Stumped_97gt stalls

[BEN_97GT]

New member, been reading posts for a couple weeks now, we are stumped.. I am posting everything I think is important plus some items which may raise a flag.

1997 GT_3800 with about 145K miles. 3800 L series unknown has plastic POS intake plenum

Recently replaced intake gasket set as old gasket LIM had blowout.
Had coolant leak at the notorious elbow on water sending unit.

Car starts great. Will heat up to 210 and shut down.

When it shuts down pressure escapes through the throttle body, a rush of air.

Black smoke on startup, when it allows me to re-start it. Smell of rich exhaust.

Heat seems to prevent it from restarting. Once she cools, it restarts.

Tested Ignition Module at parts store, when they wernt looking I kept hitting test til it was a little hot... guy at the counter was not happy (wuss) I wanted to get it hotter but he wouldnt allow it.

Replaced CKP, maybe a bad sensor from the box?
Replaced Cam Sensor just for kicks.
Also MAF Sensor replaced, no codes thrown since replacement.
Removed CAT with bypass pipe, a little more "throaty" now

Checked fuel pressure, runs steady from 45 - 50ish

Injectors ticking away

Now, on inital start she looses power when you try to drive. Sounds like she's missing on a couple cyl. while accelerating.

vac seems good, test ga. stays in the 20" zone

IAC seems good, have not replaced but seems OK. No codes, have not tested ohms or voltage output. Within 1-5/8" as Haynes states is normal position unpluged

Cleaned throttle body with MAF and others removed. TB removed for cleaning.

Does not happen all the time, intermittent fun.

Maybe a bad PCM/ECM?

Have not driven in 3 weeks now... only test rides.

Any suggestions? Looking for location of all grounds, the ones I find are good. There was one ground/bolt very close to the ignition mod, when removed the bolt had coolant inside but not pouring out. found on side of engine under / behind the IM

I see the Regals had a problem with a buss ground on the drivers side runner under the door.

I think the next step is calling a buddy with a scan tool and laptop.

Thanks to anyone who can chip in!

[richtazz]

Does it spit and sputter or just quit like a light switch was turned off?? When the car dies, does the tach drop to zero and the trac-off light come on just before? If so, the crank position sensor may be bad. Any security lights coming on?

I would also check all the grounds and battery cables, as resistance increases with heat.

[BEN_97GT]

when it dies its a rough spit & sputter for a few seconds.

I just tested the TPS with the key on and the engine off it reads 0.555V normal position and 4.21V WOT (hits 5.55 for a split second and comes down to 4.2) BUT...
start the engine and .0555 is idle, 0.9V and the engine is hitting 4K and the rev limit kicks in.

the pedel does the same thing, 1/4 to 1/2 pedel and it is WOT

Computer or sensor?

[BEN_97GT]

One more thing, the car is now starting to diesel when I try to turn it off. Still not driving around just test run in the driveway.