miss at idle

[ironbridge]

My 96 lumina with the 3.1 engine has developed a bad miss at idle. I recently changed out the plugs. The AutoZone scanner said multiple cylinder failure. It runs fine except for idle. I took off the plug wires at the coil packs one at a time at idle. It seems to have lots of spark at the coil pack. What should I try next. Thanks

[maxwedge]

Try and narrow the cyl down, get a timing lite on each wire and look for a flash, or carefully pull one plug wire at a time till there is no change in engine roughness, that is the cyl. This also be another problem other than a misfire if it runs good under load. Sticking egr for example.

[ironbridge]

Originally Posted by maxwedge

Try and narrow the cyl down, get a timing lite on each wire and look for a flash, or carefully pull one plug wire at a time till there is no change in engine roughness, that is the cyl. This also be another problem other than a misfire if it runs good under load. Sticking egr for example.

Thanks maxwedge, I did pull each wire at the coil packs and noticed no change in bad idle. You mentioned the egr.........where is it and can I just disconnect it and see what that does? Again thanks for the help.

[meuhus]

Originally Posted by ironbridge

My 96 lumina with the 3.1 engine has developed a bad miss at idle. I recently changed out the plugs. The AutoZone scanner said multiple cylinder failure. It runs fine except for idle. I took off the plug wires at the coil packs one at a time at idle. It seems to have lots of spark at the coil pack. What should I try next. Thanks

i had injectors go bad on my lumina
your problems sounds similar
it would miss at idle and at a steady speed on the high way
and was realy noticeable at around 1500 rpms
the car would jerk kind of

check the injector resitance
i have a 91 lumina
the restance for mine is supposed to be around 12 ohms
i dont know exactly what yours should be
you will prblably have to pull upper intake manifold (plenum)
i would also replace those gaskets if you do this

i changed plugs and wires and never got rid of the miss

had an injector problem before it started missing

as in one of my other postings

after changing out two sets of wires i took off the upper manifold and checked injectors again and for one of the new (reconditioned ones had failed)
put in one of my old ones all is good again

[maxwedge]

As you pulled each wire the engine should have gotten rougher, then if it is a cyl miss, one of the wires you pulled there should have been no change. Egr is in the upper intake just to rt of the throttle body, usually if this is not seating you would get a code.

[ironbridge]

I took the car to AustoZone yesterday and got them to pull the code. Multi cylinder missfire and a mass airflow sensor code. I replaced the air filter yesterday and looked at the mass airflow sensor but could not see anything broken. Would a problem with the mass airflow sensor cause the car to runn very rough at idle only? It runs good once you give it a little gas. I have recently replaced the plugs and pulled each wire off the coil packs at idle. They are all firing fine. Thanks for the help.

[maxwedge]

Make sure the ducting from the maf to the intake is not loose or cracked somewhere. A full scan can determine what is going on with the maf, and can do an injector power balance test also.

[richtazz]

Check the idle air control (IAC) to see if it's gummed up or sticking. It's mounted with two screws in the side of the throttle body, and regulates air at idle/part throttle. Clean both the valve itself and the bore it rides in and see if your idle improves.