oh man more car troubles! (and some discoveries)

Bacondoggy

Registered User
well - I found out my main problem was a bad IAC - I didn't think I would have 2 that were both bad, but alas, I was wrong. now time for some questions that I am stumped at.

#1 the ECT sensor (engine coolant temperature sensor) I got was from autozone and was a wells brand. Well I decided to check the resistance (ECT sensor just being a resistor) and was suprized to find that the autozone brand measured I think 44 (approx.) ohms and the ect from my 89 measured 11 ohms (approx.). So I took the autozone one out and put the one from my 89 in. Did they change the resistance with the years? I would think they should all be the same! and what SHOULD the resistance be for a 91 SC 5 spd?

#2 here is my problem - NEW IAC, tps and MAF cleaned and tested. No air leaks whatsoever on the intake. 95% sure no vacuum leaks - I have checked - I mean I could replace all hoses and make them BRAND NEW, and see a small performance gain but I am sure most people could do this as well if they haven't and this symptom I don't think has to do with that. My car now usually idles around 900 rpm, but stalls every once in a while... now what really bothers me is when I step on the gas and let off it, the engine doesn't drop in rpm's like it should. It slowly goes down, then sometimes hovers around the 1500 (+/- a few hundred rpm's) for a while. then when I am stopped like 10 sec (differs so much) it will drop back down to correct idle. What is going on here?!?! it is so annoying driving, then letting off the gas and hearing the car getting fed all that excess gas it seems as if to keep the engine going! this is my main concern please help!

thanks!

Mark
 
You using a OEM IAC or aftermarket? Personally...I use OEM sensors ONLY since they affect the emissions calibration and are scaled to operate correctly with the EEC.

Resistance of the ECT depends on temperature....it is a thermistor so unless you know the temp. when you measured its resistance there is no way to compare or check your readings.
 
IAC is OEM - no way would I get any other one! and, as for the ECT, they were both out of the vehicles, sitting side by side, at the same temp. and they are just resistors, I was just confused why the values were different...
 
You have to know the exact temperature to know which one was correct. The resistance varies with temperature.

Assuming you have a 5spd, the motor is supposed to maintain a higher idle until you stop moving. As you come to a complete stop it should drop to normal idle pretty much imediately.

Kind of sounds like you have a vaccum leak making the idle higher than normal and somewhat irratic.
 
my car acted up for 2 weeks after unplugging and plug back in iac, idleing at 1500 and so on until i unhooked the battery then it took 2 or 3 days until it learned to idle right again stalling sometimes for 2 or 3 days
 
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