2001 Gm Suburban 1500ls 5.3l 238,000mi

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01' Suburban 2WD 1500LS 5.3L (238,000mi). Begain to code "Random Misfire"

-New Fuel Filter

-Fuel Pressure checked 38-42psi

-Had injectors professionally cleaned "closed loop cleaner"

Seemded to reduce problem for two months then it all fell apart...

Coded Random Misfire, Bank12 O2 sensor/cat converter low.

-Replaced O2 sensors rear both sides

A screeching begain to develop that sounded like a dry bearing on belt tensioner-

Removed, tested, all tensioners.

Still had squeel with modest acceleration but not at idle.

Misfire got worse- no power now. Will idle and pull off of idle but with no power.

Code only shows random misfire.

noise appears at exhaust manifold of rear-driver side cylinder and nowhere else.

have not taken off valve covers yet.

will do a full compression test tomorrow-

Has the feel of catistrophic valve train failure... Is anyone seeing this in this style engine at this mileage?

[SouthCo]

My '03 tahoe "only" has 182,000 miles but runs like a top. biggest repair has been a throttle body replacment (at about 175,000 miles) because I kept getting a reduced engine power message on the DIC. It was a bad TPS but on these the TPS and throttle body are one unit. Good luck and please post any progress.

[txab]

Key on, engine off fuel pressure should be 55 - 62 psi

[8.1HD/ALLISON]

I have seen some camshaft lobes worn down and lifters spun. I was thinking it was in the newer ones though, not sure on an 01. I would carry on with the compression test. That will let you know if anything mechanical is going on.