Eddiekimberly

I need HELP! Have a 1988 XJ, 4.0, automatic, 4x4,134,000 miles. Generally, it runs great and will pull Hell off the hinges, then bring in the tools to put it back up. However, the last week or so, it has an intermittent miss. Runs like a 3 legged dog for the first few seconds after you crank it, the straightens up, more or less. Still intermittently misses. Have replaced the exhaust from the catalytic converter back. New fuel filter, new air filter (that was soaked in oil, so I replaced the ccv boot at the rear of the valve cover. It was heat damaged and stopped up), plugs and wires less than a yr old (cleaned and regapped the plugs last night). IAC about 4-5 months old (still gonna remove it and see if it need cleaning). Also has a very slight roaring (for lack of a better word) on the passenger side of the engine compartment, like a hose is off somewhere, but for the life of me, I can't find one. any other thoughts as to what it couls be? Thanks in advance.

Scott0821

Bump, and welcome to the forum!

Eddiekimberly

Thanx for the welcome.

541_halseth

I had a mis for awhile and for the life of me i couldnt find it, and it ended up being my crank position sensor. But its rare for those to gradually go bad they either will make it run or nothing. You said you replaced plugs and wire so i assume you changed the cap which could be a culprit, or you have a small vac leak that you are hearing. Best of luck im no ASE but hopefully someone chimes in to help you further.

Eddiekimberly

haven't done the cap or the rotor button. Maay need to put them on my list. Guess I need, also, to track down a vacuum diagram. That may also help me troubleshoot my cruise control.

Eddiekimberly

update... I went to tinker with it and decided ti unplug each injector to narrow down which cylinder was missing. I noticed that the injectors would rotate at the point where they plugged into the fuel rail. I also noticed that as they rotated fuel was bubbling out of 3 of them. Guess its time to hit the pick 'n pull to get the Mustang injectors, right?

caged

yup, or you can get some 703 injectors from a mid-late 90's sebring.

mine was doing the same thing, threw in some 703 injectors and she's all good now.

Eddiekimberly

gonna have to hit the pick 'n pull and see what I can find.

holeshot9g

I have an 87 xj with 228,000 on it. It was having the exact same problem you described here. I had already replaced plugs, cap, rotor, plug wires right after I bought it two months ago. I read through a lot of jeep forums and found a lot of other people talking about the same problem and things they tried but nobody ever said what actually fixed it or if they were able to fix it at all except for one guy that said it was his TPS. When I got my xj one of the first things I did was replace all the vacuum hoses and make sure everything was plugged in like it was supposed to be. I also found my air filter to be oil soaked. The plastic vacuum line on the back of the valve cover was not connected to the intake and the intake port where it was supposed to be plugged in had a vacuum cap on it. When I connected it my xj started blowing smoke like a B-52. It took me a little while to figure it out but I took the valve cover off and disassembled the breather valves / vents that are inside the valve cover, cleaned them out really good and put them back together with new gaskets. There was a lot of sludge buildup inside of these vents. I connected the vacuum line back where it belonged on the intake and problem solved. No more smoking and no more oil blowing out of the valve cover into the air box.

Now the intermittent miss... I first tried the map sensor. Nope. Still did it. Next I ordered a new TPS sensor. By the time it came in I had decided that I was gonna fix the exhaust leak where the manifold bolts to the head. (I had already checked for vacuum leaks at the manifold by spraying WD-40 on all the joints. The engine ran very smooth and idled very well already. No leaks detected). I pulled the intake and exhaust manifold off to replace the gasket. I left the intake linkages and fuel lines connected to keep it simple. I completely removed the exhaust manifold and found the two rear pipes cracked at the weld. Apparently I broke it by letting the intake sit on it. Found another exhaust manifold at a salvage yard and decided to replace the O2 sensor while I had it all apart and I was sure that it had never been replaced before. Got it all back together with the new intake / exhaust gasket (and finding that the exhaust leak was caused by the rear stud breaking off and having to go buy a 90 deg. drill to drill it out and remove it to replace the stud) and a new exhaust donut gasket and O2 sensor. Started up and ran fine. I didn't put the TPS sensor on because if it is not adjusted properly the engine will run like crap and I didn't want to have to figure out if it was the TPS sensor or a vacuum leak in case it ran bad after I got it all back together. It ran good and I've been driving it around for a couple of days now and low and behold that pesky annoying little miss at steady speed is GONE! So was it a vacuum leak on the underside of the intake where I couldn't spray the WD-40? Or was it the new O2 sensor??? Your guess is as good as mine but one of the two fixed it. I am inclined to think that it was the O2 sensor since the engine was running fine to begin with with no symptoms of any vacuum leaks. Hope this helps.