1996 Jeep GC multiple misfires, hesitation and bucking

[hoofan]

The long and short of it was that I put a MOPAR CPS on it and had it done at the dealership and it has been perfect ever since. My regular mechanic must have put an aftermarket one on incorrectly or it was a bad part that was "iffy" and worked when it wanted to work...

Everything is great now, but I still have a bit of an idle problem to correct. But not one "Check Engine" light or hesitation since the MOPAR CPS was installed.

Thanks for the reminder though, I need to post a recap for everyone with details.

Bryan

[Jeepster2012]

I have a 96 jeep grand Cherokee Laredo with the 4.0 6 cyl I got it about two weeks ago. My first jeep ever. I love the looks, and the way it handles, but the first time I filled it up it all started. First time was a minor misfire when I pulled out of a parking lot, the next day it had a bad misfire so I pulled into Advance and they ran the codes because it caused the check engine light to come on. It came up as all multiple cylinder misfires. So they said I needed a tune up. Next day I put champion plugs, wires, cap, and button. Took it out that night and same thing multiple misfires, but did not cause the engine light to come on. So I stopped at Orileys, and they checked for codes it gave them code p1391 needless to say that code wasn't in their books so I did the next best thing lol I googled it. Turns out it was the code for the cam position sensor. So with that said when I put the new button on the distributor shaft I noticed it had a lot of excessive play I was told this was normal thanks (AdvanceAuto) so I found out that the Cps was in the distributor, so I figured I'd kill two birds with one stone. So I went and got a distributor from Autozone it was a reman but the only one in stock so I got it and installed it the next day. After installing it I started it and it idled and drove like a champ during a one mile test drive. Took it out that night, and guess what more misfires. Then it hit me it's only doing it when the engine gets good and warm. Does fine most the time, but after lots of driving especially in town that's when it happens. So I was told that my coil was getting hot, and failing thanks AutoZone so I put a new coil on it and still as soon as it gets good and warm boom! More misfires. I was reading in the Haynes book that one of the o2 sensors I think it was the pre converter oxygen sensor does not function or send signals to the PCM until it hits it's normal operating temp of 600 degrees. So maybe that is why it's only misfiring when it gets hot, could it be sending faulty signals or no signals at all once it hits it's operating temp mark?

[Jeepster2012]

It's driving me crazy I don't know what to do next. I have been told that the fuel injectors could be getting hot and failing. I have been told that it could be the timing chain, or a vacuum leak, or a number of different electrical components failing once they get hot. I think the o2 sensor like I stated in my last post makes sense, but hey I'm just a shade tree mechanic.

[Mike75925]

My 96 gc, would sputter after hitting a certain part of rough road... always while coming in from work... that being said, it was extremely rare for it not to sputter crossing this section of road. I would get a half mile or so, from the rough patch, and felt like I was running out of gas. I would shift to neutral and Rev the engine on the decline, until I got a clean Rev, then put in gear and go. That stopped working, and my speed got so low, that I decided to shift to 2 (auto trans), shift back and forth then back to neutral to check rev-ability. Eventually, it would start doing it in other places. It got to the point, that it spits and sputters the whole time you drive it. I have been through 4 PCM's (at least), 3 cam sensors, 3 crank sensors, 2 distributors, 2 sets of wires, 3 caps and rotors... oh and 2 ignition coils. When I got it, the dash lights always self-adjusted, but it has never affected the headlights/taillights. In trying to diagnose the issue, I ran a test on the cam sensor. There are three wires: ground, power and signal... I searched for my ground first, with a voltmeter. With the key off, ground was the middle wire. With the key on, all three wires are power!! Wth... so I pull the loom off of the wires, and I look for melted wires.. none. I checked the crank sensor wires, I checked the cam sensor wires. I checked the crank and cam back to the pcm. Nothing... I forget where on which plug for the pcm it is, but one pin likes to come loose. I checked for that. Another person stated how one or more of the pcm bolts were too long, causing a short. Checked those... an hour or more at a time of constantly feeling like you are running out of gas, is exhausting, but will keep you awake, when and if you need it. Going to have someone else look at it... she runs too good to scrap... my initial crank sensor case had broken somehow... only noticed when I swapped transmissions... thanks for any advice!! She's been down nearly two years...