[catalina_dream]

I have a 1999 Grand Prix GTP. It has developed a new symptom. During the course of communting home from work, the car will seeming miss or stumble. It will then light up the TCS OFF and the tachometer goes dead. No other symptoms after this, and it seems to run OK. If you stop and restart the car, the tach comes back and the light is off. What gives??? Is there a sensor that is starting to die? No codes have been thrown at all. Any help would be appreciated.

Thanks - Kevin

[catalina_dream]

The car's condition has progressively gotten worse. The car would not idle very smoothly, and if driven long enough, would miss enough to kill the tach and light the light, as above. Took it to a friend's shop and had it scanned on a snap-on hand held scanner. "Nothing" but a bunch of recorded #1 cylinder misfires. No other irregularities recorded, up until this point never lit the check engine light either. Cleared the codes, and could not get the car to record anything while we had the scanner on it. Drove home, same conditions returned. I decided to drive it until it lit a light with a code that we could trace. During a rainstorm, the car actually died while driving it. I coasted safely into a parking lot and the car restarted fine. Fast forward to this Monday, car finally lit the check engine light. OBD 2 code for #1 misfire, nothing else. Changed plug wire, nothing. Changed plug, bingo!! Old plug (30,000 miles on NGK) was shot, idle smoothed out, problem solved (new plugs needed). NOT!! Car died again while driving. Just shut off. Restarted fine. I have no idea where to go next. Any help is greatly appreciated.

-Kevin

[LPete]

If you can't get it to act up when testing you'll end up guessing.

With that said, it sounds like you have (had) two problems. If the misfire is gone, you must have another problem making it stall. If it doesn't set a code, and only does it randomly, good luck. A crank sensor would be a good first guess. There are lots of other possibilities -- wiring, ignition module, computer, ignition switch, fuel pump (not likely)...

The only way to be sure is to have test eqipment on it when it acts up. Good luck!

[catalina_dream]

LPete: Thanks for the tips. I really hate to start throwing parts at it. I may just wait until it dies or sets off another code so that I know where to start. I posted here hoping someone else has had a similar problem.

-Kevin

[Cammer-6]

You are going to think its crazy but try replacement of ignition switch.
Had the same problem with sons 97 GTP.
It would die and restart sometimes some accessories wouldnt work.
I used the test light and started tracing the fuel pump feed back to the pump
and found sometimes it would lose some voltage.
After we traced the fuel pump feed back thru the interior,I decieded to put a real VOM on it and wella it was only 7 volts.
Funny thing is it was sometimes alittle higher so the fuel pump would put out enough.
The ignition switch as 2 seperate circuits so this is why most stuff still worked.
It wasnt a bad job replacing it,need a torx I think.
Buy the Delco switch from a Delco jobber not the dealer and save about half.

I have a new still in wrapper complete factory service manual set left from my 99 GTP.


Ill take $100 for the manuals shipped in US.
I loved my stock 99GTP much more than my sons totally modded 97.

[catalina_dream]

cammer-6 : Thanks for the tips. Did your son's car die while he was driving it? Just seem to shut off? Why would the car shut off from a lack of fuel pressure? Is it a "fail safe" built into the ECM so that the car does not run too lean? I will be checking your suggestions after I finish replacing the rest of the plugs that I bought. If I decide to keep this car, I may take you up on your offer for the books. I'll PM you and let you know.

Thanks - Kevin

[Cammer-6]

No amount of "failsafes" can over ride the fact that fuel pump needs power to pump fuel.Yes it could at times shutdown while running for no apparent reason.
It hasnt failed since the replacement of switch,I think that was about 2 yrs ago.
Now the GM reman tranny is another story. #5 is going in as I write.OUCH!

BTW My 99 had a problem with the positive lead next to the battery.
The cable was so corroded inside that it swelled up the insulation.
Check that too. It will look OK on the outside but wont get proper amount of current thru the corrosion.

[WW3]

I had a 94 Bonneville with the 3800 V6 and it had the traction control feature and what basically it did when activated was to drop out cylinders by cutting off the primary to one of the coils in the coil pack(3 of them).So when the ECM sensed a wheel losing traction under accleration it would cut power to the the drivetrain that way too.Now, I never had the TCS light come on but I did have it run like yours did and it ended up being one of the coils in the coil pack was bad.
So, I'm not familiar with the ignition system of the 99's but if it has coils like the 3.8 liter then maybe a coil is bad in yours too.