0351XJ

Hey everyone

Ive been having some issues with my 2000 cherokee sport 4.0 with 85000 miles

I purchased it 2 months ago and believe it was sitting for an unknown but lengthy amount of time.

The symptoms: rough start, low/ rough idle at a stop and would stall. Idle at around 400rpms. NO CEL AT ANY POINT DURING THIS PERIOD BEFORE REPAIRS

The preformed repairs: New starter,New CPS (Mopar), removed TB and cleaned IAC TB replaced TPS (autozone part can't remember brand), oil/ filter change with valvoline max life 5w-30, new plugs (champion copper)

Jeep ran great with no issues for about two weeks with a strong start, idle at a strong 600-700rpms

Yesterday a CEL came on and yielded a code for fuel evap leak, replaced gas cap and CEL stayed on and would stall only after the first start in the morning. The jeep would start right back up with mo CEL and run as it should from that point on.

My question is where do I go from here? Backtrack my mentioned repairs or may this be a new problem?

Any suggestions/ opinions welcome, Thank You

0351XJ

The other day I found what I hope was causing the EVAP leak



So I did the best I could with what I had and repaired that broken connection





Used a scan tool to erase the code and turn off CEL. So far so good but I'm still having the stalling issue in the morning after the first start. Its driving me insane so any input on the stalling issue would be much appreciated.

Radi

Does it stall immediately after starting or does it run a few seconds?

0351XJ

It wont run properly until it warms up to 210, everything before that is sporadic stalling and low idle. It starts up just fine and will be at a strong 1000 rpm but drop to around 400 if i don't let it warm up all the way to 210. Yesterday i didn't even make it out of the drive way. Usually stalls at a full stop like at lights or when slowing down

CCKen

Sounds like the O2S heaters aren't working.

Blown fuse and/or defective O2S Heaters Relay.

Check the heaters relay(s) fuse in the Power Distribution Center (PDC), it's marked O2S RELAYS. See below.

0351XJ

Replaced the fuse after work, the old one didn't appear to be faulty but still chucked it, 30 minute drive home went fine with no stalling but I did notice a loss of power while accelerating and on the freeway topped out at about 45-50 with the pedal to the floor and felt a rattling that felt like it was underneath the drivers seat.... Time will tell on the stalling in the morning but thanks CCKen that info was helpful and makes sense as the cause, looks like I traded one problem for another though, maybe clogged cat?

Radi

Do you have access to a vacuum gauge? You can check for a restricted exhaust with that.
Give the cat a smack with your fist and see if it rattles.

CCKen

Do you have California Emission exhaust (two mini Cats) or Federal Emissions exhaust (one downstream Cat)?

Here's a couple of links that show using a vacuum gauge for diagnosing blocked exhaust:

http://www.autospeed.com/cms/article...nostics&A=2393

Click Scenario 14 in this link:

http://www.secondchancegarage.com/public/186.cfm

You can temporarily tap into the intake manifold at the HVAC/Cruise Control vacuum fitting for the vacuum gauge.

CCKen

This may not be relevant to the rattling at highway speeds, but check it anyway. Crawl under the Heep from the driver's side and look up to the back of crossmember area. Check to see if the front exhaust pipe hangar is broken or the trans mount isolator is trashed.

Rattling with the above problems usually occurs at idle where the front exhaust pipe rubs on the crossmember.

0351XJ

Sorry for the delayed reply on this, have had a lot going on, I crawled under to check out the mount it looks intact and isn't rattling while at idle from what I could see. There are two mini cats and what looks like a down stream one as well. I hit the down stream one with a rubber mallet and there was no audible rattle inside. I wasn't able to preform the vacuum test but did use a scan tool to view live data for the O2 sensors and the upstream ones were fluctuating as they should with the downstream behaving the same jumping all over the place (the downstream should be fairly constant right?). Usually when I first start the Jeep up in the morning it has very little throttle response and power, plus stalling at idle but the problems subside after its been driven for a while (about 15 minutes at 210 degrees)

CCKen

What "Champion Copper" spark plugs did you install? RC12ECC?

Folks are having luck using NGK ZFR5N plugs in their '00/'01 4.0's.

The downstream O2S' should be cycling like the upstreams. If they stand still there's a problem with the Cat(s) or the O2S', but if bad they will trigger a CEL.

Use that scan tool to check the Engine Coolant Temperature (ECT) sensor and the Intake Air Temperature (IAT) sensor before starting the engine (after it cold soaks over night). See if the temps are about the same as the outside air temp. There should only be a few degrees difference between the two sensor readings (Max is 6*F).

The ECT does have a lot of influence over the PCM fuel enrichment programs. If it does go bad it could cause issues like you are seeing.

Another sensor that has a great deal of influence over PCM fuel programs is the MAP sensor.

0351XJ

I checked with the scan tool as you said, the outside air temperature was 19 the coolant was 20 and the IAT was 19. With the rattling coming from the rear passenger side while I'm at idle could it be the cat right before the muffler?

seanward10407

This is just an outside chance here, but perhaps the fuel pump is fading, and it is starting to lose prime. This happened to my old Crown Victoria and it was behaving remarkably similar to your description.

0351XJ

Is there a way I can test that with the scan tool?