I'm trying to troubleshoot my car, it runs really rough and it has a slight miss. I have replaced everything...new heads, gaskets, ENGINE, distributor, rebuilt injectors, plug wires, plugs, cap, rotor, fuel pressure, checked for vacuum leaks etc.

I just noticed when I shut the car off, but left the ignition on I was hearing clicking / buzzing noise.....it ended up being the IAC valve.

Is it supposed to make a noise like that with the ignition on? It's brand new, but that doesn't mean a whole lot.

Thanks!

 

yes it makes noise

take the iac out and plug the connector in and put the whole thing in a walmart bag and turn the key on

the spring and plunger should shoot out of the iac module

if not replace

if it does then put it back together and buy a helms manual and diagnose your car the right way

throwing parts at it is retarded

 

I take offense to that remark

Actually, I haven't "thrown" parts at it.....I built this from ground up....I was making reference that everything has been replaced or new to eliminate the guesswork of bad, worn parts. The parts were "thrown" at it because I built a new engine.

It's not your everyday TPI engine, and I do have the book.

Thank you

 

good for you

which book

man if you take offense to that I would hate to meet you in person.

 

The IAC should briefly make noise while it steps open trying to maintain idle. Once the alternator stops spinning and the ignition is dead, the IAC should stop moving/humming. If that continues for more than 2-3 seconds after the engine is off, there may be problems other than the IAC stepper itself.

I'm guessing that no offense was intended, and I'd have to agree that a complete diagnosis before replacing parts is typically the best method. Many times, the part in question is merely a symptom, and not the root cause of the problem.

I'm not sure I would have qualified the reverse of that procedure as "retarded, " however. Turning the timing back to compensate for crappy fuel or a poor match of cam and heads? Now THAT'S retarded...

 

On my 89 Corvette, I've noticed when I shut the car off. I hear a noise that sounds like a little electric motor is winding down. Hard to explain. But it lasts for a few seconds. Does that sound like the IAC?

 

found this thread by searching for it, i replaced my IAC last year because the car started idiling erraticially, new IAC cleared it right up, however i was pulling the error codes last week and noticed its really really noisy when the car is in diagnostic mode ?!?

Heres a video i took of it


That cant be good surely :/

 

Defiantly sounds strange. Does it stop when you start the car?

 

When you are in field service mode ( jumpering the a to b of the aldl ) the iac is commanded in. The stepper motor is bottoming out and releasing pressure off the pointless seat. This is normal.

 

Oh right, just sounds really bad ! cant say it used to be that loud.

But yeah its fine when the car is running, ive had a listen close up as obviously its hard to hear with the engine running but its ok.

 

I've recently been reading up on the IAC valve. My 89 shop manual says that when you turn the engine off, the IAC is commanded to extend to close off the IAC port. This happens in order for the ECM to know where the pintle is the next time the motor is started. Sort of baseline itself.