Thread: My Car eats sparkplugs!

Hey guys I have a 2000 Grand Prix GTP coupe. Ok so when I first bought it I noticed it had a small miss, then I drove it for about 2 weeks and the miss got very, very bad! I pulled the spark plugs and Plug #1 on the front row of cylinders was finger loose and it was missing the electrode and part of the middle piece. I pulled all the other plugs and they were at least all in one piece there but what I believe to be the original AC/Delco iridium spark plugs! My car has 155,000 miles on it by the way. So I do a compression check on cylinder #1 and guess what? 0 psi. Shoot. All the other cylinders were in range. So me and my dad pull of everything to get the head off and go to the junkyard to get a used one. Then we took it to some shop to have it boiled and checked for cracks then had the seats done and new valves and valve stem seals put in. Put it all back together with Autolite Platinum plugs. Runs really good for about 400 miles then it started missing again. Pulled the plugs and they all looked like complete crap! Cylinder #2 in the back was missing the electrode completely and Cylinder #5 was missing part of the electrode and all the other ones were bent way out and looked like they were about to give. So I did another compression check and what a relief all the cylinders were good. This time we put AC/Delco iridium plugs in and I just got done installing that 4" custom FWI. It ran good for about an hour (BTW My gas mileage went from 20mpg to 18.3mpg after that FWI) and then when I brought it home and listened to the exhaust it sounds like its missing again!!! My dad has a scanner so that will be the next thing I do and I'll post the results.

Thanks for any help!

The only mod I have so far is that FWI I just put in. When we pulled the front head all of the front cylinders and pistons were perfect. I'll let you guys know what codes are showing asap.

4 or 5 seconds while cranking it is normal.


I'm not understanding how everything was ok on the cylinder walls and pistons when you said a peice of your #1 #2 spark plug fell into the engine while it was running. I'm also not understanding how a tuned PCM could make your spark plugs fall apart.



So your telling us that when you dissembled the engine down to the bare short block to get it hot tanked that the cylinder walls were not scared at all?? Since you had it apart you should of at least honed it and put new rings in it.


As far as the problem with the plugs i'm not sure. Other then chipped pistons or you installing the wrong plugs or installing the plugs without the washer on them i'm not sure what is going on or what could cause that.

TDCRacing,

I never removed the back cylinder heads, sorry if I made it sound that way. I just removed the front cylinder heads and bought a used one then had the used one boiled to make sure there was no cracks before the place refurbished it. I never took the engine out of my car.

I didn't think that you could remove the washer from the spark plugs? Isn't it too small to fit over the threads?

A new Idea I have, My car was totalled out from a blow to the front drivers side fender. I bought it from a Body shop that had restored it. When I took the Airbox out I see that it has been damaged and repaired with some sort of resin or JB weld type of stuff. I'm thinking maybe the PCM was internally damaged in the crash, or the original PCM was destroyed and they put either the wrong one in (say one from a GT or SE) or they put one in from a junked GTP that some kid had reprogrammed for way too much spark advance or something along those lines. Another thing that causes me to think this is that the miss seems to come and go. I was driving it right after installing the new AC/Delco plugs (OEM) and everything was working right then I decided to bring it up to 113mph for a very short period of time then when I brought it home I could here a small miss and it had the Code (Miss on Cyl #4). Then I came back and started it the next day and it didn't start missing until 5mn or so after the car was running. (Its not a Major miss like it was with the broken valve its more of a slight popping every other second or so) Then I shut it off and let the car cool down then started it and it didn't miss. I drove it a few miles to get it up to temp fully and brought it back home and it still wasn't missing? This was the last time I drove it BTW. (Also I deleted the Cyl #4 Miss code the first time I started my diagnosis and now after running it 2 seperate times the code has not come back)

Thats one thing my dad suggested too so I measured the pulley and it was about 4" on the outer edge but the belt sits down in it a little farther so I am guessing that is a 3.8" stock pulley, there isn't any numbers or brands stamped on it and its just plain semi-gloss black.

Liquifire- All I have is one of those code readers, Do you know if a guy could rent a scan gauge? How do they work and what do they tell you? Also what is a PCM Flash and Case Learn? Is there a way to tell through the numbers on the PCM if its the original or not?

Thanks!