Waffeey

Left a rag in intake runner, got sucked in and probably bent valves and kissed the piston... Thats what I get for being an idiot.

Okay gotcha, truck still had good oil pressure so i will try not to look at the cam bearings! I will be going that route and doing cam/lifters/pushrods and do a crankcase oil flush. I have heard bad stories about remanufactured lifters being lower quality, any brand would you suggest?

Found it, looks like a lifter failed and destroyed a lobe on the Camshaft. Also slightly bent pushrod and scoring on another cam lobe. From how deep the groove in the cam is I assume there has to be metal debris in the engine. Seems i should replace the long block or rebuild this engine entirely short block and all. Only other option I can think of is pulling and cleaning put the oil pan, replacing just lifters/pushrods/cam and praying no oil galleys get blocked.. Any advise appreciated!

Hey all, my 2002 Silverado 2500HD 8.1L w/ Allison transmission recently started making an intermittent but rhythmic squeaking/scratching noise that seems to be coming from engine internals. Video of engine noise https://drive.google.com/drive/folders/1ANVafHeQLibrg7velXbiScdqP4Fb3hlF Noise is about the same through rpm range. Engine has 240k on it, no aftermarket modifications. Fearing lifter failure I went ahead and pulled the intake manifold to inspect lifters, did not see any loose retaining clips and felt all pushrods, none have excessive play. Attached pictures of lifters. Cam lobes that I could see looked fine. When I get off work I will spin the engine over, feel all pushrods for play as the bad one could be compressed and not showing play currently. Also will pull the valve covers and inspect springs/rockers. I know I jumped the gun by tearing down but has anyone else had experience with this noise? Sound seems to be coming from top end, not a deep noise like bottom end. I do have a one snapped off exhaust manifold bolt, rest are tight but doesn't sound like an exhaust leak to me. Appreciate any input thanks.

FINAL UPDATE: Fixed the stumbling issue! Spark plugs were simply worn out and covered in carbon deposits. Overlooked the simplest thing, stupid on my part but hopefully helps someone else diagnose their issue. In conclusion the original stumbling/stalling issue was worn spark plugs, and my intermittent no start issue was a bad cam sensor. Truck runs GREAT now. Thanks everyone.

I found the culprit of my no start! It was indeed a bad cam sensor, the replacement Standard brand one was defective. I found an Acdelco cam sensor at a GM parts dealer, no more code and solved the no start. I still have the same stumbling/stuttering issue even after a new Delphi fuel pump though.

So I tested the voltage at the cam sensor connector with a multimeter and got 11.6V (Checked battery at 12.5V) a voltage drop of .9 volts could this be it? I looked inside the loom up to where it meets the rest of the harness couldn't see an broken wires. Confirmed still throwing the P0342 Cam Sensor code. Skeptical of the accuracy of the harbor frieght fuel pressure tester so I rented an OEM tools one and tested it in the parking lot. Got 50 psi this time, harbor freight reading was 48psi. Truck started and drove fine the 5 miles there and back.

Progress! Tried the starter fluid trick to find out it's not fuel. Replaced the NEW "standard" brand cam sensor with my OLD one and the truck now runs like before.. Wow. So I still have a hard starting issue, ocassional stumbling, and P0342 Cam Sensor CEL but have figured out the no start was the new cam sensor. Also I have a harbor freight special fuel pressure tester so its probably not accurate. Thanks for your tip I will try to find an ACDelco Cam Sensor!

Thanks for the reply I will try swapping back in the original cam sensor since mine is standard brand. My new crank sensor is the updated acdelco one and MAF and MAP sensors are the originals. I tested my fuel pressure at the rail with just key on and i got 48psi instead of spec 55-62psi so i am thinking about replacing the fuel pump but the truck now will not start again. With that confirmed fuel pressure and audibly hearing the fuel pump I am thinking something else is causing the no start. So now I'm lost.

My fuel trims are -0.8 - 1.6% for bank 1 and 0.8 - 3.2% for bank 2 while idling.

So the stumbling issue has gotten worse with the truck throwing a new CEL yesterday P0342 for Cam sensor after the truck wouldn't start after a longer drive. Checked wiring harness and installed new sensor today and its still stumbling and not starting first try! Threw the CEL again too... The only other thing I can think of is a bad fuel pump causing the stall and stumble but why am I still throwing a cam code?

I have already cleaned the throttle body and IAC but I will monitor fuel trims next thanks for the tip.

P0101 confirmed code for the MAF again, going to check intake manifold bolts again and check for a vacuum leak. If I dont find anything I'll check the MAF wiring.

It didn't stall or stumble for awhile but their both back now unfortunately. I just threw a check engine light when I was towing so depending on what that code is I will likely follow what it was set for. Shame as the truck runs great otherwise. I'll get back to you with the code.

I did check everything I was able to with my scanner at home for the intermittent MAF and MAP codes and wasnt able to find anything. Another user on a different forum suggested I check the intake manifold bolts as they tend to come loose and sure enough the front 4 out of 8 bolts were loose. Torqued to 10ft/lbs spec and Truck is running much smoother now.