Low idle stumble

c1500deathtrap · Oct 21, 2017

A bit lost in the sauce on this one. First the truck, a 1991 gmc sierra with a 1996 l31 vortec block topped with an edelbrock carb manifold and adapter plates to mount a TBI unit. She stumbles at idle ONLY when in gear and when she stumbles the IAC is always closed. Any ideas?

magimerlin · Oct 21, 2017

Timing, tps sensor, vacuum leak, egr issue,

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c1500deathtrap · Oct 21, 2017

timing is at 8 degrees before tdc base timing with the timing bypass disconnected. No vacuum leaks anywhere that i can find, she also pulls 22 inches of vacuum steady needle at idle in park. No EGR at all. Only stumbles in gear at a dead stop.

magimerlin · Oct 21, 2017

Need to drop that down to about 4 degrees.... any more is just a waste most have found... myself included... I was at 6 and backed it back to 4... was much better...

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c1500deathtrap · Oct 21, 2017

I've tried from 0 to 12 and 8 works for me issue has always been there. Even with the old engine.

magimerlin · Oct 21, 2017

Well... if issues where there even with the old motor... what was used from the old motor onto this one?

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c1500deathtrap · Oct 22, 2017

all that is left is the original ecm, the injectors, and i think the MAP.

Low idle stumble

c1500deathtrap

I try

magimerlin

I'm Awesome

c1500deathtrap

I try

magimerlin

I'm Awesome

c1500deathtrap

I try

magimerlin

I'm Awesome

c1500deathtrap

I try

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