IAC goes to 0 and other problems

[GNRick]

First I blew out the #4 spark plug. Threaded part stayed in the head, spark plug wire was just dangling with the porcelain still stuck in it So I replaced the plug, car then had a lot of smoke coming out the exhaust. Scan tool showed IAC was 75 at idle and it would not move from there, no matter how much I turned the screw in either direction. I unplugged the wire to the IAC and plugged it back in. Then it came down to 54. The idle didn't even change when I unplugged it. Still couldn't get it to move from 54. So I put in a new IAC, unplugged the orange ecm wire, reconnected the orange wire, adjusted IAC to 40 and went for a ride. The car still didn't feel right and I still had smoke out the back, but not as bad as before. Checked IAC when I got home and it was 0! Unplugged orange wire, reconnected it and IAC went back up to 40. Drove the car, came home and again it went to 0. I am thinking I should replace the spark plugs and maybe that will help. Any ideas/advice is gladly appreciated. Jiggling the wires to the IAC doesn't make any difference. Of course, a wire might be broken someplace else, away from the IAC.

 

[tom j]

IAC Reset Procedure

 

[GNRick]

IAC Reset Procedure

Been there done that (more than once!)

 

[Chuck Leeper]

If you rattled the motor hard enuf to blow the innards out of a plug, the smoke may be from some broken rings, cracked piston, etc.
B4 I beat on it any longer:
1. Compression test, leakdown test.
2. Inspect/replace ALL the plugs.

 

[GNRick]

If you rattled the motor hard enuf to blow the innards out of a plug, the smoke may be from some broken rings, cracked piston, etc.
B4 I beat on it any longer:
1. Compression test, leakdown test.
2. Inspect/replace ALL the plugs.

Both knock gauge and scan tool show 0 knock. Would damage as you describe send the knock gauge into the stratosphere? When the plug blew out, I wasn't even beating on it. Just accelerating to about 40 mph. I figure the plug damage might have started from a previous beating. Car ran fine, no smoke until the plug blew.

 

[GNRick]

I don't have a compression tester but I did replace all of the plugs and the oxygen sensor. Still blows smoke, iac is real low (about 10) but tps is .42 at idle. When I adjust the iac screw, the tps changes. IAC still stays low. Any other thoughts? Could it be a spark plug wire or coil pack? One other thing- the exhaust sounds more uneven, like that wap wap wap that some V-8's with flowmasters sound like. Not as loud, but not as it used to sound. Could the cam sensor have been nudged a little? We were messing on the passenger side of the motor, trying to remove the valve cover to replace the gasket. Would a vacuum leak affect the IAC?

 

[TurboMonte 2]

Would a vacuum leak affect the IAC?

YES

And, oil smoke not likely related to IAC counts,
And, per procedure, IAC & TPS settings interplay w/ each other--need shut off ign after each adjustment...

BTW, what is your in. Hg vac @ idle?

 

[GNRick]

YES


BTW, what is your in. Hg vac @ idle?

I disconnected the hose at the MAP sensor and tested vacuum. Guage said 17. Does this help? Did I do it right?

 

[artrenee10]

Your IAC is about to take a dump...get a GENUINE A/C Delco unit and save yourself some time...
HTH
Steve Chambers

 

[GNRick]

Your IAC is about to take a dump...get a GENUINE A/C Delco unit and save yourself some time...
HTH
Steve Chambers

Hi Steve,

I replaced the IAC with an AC unit that I won off E-bay. It was new in the box. I can swap one off one of my other GN's and see if that makes any difference. Thanks for your help.

Rick

 

[GNRick]

YES

And, oil smoke not likely related to IAC counts,
And, per procedure, IAC & TPS settings interplay w/ each other--need shut off ign after each adjustment...

BTW, what is your in. Hg vac @ idle?

I'm not sure the smoke is from the oil. I think it is just running rich. I'll try replacing the IAC again and see if that makes any difference.

 

[83ttypecooled]

Hi,
You have had a lot of posts about this problem, but the common issue seems to be idle control and, more importantly, smoke. What color does the smoke seem ro be? Black equals rich exhaust,while light blue is oil consumption.A leaky turbo is a good possibility, and you might see some oil on the inlet side of things, too. Rings on our full skirt pistons seem to last a long time,and that other source of oil consumption, valve guides, are rarely an issue,so the turbo is a likely possibility.I recently completed a 1500 mile run with one of my vehicles,and used 2 quarts of oil on the drive. I pulled the intake hose off, and it had oil in it, so I am fairly certain the turbo passed most of that 2 quarts. 'nuff said?
Regarding your idle issues,for $45 or so, the IAC can be replaced with a known good unit,and you won't ever have to worry about that possibility again.Idle on our cars is screwy at best, with lots of hunting and loping.That said,it is imperative to have the minimum authortity (base idle) and tps set accurately.First, set base idle, then the tps, and consequently,leave both of those alone.Any other issues will be from other areas,so once these are set,LEAVE THEM ALONE.
That's it from me, good luck with your tribulations.

 

[GNRick]

Hi,
You have had a lot of posts about this problem, but the common issue seems to be idle control and, more importantly, smoke. What color does the smoke seem ro be? Black equals rich exhaust,while light blue is oil consumption

Smoke is not black. It is white (or light blue). I'll try swapping the IAC tonight and see what happens. Does anybody know if my vacuum is ok? Guage reads 17. Thanks.

 

[GNRick]

I checked with my regular mechanic and he confirmed a vacuum leak would affect the IAC, and would also cause it to run rich and send smoke out the back. So, I blocked off each of the 6 vacuum lines coming off of the vacuum block on top of the throttle body. I did it one at a time. I reconnected them after capping them. Maybe I should have left them capped, until all 6 were capped, to rule out multiple leaks. No affect on IAC. I even capped the two lines from the wastgate and turbo to the boost solenoid. So are there any other vacuum lines that could be leaking? How about underneath the car, at the transmission? Maybe the vacuum block itself is leaking? My guess is we messed up something on the passenger side while struggling to remove the valve cover. My mechanic said he has a smoke test machine (but I would have to pay him, of course). Thanks.

 

[GNRick]

My mechanic found the problem in about a minute. After telling me that he thought I could have blown a head gasket or a ring and other doomsday scenarios, he put his stethoscope on the motor and found the #6 injector was not firing. He pushed down on the electrical connector and voila! That fixed it. The plastic connector was broke and the wire clip wasn't holding very well. I'll call Caspers and buy a new one. IAC is back to normal, around 25 at idle. Then I went to my autos class at night school and removed the passenger side valve cover, to replace the leaking gasket. It's an aftermarket one that Paul Ferry used to sell. Had to remove the downpipe, remove the bolt from the engine mount, and shift the engine up to give me access to the back allen head bolt. Only took 4 hours