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

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jimboe - 12 Jan 2006 05:17 GMT

This thread details this beast what I've done, and still outstanding issues:
http://www.carkb.com/Uwe/Forum.aspx/jeep/9218/93-GCL-ZJ-Low-idle-engine-noise-ot
her-probs-long#58c293b518dbauwe

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.

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Earle Horton - 12 Jan 2006 12:42 GMT

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

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

http://www.carkb.com/Uwe/Forum.aspx/jeep/9218/93-GCL-ZJ-Low-idle-engine-noise-ot
her-probs-long#58c293b518dbauwe

> but simply put: 210K mi's, just had a tune up and it idles low, ~600-620.
>
[quoted text clipped - 24 lines]
>
> Thanks.

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DougW - 12 Jan 2006 23:35 GMT

Earle Horton did pass the time by typing:

> 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.

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.

Signature

DougW

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jimboe - 13 Jan 2006 22:17 GMT

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.

Jim

>Earle Horton did pass the time by typing:
>> My thoughts are that a stuck or going bad IAC is a good guess. I am in
[quoted text clipped - 21 lines]
>Do a quick check of the vac hoses. Especially the one running to the
>brake booster. Clamp it off and see if that helps.

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jimboe - 27 Jan 2006 23:02 GMT

Just want to update you guys as you may find it interesting,

Upon getting the new IACV @AutoZone ($40, Wells) and comparing to the old, I
noticed on mine that the pintle looked as if it was sticking out way to far.

So, pulled back the "sheath" on mine, and turned the pintle clockwise several
rotations until it was the same length as the new, put it back in, and
problem solved.

I suppose when I was cleaning the IACV and throttle body several weeks ago, I
must've been playing with the pintle subconciously and opened it up (or maybe
loosened it to a point where it would continue to open). This of course
caused the air bypass to ALWAYS be blocked, even when the IACV "pullled back"
its' sheath, causing my no "cold-idle" problem.

Interesting note about the new IACV BTW. I at first bought it at one AutoZone
and was charged $58. Then later on that day, I passed another and decided to
ask if they had any other brands of IACV. They had only the same exact one
(Wells) I bought at the previous location, except for some reason it was only
$40. Naturally I bought it there and returned the other one.

Same exact part manufacturer, model, UPC on box, and on receipt for purchase.
Identical. I couldn't and still can't believe it. How could one AZ have a
completely diff price for the same exact, new, never "bought-returned by
anyone", part?

Anyhow all's well that ends well. Off to return it anyway.

Jim

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jimboe - 30 Jan 2006 08:29 GMT

Welp, seems I spoke too soon.

Not 3 days later, and same thing happened again this morning, so I have to go
re-buy the part.

Either the pintle is loosening/opening back up to where it was (fully
extended so it protrdes into the throttle body) and/or the sheath is not
retracting when it should..

O well.

Interesting experience.

>Just want to update you guys as you may find it interesting,
>
[quoted text clipped - 25 lines]
>
>Jim

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