Engine looses power and Back fires


Asked by Jan 18, 2015 at 01:07 PM about the 2002 Chevrolet Silverado 2500HD 4 Dr LS 4WD Extended Cab LB HD

Question type: Maintenance & Repair

The engine looses power when shifting down a gear on hills, the passenger side exhaust manifold is cherry hot . I changed the fuel pump, filter, EGR valve. Had the codes read and reset , Knock sensor comes up and O2 sensor. Where should I look now?

5 Answers


Sounds like it may be a timing issue. Does the engine have a valve tap? If so, the knock sensor may be hearing it and severely retarding the ignition timing. The knock sensor is like a microphone. It listens for pinging in the engine. If pinging is heard it retards the ignition timing until the pinging stops. It will do the same if it hears a valve tap. Did you replace the knock sensor? HTH. -Jim


no I have not replaced the knock sensor yet. The engine does not have any taps that I can hear. Does have an exhaust leak.

1 of 1 people found this helpful.

The exhaust leak is most likely what's triggering the O2 sensor (lean) code. That'll sometimes happen. What knock sensor code are you getting? HTH. -Jim


The engine seem to act up when it gets warm. When its cold it runs fine. Not sure what code for knock sensor will check this weekend.


Ok, I replaced both Knock sensors. The engine light went out but it still has same problem. It seems it runs fine on the flat but when come to hill it losses all power. Back fires. Any help any one. Should I start replacing coils, plugs, wires???

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