Why does 1997 Chevy Tahoe run fine at idle-but backfires, and runs rough while driving?

two possibilities fuel pump or timeing chain. i would check these both.

Can you tell me how to check both?

Because it runs well at idle I did not think fuel pump

I just asked-and the fuel pressure was checked while the vehicle was running-and it was 60 lbs pressure

yes but it requires less fuel delivery at idle when you accelerate more volume is required the bogg and backfire together really to me seems like fuel delivery prob.This is just something that should be checked not common for a fuel pump to act this way ,but i have seen it.

another possibility is a restricted exhaust system

Do you think it could be the distributor cap?

yes it is a possibility that the distributor cap or rotor has failed cracked I thought you had tuned it up sorry my mistake.so fuel pressure is ok now we have to believe it is electrical i would replace that cap and rotor so it can be eliminated.

We did replace the rotor-not the distributor cap. Today we replaced the crank position sensor-the first one we replaced was the cam position sensor. It seems to have more power-but still backfires. There is a lot of condensation coming from the exhaust-even though we previously ran seafoam through it

The code is P1345-which is cam sensor/crank sensor correlation-but both of the sensors are new

this sounds like a timeing chain .olease repost your question and hopefully our gm guys can help

If it is timing chain-would it still run well at idle? Thanks for all your help

yes it could if chain is stretched beyond the parimeters of the cam and crank sensor.just normally when nothing else makes sense it ends up being a chain prob. if you take the dist cap off and turn the crank pulley and see how much the eng has to turn before the rotor moves that will tell you how much play is in the chain.

I have a 1998 Tahoe 5.7 engine. sometimes when at idle will run rough and backfire. If you attempt to drive it you have to pat the gas. It will not go up a hill without patting gas. Other times it runs great. I have replaced fuel pump plugs wires cap rotor button crank sensor. All 4 O2 sensors. PCM. timing chain is new. This engine was in another vehicle and run great with no problems. Fuel pressures are good. I'm at a loss on what is going on with it. Any ideas to help will be appreciated.

Hello, I'm Danny.

You've attached a reply to a question that is years old. What we ask you to do is start a new question and include all your vehicles information. Here is the link:

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