ECM Toast?

[XfireZ51]

Originally Posted by gbmidyear66

Dom, regarding the IAC values - yes something is not 100% right here.

When I can get the idle to behave, car runs at about 775 RPM with IAC=0, if I turn on the A/C, it runs at about 725RPM with IAC about 13 or so(from memory). I agree - with A/C off I should not see IAC = 0 and 775 RPM.

The above implies a "leak ", but I don't think it is the typical situ with air leaking in from various hoses/tubes, etc given that I can stall the engine by blocking the throttle body.

I started out thinking I had an issue with a sticking throttle plate(s) - but the SES indicator and CAGS no longer working led me to suspect the ECM.

The IAC counts should be somewhere at 10-20 at idle. I think mine are at about 5-10. A/C should require more IAC steps to deal with drag of compressor. Again, it could imply a leak but if the IAC is opening up when AC compressor is on, it could be the Min Air adjustment. That would be consistent with the stalling motor when blocking TB. As for the SES light, are you saying it does not come on with ignition ON only, no engine run?
If you close up the throttle blades and see the IAC counts increasing, then there's no vacuum leak.

[gbmidyear66]

I spent some quality time with my FSM last night. Regarding the ECM....

You put the ECM into diagnostic mode if you connect ALDL pins A and B (on a 90 - Ign on, engine off). If the DIC flashes 12, 12, 12, xx, xx, xx, 12, 12, 12 (xx indicates a stored fault code, there may be none, or multiple) - then the ECM has passed all its internal self tests and is presumably good.

Mine indicates good. I'm going back to looking at the throttle body for my issues.

[GOLDCYLON]

Originally Posted by gbmidyear66

I'm going back to looking at the throttle body for my issues.

[gbmidyear66]

Well, I eliminated one suspect leak tonight (vacuum pipe connection to PCV header (Breather Mold).

I then started the car and let it warm up, everything was beautiful - idle drops to 675 RPM, IAC at 6 steps. Almost ready to hit the couch and crack a beer, but I thought I would blip the throttle a few times to see what happens. Well, it won't come back down below 750RPM, and IAC is at 0.

I think this is telling me that the butterflies in my TB are not sealing reliably?

I thought I read somewhere that you can grease the circumference of them as an interim solution? Anyone done this?

Glenn

[XfireZ51]

Glenn,

I clean my throttle blades, the bores and the shafts.

[tomtom72]

Originally Posted by XfireZ51

Glenn,

I clean my throttle blades, the bores and the shafts.

Just make sure you use Throttle Body Cleaner and not carb cleaner. Also, be careful when cleaning the DAG, gently is the key or you might start to remove it and loose the seal.

just a thought you're sure that the cables and their cams are not gummed up & binding a bit?


Tom

[XfireZ51]

Originally Posted by tomtom72

Just make sure you use Throttle Body Cleaner and not carb cleaner. Also, be careful when cleaning the DAG, gently is the key or you might start to remove it and loose the seal.

just a thought you're sure that the cables and their cams are not gummed up & binding a bit?


Tom

Tom,

I've heard and read about the DAG but my TB is bored out to 63mm. My idle w the cams is now in the 775-825 range.

[ScottZ95ZR1]

Originally Posted by gbmidyear66

Well, I eliminated one suspect leak tonight (vacuum pipe connection to PCV header (Breather Mold).

I then started the car and let it warm up, everything was beautiful - idle drops to 675 RPM, IAC at 6 steps. Almost ready to hit the couch and crack a beer, but I thought I would blip the throttle a few times to see what happens. Well, it won't come back down below 750RPM, and IAC is at 0.

I think this is telling me that the butterflies in my TB are not sealing reliably?

I thought I read somewhere that you can grease the circumference of them as an interim solution? Anyone done this?

Glenn

Not sure the post linked below is where you read about greasing the TB plates, but I remembered Scott stated he does.

http://www.zr1.net/forum/showpost.ph...1&postcount=12

[gbmidyear66]

Thanks for digging up the link to Scott's post.

Well, I tried greasing the circumference of the plates today, but this just made the idle hang situ much worse. So I get out my trustry can of TB cleaner to remove some of the grease on the plates and I skillfully manage to shoot the plastic extension straw off of the can and down into the Plenum. Managed to fish it out with some double sided tape on my telescoping magnet, and get back to where I started at the beginning of the day.

If I apply finger pressure to the primary plate - my idle drops down nicely, I think my next step will be to send it out to Marc Haibeck to have it serviced this winter.

Glenn