JNNelsen

Runs rough and very rich, the check engine light is flashing! It was stumbling at low RPM and I changed the plugs. It got way worse!?
The question is why?
Any guidance / suggestions would be appreciated.

Irish_alley

maybe a poor connection with the plug and wire. but need to see what the code is and go from there.

vortec5.0

just a shot in the dark but have you tried unplugging mass air flow sensor yet.

Z7145ACP

Like what Irish said, check wires, etc. Hell, I put in new plugs, wires, one-at-a-time even and cap/rotor and still managed to get #3 and #5 crossed over!
Easy to knock a vacuum line off too, check all the obvious.

This little reader is great for the money. Does the basics plus a little more. Just hook it up to you laptop and see what's going on.

JNNelsen

Thanks all, I have traced all the plug wires, all on correctly, I replaced both upstream oxygen sensors, no change. I did unplug the mass air flow sensor and 'no change' at idle. I will double check the vacuum lines and head to the pawn shop and buy a nice scanner my buddy Kelli has for $50!

Irish_alley

i want to say if you unplug the MAF sensor and there is no change in anything thats a sign its bad

JNNelsen

Thanks, changed the MAF, no improvement.

Irish_alley

ok lets start with the basics. double check your plug wire connections and make sure you didnt cross number 5 and 7 wires. then test your fuel pressure

JNNelsen

OK, a little more background. New fuel pump and injectors in Feb, fuel pressure is fine. All the plug wires are on correctly, the plugs are new and the cap and rotor were replaced in Feb. The misfire is now 'random'. I will be looking at the timing and checking the intake for leaks when I return from vacation.
Thanks for the suggestions.

Z7145ACP

Sometimes the ECU won't throw a code, hence you get no CEL. Before you get another headache, run a scan. Again, even if you have no CEL