96 4cyl no fast idle when cold

[jacobkk]

I have a 96 2.2 4cyl which has no fast idle when starting cold. It used to stall when cold until I took the throttle body off and did a thorough cleaning, which fixed the stalling but I still have no fast idle, it always starts and idles below 800rpm or so, never idling high like it should for a few minutes. as per the Haynes manual I tested the IAC valve by using a jumper wire between TE1 and E1 in the diagnostic connector when the engine is warm, this activates the fast idle for 5 seconds like it should, and the IAC valve also has 21.4 ohms of resistance, which is right where is should be. I also tested the ECT sensor (the one under the green cap) and it seems normal, with the resistance steadily falling as the engine warms. Now I'm not sure what else to check, I'm assuming the IAC valve is good if both tests are normal. What else controls the fast idle besides the ECT sensor? Thanks in advance for any help.

-Jacob

[uibalnme]

Search for IAC valve. It's involved with cold start idle speed. There will be a few threads on cleaning it, which will fix that problem.

[jacobkk]

As I said I already removed the throttle body and cleaned everything, including removing the IAC valve, it's as clean as it ever has been, and the tests would indicate it's working fine, just not being activated when it should be, if my thinking is correct. I've been reading through lots of threads about it for days but that isn't bringing my fast idle back.

[AliRazoR]

DIY removal & cleaning of IAC
EGR Valve Replacement, DIY.

[Stillrunning]

Originally Posted by jacobkk

Now I'm not sure what else to check,

Given it's a 96 you obviously have no trouble codes since you've made a good start at initial diagnosis. Even though I have a 95 there are some possibles that don't involve a code that might also be areas to check in the 96 which don't point to the IAC. I also assume you get normal engine operation above idle.

1. Possible TPS signal that is not off at idle position and may be causing slight flooding.

2. If you have a MAP that could also cause poor idle if malfunctioning.

I would also (carefully) see if spraying starting fluid or like while at low idle does the idle increase. That would show poor fuel delivery/excess air at idle.

I guess it's possible that a leaking EGR valve might cause poor idle (vacuum leak), but usually they cause stalling if stuck open. Is the idle rough or smooth?

Even though the IAC resistance may check out, if it is not opening fully you will get low(er) idle. You might try manually triggering the IAC without the ECM signal to see if you get better idle. If you are not getting a voltage signal from the ECM to the IAC that could also be the problem. My manual says it should get 9-14V.

[jacobkk]

Thanks for the help, but I got it working ok now. Even after an extensive cleaning the valve was still sticking, so I took it all apart again and made sure it was moving freely this time and tested it with a 12v source and it's all good now. This leads me to another question though, the Haynes manual says to jump terminals TE1 and E1 in the "check electrical connector" and this will activate the IAC valve and raise the idle for 5 seconds, then return to normal. This worked for me but out of curiosity I did it with the IAC valve electrical connector removed, and it still raised the idle with the jumper installed, so how is this a test of the IAC valve at all if it still works when disconnected? Is this just the Haynes manual being dumb again?

[Stillrunning]

Originally Posted by jacobkk

so how is this a test of the IAC valve at all if it still works when disconnected?

My Haynes has this test as well. I assume it connects the IAC to battery voltage to activate the IAC coil and open the valve's intake to increase idle without the ECM signal. My FSM has the same test but it says only hold the E1/TE1 jumper FOR 5 seconds (idle should be 900-1300) then disconnect and IAC should return engine to normal idle. I think Haynes has a misprint.