Injector problem

Asked by Shadowrepair Sep 06, 2018 at 05:33 PM about the 1994 GMC Sonoma 2 Dr SLE Standard Cab LB

Question type: Maintenance & Repair

Just rebuilt the entire top end from a blown head
gasket and a broke valve spring. Got it all back
together with new injectors and new regulator
along with new plugs, wires , filters. I have two
cylinders running rich(#1) while 3&4 are
burning little less than tan. Went through two sets
of injectors but no help. Engine runs rough at idle
but smooth as long as it's above 1100rpm.
Anything less than 1000 it gets rough and bumps
like it's trying to die.

9 Answers

So far I haven't found a vacuum leak. To my knowledge everything is hooked up right except for the evap canister. I have it capped off due to rotten lines

It was running good till it was overheated and blew head gasket. Replaced injectors due to all of them had cracked. Checked for vacuum leaks with starting fluid.

9,530

Did you check the heads to see if they're warped? Also engine block. The very next thing I would do is a compression test. You may have broken piston rings if the top ring is cracked it won't necessarily burn oil, I had a 93 GMC that missed after a valve job and it turned out to be metal chips in the valve guides left over from machining

The head was shaved nearly .010 to get it back flat. As far as compression, 140lbs both hot and cold. I always rewash heads when I get them back from machine shop. Not sure about block rebuilt top end while still in truck. Forgot to mention earlier. When you raise the rpms to 1500 to take off in first it doesn't have enough power to pull itself even at 3000 it moves maybe three feet before rpms drop dramatically.

Got to check for leaking injectors but not sure how when the intake is the fuel rail band don't have enough room to take intake off with everything still attached

9,530

I forgot about that fuel system, yours has a popet at the end of each injector, If this is the one I think it is GM made a retro kit, check with dealer. Sounds familiar the intake comes apart to show you injector tubes and popets.

Yes two piece intake. I guess upper and lower. The lower has fuel passage ways for the bottom feed injectors. Bad part is have to take lower off to see injectors undr pressure. I guess my problem comes down to either ecm or injectors unless you have another idea

9,530

Injectors like I said check with GM or maybe parts store for retro-fit kit. I can't begin to tell how many we've changed, It wasn't a recall but it was close.

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