Another Stalling XJ...OBDII Gurus plz help!

[angryjeep]

After searching the internets twice with google, bing, yahoo, hotbot, lycos, and manually with a comb... I figured I'd quit lurking and ASK for help.

So, here's what I've got: Daily-driven 2000 XJ, 4.0, Auto, Silver & Black, Winch-bumper w/out a winch (it holds tools nicely-- bangs knees even better).

The stalling problem is very very specific. Here's the rundown:

• It does *not* stall during the winter
• It typically stalls during warm weather
• It idles GREAT so long as the car is moving. Does not stall even when going 0.5MPH
• As soon as speed hits 0MPH, LOW IDLE and/or STALL.
• Two-foot application of brake/accelerator will overcome the stall.
• Low idle / stall is not accompanied by lurching, jerking, or any other trans-type indicators
• Still stalls when Trans is in Neutral
• Stall is sometimes preceded by a <CLICK> sound from under the hood (Electric fan engaging?)
• Driving without A/C reduces frequency of stall, but marginally so
• IAC *sometimes* will adjust, overcome the stall, and settle at normal idle (in noticeable increments)
• CEL IS CLEAR and CODE FREE

The problem existed prior to all this recent wrenching:

• New Champion Copper Spark Plugs
• New Coil (THAT brought the idle up some... didn't fix stalling)
• New Radiator (following overheat due to leaky hose / low coolant... oops)
• Rebuilt Cylinder Head & New Head Gasket (coolant in exhaust due to oops)
• New timing chain (just because I was in there)
• New Water Pump, Thermostat, and hoses (to prevent future oopses)
• New blower motor (irrelevant, but nearly as difficult as the head-gasket job)

I suspect that winch-less winch-bumper is the root of the issue-- but that expenditure was shot down by my Wife. Additionally, I've read dozens of, "I've replaced every sensor twice" threads... if I could afford to do that, I wouldn't be driving an XJ (or would be driving one with a winch).

It will literally idle perfectly for 500 feet, rolling down-hill on the slightest of declines at nearly-nothing MPH, but as soon as it hits 0MPH: CLICK-ugh-ugh-STALL.

I've considered disconnecting the electric fan, to rule it out-- but given the whole 'overheat == blown radiator * warped cylinder head' equation; I'm somewhat timid about that line of troubleshooting.

I would really LOVE to see a flowchart or document that outlines in granular details the order of operations of the Jeep OBDII system. Something that says, "read speed sensor, when at 0MPH do XYZ." If such a thing exists....

Anyhow... I appreciate any advice you can offer.

-angryjeep (aka Kevin)

 

[souske]

The click is your ac clutch cycling on.
the ac cycles auttomatically, even if its off.

Does it stall if throttle is applied?
Opening the butterfly takes the IAC out of the equation.
my bet is a lazy IAC.
My other car has a bump idle above 5mph, almost to the point of being annoying.
Wouldnt be suprised if the xj uses a similar trick

I have a 96, so i could be off track. Hopefully a late model guru will chime in

 

[joe_peters]

Try unplugging the A/C compressor and drive it.

Post up what happens.

 

[Tim_MN]

Try unplugging the A/C compressor and drive it.

I agree, easy enough to do.


Are ALL your tune-up parts fresh ? Heat related stalling usually points to a weak OBD sensor, or poor wire connections due to corrosion. Heat increases resistance, especially in already marginal circuits. Tested any sensors yet ? As suggested, tested/inspected/cleaned the IAC ? Tested the battery and the alternator ? Removed, cleaned and snugly reinstalled all the wires and grounds to the start and charge systems ?

 

[xjtrailrider]

I've had issues with the CPS on my 2000 giving out in hot weather. I was only able to fix this with a new CPS.

You say you have a new coil? The 2k is COP so are the other coils good?

 

[brewed4you]

Test your TPS. I had almost exactly the same symptoms when mine was bad just recently.

If you replace either the CPS or TPS replace it with a mopar sensor.

 

[angryjeep]

I haven't been ignoring this thread... just been busy. I appreciate all the advice, and Here's what I think I'll do next:

Sometime back I bought a used throttle-body off eBay with all the goodies installed-- going to track that down, and start with the TPS. If the behavior changes (for better or worse), I'll go from there. Next would be IAC, as I believe that stalling caused by the A/C compressor would REALLY be caused by the IAC instead.

Admittedly, I haven't checked all my ground connections or performed exhaustive testing of sensors. I haven't found test procedures within Haynes for each sensor, so if someone can point me in the correct direction for those instructions; I would greatly appreciate it.

Hopefully I'll have time to spend wrenching on Wednesday.

Thanks again to all who have offered suggestions!

-angryjeep

 

[angryjeep]

I've had issues with the CPS on my 2000 giving out in hot weather. I was only able to fix this with a new CPS.

You say you have a new coil? The 2k is COP so are the other coils good?

I replaced the CPS a couple years back-- albeit with an autozone unit. Certainly possible it's gone south.

FYI: It's impossible to replace less than all six coils on the 2K 4.0... they're all together on a single "bar."

 

[souske]

That cant be cheap

 

[O-Gauge Steamer]

To me, it sort of sounds like the IAC may be on the way out. When the A/C is engaged, the IAC opens up a bit to compensate for the drag on the engine by the compressor.

When was the last time the IAC was cleaned out? They do tend to collect stuff...

 

[XJCreeper]

Hi Kevin,

Sending you a PM with all the instructions from the FSM you will need to test the parts / areas in question.

Good luck checking, cleaning, and testing with the multimeter. Hopefully through this diagnosis you can pinpoint the exact part.

I totally here ya on the first I bought an IAC, then a TPS, and a MAP sensor ect. That assgas: