I have a 2002 GTP that cuts in and out at about 122 mph. I am at a loss as to what is causing it. For mods, I have a cold air induction, Autolite 104 spark plugs, DHP Ver 1 PCM, and a 3.4 pulley. For exhaust, I have a Catco high flow cat convertor, u-bend and resonator were replaced with straight pipe, along with 2 Flowmaster 40 series mufflers. The only pipe that is 2 1/2 is the U-bend/resonator replacement. The rest of it is stock piping. It starts cutting out at around 123. Before I installed the pulley, it would cut out at 123 then stopped after installing the plugs, but wouldn't hit any higher speeds. Once in a while I would be able to hit 129. After installing the pulley, it is cutting out at 123 again and will not go any higher. I do have an enhanced Autotap if it will help any. If I am correct, wouldn't I have a SES light if I had a true knock retard? I'm at a loss on this one. Thanks
2002 GTP problem
Jan 01, 2005
8 Replies
Do you think the problem is really speed related or is it rpm related?
Could be a speed/rpm limiter? I have a '96 grand am that cuts out at
104mph. Did it once and scared the crap out of the wife who wanted to know exactly what I thought I was doing at that speed.... :)Hey Johnnie Lightning,
What highway are you on? I'd like to avoid it if possible.
How often and how many continuos miles do we crusie above 122 mph?
========= Harryface =========
1991 Pontiac Bonneville LE 3800 V6 ( C ), Black/Slate Grey _~_~_~297,525 miles_~_~_~_~_~_~_U.S.A._~_~_~_~_~_
~~~The Former Fleet ~~~
89 Cavalier Z 24 convertible 78 Holiday 88 coupe 68 LeSabre convertible 73 Impala sedanAlex, the reprogrammed pcm has the speed limiter removed
All GM cars since 1993 have a computer program limiting the speed to the speed rating of the tires that the car was assembled with.
This was a particular issue with Firebirds and Camaros with the V8 engine. Two versions were made. One with the Z rated tires which would limit the speed to 149. The other was assembled with S rated tires with a speed limit of approx. 112.
Check the speed rating of the original tires and find a web site that gives you the speed rating of the tires Bob K
That's ok, this car shouldn't be visiting those speeds anyway. :)
Why do you want to go that fast? Man, I've had my 2000 GP up to 100 once for about a second on a long stretch of straight highway and that was scary enough.
Bob, the reprogrammed computers (PCM) for the Grand Prix have the speed limiter removed.
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