dboldt

My stock C5 breaks-up at high rpm. 32K, dry engine, not sure if/when plugs/wires were changed, idles fine runs good under normal driving. I can't do much mechanically. Any recommendation?

Bill Curlee

WOW! Not much I can do without you reading the DTCs using the DIC. When the engine falls on its face, SAFELY,, pull up the DTCs just after the event and see what pops up (without turning the engine off).

I would say, start with new GM Red Performance wires, check the air filter, clean the MAF with MAF Cleaner. Clean the throttle body/blade. Check the fuel pressure. Its TOUGH to check it at speed when it falters but, you may be starving for fuel at higher RPMs. Something to think about. Get the wires at www.gmpartshouse.com Good price good people...

The DTCs will help us go in the correct direction. What is the condition of your battery??? C5s are battery voltage critical/ I would have it and the charging system checked to make sure everything is good there.

When the engine falls on its face, do you see the CHECK ENGINE LIGHT (CEL) flashing????????? Important info!!


Bill

dboldt

hey Bill.....Thanks for your response. Battery is good and no check engine light. I'll check for codes and get back.

dboldt

Hi Bill. Some codes detected but each was followed by an H. Thanks.

Bill Curlee

H dtc are important too!!!

T_Vert

Sounds like a weak valve springs. Any valve train noise? If it was a misfire you'd get a dtc and maybe a flashing cel when it's sputtering.

WICKEDFRC

D Bolt - If you ramp up slowly, does it make the same symptoms? Or, is it ONLY under WOT, ramping up really fast, and after 5200 RPMs (or thereabouts) it feels as if you are hitting Rev Limiter?

I had this issue what I am describing and it was a cracked spark plug. Usually comes with a MISFIRE engine code.

Swap your spark plugs, or, check them very carefully, one by one.

Mine had a hairline crack and was hard to see. So, under normal driving, it was fine, but WOT, it was arcing under load.

dboldt

It sputters only at high rpm (5K plus). Next time I get lead-foot I'll check the rpm's. Rums fine otherwise. How high is the rev limit set? I didn't see any active codes but will check for historical codes as well. Thanks.

jusmchmidt

Dbolt, did you ever reach a resolution with this issue? Just experienced the same issue this morning while accelerating onto the local highway from a stop. Car runs beautiful other than the high end.

I'll start with the suggested basics, hope your was resolved.

uncle wilson

Having same issue ! At low rpms ! Changed plugs gonna clean map sensor next!

Bill Curlee

Do you mean clean the MAF sensor (Mass Air Flow sensor)
???

uncle wilson

Yes the maf sensor! At other ideas ?

uncle wilson

Cleaned maf sensor doing great so far!!!