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Amedee, Jeep Technician
Category: Jeep
Satisfied Customers: 26598
Experience:  ASE certified Technician advanced level specialist. Wisconsin certified emissions state inspector
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1999 TJ - 4.0. Runs rough when it runs. Not alot of power.

Customer Question

1999 TJ - 4.0. Runs rough when it runs. Not alot of power. Will at times stop altogether - wait 10-15 minutes and most of the time starts and runs - but roughly again. Sounds ok at idle and no load in the garage but out on the street it bucks and sputters - not too strongly but enough that it doesn't accelerate enough to make it viable on the street.

Have replaced fuel pump, ignition coil, crank position sensor, alternator, dist cap, plugs, plug wires. Mechanic did most of this - I did ign coil and alternator. I believe he replaced fuel filter - least I asked that they would. I charged battery and cleaned all grounds.

Haven't OBD'd yet but will today. Need to go to O'Rileys to rent one.

Check engine light is sporadic - its on now. It just started after going through a 10-15 phase of not starting.

Vacuum lines and flow seems good. Not sure about O2 sensors - can't tell if they are new or not.

Having alot of electrical work done, I'm not sure what to work on next. Air... Fuel... Spark...

Any suggestions?
Submitted: 6 years ago.
Category: Jeep
Expert:  Amedee replied 6 years ago.

Do you know the code number in the computer?
Customer: replied 6 years ago.

No. I haven't had a chance to get it to a store where I can use an ODBII thing. Is there another way? I heard something about turning the ignition on 3 times but that didn't seem to work.


Expert:  Amedee replied 6 years ago.
That is correct!

Turn the key on and off three times and then back on all within 5 seconds and it should display the code or codes.

Most of the Chrysler vehicles do this, but not all of them. You can sure give it a shot!
Customer: replied 6 years ago.

That isn't working on this car. Just the mileage is displayed.


Expert:  Amedee replied 6 years ago.
Ok.. does the engine sputter like it is misfiring or is it the whole engine that is stalling out?
Customer: replied 6 years ago.

More like the whole engine has lost power - with a few spits and sputters randomly. When I press on the pedal, it starts to gain rpm ... but then bogs, spits, coughs, sputters. I let up and it seems to try to run smoother at that rpm... if it doesn't need power (for instance, going up a hill). Sometimes if I keep trying to accelarate, the sputtering gets worse and the whole engine shakes a bit.


I will be going to O'Rielly's today - when my wife gets back from work, to get the ODBII thing. I've never used one so don't know how dependent we are on that?

Expert:  Amedee replied 6 years ago.
Your local auto parts store might just scan your computer for free.

It sounds to me like you might just need a full tune up. If not, your camshaft and crankshaft position sensors could be bad. These both are very common!
Customer: replied 6 years ago.

Yeah... I'm going to try to get to O'Rielly's this afternoon to see about the ODBII reading.


I put in one of my notes that I've replaced the Crank postion sensor - camshaft one? Didn't know there are both.


Its had a full tune up as all plugs, wires, dist cap have been replaced. About the only thing that hasn't been replaced electronically wise is the distributor shaft. Ignition coil and alternator have been replaced as well.


Fuel pump and I believe filter have been replaced.


I've paid for a 'tune up' twice in the last year. Even asked if they did the ODBII reading and they said 'yeah', and nothing more. I asked it it said anything and one said 'Nope' and the other talked about doing the tune-up. So I did it ... again. Ran great for 20 miles - over a three week period.


I do notice the air conditioning unit is squealing - sounds like a bad bearing - but thats the only indication of anything out of whack.


Can I contact you once I have the ODBII readings? If so, how?




Expert:  Amedee replied 6 years ago.
You bet you can!

Just reply back to this page and I will get it!

I will be looking for your reply!
Customer: replied 6 years ago.
Thanks. I will get back as soon as I get a ODBII reading.
Expert:  Amedee replied 6 years ago.
Sounds good!
Customer: replied 6 years ago.

Hi... back again.


I didn't get any codes on the ODBII. It did say that only 3 of 6 drive cycles were completed.


So, I reset the engine light to off and drove the jeep to take back the ODBII. Ran pretty crappy all the way there - engine light didn't come back on. Bought some Seafoam. Drove back home - ran pretty crappy all the way back. Turned it off, poured in the bottle of Seafoam and let it run.


I did notice that it surges a hundred plus or so rpm - sometimes in 10-15 second cycles - sometimes up to 30 second cycles. Almost like when the air conditioner kicks in - although its winter and its not on. Plus, the compressor is free wheeling.


I'm at a loss as to what to do. Have put lots of parts in to no avail. The vehicle is worth every penny so I'm not wasting that - but I do need it to be dependable. You've heard the story...


Any direction I should be heading next?

Expert:  Amedee replied 6 years ago.
Sorry for the delay!

Is this surging only happening at idle?

How does the engine perform under wide open throttle?
Customer: replied 6 years ago.

Thanks for getting back to me Amedee.


I can only sense the surging at idle.


WOT - it bogs... spits a bit, chokes, gasps and is guttless for power. Feels so bad you think its bad for the engine - and I'm sure it is.



Expert:  Amedee replied 6 years ago.
What is the fuel pressure at?
Customer: replied 6 years ago.

I'm sorry I don't know. But had the fuel pump replaced 3 months ago and the guy said it was dead on. Ran ok for a week of light driving... then same symptoms - went to another guy who re-did the tune up. Shortly after, with light driving again, its the same problem.


Expert:  Amedee replied 6 years ago.
Ok.. we will need to check fuel pressure to be sure it is within specs.

Also, you could have a bad tps, bad oxygen sensor or even a broken or cracked flex plate.

IF you can get your hands on a scanner that can read live data, you can check the cam crank sync signal. Also, check the hold-down clamp on the oil pump drive housing to see if there are marks indicating that the oil pump drive housing has rotated.

Potential Causes:
Camshaft Position (CMP) Sensor
Crankshaft Position (CKP) Sensor
Broken Flex Plate
Seized Oil Pump Drive Gear
Powertrain Control Module (PCM)
Timing Chain
Amedee and 7 other Jeep Specialists are ready to help you
Customer: replied 6 years ago.



I did replace the CKP - but can't find reference to CMP. I'll keep checking in the Hayes manual.


And I'll try to find a place that will give a live reading. Hope its mobile.


Thanks for the help. Some value in what you didn't say too.



Expert:  Amedee replied 6 years ago.

Thanks for the accept!

Please let me know if you have any further questions!