So this problem has been somewhat erratic over the past 2 weeks. When driving, something comes over the car and the idle will shoot up to 1700-2000 rpm. I have a scanner at the house right now from my friends shop and it's saying there is a Fault code #35. Any help would be much appreciated.

Thanks,
Scott

 

Check to see if you tps or iac are disconnected if so then one or both of the two are probably bad.

 

So I thought that I had fixed the problem yesterday, or atleast the problem went away after fiddling with it. But now it's back. What it does, is when you start the car up it will idle at around 1700rpm, then on the way back it will settle down to around 1200, but then there is absolutely no power. I'm talking 3/4 throttle to keep up with the rest of the traffic on take-off. I got the car home and put the scanner on it and It's reading 98 counts on the IAC, where when it was Idling perfectly yesterday after messing with it at 14 counts. Also it's saying the knock retard is pulling 15 degrees at idle even though the scanner is saying there isn't any knock signal. I'm about fed up with it after messing with it for ten hours yesterday. So anything would be very appreciated.

Scott

 

??? only oth things i could think that might cause the lack of power would be clogged cat, or maybe the o2 sensor but those are really trial and error, its no fun to just throw parts at the car and hope it fixes it lol.

 

Yeah, I hate chunking parts too. But the catalytic converter has been gutted. Also, since the computer ignores the O2 sensor on warm-up wouldn't that not influence the IAC counts? Either way the O2 sensor is giving an average of 6 cross counts once the car's warmed up.

 

IAC is a funny thing, ain't it? Try this. When you go to try to fix it again, take the IAC out of it's bore with the key on, engine off, and the connector connected. You will need to point the pintle end of the IAC into a rag or something for this. If the IAC is working, when you turn the key off, the pintle will end up getting shot out of the end of the IAC and into the rag (because of the balance spring). If not, nothing will happen. It seems to me that you have a similar problem as I do, in that the IAC is not retracting properly... At least you have a lower idle speed than I do when my IAC is OPEN... mine shoots up to 3K sometimes.
Code 35 means that the ECM is unable to control the engine's idle speed, IIRC... Or is that one different? I know mine keeps throwing the Idle speed control code...

 

I tried that just now. It does extend all the way and the engine still runs at 1700-2000 rpm. I did notice one thing however, the AIR request is on, according to the scanner and the engine is cool, well (68 dgrees celcius), but I removed the smog pump because the previous owners gutted the cat and crimped a bunch of the hoses. Still lost towards progress

 

Have you tried jiggling the wiring with the engine running? It's either the IAC or some air getting into the engine where it's not supposed to... The IAC is supposed to control the amount of air going in at idle (hence the name, idle air control motor). I know the connector for mine needs to be replaced, and I can't wait until the new pigtail gets here. Got it off of eBay for 1/10 of what GM wants for it... $85. P/N 19115673 if interested.

 

Well now the car has fixed itself. the interesting thing is that the AIR is off at idle now and it seems the default IAC count is 101 when ignition is on, engine off. So when I start the car now that it is running right the IAC counts drop to 12. When it wasn't working the counts would not move from 102. So is it possible something with the retracting circuit is bad?

 

I shook the harness like an earthquake while the engine was running and nothing

 

Yes, it does seem that there is something going on with the connection between the ECM and the IAC. If you could do it easily, I would do a resistance test on both ends of each of the IAC wires, between the motor and the ECM.

When the engine is off, the ECM extends the IAC pintle (to the 101-102 count you see) to create a fuel rich environment in the engine for easier starting, similar to the choke plate in a carb. Once the engine starts, the ECM retracts the pintle (to 12, I would guess is where your ECM likes it) to maintain a certain idle speed, between minimum and about 1300 RPM (when warming up).

 

Well, the car acted up again on the way home from school today so i decided to look into the issue again. Well, the wires between the ECM and the IAC have 0.1 ohms on them so I'm pretty sure that won't matter. Also I did shake the wires while taking the measurement to see if it varied at all and it didn't. But that leaves the connection at the ECM and the IAC. Also the IAC motor itself is under question. When the key is put in the on position, does the IAC retract to the 102 count position from the 0 count position it's in when the engine is off. What's really annoying is when I ground the ALDL to activate all the stuff, the IAC fully extend when it is out of the throttle body, but that doesn't mean it's acting properly when it's in the TB.

 

2 things wrong here.
1. You have to measure the resistance of the wires BETWEEN the ECM connector and that of the IAC. Long reach, I know, but it's the only way to ensure that the wires are good. I hope to g0d that you didn't try to measure the resistance between each set of wires (the blue ones and the green ones), because if you did, you may end up with a fried ECM, which doesn't like the high voltages that a DMM puts into each wire to test the resistance.
2. Next time you have access to the scanner you have been using, try looking at the IAC counts when the engine is off and when you start it. The counts SHOULD change. If not, the IAC circuit is in question.

And now, a question for the experts. How many connectors does the IAC circuit pass through between the ECM and the IAC motor? I replaced the IAC connector AGAIN, with a NEW one, today, and it's still not working. It's possible, but I seriously doubt that my NEW $40 IAC that I bought last year is bad... I have 3 others I can use to test this, but I would like to hope that it's the wiring and not my NEW IAC that's bad, because that would make me .

 

Fixed mine today. Ended up using my 3rd spare IAC motor from my 3100 top end setup, after switching wires around in the ECM connector, resistance testing the wiring (0.2 ohm per wire, right where it should be), and a whole lot of swearing... 1200 RPM cold, 800 hot (have it turned up for the winter months).

 

The bore in the T.B. where the IAC seats itself was gummed up with deposits. The pintle was getting stuck. Took the T.B. apart, cleaned the IAC bore out with some carb cleaner and a rag. Runs MUCH better now.