2002 grand prix, friend's son needs help

[Kaeghl]

My buddy's son (21) has the anniversary edition of the 2002 grand prix but just the gt engine.
He has this misfire that he's been trying to chase down for half a year, he's replaced plugs, igniter, coils, I think injectors are next but he just can't seem to chase it down and he took it to a couple of shops that had no idea.

Does anybody know someone that could help him out. At this point he is half considering paying someone to do a top swap and be done with the plastic intake. So if someone wants to earn a bit of money in either troubleshooting the misfire or doing a top swap to the gtp or pulling the engine and trans and replacing it with a l67 and 4t65ehd, he is very interested.
He is in the military but is going to home for a few months and already built of funds.
So his ambitions are:

1. Get it running right.
2. Possible top swap.
3. Full engine and trans swap from gtp.
4. Turbo kit for the gt? I dunno, I guess its an option.

thanks for any help.

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[Jimy Bilmo]

Have you tried turning it off, and then on again?













Good luck

 

[Mook]

Turbocharged400sbc...@Ktj100?

 

[bikrboy128]

It's missing spark, fuel, or compression. Diagnosing that shouldn't be too hard.

As far as mods go. Turbo/rockers on the stock engine (assuming it's still ok) and pray the transmission holds together. Even on low boost it'll be faster than an M90

 

[CMNTMXR57]

When you say ignitor, you mean the ignition module plate, right?

 

[Kaeghl]

When you say ignitor, you mean the ignition module plate, right?

Oh my mistake, yeah. On my supra its just called an ignitor. But the plate under the coil packs was replaced as well on the gt

 

[bs009]

Is it constantly misfiring or are there certain conditions that it will misfire for? For example, misfiring only under heavy throttle or only when it's raining out

Is the check engine light on? Can you scan for codes if so?
There might be a Should have a 300 code or 30X code where X is a number between 1 -6 to indicate which cylinder is misfiring if it's consistently one cylinder.

 

[Turbocharged400sbc]

i never have time but i can probably provide good used test parts like an injector or two.

frankly this needs to start with a quick drive with a scanner, a few quick swaps for some "see if it changes holes" tests and finish with injector swapping

sweetest setup ever is a 97 TurBonnie stockness with a 60-1 iirc

the Tq curve was a damn vertical line at 2000rpm

 

[Kaeghl]

Is it constantly misfiring or are there certain conditions that it will misfire for? For example, misfiring only under heavy throttle or only when it's raining out

Is the check engine light on? Can you scan for codes if so?
There might be a Should have a 300 code or 30X code where X is a number between 1 -6 to indicate which cylinder is misfiring if it's consistently one cylinder.

I am told that if you just put put around it is okay but if you give it any gas the misfires start, it also gets horrible gas mileage, the last thing I told them was to check for a stuck injector.

I'll ask them for the exact codes tonight

 

[Turbocharged400sbc]

This sounds like it may be potentially a clogged cat situation

 

[Kaeghl]

This sounds like it may be potentially a clogged cat situation

pretty sure that was replaced recently, along with all the o2 sensors, but I will confirm

 

[boostedguy05]

Plug wires seated all the way?

 

[Kaeghl]

Plug wires seated all the way?

Thats a good point. The guy they bought the car from ran aftermarket wires, I sold my gtp in 2004 but I always was told that the aftermarket wires kind of sucked compared to oem. A full set is pretty cheap so i think I'll just buy a set .