Decided to change spark plugs to see if I could get better gas mileage for my commute to work. I took out champion plugs rc12mcc4 copper I think. Put in platinum ac delco 41-806 gapped @ .040" and truck started but stalled. Lol. After a couple of tries, checked for codes and got p0508. Changed gap to .047" and same thing. Found out gap should be .045". What should I do? Or what happened? Is .002" that much? Considering the gap in old plugs where all at .069" lol. I unhooked the battery and hope it resets with no code . Might try put old plugs back in.

 

My guess is you left something unhooked or broke something the code is for the idle air control valve which if you left that unhooked it will cause exactly what you are describing. Its on the throttle body

 

 

junk those platinum plugs, autolites 3923 plug gapped at .040 should do the trick. they are a step cooler than stock and help with stumble and idle

 

What engine do you have? I'll assume it's a V-8 but what code N (0.044") or J (0.040")

 

N type. Today tried with old plugs since it was running fine before and still stalled. Not sure how I damaged iac or etc. Did notice previous owner had a wire from first firing plug to ignition and back to parking lamp fuse. I might rig the throttle open to rev at 850 rpm at idle and ignore eng. light. Tried it for a bit and worked. Forget emissions

 

Probably pinched a wire or perhaps the vaccum line i'd look them over and check that the connector isnt loose Before replacing anything. They run near the drivers side rear of the motor near where you'd have turning a rachet to pull the plugs. Although the iac is a relatively cheap part and easy to change.heck I got my last one for 2 bucks at the junk yard, came off a jeep liberty iirc.

 

an hour from any yard. i temporarily adjusted throttle screw to open flap while i order or find part i need. revs, idles all good for now. all vacuum good. sure somehow iac went bad. will order iac and tps from rockauto.

 

[QUOTE=jkeaton;3420385][/QU
how do you notice the diff?

 

N type. Today tried with old plugs since it was running fine before and still stalled. Not sure how I damaged iac or etc. Did notice previous owner had a wire from first firing plug to ignition and back to parking lamp fuse. I might rig the throttle open to rev at 850 rpm at idle and ignore eng. light. Tried it for a bit and worked. Forget emissions