I'm at wits end and about to look for a cliff for this car.
I'm desperate for quad 4 pro's.
It is in a 97 Grand Am, 2.4 quad.

I have a random cyl misfire code.
engine shakes and misses at idle. Runs great at higher rpm, lots of power.

seems like fuel issue not ignition because it runs great at higher rpm.
did swap out the coil packs and install new plug boots.
new plugs,
cleaned and tested IAC, ok
tested TPS, ok
pulled fuel rail to check for injectors bleeding/leaking. cycled fuel pump several times, still dry.
Checked injectors for nice spray, ok
unplugged one injector at a time, major stumble with each, seems all are working.
No apparant vacuum leaks detected with spray, new intake manifold gasket.

It runs so well at higher rpm I'm thinking it is getting too much gas at idle. sound reasonable?
No gas in vacuum line to fuel pressure regulator indicating a ruptured diaphram.

how about a bad fuel pressure regulator? possiby stuck on high pressure mode?

I know the quads idle a little rough anyway (or some at least) but this is bad.
going crazy.
any ideas?

oh, more info..

this quad4 just had a waterpump/head gasket replacement. They guy that did it bent two intake valves on re-assembly (I assume).

I put in the new valves/lapped, new head gasket, new intake gasket, etc.
Compression is great on all 4 cyl.
I do however have the low coolant light on. I thought this would burp its self out with a few full engine temp cycles as the overflow bottle is full. The low coolant light is still on however. Maybe the sensor its self on the overflow bottle??

Is the rough idle also possibly related to a coolant temp sensor? Air pocket at the sensor?

Just a little mor info in case it triggers any other thoughts.

thanks again!

sorry to keep adding info, but I don't know what might be relevent..

When I unplugged the temp sensor (by water inlet, back of head? , drivers side) the car would not start at all and smelled rich while cranking.

When I unplugged the vacuum line off the fuel pressure regulator there was no change in the rough idle at all either.

am I in the wrong area thinking too much fuel? Possible coil issues and weak spark not igniting the fuel at idle?

looks like it IS spark issues.

Flipped the aluminum cover that holds the coil pack upside down with the plugs connected.
Only had spark on #2 and #3 (same coil) had two other coils from another coil pack and swapped both out one at a time with the bad one (1&4) with no results.
Hard to believe that many coils are bad but..
So then I tried switching the 2&3 coil with the 1&4 coil and now NONE of them are sparking.

grrr (crazy quad4's)

I heard somewhere there can actually be a problem with the alum cover / grounding out issue?
anyone know anything about this?

Hate to start buying all the new parts, my stimulus package has not yet arrived.

maybe I'll try a whole new set up from the salvage yard.

ideas??

Try replacing the plastic piece that goes in between the coils and the boots. My car did the same thing recently. Would stumble at lower RPM's but was fine when they came back up.

I had the same problem, I just replaced the whole coil pack and it worked fine.

Look for a complete unit from the wreckers.

If you recently replaced the coils on the pack and now none are working, Obviously the problem lies within the coil pack.

But what do I know.