'96 4.0 ZJ stalling problems.

[blackjeep]

I know this is probably beating a dead horse but, I am having problems with my '96 4.0 ZJ starting, stalling and backfiring. I have done a search on this forum and other Jeep entusiast forums...they have lead the way for my DIY actions the past 2 weeks.

What I have done:
I have replaced the fuel filter, TPS, IAC, igniton coil, distributor cap and rotor, plugs and plug wires, crankshaft pos sensor. I have done the OBD tests from AutoZone's computer 5 times in two weeks. I also have done the ignition codes..I get 12 & 55 which mean there is nothing the CPM can find thats wrong. I ahve used injection clenaers, Sea Foam checked all fluids...still nothing out of the ordinary.

The first OBD test revealed the ignition coil was bad...other than that, nadda, nothing on the OBD and ignition codes.

I called the Sltealership last monday to see if they could run their diagnostic check scanalyzer...this would be an additional $75. The problem is, my brother and Mom's Jeeps have been in numerous times for different probleems with mixed results (read waste of labor money) to our local crappership. I would rather fight through this and DIY than to break down and take it to the Stealership.

Anyway...the problem is not going away no matter what parts I throw at it. It has'nt backifired this week, but still it will stall out going down the road then take a few times to re-crank. This happens whether it is hot or cold. I am in Florida, it is 72 degrees so I am able to get out and work on it freely without extreme temps influencing the problem.

I am at a loss as to what to do...if I take to the stealership, they will keep it for a week "they said they were backlogged with work", and I am not sure they can fix the problem.

I have gone to various online repair Q/A's for the JEEP STALLING..I have tried the gas cap thing, key change, all sorts of small cleaning/inspect of parts, vacuum hoses, TB, unplug, re-plug wires, put dialetric grease on prongs and connectors. Checked for cracked hoses and wiring harness integrities...if anything, I have gotten know my ZJ better than I ever thought I could. I am certified Yamaha jetski mechanic so tools and torques are not unfamiliar to me.

I just need someone to take another stab at pointing my craftsman's in the right direction.

If i have left out anything please...by all means fire AWAY!!!

It has 150,000 miles on the od and has been great until now....I have a new ECU that will be here on tuesday..I have feeling that this not the problem either.

Any..I mean ANY suggestion will be appreciated.

Oh, BTW...this is a great site!

Mike

 

[Sound_Man]

Try swapping the fuel pump relay and the A/C relay. I had a bum relay that would go out for no reason from time to time and then work great for a couple hours. It was really frustrating to track that down.

 

[Bounty__Hunter]

It's possible you could have bought a flawed coil, it still sounds like the coil is the problem.

 

[blackjeep]

Soundman..where are they and how do I switch them? You mean physically switch the 2 relays?

Thanks..a little detail for the new village idiot.(me)

Bounty...could be, I have a Nick Kolack igniton coming this week..with the MSD coil and Magnecor wires sooo that would eliminate another possiblity.

Mike

 

[Sound_Man]

Soundman..where are they and how do I switch them? You mean physically switch the 2 relays?

There should be 4 relay's under the hood on the passenger side. If I am not mistaken the one closest to the firewall is the fuel pump relay and the second one back from the front is the A/C. Yes physically swap the 2 relay's. If it the problem stops you know it is the relay and it is a cheap part to replace.

 

[XJNick]

my '96 4.0 ZJ

I don't think the Grand Cherokees have the relays in the same location as the Cherokees do? However, Sound Man's idea is valid, you may have a bad relay.

I have a new ECU that will be here on tuesday

Your Jeep's computer is actually referred to as a Powertrain Control Module (PCM) (OBD-II). Pre '95 Jeeps have a computer called an Electronic Control Unit (ECU) (OBD-I). I know this doesn't really matter, just some good trivia facts. :mrgreen:

However, it is highly unlikely the PCM is the problem, it usually ends up being something smaller that throws the PCM off and causes problems....

Have you checked for bad gas? :wink: :mrgreen:

-Nick :!:

 

[blackjeep]

Well Nick...I have been through 2 tanksince this has been happening. The first tank was about half full...ran ir down with the injector cleaner "Sea Foam"...then put in 93 octane to about the 3/4 tank mark..ran it down. Now I have a full tank of 93 and it has not affected the problem in anyway. Trust me..I have watched this part of the equation closely. After I had changed the fuel filter, I knew fuel could be a possiblity. I am going to a friend's shop today and check fuel pressure.

I would like to get this resolved BEFORE the upgrade mods get here.

The reason I said ECU instead of PCM, I knew everyone would know what I was referring to..hopefully.

I have been at my wits end for the 10 days now...I really do not want to send it to the schittership.