rough running 2.5 JXI
#1
09-06-2009, 01:29 PM
rough running 2.5 JXI
Problem: The car runs rough, but not all the time. So this is what I tried to date: 3 new sets of spark plugs (currently installed are OEM Champion plugs), 2 new sets of wires (currently installed Bosch wire set), 2 crankshaft position sensors (currently installed factory OEM), 2 distributors (currently installed Cardone Select), new battery, both new O2 sensors (OEM), new EGR Valve, replaced PCM and had it the replacement reflashed with the latest software updates. cleaned intake, checked all vacuum hoses. The less recent stuff ,,less then 2 years,,,timing belt, fuel pump. So that about takes care of everything. No codes are thrown from either of my code scanners. During the course of these parts replacements the car would sometimes run fine. For example it ran perfect one time for about 11 miles (20-25 minutes) under all conditions {idle in neural or drive, acceleration, cruise} but when I turned on the A/C it instantly ran very rough and then when the A/C was turned off it did Not return to smooth running. The two last things I did were to change the wires (twice). It was running fairly good before that with a misfire sometimes on number 3 cylinder. I changed the no 3 fuel injector (since the plugs were brand new). So I then decided to change the wires and used Federal Mogul premium wires which resulted in multiple misfires and threw codes (the wires were definitely on right and installed tight in the cap, etc). So I changed to Bosch wires and then have a steady backfire now out the exhaust. The very last thing was a replacement PCM that was tested and reflashed with the latest software updates. This car is the car from hell. Never saw anything like this ever.
#2
09-06-2009, 02:55 PM
Might want to check the operation of the ECT (engine coolant temperature) sensor and the MAP (manifold absolute pressure) sensor, the IAT (intake air temperature) sensor, (TPS) throttle position sensor and idle air control motor.
Not saying that they are necessarily bad or they should be replaced, but at least check them for proper functioning. Sometimes a sensor will give erroneous but still reasonable readings that the computer does not recognize as outside the expected range. The computer will therefore act on them, assuming they are good, when they are not.
Also, check for bad grounds anywhere in the circuits.
Good luck, and keep us posted with any success.
Not saying that they are necessarily bad or they should be replaced, but at least check them for proper functioning. Sometimes a sensor will give erroneous but still reasonable readings that the computer does not recognize as outside the expected range. The computer will therefore act on them, assuming they are good, when they are not.
Also, check for bad grounds anywhere in the circuits.
Good luck, and keep us posted with any success.
#3
09-14-2009, 12:36 PM
Problem found
Valve timing was the problem. It jumped one (1) tooth. This engine runs very good but has 233,000 miles on it. The last time I changed the belt was 60,000 miles ago,,did the water pump, belt and the tensioner and idler pulley but did not change the tensioner (since the parts place did not have it there in the store). This engine hits redline a few times a day, at least, so with an original tensioner (with 233,000 miles on it) I could maybe assume that might have helped it to jump one tooth.
I was originally wondering about the valve timing , but sometimes the thing ran smooth, like it was brand new. Every mechanic I talked too ruled out the valve timing for this reason (and me too). Obviously the adaptable engine management system sometimes was able to overcome the valve timing issue at some times. Pretty wierd,,I didn't expect that. So now a new belt, tensioner and pulleys are on order and will be replaced shortly. Since I changed most everything twice before this, I have plenty of tune parts for the future, ha. So we'll see if it gets over 300,000 miles...(233,000 miles right now). {I had also changed the IAT and removed and cleaned the MAP sensor, so got about everything,,,this was the last thing}
I was originally wondering about the valve timing , but sometimes the thing ran smooth, like it was brand new. Every mechanic I talked too ruled out the valve timing for this reason (and me too). Obviously the adaptable engine management system sometimes was able to overcome the valve timing issue at some times. Pretty wierd,,I didn't expect that. So now a new belt, tensioner and pulleys are on order and will be replaced shortly. Since I changed most everything twice before this, I have plenty of tune parts for the future, ha. So we'll see if it gets over 300,000 miles...(233,000 miles right now). {I had also changed the IAT and removed and cleaned the MAP sensor, so got about everything,,,this was the last thing}
Last edited by aifam55; 09-14-2009 at 12:40 PM.
#4
09-15-2009, 07:05 PM
at 233k+ miles you may want to consider replacing the crank gear... which is where the timing slip would likely have come from since the belt had been replaced before...
without it it is possible that it will slip at redline again even with a new tensioner in place.
without it it is possible that it will slip at redline again even with a new tensioner in place.
#5
11-22-2009, 01:30 AM
Just finished the timing belt, ( I was busy & has little spare time, but it's done now). I still have the same problem, steady backfire out the exhaust and rough running. I have MAP sensor and IAT sensor on order. About the only thing left? BTW, I can easily check the valve timing now, at anytime without pulling much apart, as I cut an oval shaped hole in the upper rear valve timing cover to check that mark also,,everything is lined up perfect).
#7
11-22-2009, 06:58 PM
Might want to run a compression check. It's a cheap way to rule out valve damage due to mistiming.
#9
12-20-2010, 01:28 AM
Update on this. I hardly touched this car for a while. Did the motor mounts, low ball joints, ignition switch and put in a new ECT (engine coolant temperature) sensor and the MAP (manifold absolute pressure) sensor, the IAT (intake air temperature) sensor. I check the compression on all cylinders are good compression (all almost exactly 205psi). This thing was almost running good and then I changed the wires to a high performance type (PowerMax) and had a steady light backfire out the exhaust every few seconds at idle. It runs a little rough but the backfiire is not right. So I got a set of Bosch wires but that made no difference. Then I discovered the valve timing had jumped one tooth so that is when I put in the new belt, pulleys and tensioner. The connections on the wires look solid and clean and the vacuum hoses are fine. The little vacuum hoses to the upper intake are good and on tight. And rechecked the firing order, 3 more times just to make sure. Also plugged the egr opening on the intake to see if it made a difference to eliminate the possible of the Egr, which is new anyway.
Any one have any ideas? This thing is like a Rubik's cube puzzle. My next thing is to try another brand of ignition wires. I think the ones I was using before were Duralast brand from Autozone. I heard that the Chrysler electronic management system is pretty sensitive to some aftermarket parts and this sometimes drives people nuts trying to figure something out. Not sure if this true. But it does seem to have some truth to it, as I read a few cases where people had a very hard time troubleshooting. I never have liked the black mystery boxes with the computers.
Any one have any ideas? This thing is like a Rubik's cube puzzle. My next thing is to try another brand of ignition wires. I think the ones I was using before were Duralast brand from Autozone. I heard that the Chrysler electronic management system is pretty sensitive to some aftermarket parts and this sometimes drives people nuts trying to figure something out. Not sure if this true. But it does seem to have some truth to it, as I read a few cases where people had a very hard time troubleshooting. I never have liked the black mystery boxes with the computers.
Last edited by aifam55; 12-22-2010 at 10:16 PM. Reason: giving more complete information
#10
12-20-2010, 10:10 PM
You might have a clogged cat. converter. My old truck used to have a partially plugged cat that would clear itself and run better, then it would start to plug up and barely run. It ran great after I replaced it.