99 Tahoe, Dirty valves?

[99TahoeST]

99 Tahoe runs very poorly at high rpms (20000-ish). Shakes a lot. Usually happens when I have to get my foot in it, like going uphill. If I totally let up on accelerator for about 3 seconds, it quits shaking, but I have lost momentum and peple behind are shaking fist, etc. If I try to keep foot in it, Check Engine light comes on.

Dealership said because of local regs on fuel, carbon/gunk buildup on valves could be the culprit... an expensive fix. Said try a top-end cleaner/additive (like Lucas, won't hurt injectors).

Any thoughts or suggestions?

Thanks

[maxwedge]

Barring anything else causing this there is a TSB regarding these symptoms. 96-2000 5.7's, the valve guides were machined with too little clearance and carbon build up causes them to hang up in the guides, hence the misfire, top engine cleaner is a temp repair at best, heads come off to machine the guides to attain .002 clearance, big job!

[99TahoeST]

Thanks for that. Sorry, but what is a TSB?

[maxwedge]

tecnical service bulltin issued by the mfg, for field repairs and diagnosis of ongoing issues.

[glenncof]

You're missing key information. You need to know what code the EMU is throwing when check engine light goes on. It is tell you something is wrong and No... it can not detect carbon build-up...misfires ...yes & will record a history

Also you did not state the mileage, recent maintenace history, or any other conditions.

I have a 1997 that has 140K miles (I put over 100K) and never heard of carbon build up issue.

Actually sounds like a tranny problem (yea codes for that also...) if the shaking harsh.