Thread: 99 GTP Hesitates / Dies while driving

Hello everyone. My first post here and I need some advice.

I changed an alternator about a week ago on my 99 GTP (220K Miles) and that's when my problems started. The first time out, the engine started over revving, about 4000 RPM going 55 MPH. I was able to limp back home and take it to my local mechanic. He couldn't find anything wrong and told me the competer was just resetting itself. Said it was OK to drive. Took it out later and it proceeded to die approx 10 times in a 10 mile trip. It would die randomly going about 30-40 MPH. It will start back up easily in neutral. I finally got a error code saying the MAP and MAF sensors were bad. Changed both. the over-revving stopped but the dying problem has persisted. Went back to my local mechanic and this time he said he found (and fixed) a vacuum leak. Reset codes. Car was OK for one day and has been acting up again. It now hesitates like the ignition is turned off going about 50-60 MPH for a split second then will resume OK. This morning I noticed some bucking going about 30-40 MPH.

Anyone have any clues. I asked my mechanic about the Catalytic Converter but he didn't think it was the problem. there are currently no error codes on being displayed.

Get a voltage meter and make sure your cars not OVERCHARGING IE: over (14.5 volts)...but check to make sure the plug (two wire) going into the alternator isnt unpluged or the wires are frayed.

Otherwise have your mechanic throw a scanner on to check for cam/crank signal abnormalities, fuel pressure, or even a bad gas filter

Further developments. When I accelerate on the expressway, I can see the boost go up. Unfortunately it does no go down. It gets stuck at about 5 bars and the engine will rev at about 3500 rpm (1700 is normal). I touch the gas an the car jumps and RPM goes further up. Could it be the Boost pressure controller or solenoid acting up?

I found some information on the net yesterday saying if the P0101 trouble code persisted after changing the MAF sensor the problem could be related to the PCV valve. I figured for 3 bucks it's worth a try. Go figure. The service engine light was off before I left the garage. The car did not miss a beat this morning and gas mileage was over 25 MPG. Really good since it was snowing near Chicago and road conditions weren't the best.