oldsmotion

I have a 86 5L with around 120K. It starts fine but within seconds it quits. If I feather the gas it will stay running and then idle between 650 and 1200rpm. Sometimes it will settle in at 1000rpm. When I hit the gas it hesitates real bad.

I have rebuilt the engine top to bottom. The rebuild has about 50 miles on it. Any thoughts would be appreciated.

86 5.0L

congrats you own a 5.0L, I'd be freaked out if it DIDNT do that

haha just kidding, start with pulling ecu codes

AdderMk2

check for vac leaks, pushrod preload, faulty EGR valve, and faulty IAC motor

zebo87

i second the vac leaks, iac and egr. what kind of fuel pressure are you getting. running codes should be first priorty though.

cholericfc

+1 on the IAC, VAC leaks, and KOEO/KOER tests.

Also, what is your timing set at? depending on the results above, you may need to do an Idle Setting Procedure if you haven't already.