engine problems

I recently replaced my oil pan gasket. Since replacing it, I have had some trouble with my engine. Here we go:

While driving and accelerating, the engine will backfire through the air box, and cause the Jeep to jerk and studder. The faster I try to go, the more it pops and sputters through the air box. If I am going up a hill, I have to punch it to the floor before it will start to accelerate.

I have replaced the following AFTER the Jeep started to do this.

CPS
ERG valve
cap and rotor
spark plugs
Cat
swapped the TPS and IAC from one of the other XJs that run fine.
put in a fuel injector cleaner
Had the "ever wear" treatment done Ever Wear

Other things that are about a year old or newer are the fuel filter, gas tank, exhaust system, battery, rad, water pump, t-stat, head gasket, valve cover gasket.

The XJ did not do this before I replaced the oil pan, but I did not touch anything other than what is required to do the pan.

I have no idea where else to look. So any help is appreciated.

Thanks, Adam

If nothing else was disturbed, such as vacuum lines, plug wires, etc, then perhaps its nothing to do with the work you did. Could it perhaps be water in the gas, or otherwise contaminated gas? If not, I would check fuel pressure.

I have went through a couple of tanks of gas already, and no change.

If your getting backfire through the air box its apperent your getting spark in your cylinder before the intake valve is fully closed. I would start by making sure the distributor is timed correctly. This may help your problem.

Good luck wrenchin.

when I had a sticky EGR valve it would make the whole XJ jump. You may have your EGR engaging at the wrong time. I now it electro/vacuum item but think you may have a vacuum issue. Have your replace the CCV tubes connected to the valve cover. In my book it says to replace those every 50K miles.

Also you talk of a lack of power. You could have a bad knock sensor which is fully retarding the timing. You may want to repalce that just because of age and may of damaged it or the wiring when wresting the pan in and out.

It also may be worth paying a mechanic 1.0 hour of time to figure out the problem. I found a mechanic at the dealer who understands the Renix control system. He has saved me from replacing parts on a guess.

Also while you have it in to the mechanic he should hook up the test set and verify your TPS is set correctly. You also may want to check the Cat converter, it may be partially bocked and that would explain why you are flooring it get up hill.

Have you done any of these?

Check to see if you knocked the wire off the oxygen sensor (on the exhaust header pipe) loose when you did the oil pan. If it's a Renix ('87 thru '90) also cjheck to see if you disconnected or damaged the knock sensor (lower side of block, driver's side.)

RookieJeeper said:

I have replaced the following AFTER the Jeep started to do this.

CPS
ERG valve
cap and rotor
spark plugs
Cat
swapped the TPS and IAC from one of the other XJs that run fine.

Click to expand...

I just replaced the cat the other day.

Check to see if you knocked the wire off the oxygen sensor (on the exhaust header pipe) loose when you did the oil pan. If it's a Renix ('87 thru '90) also cjheck to see if you disconnected or damaged the knock sensor (lower side of block, driver's side.)

Click to expand...

O2 sensor is fine. I will check for the knock sensor today.

I am thinking about taking it to the dealer to have them scan it for any problems.


I also forgot to mention that, it only does this while I am driving. It will not do this in park or neutral.

Thanks for the great responses people.

Later, Adam