Hey...just want to pick your brains for advice.
I just picked up a mint 1991 Formula 350. The car runs great upon start-up, but as it gets progressively hotter, it runs rougher with a pronounced "miss". The previous owner had the distributor replaced and I just changed the plugs and wires, which were in bad shape. I was thinking the coil would be my next move, but I'm open to suggestions. Thanks in advance! Ben

 

Did any of the plugs look greenish? you may have a blown head gasket or a cracked head.

 

Well, I've had a head-gasket go before and the Formula has none of the symptoms. The plugs looked/smelled "wet" with fuel, which I thought backed the ignition theory... I replaced the coil last night with no improvement.
Any ideas?

 

Hows your fuelling ? is it getting the right mixture when hot ?

 

I would run a cylinder leakdown test. Or pull the plugs and put pressure tester on the radiator. see if you get any water.

 

ohm your injectors, should be between 14-17 ohms.mine did the same thing one was at .005 ,later jimmy

 

Thanks for the replies, guys. I think it is the injectors. I'm really pressed for time so (don't laugh) I'm having the Pontiac dealership do a diagnostic on the Formula. It barely made a 7-mile trip...

 

Maybe ignition control module???

 

Yeah it could be the ignition module and/or pickup coil to.
Had similar problem, runned good cold, but a as soon as the car got running temp and the sun hitting the hood, the dist started to miss, and was really hard to start sometimes when it was hot. Turned out to be a really bad ignition moule and a "on the way" pickup failure..

Got new parts from MSD (warranty) and im on the road again.

 

***Update***

The dealer found 10psi at the fuel-rail, so they replaced the fuel pump and that seems to have fixed it. They are taking it for an extended road test to make sure there are no other issues. I need to get some diagnostic tools for the 3rdGen...

 

"Extended Road Test"? Are you going to follow them around?

 

To the local drag strip fortest and tune .

 

Got the Formula back yesterday and it is running fantastic. Thanks for the input guys!