Rough Idle

Don't Know How To Fix A Rough Idle.
Tried Fuel Injector Cleaner. Still Idles
Rough.
Deler Replaced A "bad" Spak Plug And A
Coil Pack.
What Else Could It Be? Anyone Had This
Problem?

Does it run rich when idling or is it more of a miss?

Replaced 1 bad plug? Why not do them all with new wires to eliminate that as a source of your troubles. When I did mine at 85,000 (engine was missing) I found that someone had changed the front half (not platinum tip) and not the back. One plug was barely gapped at .030 and was burned up, I don't know how close it was to begin with. Several platinum tips were missing in back. I could hear a wire "snapping" behind the coils.

After new parts were installed it still had a slight irratating miss when gently on the gas going from about 45mph in higher gears. Could not tell at an idle that it was missing. Went and bought a coil and started on the left side changing out coils. As soon as I did the third coil over it was magic. All better. It was the same coil as the badly gapped plug.

Motor ran smooother than it did the previous two years I owned it and I didn't think that was possible.

I don't think it's running rich. It just feels a car that needs a tuneup or something. It only has 32,000 mi.
The dealer diagnosed the plug and coil as bad. It's
under warranty. Guess i'll have to go back again.
Gotta get it running right.

This should fix it:
1. Install a set of NGK-Iridium spark Plugs(nothing else)(sold at www.NGK.com)
if still bad go to #2
2.Install a set of Borg-Warner high-resistance spark-plug Wireset ($157 at www.carparts.com)
if still bad go to#3
3.Start changing coils one by one
if still bad go to #4
4.Change both O2-sensors and EGR valve
if still bad go to #5
5.Power-clean the fuel-system/injectors at dealership-check fuel-pump pressure
if still bad go to #6
6. Sell the damn Aurora and buy a Toyota
(p.s. I'm not a mechanic, I just slept in Days-INN last night)

The engineers put together a total package for the North Star motor. They did not use parts that were made for something else or from the aftermarket. You can actualy ruin other eletrical parts under the hood by running the wrong wires.

The AC Delco parts are what the system is desighned to work best with.

If the EGR valve was the problem, the motor would run rich, like the choke stuck on a motor with a carb. You don't need to preplace them(usualy).

Qoute from a GM engineer
"Two things can happen with the electronic EGR valve: 1. Deposits can build up and hold the pintle off the set. 2. The shaft can build up deposits that cause it to stick in the base of the EGR valve (between the EGR passage and the coil above) when the shaft gets hot and the valve is opened.


"The deposits part is pretty easy. Just go in there with a small round wire brush and clean the passages and the walls of the passage.

The shaft can be cleaned with the carb spray...just hold the valve right side up so that solvent doesn't run down the shaft into the coil. The solvent will not hurt the "valve" part of the valve, just the coil windings in the can above.

Just get the big deposits out. The exhaust will cover the passages with soot soon anyway, so you aren't looking for squeeky clean...just get the major loose deposits out. If you hold the valve pintle open and bend a little "hook" on the rifle cleaning brush you can swish it around the seat from below. Getting the shaft clean is the most important thing I think unless you see some really big chunks of carbon in the passages.

Sometimes, if the valve hangs open on a piece of carbon, it really isn't from the valve itself, but came from the exhaust manifolds. I have even seen tiny bits of welding flash (or "grapes" from the sheet metal or tubular fabricated exhaust manifolds) caught in the valve. In that case all that is required is to remove the offending piece of debris."