meach

Ok folks I have been dealing with this ongoing problem for close to a year now and I have not been able to pinpoint the cause through research or troubleshooting. I have spent a lot of time and money chasing this gremlin and I’m not sure what is left to do. Before I start here are the specs.

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2001 Cherokee Sport 4.0 A/T

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Parts replaced:

IAC valve

TPS

MAP sensor and small elbow

IAT sensor

Alternator

Coil pack rail

Plugs

O2 sensors

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I have also checked voltages and resistance through the testing procedures. Compression is good. Fuel pressure is normal.

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So here is the deal, under normal driving conditions through town or on the high way everything runs as normal. The issue I’m having begins when I let the Jeep idle for an extended period of time or when I’m going slow on the trails/ crawling. It starts after the Jeep heats up enough to cause the e-fan to kick on. Once the e-fan does its job of bringing the temps back down the problems begin. *The idle will seem to drop very slightly.

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In park/neutral I can hit the throttle and engine will stumble and stall or just flat out stall. If I let off before it stalls the engine will catch itself but it will surge up and down till it eventually stalls. After each stall it starts back up with no hesitation and won’t stall until throttle is applied.

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In drive the same thing happens. It will stall completely but sometimes I can get it to drive through the hesitation (around 1500 rpms) but if I come to a stop and let off the throttle it stalls.

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Im pretty sure it is a heat related issue but not sure where to go from here. Is there anything I missed?

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Im close to the next diagnostic step being gas and some matches to burn the little Gremlin out.

Firestorm500

Does the fuel pump get noisy when it does this?

Go to the back of the Jeep and listen next time.

Rogue4x4

Have you tried this yet?
https://www.cherokeeforum.com/f2/jee...t-soak-117056/

meach

Haven't listened to the pump while it does it yet and I have the #3 injector wrapped. I will report back once I listen to the pump and I guess I might as well wrap the whole fuel rail and all of the injectors while im at it. Thanks guys.

meach

Well no change after wrapping the injectors and the pump sounds normal. i bumped up the idle a little since it was around the 500-550 range but no difference. Still stalls immediately once you hit the throttle.

DFlintstone

Might as well do the CPS...(since almost everything else is new). "stalling" and "warm/hot", come up plenty with CPS issues. Sometimes the gauges act goofy. Codes?...

Ron's link, in post #11, TJ mentions a TSB...

Bobolink

Have you messed with the throttle position screw at all (the little screw that opens the throttle plate)? Lots of folks want to open the throttle plate a little, trying to up the idle RPMs, and end up causing all sorts of issues, including off-idle stumbles and symptoms like you describe.

meach

Oops forgot to add CPS to the list of parts replaced

meach

I messed with it yesterday but it was doing this before I raised the idle, it was so low the a/c would almost kill it when it kicked on.

meach

No codes at all either

meach

As far as the tsb Ron mentioned its not exactly the the same issue. This is happening while the Jeep is still running. Ill try to take a video of it today and post. Yesterday I got it to do it with A/C on and just idling for about 10 minutes

Also I forgot to mention that I have the big Hyline offroad hood louvers on it as well

Bobolink

This is what I was getting at when I asked. If I understand you, you didn't make any adjustments to the throttle stop screw until after these problems had already started. Is it possible that anyone else (a previous owner?) messed with the screw? The problems of low idle with A/C or other idle problems cannot be solved by adjusting that screw. It's only there to prevent closing the plate so much that it binds in the throttle body throat. All RPM adjustments in reaction to different loads and environmental conditions are designed to be handled by the ECM via the IAC. Trying to increase idle RPM by adjusting the throttle plate stop screw just leads to more problems. I'm not sure about your engine, buit in the Renix engines there is a relay associated with the A/C that tells the computer when the A/C clutch activates, so that the computer will open the IAC to compensate for the additional load, and adjust the idle RPM accordingly.


The whole thing really sounds to me like a maladjusted TPS, or a dirty or partially blocked idle air bypass passage in the throttle body (you replaced the IAC, but did you clean your TB, too?).


But I've been wrong once or twice before...........and likely will be at least once more.

meach

Ok so I bumped the set screw back down to where it was before so I dont add to the problem. Guess ill pull the TB and give it a good cleaning. If it still does it ill have the video up by tonight

Bobolink

When you pull the TB, unscrew the throttle plate stop screw that we've been talking about until the throttle plate is completely closed. Then screw it back in until you barely perceive movement of the throttle plate. Double check that there is no binding as you open the throttle by hand. This should put it at the correct setting.

DFlintstone

Bob is correct. The screw is just to keep the plate from making a groove in the tb. The plate should close, and from there the IAC controls any flow.

Some of us are pretty finicky about where crucial sensors, like the CPS and 02's come from. I carry a spare CPS... Idk, I might put the original back..Hey...take a really good look at the wires down under, both to the CPS and the forward 02 sensor. The only problem I ever chased for a year was a fricken chaffed wire!