Thread: Issues " Grand Prix GTP not starting correctly "

Well I finally feel I have found the problem with the " Starting issue when Hot " I will drive it a few days to make sure. I drove it yesterday after I worked on it and got it hot and then shut it off for about 10-15 min and then started it up, it started right back up. I started it 4 more times when it was hot and no problems. I am sure that no diagnostic test equipment would have found the problem. I thank everyone on the forum for input and help.

Just to clarify the initial problem. This is the 2004 Pontiac Grand Prix GTP Supercharged motor. " The starting after the car had run for awhile " The car would not start. The motor would turn over and then even when I let off on the key it would want to keep turning over for a few seconds. This is important as other posts indicated other problems. The car would NOT start even if the Gas pedal was pushed as the issue was NOT the Throttle Body carbon build up " as others have experienced " After the car had finally started it ran PERFECT. Here is all that I did to try and fix the car.

1) Due to the car turning over even after the Ignition Switch was let go and the motor kept turning over, I replaced the Ignition Switch and theft module, which made sense? THIS DID NOT FIX THE STARTING ISSUE Please note on this issue, some have reported that the switch could cause the issue. The switch in my case was even removed a second time and throughly cleaned and inspected. The switch is not an issue with symptoms like this even though other reports claim it is.

2) I changed the Starter as some thought the issue of the motor kept turning over could be due to the starter. THIS DID NOT FIX THE PROBLEM

3) With further testing I seen a variation in fuel pressure when the car did not start correctly, I had the fuel pressure gauge hooked up on the Schroeder valve doing some testing and the other person helping me noticed a drop in the fuel pressure. Well after a week of further looking and thinking, I replaced the FUEL PUMP. DID NOT FIX THE PROBLEM

4) I kept thinking over and over, HEAT HEAT HEAT, well the first thing that came into my mind was " the cam sensor " as others had had a similar issue with it and it did not through a code. I changed the cam sensor DID NOT FIX THE PROBLEM.

5) Kind of out of order but I had the car scanned with the NEW Snap On Scanner and NO CODES WERE PENDING OR PRESENT.

6) Well after a LOT of money spent and still the thought of HEAT on my mind I turned to one of the last thoughts in my mind. CRANK SENSOR, well I had to do it, even though it was not a talked about topic on the forums of a problem like this I would need to get it out of my mind. The Crankshaft Position Sensor in my case was NOT EASY as for some reason it seemed to be rusted on. I broke two extensions getting the bolt out, but finally came. The one area that my friend noticed was some metal shavings on the pulse pulse ears, but to me it still would not cause the issue of starting. Got the Crank pulse sensor replaced and drove the car the next day.

END OF STORY. The car has started and has ran ok. The Crankshaft Position sensor is a HALL EFFECT Sensor and can cause issues like this, but normally is not noted on Bulletin boards on causing this type of issue.

If you ever have an issue like mine, please make sure the issue is exactly like mine as the TB is a common issue, but the type of issue I had is " even though similar it is not the same issue "

Thanks !

Even though many said it could not bee, I think I found the col pert and so far it is running and starting ok. I will run it for a few more days and then post the final word on this story.

In my case the Crank Shaft Position Sensor was NOT easy to get off, broke two 1/2" drive extensions and also had to heat it up some. It was all worth it and hopefully with lessons learned for everyone. thanks again everyone for your input. I ran the car again today for over 100 miles and started it a few times and NO PROBLEMS AT ALL. I have even seen an increase in mileage !! as we all need now.

Originally Posted by offroadfury6

dang dude well congrats on urs being fixed...my issue seems it wants to missfire on startup whenever it's COLD. and I drove for months with no codes, one day I put some lucas fuel injector cleaner in it and bam it threw P0300 code. CPS has been changed, plugs, and wires so far, still missfiring...

