New IAC, same old problem.

Topic: New IAC, same old problem. (Read 1015 times) previous topic - next topic

New IAC, same old problem.

October 05, 2005, 09:31:15 AM

A while back I had brought up a problem I had with my engine reving way to high on occasion. Well the other day I picked up a new IAC and installed it. Everything seemed kosher for a while, at least untill the next morning when I started it up and it reved up like a cat with a hot coal up it's hind end.

I have been told looking for a vacspooge leak of some sort, but in all honesty, i'm not seeing that as the case. The reason I say this is because after driving it for x-amount of time and allowing the engine to get up to temp, then shutting it off and restarting, seems to clear up the problem. I have been reading what posts I can find in relation to this and i'm wondering if something like the ECT, TPS, EGR valve, or even the MAP could cause this problem. I must also point out that I do have an exhaust leak, and leak from the rear of the lower intake manifold. I'm getting kinda fustrated as to what the problem might be. I'm going to try to get to checking my TPS tonight, but at the moment i'm doubtful that it is the cause.

Anywho's I could really use some fresh idea's to try to narrow down the problem, Instead of throwing a whole bunch of new part at it to no avail (though I don't mind doing that too much in the long run!).

Re: New IAC, same old problem.

Reply #1 – October 05, 2005, 09:38:42 AM

Quote

shutting it off and restarting, seems to clear up the problem

I got the same problem now and its been on and off for 8 years now... I too replaced the iac for the hell of it..

I'm going to clean out the 10 pin connectors (salt and pepper connectors that clip onto the "5.0" plate) .....and see if that helps. If not maybe I'll throw a tps at it... I don't know I really don't feel like being bothered with it right now..

Re: New IAC, same old problem.

Reply #2 – October 05, 2005, 09:57:19 AM

Look at the TPS...I had the same issue on my Scorpio...to the point that I just disconnected it and said the hell with it. Even a "new" one from a 95 GT did the same thing on me. I might have a buggy TPS, but it appeared koscher when I tested/set it.

It could be a dirty connector as well *shrug*. The IAC is one of my least favorite parts of the factory controls. They should just shut it off once the car is warm and just use PWM to control the idle *shrug*. I wonder if you could wire in a temp. switch of sorts that goes open when a certain temp. is reached and shuts down the power to the IAC?

Re: New IAC, same old problem.

Reply #3 – October 05, 2005, 09:59:07 AM

It's common for the TPS to cause a high/hanging idle problem if the closed throttle voltage is over 1v. Restarting fixes it... for a while... Sometimes all that is needed is to adj the sensor so the voltage is .95 or less(may have to elongate mounting holes)

Re: New IAC, same old problem.

Reply #4 – October 05, 2005, 10:15:50 AM

So, when I go to test the TPS, does the car have to be running, or just have the ignition in the on position. Also, pending the posiblity of requiring a new one, i've got a choice between Echlin (the napa brand) or Delphi, any opinions on that?

Re: New IAC, same old problem.

Reply #5 – October 05, 2005, 10:45:39 AM

Quote

So, when I go to test the TPS, does the car have to be running, or just have the ignition in the on position. Also, pending the posiblity of requiring a new one, i've got a choice between Echlin (the napa brand) or Delphi, any opinions on that?

key on engine off

Re: New IAC, same old problem.

Reply #6 – October 05, 2005, 10:58:25 AM

my TC had the same problem, but when i sat at a light, the idle would jump to 3K, and then 3500, and 4K, and then id shut it off, and then it would od it all over again untill i put it in motion

Re: New IAC, same old problem.

Reply #7 – October 05, 2005, 11:03:23 AM

OK....I replied to this thread again...and it vanished.....weird.....

Yes, KOEO and the NAPA-brand stuff is pretty good

Re: New IAC, same old problem.

Reply #8 – October 05, 2005, 07:09:03 PM

Ok, I just got back in from installing a new TPS (i've got "some" extra scratch around, figured why not). I have to admit I never thought it would be so hard to get that thing down to .98 v's . I'm acutally not quite dead on, but I think it's within .05 or so. Is that going to affect it much? if so i'll prolly have a friend help me when I go to do it again.

Anyway's the car seemed to idle better, on start up it would rev up and take a couple moments to idle down to where it needed to be, and it always came back to the right place when I put my foot in it. Tommorow will be the big test as it'll have cold start to look forward too. I'm thinking about getting the codes pulled and cleared also as a just in case.

Re: New IAC, same old problem.

Reply #9 – October 05, 2005, 10:14:04 PM

.98 is good, as long as its just below 1 volt, and never exceeds it at idle

mine is at .96