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Tuning 99 GTP stock

tomtom123

tomtom123

New member
I have a 1999 Grand Prix GTP that is stock other than AL 104's and a 2.5" catt'd downpipe. I am considering getting an Overkill tune, but is this the right step? I want to get a tune and then work on saving up for a MPS with 3.5" pulley, or maybe even 3.4". My car has about 192,000 miles on it. I did a tune up on it a few months ago and put the normal plugs back in it because some of the plugs I pulled out of the car were destroyed. After a month ish with the new plugs some of them were destroyed so I replaced them all with AL 104's because they were cheap and the car was running lean so I thought maybe that would help. Then I found out I had a bad boost bypass solenoid and replaced that so I don't really have the issue of running lean anymore. But I still get plugs that randomly become destroyed and I'm not sure why. For example, after I fixed the boost bypass solenoid I had a cylinder 3 misfire, and replaced the plug. After that I randomly got a cylinder 4 misfire, and replaced the plug. Recently I had a cold that read something like cylinder 5 is starting to try to misfire. I'm not sure why random plugs are being destroyed. I have a few pictures on my photobucket of the pictures. The most recent picture was the plug from cylinder 4 when it was misfiring. But it wasn't misfiring bad enough that the car was acting up or the CEL was flashing, it just would misfire enough that it popped a code saying "cylinder 4 is under misfire conditions" basically.
http://s1334.photobucket.com/user/thomas_creg/library/?sort=3&page=1
So I'm wondering. Does anyone think a tune would help my car with this issue in any way? Because to be honest, I'm not sure why it keeps eating spark plugs. Colder plugs or regular temperature plugs the thing just destroys them all. Thanks in advance for any help =)
 


Chances are you popped a few pistons.

AL104 are too cold for a stock pulley, but them being destroyed is not because o that, but more of because something is hitting on them (Part of the piston.) Are you using 91 octane at a minimum?

Seeing that, I'd fairly well guess that your engine is fubar.
 
How would I know if I "popped a few pistons"? My car seems to run fine, and the reason I went to AL 104's is because it was running lean and I was told that could help to keep it running a little colder and keep it from destroying the plugs. Now that I fixed the lean issue, I don't have to worry much about it burning plugs. But that doesn't explain why it keeps ruining spark plugs? I'm not sure what to do since this is my only car and I don't have the money to buy a new one. Hm. Not quite sure what to do here.
 
Look at your spark plugs, they're smashed, it usually means that your pistons chipped. You car may run fine, but if the plugs are getting smashed like that, it means something, in the cylinder, is smashing the spark plug, usually this is a part of the piston.
 
If you are down for a drive I could tune your car for $50. My old car had plugs like that and I had 3 chipped pistons
 


I'm pretty sure, then, that all of my pistons are probably messed up since one time I had cylinder 3 plug that got messed up, cylinder 4 plug, and cylinder 5 plug messed up. So far those are the 3 I've had problems with. And each one was only once I think. What would cause the pistons to come up and hit the plug like that?
 
It doesn't come up and hit the plug, it chips and send a part flying on the plug and valves and everywhere.

What happened here, is that you had a lean problem, lean is bad, if you went hard on it, or if you used 87 octane as well as the lean condition, you popped the pistons.

Your pistons probably look like that.
engine1.jpg
 


If you're going to swap the motor get an N/A motor from a JY and use the bottom end, then use the top end of your existing engine (Assuming it's still usable) and topswap it and end up with more power than before. Topswap = Moar Powerrrr. Moar horsies = go fast. :th_biggrin2:
 
I think I remember reading somewhere on the GP forums that it is more powerful topswapping the N/A with the GTP top because the N/A engine had higher compression, but it was a lot tougher to get the tune right
 
Yeah the higher compression bottom ends will give you nice gains in the power department. Nothing on these cars is really that hard to figure out. So if you have to replace an engine and want to get something with some nice power gains top swap it and get some headers and you'll be happy.
 
You're in MI there are quite a few there that have the know how. If you want to drive down here we could do a motor swap in a day.
 


I'd just keep driving it then. A car with chipped piston's will run and drive just fine but may use some oil.
 
Maybe if I can save up some money over the summer when I have the summer off of classes I'll see if I can get a N/A 3800 and do the top swap. If I can get a reliable good shape engine, I want to get a tune so I can drop a pulley size or two. I was thinking going to a 3.5 on my car because a lot of guys say it doesn't make it much less reliable than stock. But right now I a tune and a MPS away from that
 
tomtom123 said:
Maybe if I can save up some money over the summer when I have the summer off of classes I'll see if I can get a N/A 3800 and do the top swap. If I can get a reliable good shape engine, I want to get a tune so I can drop a pulley size or two. I was thinking going to a 3.5 on my car because a lot of guys say it doesn't make it much less reliable than stock. But right now I a tune and a MPS away from that
Click to expand...

If you install a higher compression bottom end, you will want to scan it and do supporting mods before dropping a pulley size. The higher compression bottom end with a stock pulley will be similar to running a stock engine with a smaller pulley.
 
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