Hello. 20 year mechanic here but I worked on busses and diesel engines mostly. I fix cars but some of the more complex issues I dont have alot of experience with.
I've got a 2008 Chevy Impala LT 3.9l. I've been hearing a ping from the engine that sounds like pre ignition to me for quite some time but could never verify it because it's hard to hear while driving and it didnt change with higher octane fuel pr
e85. Then it started to cut out when trying to accelerate at highest speeds. If you let off the accelerator and hit it again it will cut back in and accelerate. Almost feels like a tps issue, however I replaced the pedal assy and the tps on the throttle body a year or 2 ago due to active trouble codes and the reduced engine power on the dic. I did get some trouble codes before this started happening related to the pedal and throttle body with the reduced engine power light on, so I cleared it to drive and it didnt throw the code again. I pulled put the throttle body and verified it opens and closes appropriately with the pedal. I tried to monitor the tps commanded tac and pedal positions on my scan tool but I'm not sure how far off the numbers should be. The commanded and tps seem to match but the other positions values are are different. It doesnt throw a code so I assume they are valid.
The other thing is the tick in the engine. At an idle you can clearly hear it. I removed the belt to verify it's in the engine and it is. Same noise with belt off. Louder than a lifter tickbut not a knock like a rod.
My thoughts are fuel pressure starving the injector maybe? Would that cause a injector to make that noise? No misfires or hard starts. Just no power when at highway speeds and pedal is pushed down to accelerate. Falls on its face like a tps issue but no code and cant see anything goofy on the live data, but not sure what exactly it should look like. I do not have a fuel pressure tester, but if someone tells me I need to check it in could rent one.
222k miles on this impala. Afm works still. Or dod, whatever it is called. Cleaned the maf... plugs and wires are new.well maintained by myself since I bought it at 100k. New air filter. Original fuel pump as far as I know.
Any gm techs out there seen this before? Or anybody else have any clue where to start? I dont have alot of money so I cant afford to throw parts at it. I'm in school for IT now because I never liked being a mechanic. Any help is greatly appreciated.