I have a 1989 yj with 4.2 engine and is an automatic transmission. I have done the nutter bypass, installed rebuilt MC 2100 from ebay guy, changed plugs, checked distributor-good, new fuel filter, took to mechanic and he found vacuum leak and fixed it, adjusted timing and carb. I checked wires at night and saw no arching. All that said, I still have problem with sputtering at low rpms. It does not happen when put gas to it. It kinda seems it is fuel starved. It also stalls out after it warms up only when going down hill. Guys, I and the mechanic are out of ideas. I have contacted ebay guy, he has not responded yet. ANY IDEAS? Has anyone else had this problem before? If so how fix? I am not engine guru, so I may need good explanations.I have done Sea Foam spray x 2. This helped a little, but it still dies when driving doen hill. Could be float problem in carb? Thanks in advance...Scott
I can relate to this problem. In fact identical except for the fact mine is a 5 speed and that it also doesnt completely stall out but tries to. It is a lot worse when cold. I also have installed an HEI distributor thinking that may help for some reason but no luck.... any help here guys?
Forgot to mention good luck with the ebay guy. I've gotten one response from him in over a month now and it did not answer my qestion at all. It took him almost 3 weeks to get back to me. I responded to him and rephrased the question thinking he didn't understand and now haven't heard back at all. All it was was an electric choke issue but oh well I haven't needed choke yet just pump the gas.
I also noticed this morning while driving the rpm gauge will drop from 1500 all the way to zero and come back up again, the jeep seems to sputter a bit when this happenes, it happenes randomely. Any ideas?
Have you checked for cracks in the manifold? Are you smelling exhaust in the cab?
If so then it could be a bad cat.. but that would cause issues when accellerating also.
I would take carb cleaner and spray around all hoses and the manifold to check for leaks and cracks..then post back
Not trying to thread jack here but done it before with no results. Also my jeep has no cat. Somebody beat me to it. Just a side note mine also did this with the stock carter carb and stock distributor.
I checked around carb & hoses with starter fluid, no increase in rpm. Cleaned with sea foam x2, no help (mechanic went nuts when I told him I did that. He DOES NOT like that stuff. Says it does too much damage if breaks loose big carbon chink.) I do not smell exhaust in cab. I have full doors & hardtop, I would definately smell exhaust. I am out of options. Other forums have said crank sensor, ignition control module, O2 sensor, engine temp sensor, & cat converter. Any ideas guys? Thanks for input so far!
Well... I'm pullin straws here but because I replaced my carb and my distributor the sensors you mentioned don't come into play. The computer is a sitting brick at this point and yet it runs the same... Just food for thought.
If you're over 88,500 miles you need an O2 sensor. Could be causing your problem or not but it would have to be replaced anyway.
Just to add that the Ignition Control Modules don't last either. It seems like all of the 89's are starting to go now. Replaced mine with a new Cat and O2 sensor and it never ran better. My Ignition Control Module was sporadic so the only way I knew it was bad was when I replaced it and there were no symptoms.
It is actually doing it at all rpms. I was driving very carefully first time. I hammered down this time to see if it made difference. It did not. I am taking to muffler shop today. Exhaust from manifold back needs to be replaced. Maybe that will correct. Exhaust system has major leak and is trashed. Maybe clogged up, so we will see. Thanks for all input. Please add more if you think about it or have gone through this before.
Yes I believe it is a manual pump. Did changing to electric help? What year did YJs start having an electric pump?
I changed the stock mechanical fuel pump on my 89 4.2 with a new stock mechanical fuel pump only because the original one had almost 100,000 on it and I didn't want to get stuck, with no problems. Just make sure you get the correct one (check your fuel pump and check to see if the inlet is facing to the front or rear) and you'll be fine.
Got it back from muffler shop. They replaced exhaust pipe and new muffler, fixed exhaust leak at manifold and put in new gasket, MUCH quieter. I replaced O2 sensor and changed oil. It runs great now. Still has a little putt-putt when idling right as I start it up. Much better though. Thanks for all the help. I hope this has fixed it.