Suburban miss fires after going up a hill?

[elorenzo39]

I thank you very much for your advise. I try it out.

thanks,

[JoleneFraser]

Originally Posted by 99subhelp

I have a 99 chevy sub with the 5.7 and I had the seal replaced under the intake manifold and now it miss fires when I climb a hill and get to peak it will missfire badly. It will never do it when your climbing the hill or on flat ground but only when the engine has been enganged on the hill and then comes off of a little. It only happens at speeds over 50 MPH. I have replaced the plugs, wires, cap & rotor, and the fuel filter. The dealer wants to replace all these parts again and charge me 500 for it. I need some Ideas. I took it to another mechanic and he sees it misfire with the scope while driving but can't pinpoint it.

Thanks

Tony

I have a 99 chevy had the same problem one of the valves in the transmission was blocked have a transmission anaylisis done

[mmoss10]

Can someone explain how cam position sensor helps this condition? It's about the only part I haven't changed on my '99 Tahoe 5.7 to try to cure this poblem. I have done plugs, wires, EGR, Dist cap, rotor, Seafoam, cleaned mass airflow, still no cure.

[Rconce01]

guys same problem misfire codes and problem here. Car misfires heavily at idle lots of black smoke poor MPG. We replaced rotor, cap, wires, a lot of plugs, coil, coil module, inatake valve seals, crank position sensor, and still the same problem. Intake gasket has been replaced 5 times. We tried the GM OEM twice one the autozone one the advance auto parts one, even a home made one out of gasket material. The car will run fine upon the change of the intake gasket (it even clears codes automatically) but within 24 to 72 hrs it will end up in the same condition.

[jtmarten]

Originally Posted by Rconce01

guys same problem misfire codes and problem here. Car misfires heavily at idle lots of black smoke poor MPG. We replaced rotor, cap, wires, a lot of plugs, coil, coil module, inatake valve seals, crank position sensor, and still the same problem. Intake gasket has been replaced 5 times. We tried the GM OEM twice one the autozone one the advance auto parts one, even a home made one out of gasket material. The car will run fine upon the change of the intake gasket (it even clears codes automatically) but within 24 to 72 hrs it will end up in the same condition.

Dead thread. But, have you checked the O2 sensor(s) and the fuel pressure regulator?

[Rconce01]

Yes fuel pressure is good and 02 are good too. The problem obviously is the intake gasket when we replace it the problems goes away then it returns as the days go past. Why this happens beats me. Why do you say the thread is dead?

Originally Posted by jtmarten

Dead thread. But, have you checked the O2 sensor(s) and the fuel pressure regulator?

[elorenzo39]

I have fixed the problem. Thanks for the SeaFoam advise. I have poured Seafoam in my crankcase and fuel tank and fixed the problem overnight. I even passed my CA smog with flying colors. I highly recommend Seafoam to everyone who has been having the same problems with their Suburban.

Thanks again.

[J-Ri]

Originally Posted by Rconce01

Yes fuel pressure is good and 02 are good too. The problem obviously is the intake gasket when we replace it the problems goes away then it returns as the days go past. Why this happens beats me. Why do you say the thread is dead?

The thread was dead because it was over a month old. When a thread is dead, start a new one.

[LastOne]

The problem will come back. Sticking valve guides in the heads is most likely your problem. Seafoam will free it up for awhile but be ready for the return of the miss or as I call it the 1500-2000 RPM Shake

[maxwedge]

We discourage continuing a thread for more than 3 months, all the topics/possibilities have been thrashed over sufficiently at this point.