98 TJ Hesitation and Idle issues....

Okay, I have been having this problem for some time now, and I'm hoping it sounds familiar to somebody...

I have a 98 Wrangler 4.0 liter, if I start it from dead cold, it starts and runs fine all the way until I get to my destination, now the issue... if I stop and shut it off for a few minutes (to run into a store or something) when I get back in and start it again, I get an extreme hesitation and serious RPM fluctuation at idle.

If I am sitting at idle, the RPM's fluctuate between 300 and 1000RPM's (at

300 it ALMOST stalls, but then it catches itself and the RPM's jump back up to like 1000, it does this repeatedly)

When I put it in gear and go, the engine hesitates, to the point where it seems like it will stall. The only way it will drive is if I floor the gas. After a few minutes the problem works itself out, but until then, it is virtually undriveable.

My first thought was that it was the TPS (so I replaced it), but the problem is still there. Has anybody had a similar problem, and if so what fixed it? I am pretty handy, doing 80% of the work on my Jeep, but with this issue it seems like I could just keep replacing sensors until I'm in the poor house.

I am getting NO "Check Engine" light, so I don't even have that to start diagnosing.

Thanks for any help in advance,

-John

Reply to
jmorrison
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jmorrison did pass the time by typing:

It do.

"Hesitation after heat soak"

There is a TSB on this (can't find it right now, sorry) but it calls for some insulation being put around injector #3 to protect it from excessive engine heat that cause fuel to boil in the rail. That vapor then causes all sorts of headaches for the injectors till it clears. If you have an external fuel filter it might also be needing replacement.

Reply to
DougW

OK, that actually sounds promising. My only question(s). What do I use, and what is the procedure for insulating the #3 injector? and Which injector is #3?

-John

Reply to
jmorrison

jmorrison did pass the time by typing:

It's an insulating sleeve. You can get them at most racing parts stores.

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is it requires taking the rail off and putting it back on. If youdo this, take it easy and put a bit of oil on the rings before putting therail back in. The bolts holding the rail to intake only go to about 17 ft.lbsI always recommend new O rings each time the injectors come out. Just saferthat way.

You might be able to find an insulating wrap that can be secured with simple plastic zip-ties. Zip ties can resist fairly high temps. That would save on having to mess with the fuel rail.

#3 is third from the front.

Fan [ 1 2 3 4 5 6 ]

FWIW, I'm going to be doing my whole fuel system from the firewall. Just as an experiment in heat reduction. The less heat into the engine the better the performance.

Reply to
DougW

DougW did pass the time by typing:

Hmm..

It's off of

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Reply to
DougW

Reply to
L.W.(ßill) Hughes III

OK, this is odd, I now have a new symptom, I don't know if this changes anything. When I drive the Jeep now, if I push in the clutch while it's moving, the idle jumps up to 1500 and stays there until the vehicle comes to a complete stop. Only after it comes to a complete stop does the idle kick back down.

I even tried it on a big hill on my way into work. I got going and then pushed in the clutch to just coast. The whole time I was coasting the idle was at 1500. When I got to the end of the coast and stopped, it kicked back down to around 750 (the normal idle)

Does this change anything, or should I still try the insulating of the fuel rail?

-John

Reply to
jmorrison518

jmorrison518 did pass the time by typing:

High idle is different than bucking/stalling after heat soak.

That said, I'm not familiar with how a standard affects idle. I would expect the idle could remain high as the jeep is expecting to be put into gear.

Have you cleaned the throttle body IAP?

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Do that first then check. Sometimes the Idle Air motor will stick.

Reply to
DougW

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