kenjen11

Hello, I am the happy owner of a 2001 Cherokee Sport stock 4.0L auto tranny with 115,000 miles. I have had this current problem for a year and a half. When I start up the cherokee in the morning it runs fine and idles great for about 4-5 mins, I'll drive it up the road to the stop light and when there it will idle rough and then stall. It always seems to start right back up no problem. Sometimes it will stall at the next red light also but once the operating temp goes up it idles fine and doesn't stall out. A few times on start up it did stall while idleing. It seems to only happen after it has cooled down too. If I drive it to work and let it sit in the parking lot all day it has the same stalling issue. Since I had the jeep I have replaced the battery cables (corroded), Crankshaft position sensor, Camshaft position sensor, I have had the battery tested along with the alternator (both good), new champion plugs, I see the recall heat shield on the intake manifold and cover for the #3 fuel injector, New fuel pump/filter, TPS, IAC. The jeep died on me at home and needed the fuel pump. A few months ago it idled high and needed the TPS. It died on me 2 months ago and needed the Crankshaft position sensor. Other than the stalling it runs fine and I four wheel it.

kenjen11

Sorry, I have put in a new air filter, and the battery was new when I bought it. I took it to a mechanic and they told me there were no codes and thought it was the computer.

Burgy

I had something very similar happen on a 98TJ. The Jeep wouldn't stall out, but almost would. The engine would sputter, backfire, and struggle to continue running. It ended up being a downstream O2 sensor that was bad, but wasn't throwing a code because it was only in certain temp ranges. As soon as the engine passed the temp range it would return to normal. This took me several months to diagnose, the dealer and every other shop I went to was clueless. finally a mechanic buddy of mine hooked it up to his diagnostic machine and watched the fuel trim levels as it sputtered. Sure enough they were plummeting in that temp range as a result of the failing o2 sensor. I put a new one in and never had another issue with it. The problem you'll have with a 2001 XJ is that there are 4 O2 sensors, might be harder to find out which one might be the culprit.

tjwalker

Not likely to be the computer and I would not replace it. Computer replacement should be a "diagnosis of exclusion" meaning every other thing has been ruled out. And you're not there yet.

I think an engine management sensor may be in play here, but the question is......which one.

The fact that it runs great when you first start it cold but then starts acting up after a couple of minutes may indicate that the problem has something to do with when the engine goes into "closed loop".

If this were mine, I would get a scantool or engine analyzer (as burgy mentioned) and somebody that knows how to operate it, and watch every input very closely. With "real time" data, you may be able to isolate this pretty efficiently.

With no code, scantool monitoring is the next best thing. And far more efficient that installing parts on a hunch.

Good luck!

kenjen11

Thanks Burgy I will have to check out those O2 sensors!

kenjen11

Thanks TJWalker I will look for a shop with an engine analyzer and have it checked out.

JrRifleCoach

There is a program set (computer) that when the engine is still in open loop (cold) the AFR is set based partly on TPS-RPM & controlled by the IAC. This sets and hold RPM while idle. I'd check the value on the TPS and inspect/clean the IAC while your at it.

Or have your shop do it. No reason to start throwing parts ($$) at it yet.

:cheers

kenjen11

JrRifleCoach thanks for the help, the IAC was what I first looked at. I cleaned the old one and also cleaned the TB. Stalled afterwards like it did before. So for the heck of it I put in a new Crown IAC but still the same results. A few months ago the RPMs were jumping up with a rough idle and the engine light came on for the TPS. I replaced that with a dealer TPS and the RPMs have been steady since with the light off but it still is stalling.

CodyBEAN

Ralph77

I don't know if this is even relevant but I have a buddy with a '96. Was running like crap. New plugs, wires, cap, rotor ,and a new fuel filter. No joy. Drove him nuts until he figured out it was the temp sensor in the thermostat housing.

CodyBEAN