adriaanvn99

Good day all

Been having a strange issue the last 3 weeks. I would take the Jeep for a drive, about 10-15 miles, come home and park it. Would take it for another drive about 2/3 hours later, and it would struggle to start, about 4-6 swings before it takes, but on cold starts it is perfect (say now its been sitting for 2 days). I initially thought it was my fuel pump, but why would it start normally on a cold start?

So yesterday I had driven about 15 miles and took the exit off the interstate, and as I approached the ramp the Jeep just cut out, kind of spluttered and just died, had to pull off and stop because had to put it in park to restart it. Anyways it restarted perfectly and drove home without a problem.

Update: Just went to the store, got to a red light, tried to pull away and Jeep just died, immediately put into park and restarted again without an issue.

The only thing I have done recently was to put in Lucas Oil stabilizer, so it could be that the oil might be a little to thick and my oil pump is starting to fail.

My thoughts are either a fuel pump (but it starts fine on a cold start?), or a oil pump, or either a sensor (TPS or CPS)

So now I am trying to diagnose the issue. Anybody perhaps have an idea what it might be?

Thanks for your input

investinwaffles

Sounds like a MAP sensor? TPS doesnt usually cause the engine to completely die (in my experience). CPS would cause a no-start condition but would also cause the motor to stall if it's bad (both are easy to test)

https://www.cherokeeforum.com/f2/map...rocedure-7416/

adriaanvn99

Thanks a lot, appreciated.

I am going to go test that now, and if all good I will go get a fuel pressure tester and see whats up there.

BlueRidgeMark

Fuel pumps can be intermittent, but that's probably not your problem.




Your oil pump cannot cause this kind of symptom. Don't waste time or mental energy considering that.

Most likely cause is a sensor, and you have several that can cause your problem. CPS, CkPS, TPS, O2, and MAP.

Time to start testing, instead of guessing.

adriaanvn99

Yes, sure. Thanks for the feedback

Tested MAP sensor this afternoon and it is getting the voltage needed on the plug, will test the actual sensor tomorrow and the rest of the sensors.

CCKen

It may be your ignition coil. First inspect it for cracks, which would be cause for rejection. Testing it can be accomplished but it would be tricky try to find a fault when its not hot.

offroadXJ1999

I HAD THIS EXACT PROBLEM TO THE T! Cleaned the idle control valve with throttle body cleaner and it works perfect now! Hope this helps

BillyBoy

My wiring harness that goes across the top of the engine well got on out. The wires inside stared to break and wear out. Start it. Grab the harness and wiggle it. Wear gloves. The other thing is wiggling the wires and connections all over. I also had a no start issue because of a poorly connected coil. Good luck man. Wiggling don't cast anything, in time or money.

adriaanvn99

Thanks! I have a new coil that's ready to go in, I'll give that a try

adriaanvn99

Sure that's also a possibility. I cleaned it about 3 months ago but I'm sure it wouldn't hurt giving it a good clean again!

adriaanvn99

I'll give that a try now! Thanks

adriaanvn99

So I quickly ran a diagnostics tool and it gave code P0320, which upon further investigation is related to the ignition circuit, and in most cases with the 4.0 it's a failing crankshaft position sensor. So I'm pretty certain that's the culprit

Will let you guys know what's happening!

investinwaffles

https://www.cherokeeforum.com/f51/testing-cps-5563/

BlueRidgeMark

Yay! We have testing!


Testing is good!

adriaanvn99

Update:

Since last post jeep was running normally (last 2 days). Tested the MAP sensor and was getting correct measurements as per test procedure.

However, this afternoon I went to go give the Jeeps engine a high pressure hose clean. Being very careful of all sensors, it cleaned very nicely. After the wash it started up perfectly. On the way home from the wash the jeep cut out (tach drops to zero). Pulled over, put in park and made it home pretty fine. Back to testing... Test the resistance on the CPS between terminal B and C, and apparently reading should be infinite. Mine was reading 198, which is low and wrong (I speak under correction).

So, out comes the CPS, give it a visual inspection, give it a nice clean (hoping it might make a slight difference some how) and I put it back in. Start up the Jeep, immediately revs jump up to 1800 while in park, jumps back down to 800 once in drive. Put in drive, can't even take off as it is sputtering too much.

So off to the parts store it seems tomorrow morning. Oreillys stocks a BWD CPS, which I have not had bad luck with. However lots of folks recommend going Mopar replacement.

Just an interesting observation from today - why would it happen all of sudden after the engine clean (the connector was dry as well as the actual unit) or was it just bad luck...

Thanks again!