RPMS Jumping 97 sierra

darr32

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I recently bought a newer truck after my old S10 gave out on me. I got the truck for a steal at least i thought at the time, 1500, while driving down the highway it overheats dies, gets towed him, then i have my neighbor and mechanic come over and he diagnosis it as a blown head gasket. So i fix that over a two week period, get it to start after alot of adjusting, but now the rpms are jumpin from about 400-500 to 1000 and the motor sound like it will die but then restarts.
So far what ive done:
Fuel pressure check
new distributor cap
new spark plugs

What i think it is:
Either the distributor is wrong because my neighbor was saying something about the wrong number on it, even though it ran perfectly before it blew up.
The valves were not correctly adjusted, what the chitltons i rented said is get the piston to TDC then adjust that cyliders push rods to 0 Lash then half a turn after.
What my question is, What do you think it is from what i have said?
Truck info:
1997 gmc sierra SLT extended cab Z71 5.7 with 139 thousand miles no rust
Thanks for looking, and hopefully i can fix this soon, i want my truck!:(
 
Re: rpms jumping

Sounds to me like an intake leak and your air idle control is trying to compensate
 
Re: rpms jumping

There are very simple ways of finding leaks on your intake outside like an unlit propane torch. There were two times that I have seen a intake gasket... maybe over torqued or bumped on install but for whatever reason they were pushed out the bottom sucking air from the inside of the eng. both times were on that same 5.7 eng.
 


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