tach problem

[billy6351]

I have an 03 trailblazer and I had a code for the therstat but the truck would buck and the tach needle would jump when the it hit 1800 to 2100 rpms but the speed do would be ok. the only code was for the thermostat which I replaced and alos replaced the fuel filter, blet and put in ac delco plugs code was cleared themp ok but still have the same problem when at 1800 rpm , stepping on the gas pushes thru the problem but whne the tach hits the same area it bucks.

I was thinking of chamging the vss but doesnt that only work to tell the tranny to shift, my last resort to to have the cylinders checked for leaks, I was told it could be the valve seats could be wearing that meand a new head and motor work.

Please advise with any help

 

[The_Roadie]

Checking compression is always a good thing, but more importantly if you're getting misfires. No codes? No flashing SES light? How many miles? Check for vacuum leaks, and an oily CPAS unit. Valve timing could be messed up by a bad CPAS, which may or may not throw a code.

I don't think it has anything to do with the VSS.

 

[billy6351]

Checking compression is always a good thing, but more importantly if you're getting misfires. No codes? No flashing SES light? How many miles? Check for vacuum leaks, and an oily CPAS unit. Valve timing could be messed up by a bad CPAS, which may or may not throw a code.

I don't think it has anything to do with the VSS.

ok the truck has 109,000 miles run strong but I do notice that three out of the six plugs had oil on them when I change them, where is the cpas located soI can change it

 

[Wooluf1952]

Sorry if I'm miss-reading, but, is there an actual miss? Or is the tach just jumping?

Is there oil on the tip of the plugs? Or just the threads?

If it's just the threads, it's probably just a leaking valve cover gasket.

 

[billy6351]

the truck bucks and feels like it losing power but when its given gas problem goes away, I did see oil on the threads and I cant be sure it was on the tip could have been

 

[Ace1875]

ok the truck has 109,000 miles run strong but I do notice that three out of the six plugs had oil on them when I change them, where is the cpas located soI can change it

the CPAS
How to: Camshaft Position Actuator Solenoid Cleaning - Chevy TrailBlazer
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