I see this topic is fairly common on these forums and while my Jeep exhibits symptoms similar to many of the current posts none of them match my problem exactly.
I bought the Jeep with a blown radiator, replaced that to find a very rough idle which goes away at 2000 rpm cold and 1500 rpm warm in neutral and it goes away almost instantly when driving. The check engine light came on as well so I put the code scanner on it and got multiple cylinder misfire, cylinder #1 misfire and cylinder #2 misfire. So far I have replaced the dist. cap and rotor, plugs and wires, the IAC, and the #1 and #2 injectors. I have also run seafoam and fuel system cleaner through it, and checked for vacuum leaks. The Jeep also had a weak alternator and bad battery which I have also replaced. When the Jeep is at idle I can pull the connectors off of both the #1 and 2 injectors and idle does not change at all, but at higher rpm's pulling even one off of course makes it run like crap. When using a long screwdriver to listen to the injectors I can hear the #2-6 injectors firing happily away, but the #1 sounds much quieter even though it is new. Nothing I have done so far has helped even a little bit. The oil is clean and no sign of the milky goo under the valve cover so i don't suspect the head gasket, although that is what many people have been suggesting.
I haven't been driving the vehicle other than a few test drives and other than idle it runs and drives great, no overheating, no smoke, no antifreeze smell from the exhaust.
Im at my wits end with this thing, any suggestions on where to go from here???

 

Hey! I have a similar issue with my 97 sport. Ive done similar process of going through the same random annoying 1500rpm splutter and occasional dodgy idle thing - have replaced o2 sensors, ignition leads, coil, dizzy cap, rotor, plugs, injectors and Im now looking at ripping out the fuel pump and giving that a seeing to.
Mines a face lift 97 4.0 Sport. I heard they had issues with their pumps dissolving themselves and bunging up the filter and jets on some blog somewhere late at night ...
Theres been no loss of fluid in 1 years motoring and im hoping it not internal bleeding or knackered insides..Any ideas? Did you get yours sorted?

 

Maybe it's time for a compression test. When the PO "blew the rad." could be it got a little hot. #1 & #2 might be weak and smoothing out at higher RPM's.

Always good to check wiring connections and grounds. I guess that braided strap from the rear of the engine to the firewall is a known culprit. There's also grounds at the dipstick mount bolt I think. If the PCM & sensors don't have good grounds no telling what can happen is what I'm gathering.

 

I am in agreement with the man from bedrock, sounds to me like you have a wiring problem on #1 and #2 injector ( could be an intermittent open at the connector itself, take a close visual at those connectors and also ohm the connectors out for solid continuity.)

good luck sir

cheers!

cpnwrench

 

I know its been a month now, but I would also like to see if you solved the issue with your jeep. I've been researching like crazy on all of these XJ forums. I have a very similar problem with my 98 XJ. It seems like tons and tons of people have the exact same problem and either no one can figure it out or people just do not follow through on the forums by posting their fix.

My particular problem is not the dreaded heat soak issue(I believe) because it does it everytime I start it, hot or cold, first thing in the morn, or late at night.

Their has to be a common fix and I wish, along with probably hundreds if not thousands of others, that all of the forums would come together and post a common sticky on the fix.

Any help on the issue would be greatly appreciated,

Thanks, Chris.

 

I had random multiple cylinder misfire on a 97 4.0--- Replace the TPS.

 

I just went through this with my 96. Random misfire codes, ran rough, sputtered etc. New crank position sensor fixed it.

There's one on eBay for $23 including shipping. I can't speak for the quality of the sensor but it's working and running like it should now. There is also a bulletin about a known bad connection on the CPS. Might just check it's connection.

 

OK...So I dont do what I accused so many others of doing...I worked on the Jeep over the Holidays...Codes were random misfire, cylinder 5 misfire, cylinder 4 misfire, cylinder 4 injector open.

I cleaned the throttle body, removed IAC and it was horrible gunked so I replaced it(made it run smoother, but didnt cure misses)...inspected cap/rotor/plugs/wires(all horrible corroded and worn, the terminal for the number 5 cylinder definetely the worst completely corroded and rusty.)....replaced the coil for the heck of it...all of this fixed everything but the cylinder 4 miss and open.

I even seafomed the intake and the gas tank...the thing runs like a top, better than ever!!! However I still have the intermittent misfire on cylinder 4 with the open injector circuit....I'll have to look at the harness very well soon, any info would be greatly appreciated. Thanks.

 

Well, it sounds like you got it covered as far as a good tuneup, but 'misfire/open injector circuit' remains. Post what you found out with the harness and injector. I know you can test the injector for ohms (12-15 ohms) iirc.. and you can put 12v on 'em to see if they're clickin'.. good luck

 

Ok..1997 4.0L cylinder one misfire code...jeep sahara

I've replaced plugs, plug wires, coil, swapped injector one with injector 2 (still showing cylinder one misfire), checked fuel pressure, cam shows no sign of wear, valve springs good, head gasket appears to be fine....checked all injectors and injector connectors....also cleaned combustion chamber with B-12 combustion chamber cleaner

engine has 250K miles....runs unbelievably well, no hissing, spitting, or missing....only shows misfire at idle...don't think it's a bent connector as there is no unusual noise, compression test revealed 110 psi on cylinder one versus 120 on cylinder two....therefore not significant, well withing 30 psi differential range albeit a tad low....I cant' get the damn thing inspected until I figure this thing out...

looks like Im joining the ranks of the confused? short of changing an engine and spending tons of money to do so....what say you? Help please

CW

 

Pull number one and number two plugs both out and run a compression test if it got to hot when the radiator blew it could be the head gasket between two cylinders

 

I had a very similar issue. It was intermittent. It ended up being the wiring harness rubbing against the firewall. It rubbed through and was shorting the wires. It was the one that runs behind the motor up high on the firewall just underneath the hood behind the valve cover.

 

I just noticed it only took me 4 or 5 years to post how I fixed my problem!

Haha!

 

Mine is doing the same intermittent thing. Before it wouldnt even run. Turns out my main power to my ecu was shorted. After it got fixed it started running like crap. Im going to look at the wires tonight. Did you just rewire the the wires that had been shorting?

 

Replaced wires that were bare wire and put rubber behind the looms so they didn't rub on any sharp metal edges.