Okay guys, some of you may remember a few weeks back my car was idling up and down, and stuttering. Well I replaced the fuel pump and that solved that problem. But it was also idling at like 1250 and that problem still exists. I've tried setting minimum air, and all that happens is when I reconnect the IAC, the idle goes back up to 1250 or so, 800 in drive. Sometimes it even reaches as high as 2000 and 1200 in drive. So I cleaned the IAC and put it back, same thing. When I turn the car on with the A and B terminals of the ALDL grounded and the IAC connected, I hear a ticking noise coming from the IAC. Does it sound like I need to replace the IAC? Thanks in advance.

 

sounds to me like it needs replaced... they are cheap enough, so if I were you, I would do it to see... can't hurt.

 

intake manifold leak...................

 

When the ECM is in the Field Service Mode (with the diagnostic terminal grounded) the IAC will drive the pintle completely closed, then continue clicking until the jumper is removed or the ignition is turned off. That's completely normal.

I'd agree with TealRS. You likely have a vacuum leak, a sticky throttle shaft, or dirty IAC air passages. Try cleaning the throttle body and IAC before replacing it. If you follow the procedure for setting minimum air and cannot get the idle low enough, the problem is likely as leak or worn TB, not the IAC.

 

Well I replaced the IAC anyway, and the RPMs are back down to like 950 in park and 750 in drive, but still not where they should be. When I had the TB off, I cleaned it. And I can't find any leaks

 

Vader- are their any common places on a TPI where a leak will appear?

for example- the buick 3800 engine in FWD applications usually developes an intake leak nearest the EGR valve
it is presumed theory that because the EGR valve gets so hot, it wreaks havoc on the gasket

i'm not sure if there are any area's of a TPI manifold gasket that are "weakest links" or that are affected by other things, such as my example above

 

I just replaced the manifold gaskets last spring. I gotta replace them again anyway when I put on the LT1, but that wont be til spring.

 

Metallic,

Since you replaced the IAC, you should have performed the procedure for setting minimum idle air position of the throttle blades.

If you cannot achieve minimum idle RPM with the IAC disabled and the throttle fully closed, you have a vacuum leak. Check the PCV system and brake booster first.

 

Vader- Before I replaced the IAC, I was driving with the IAC disconnected and just min. air set. It was a little roguth when cold, but after that it was just fine. I can get min. air to be about 500, any lower and it nearly dies. Then when I plug the IAC back in and turn on the engine, it idles at 1000

 

Metallic,

With a stock EPROM, the target idle in DRIVE should be 650 RPM when the engine is at normal temperature. If you can only set the minimum air down to 500 in DRIVE, that should be close enough. If I recall, the specified setting is 500-550 RPM. Once the engine is warmed and the CTS is at 176°F or higher, the target idle should be as stated, and that's where the IAC should control it.

Is the CTS reliable?

 

Hmm, now that you mention it, I dunno if the CTS is reliable. The temp gauge doesn't work, but I always thought I messed it up when I did my white faced gauges.

 

Metallic,

The CTS is a different system and sensor that the one used for the dash gauge.

Your gauge sending unit is mounted to left cylinder head. The CTS is mounted to the front coolant crossover on the intake base. You can unplug the CTS and test the resistance to see if it is in range.