::Sigh::

Hi,

Well you may have a much smaller issue then I had, HOPEFULLY. If you get a chance try and find another coil pack and try that. I know many that I have fussed with myself and found out that most of the GM 3800 coil packs are the same, the number on top mean nothing other than the factory spark plug configuration. I just changed my neighbors out a couple months ago, so I have seen exactly what you have mentioned.

I have also had to chanter NEW plug wires a few times Yep brand NEW plug wires.

I have seen one more issue, hopefully that is not your issue. The car was a Buick, but it had the 3800 Series II motor. My neighbor wanted me to test the car out, I drove the car and it ran good, but when it shifted it would not shift into high gear and it would start missing at about 3000 rpm. I mentioned the transmission was not shifting right, they took and and had the transmission checked out and found out it had a bad shaft in the transmission. After the transmission was fixed the car ran fine.

Many things can cause problems !! Keep in touch and let me know how you come out?

I have just gone to a junk yard and picked up a whole coil pack, all three of them for a few bucks. The coil packs seem to work through many years on the GM 3800 motor. The plug wires seem to have caused more of what you have described as far as missing. If it is WET then I have seen the coil packs really cause some issues. Where you located??

OK, sorry that the coil packs did not make some difference. Let's try and get back to the basics of the issue. Missing. You may need to refresh my memory a little.

1) the car is missing when pulling up a hill some?

2) Does it miss more when wet?

3) No codes come up or have come up ?

4) Have you had it checked with a Scanner like a Snap On type Scanner Not just a normal scanner. I have the normal scanner, but does not detect a lot of the other functions that could be causing you the problems.

5 ) If you changed plug wires, did you put the good ones on the car like the NAPA or just a replacement brand? I had to change mine 3 times as the plug wires even though brand NEW just were JUNK.

6) Not highly recommended, but I have seen others start the car and then spray a light mist of water over the engine to see if they get any missing, but again with so many sensors on a car it is not highly recommended.

7) Is the car shifting OK? through all the gears?

8) I had a spare coil pack module which is under the coil packs, I even changed that on mine, but I do not recall the symptoms of the coil pack module effects on a symptom like yours. I would think it would either work or not work. Some say heat can cause the coil pack module to malfunction. I made sure mine was clean and then put some heat sink compound on it.

9) When car misses, 99% of the time a code would come up and give you a route to follow to find the issue. What year did you say your car was??

Just thought more on the code you talked about coming up

Common Problems That Trigger the P0300


Worn out spark plugs, ignition wires, coil(s), distributor cap and rotor (when applicable)
Incorrect ignition timing
Vacuum leak(s)
Low or weak fuel pressure
Improperly functioning EGR system
Defective Mass Air Flow Sensor
Defective Crankshaft and/or Camshaft Sensor
Defective Throttle Position Sensor
Mechanical engine problems (i.e.—low compression, leaking head gasket(s), or valve problems
Common Misdiagnoses

Fuel Injectors
Oxygen Sensor(s)
Power Train/Drive Train problems
Polluting Gases Expelled



You can unhook the Mass Air and start the car, see if that does anything?

Wish I was closer I would try and help out more !

Hi,

Still sticks in my mind the scanner like Snap On will do you some good. I am not sure how much you get into the engine, but with some of the problems you are having seems like the Injectors can cause some issues. Have you ever put a can of Sea Foam in your gas tank and ran it? I do it every so often, it has kept the injectors clean. I have a set up " an older GM fuel rail that I use to check the injectors " I have pulled all my injectors out and put them on the fuel rail and individually tested each fuel injector for the spraying. I have a solution I obtained off the internet I used to clean the injectors.

Missing when not wet, I would feel takes away the plug wires and such. The car being a 2006 so it is a series III, same as mine then. Bad fuel, crap in the fuel all can cause the fuel injectors to act up. I had to replace all my fuel injectors on my 2004 GTP as it sat for awhile and the injectors gummed up and I could not even clean them out. Luckily the injectors on the Supercharged 3800 are easy to get to and change.

Hope you get to the bottom of the problem soon as I am sure you are getting Tired of wondering what the problem is.