Having issues with a 1990 Suburban TBI 350

Wont run unless MAP is unhooked and throttle is pressed. And its still a fight to keep it running. It will sputter to a stall in less than 5 seconds after release of throttle.

New: O2, MAP, Knock, Plugs x2, wire set, distro, cap, rotor, coil, timing chain, intake gaskets, IAC, fuel filter, egr switch, oil press sending unit, TPS, spark control, fuel sending unit,

Rebuilt TBI, no CATS, no oil in water/no water in oil, checked vacuum lines.

No codes

 

Any idea? ANYONE?

TTT

 

Any troublecodes? what is your fuel pressure? It almost sounds like a fuel issue (as opposed to spark)...

 

I know you don't want to hear it - but double check firing order. Check plug wires for continuity (I've often gotten bad wires brand new in the box), make sure they are all securely on the plugs (the terminals inside, not just the boots). Try another MAP sensor - pass on Autozone and Advance, try a AC Delco from CarQuest. All I can think of right off.

 

What is your SES doing when you cycle ignition from off into run position???

Normal SES on- blink off - solid on until engine starts.

Do this basic check before any parts are swapped.

//RF

 

No codes. Just the MAP from it being unplugged.

Just got the kit last night. Will be checking FP ASAP!

Firing order is good. I think we already tried two sets, but may test anyway. Im glad you mentioned it too as I need to put wires on my LS1 and Id hate to have to do that twice.

They are deff secure as we have changed the plugs multiple times and no change has happened.

SES is normal. Code is from pulling the vacuum off the MAP and only then. Nothing else... I did say no codes


I should mention the spark plugs had a bit of carbon on them. I always thought if I have a dieing FP then I would run lean, therefor would have white soot buildup on the plugs.

Thanks for the input guys!

 

Perform Fuel pressure check. The reason for this is that your engine will only run with MAP disconnected and by playing with the throttle. By disconnecting MAP you are forcing ECM into limp mode (setting off MAP high) which tends to provide rich mixture and additional throttle action adds more fuel. Stock TBI needs 13 psi for normal operation, although we have seen some engines run with 6 PSI (like poop, but still run). In high millage cars and trucks fuel pump and in tank plumbing are known failure points. You did replace sending unit, but did you replaced fuel pump and pump output hose??

How is your idle vacuum? Can you measure it?

//RF

 

Turned out to be the hose from the fuel pump to tank. It was barely on.

Runs great! Thank you guys sooo much!