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Hey guys, about a month ago I bought a 1989 4.0 inline 6 that's 2WD. It sounded and seemed to run well when I test drove it, so I bought it and trailered it home. Once I started driving it around, I noticed the idle sounds worse, like it's stuttering. RPM barely changes, though. It also started to occasionally stall when coming to a stop or accelerating from stopped. I got stuck in road work and every time traffic came to a stop, it'd shut off and I'd have to start it back up. I've done Cruiser's tips 1-5 and so far nothing has made a difference. I did a smoke test in several spots and the only leak I've found so far was at the crankcase breather gasket at the back of the valve cover - I have a new one ordered. I've read that the exhaust manifold commonly breaks at the bottom weld, so I was looking to see if any smoke came out there, but I never saw any. Is there a better way to test this? Also I hear a quiet knocking that doesn't change with RPM, I'm going to get a stethoscope to try and figure out where that's coming from. So far I've replaced: Spark Plugs + Wires Distributor Cap + Rotor ICM + Coil MAP Sensor + its vacuum line Both Vacuum Harnesses O2 Sensor IAC valve Big 7 Wire upgrade I'm pretty new to wrenching and I'd greatly appreciate any help or insight. I love this little truck and hoping to get it to a place I can confidently daily drive it.

Hello, I have a 1988 jeep comanche eliminator. It has a 4.0 i6 with Aw4 trans with 82,000 original miles. I just put an all new champion 3 core radiator and put new battery cables on. I finally fix the overheating problem and drove the truck for a day and it drove better than ever. At the end of the day I went to the store and as I drove down the street the truck drove great, and as soon as I came up to a stop sign the truck dies in drive. I put it in park and it started right back up so I decided to head back home because the trucks never has done that before. on my way home it died about 2 more times only when coming to stops. I got home and decided to park it and try it again in the morning when the truck is cold. This morning the truck started just like it does everyday so I drove it down the street and when I got to the stop sign it dies. This is when the truck is cold. right before it dies it sputters. The tachometer stoped working two days before this problem so I don't know what the idle is right before it dies. Any help would be awesome, Thanks.

here we go again 86 jeep comanche 93 jeep cherokee 2.5l engine low idle runs good when cold as the idle drops to normal begins to misfire and it gets worse the warmer it gets to the point it dies and starts itself again.... driving down the road at a low rpm runs fine put any type of pressure on the pedal to accelerate it begins to buck and misfire terrible....... drove to work today stopped to turn and the truck died went to start it, and had to hold my foot to the floor to get it to start.... seems like it lacks fuel but pump sending unit resistor and pressure regulator are brand new. i pulled the plugs to see what was going on and all of the plugs had a nice brown tint to them except the furthest back plug which was still sorta white.... list of parts i changed today with no changes.... TPS Distributor temperature sensor Crank sensor fuel pump fuel injector o-rings parts changed recently..... fuel pump ballast resistor fuel pressure regulator spark plugs spark plug wires cap rotor I checked to see if it was the o2 sensor by unplugging and starting the engine and it did not run any better. i am running out of parts to replace and I'm begining to get annoyed at this point.. I'm about to replace every injector and the coil. i checked the ohms rating of each injector and they were all the same across the board..... i checked the primary and secondary of the coil and it was within the ohms ratings.....

Hey everyone. Recently purchased a 1990 Comanche 4.0L. Truck runs great but recently has been stalling after I drive. It starts no problem and idles fine at first, but after it runs it stalls occasionally when I let off the gas or it will idle very rough, from close to 0 - 2,000 RPM's. No issues overheating. Just cleaned all the lines from the valve cover and vacuum lines from IAC and replaced the valve cover gasket. Emissions Maintenance light has been on since I bought the truck from my neighbor, close to two months ago and I don't know of anyone with the OBD1 diagnostic. At the time he said it had a bad O2 sensor, but wasn't giving me any problems. It has a very slight exhaust leak in the cat converter. It also seems to happen a lot less often if I keep the RPM's under 2,000, which is making me wonder if it can be the throttle positioning sensor. Any helpful information is greatly appreciated.

I have and 88, 4.0, standard. I put a new engine in 2 years ago (pulled it all by my tiny self, hence the self portrait in the left corner). This Comanche is truly a labor of love. It was running great afterthe new engine, but the honeymoon is over. I'm having trouble diagnosing the latest challenge. It started to kind of hiccup and/or stall while driving one night. Then completely stalled on the highway and would not restart. It had plenty of power to turn over but wouldn't completely start, though it valiantly tried. I guessed fuel issues so I had my son bring me a fuel filter... it was worth a try. I put it on and it started. Wow, did I actually fix it on the side of the road??? Well, no. It drove home then started to do it again the next day. I was almost on E, so I got gas and suddenly it drove great! It stayed running for a couple of weeks, so I figured I had gotten bad gas. Well, no, again!! it started doing it all over, and I had just gotten gas at Shell, the gas couldn't have been that bad, right? I did some goggling and tried replacing the MAP. Nope, didn't fix a thing. It barely wants to idle and the idle is all over the place like it's trying to figure out how much gas it needs to stay running, and will eventually die. Plus, it is very rough sounding, almost like a timing issue, but I don’t think that’s it. I bought a fuel pressure gauge and goggling tells me it should read 39-41 psi, providing I have MPI (I think I do?) I will describe what the fuel pressure gauge did because if I had to guess, I would have called in a priest for an exorcism. One friend actually suggested I park my truck in a church parking lot over night to see if that would help. Anyway, the gauge violently bounced from 35-40psi while it tried to idle, even after it had warmed up. I had my son try to hold the rpms at about 1500 and the gauge would drop to 30psi and be slightly more stable but not by much. Even when the throttle was held at 1500 rpms, there was still a lot of fluctuation like it was confused and unstable. Also, I have checked all the vacuum hoses and they are all in place as far as I can tell. My gut tells me it's some kind of sensor or vacuum issue. From what I have read here in some of the forums, I think I need to do a vacuum test next and I'm guessing again (I do a lot of that) that I need to buy another gauge. There is a lot of talk in these forums about valves and sensors like: Exhaust Gas Recirculation (EGR) valves, Idle Air Control (IAC), Throttle Position Sensor (TPS) and the Electronic Control Module (ECM). I hope it's not the computer $$$! I don't know where to start with these, is there an order to go in and can you test or clean them, maybe even bypass one or two? The last car I did a lot of work on was a 72 Cutlass with a 350 rocket, it was so simple, sigh... I could sit in the engine compartment with plenty of room for beer and tools. There wasn’t much in the way of electronics or vacuums. So if anyone can point me in the right direction with out kicking me in the a$$, I would be grateful. Many thanks in advance!