2002 Jeep Grand Cherokee - Rough Idle After Highway Run

Maintenance/Repairs
1

After running for a while (about 75 miles at normal speeds) the engine begins to idle very rough. I have to pump the gas pedal several times quickly to smooth it out but it returns. running at normal highway speeds it is fine.
Error codes show P0152, P0153, P0158

2

Assuming there are no other issues with your car… loud or broken exhaust?

I would say you have a fuel injector that is getting stuck open dumping too much fuel down the engine on bank 2 of the engine. I think the P0152 is the key error code as the other 2 would follow.

It is possible the bank 2 O2 sensor 1 has failed but it would be odd that the engine runs OK, then later in the trip runs rough. I’d hook a scanner to the engine and look for what the B2S1 O2 sensor signal looks like when the engine runs well and then compare that to 75 miles later when the engine runs rough. I’d also look to the bank 2 long term fuel trim to see if the ECU is trying to lean bank 2 down. If the O2 sensor switches normally and then goes full rich and stays there, I’d say a bank 2 injector is stuck open.

That’s my guess considering you didn’t tell me what engine it has nor the miles on it. Or really anything else about the SUV.

1 Like
3

thank you very much for the valuable information. the engine is a 4.7L and just overhauled 500 miles ago. I did check each injector by disconnecting one at a time. they all had an effect. it did this also before the overhaul. also put a new ecm/computer in.

I will do as you suggested before and after 75 mile scan.

thanks again

4

So they pass fuel, and they stop, that doesn’t mean they are not leaking. You didn’t say if you replaced them. If you went to the trouble and cost to rebuild the engine, why use the old injectors? Same for the O2 sensors. At least the upstream O2 sensors. I’d have replaced all that since they were as old as the engine, weren’t they?

5

I did replace an oxygen sensor but forgot which one but I agree with you and should have replaced the injectors. I will do that the see if that does the trick. since b2s1 and b2s2 both show high voltage I’ll replace them also.

thanks again. I appreciate you info

6

If you post the short and long term fuel trim data here you’ll get some more ideas I bet.

7

thanks, I’ll do that