93 ZJ 5.2 GJC: Difficult start today- any ideas?

Question

This thread details this beast what I've done, and still outstanding issues:

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but simply put: 210K mi's, just had a tune up and it idles low, ~600-620.

Monday noon drove it about 35 highway miles home (~72mph, hit 80-85 a couple times), parked it for 6 hours, ran it for two short 5 minute trips parked it until Wednesday, 2PM.

7/8 tank of gas in it, it started right up, then shut right down. 4 times.
5th and 6th time I tried pumping the pedal a couple times before the start which made no differnce. 7th time I held the pedal to about 2K rpm's for ~15 secs, then eased off over the next 10 seconds and when I let go-- it shut.

It was as if it had no idle at all.

Several minutes later (after fiddling with the plug wires by pushing down on them firmly, on both ends) I tried to 2 more times (in the manner of the very

1st attempt) and it just shut.

I decided to try one more time like time #7 before calling a tow, and this time, it stayed running-- with the normal (for this car) idle.

10 minute discussion with my mechanic led to the possibiltiy of IAC-- which I cleaned very well only a few weeks ago. Could the IAC get "stuck", perhaps be going bad? I postulated the fuel pump (bad pressure perhaps-- which could also be the source of my low idle).

Any thoughts?

Thanks.

Earle Horton · Accepted Answer

My thoughts are that a stuck or going bad IAC is a good guess. I am in principle against swapping components "blindly", but if the IAC doesn't cost too much then you can't go too far wrong replacing it. I would probably remove and thoroughly clean the throttle body, replacing the base gasket of course, because it's easy and then you eliminate that as a potential problem.

Earle

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DougW · Answer

Earle Horton did pass the time by typing:

You can pull the connector off the IAC while the vehicle is running. All that does is eliminate the ECUs ability to control RPM but the engine will settle down.

That will tell you if it's causing the problem. But not entirely. A bad O2 sensor, intake leak, or dirty wires can still trick the ECU into making poor adjustments.

Keep in mind it's a stepper motor. If the harness ground or any of the wires are bad, the motor will be erratic.

If you do take it off, NEVER try to start the car with the solinoid exposed or the little pintle will go flying and your then stuck with getting a new IAC.

Do a quick check of the vac hoses. Especially the one running to the brake booster. Clamp it off and see if that helps.

jimboe via CarKB.com · Answer

Thanks for the tips Gentlemen, I will try some of them this weekend.Since that incident Wednesday, the truck has not had any problem starting.JimDougW wrote:

93 ZJ 5.2 GJC: Difficult start today- any ideas?

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