3.1L stumble/low rpm miss. I got 2 that do it.

[GPSonoma]

Wassup? Just registered, and I have a question.
My wife and my mother-in-law have 3.1 powered Grand Prixs.
One is a 90 the other a 92. They both have a similar problem.
The 92 at one point acted like it had one dead coil. I replaced all
3, and the module (the module ended up dying) and that fixed the
incredibly rough operation. Now, it runs rough under 2000rpm, as
does the 90. They both run strong, but the 90 stalls intermittently,
mainly when putting it in drive after backing up,
and they both hesitate when accelerating from a stop, though the 92
isn't as bad (it's barely noticable). Both have new plugs and wires, which
helped, but didn't eliminate it. If I slowly increase the rpm while parked,
they both miss until they get above 2000. After that, they smooth out.
The 92s engine has been rebuilt a couple of times, and it has ALOT of
miles under it's belt (it was owned by a construction worker). The 90
appears to have had the top end apart at some point before we bought it.
No SES light on either one (except the 92 before the new coils and ICM).
Oh, and the gas tank on the 90 hisses like crazy when removing the cap below 1/4 of a tank. I haven't replaced anything other than what I
mentioned above, but plan to do the fuel filter on the 90 in a couple days.
I have limited funds and wanted to get a few opinions before I start buying tons of parts that don't fix anything. Thanks in advance if anyone replies.

[bszopi]

RE: 3.1L stumble/low rpm miss. I got 2 that do it.

I'd replace the fuel filter on both and go from there.

[GPSonoma]

That's my next step, it doesn't appear to have been changed in a LONG
time.
Oh, in addition to what I've already said, it doesn't make a difference
if the cars are hot or cold. Though the 90 is more likely to do it when
it's cold, both cars will do it when they're warmed up, also.

[Zerorsica]

Also sounds like the upper intake gaskets are finished?

[slowbird]

Upper gaskets sounds right.


Try unplugging the EGR first...that was my stalling and surging problem.

[GPSonoma]

Thanks, I'll check into those two also. I noticed a little blue-goo peeking out from between the front head and intake, so I figured it must've been apart before. The intake gasket thing was one thing I was wondering about, cuz I heard that these engines are known for that.
The 90 is running alot better lately, still misses, just not as often.
I still haven't changed that fuel filter, lol.