missfire

[nikos]

Hi everyone! I was wondering if perhaps I could get some advice on my dilemma. I have a 99 4.0 jeep wrangler which has been intermitantely giving me problems. It feels as if the jeep misses a beat and the other week going out to pismo the mil light started flashing but did not throw a code. This hesitation comes and goes and on long loaded trips the mil flashes but goes away. What could it be? Ive done a complete tune up but I need to move beyond that point! what would cause this to happen sometimes but not always. I took it to Dick Wagoner and after spending money I came out with nothing. Thanks!

[RAT]

Hi everyone! I was wondering if perhaps I could get some advice on my dilemma. I have a 99 4.0 jeep wrangler which has been intermitantely giving me problems. It feels as if the jeep misses a beat and the other week going out to pismo the mil light started flashing but did not throw a code. This hesitation comes and goes and on long loaded trips the mil flashes but goes away. What could it be? Ive done a complete tune up but I need to move beyond that point! what would cause this to happen sometimes but not always. I took it to Dick Wagoner and after spending money I came out with nothing. Thanks!

Does it stumble on acceleration a lot? Check the TPS (throttle Position Sensor).

[kcruisin]

Does it stumble on acceleration a lot? Check the TPS (throttle Position Sensor).

'And the CPS/crank position..

[Old Fart]

Don't know how much similarity your motor has with mine (94 4.0), but I had the same symptoms - turned out to be the coil

[nikos]

The coil is a new msd one, hope thats not the problem. I just picked it up from Dick Wagoner and they claim its unburned fuel dumped into the exahaust system causing the secondary o2 sensor behing the cat to send weird signals to the pcm. Why would I get this random misfire most noticable on long trips with load and perhaps grate. The blinking check engine lights got me worried! Other than that, it runs great!

It does not stumble on acceleration! Cps, maybe but it does not always act up, its really strange. Off course it didnt do it at the mechanic, off course!

Thanks

[IPSteeler]

I dont know if there is any differance but my jeep was doing the same thing every time i pull my quad on the trailer it would act like it was hickuping every now and then. My Check engine light would come on for about 1 minute and then go off.
It ended up being my CPS.
I changer my coil first and then it was still doing it and then i was told it would be my pickup coil of CPS.

[Jeeperator]

I have a similer account My 97 tj threw a mil code for miss in #1 cylinder and wouldnt you know it! I needed to go get it smoged. Well with a compression check #1 was lower than the rest. I put it on a scanner and could watch the intermitent miss. But when I gave it some gas the miss went away. So what I did was turn the idle screw under the manifold up a little and it passed with awesome results of course the new cat helped also. I think it might be a bad or missfiring injector though.I eventually will swap it with another and see if the miss follows the injector to the next cylinder.Btw I noticed it didnt miss when I was in higher elevations it seemed to run real smooth.

[nikos]

Thanks for the replies. I have the jeep in the shop again! I had a new clutch and the teralow 4:1installed about 2 weeks ago! The jeep went in the shop without any such issues and when I picked it up, about a few days later it started to judder upon acceleration. I thought pinion angle, but no, I ruled that out after inspection. Its the clutct. The mechanic who did the job said I needed to learn how to drive a clutch and bla bla bla.

Well after 2 weeks of frustration and back and forth, they pulled everything apart and its the flywheel. The machine shop &^%$$# up my flywheel. I bought a new oem flywheel and those things are expensive. This sucks! Isnt it there responisiblity to fix my problem since it was thier machine shop you messed my flywheel up?

Excuse the long post, had to vent! I'll then change the cps and see if that changes anything.

[nikos]

I dont know if there is any differance but my jeep was doing the same thing every time i pull my quad on the trailer it would act like it was hickuping every now and then. My Check engine light would come on for about 1 minute and then go off.
It ended up being my CPS.
I changer my coil first and then it was still doing it and then i was told it would be my pickup coil of CPS.

What exactly would your mil light do? Would it flash. Hick up you mean there would be like a loss of power for a second and then back to normal? How did you find the problem? Thanks.

[nikos]

So, I've got the jeep back and now I've noticed it takes a few or more cranks to start the engine. Ive noticed that a few times now. Any suggestions? The check engine flashing and like a pop, jerk, hestitation ring any bells? Thanks.

[Jeeperator]

Make sure you dont have bosch platinum plugs in it. I have first hand experience they are the worst plugs you can get. They can cause ignition problems on most vehicles.

[nikos]

Make sure you dont have bosch platinum plugs in it. I have first hand experience they are the worst plugs you can get. They can cause ignition problems on most vehicles.

I've since then changed the plugs with champion, again replaced wires, and replaced the new msd with the accel coil and put new 02 sensors. I gapped all plugs .35 and torqued them to 25 lbs. I have not really tested the jeep out, but Dec 13 in Calico I sure will find out!