Buick grand national has a stutter

[Theserg2008]

I have a 1985 buick grand national has upgraded 65mm turbo I think, 42lb injectors. Upgraded walbro fuel pump turbo tweak chip. And has a 86-87 ecu. The issue I am having is when I first turn it on and drive it around runs great just has a little stutter under super heavy boost. Then I park it and come back to it after 20 minutes and the moment I touch the gas it stutters bad to the point where it is undriveable. Like it’s so bad it struggles to get to 10 mph. So I limp it home then the next day I go to turn it on and runs great. I’m completely lost. Checked tps it’s good, map sensor is good, vacuum lines I think are good(I followed a diagram for the vacuum lines) spark plug wires got them brand new, spark plugs are brand new and gapped to .32. Maf I checked it by unplugging it while it is running and the car dies, so I’m guessing that’s good. I’m just really lost please any help is appreciated!!!!

 

[Chuck Leeper]

Maf I checked it by unplugging it while it is running and the car dies, so I’m guessing that’s good. I’m just really lost please any help is appreciated!!!!

A "tap test" on the maf. At idle, tap on the mf with a screwdriver handle. Stumble?
Shouldn't quit after unplugging it.
What are the Scanmaster, Powerlogger data readings?

 

[SCOOBY DOO]

Out beating on it when it isn't running right...seems to be an epidemic around here. Like Chuck says, give us your SM reading with the engine at operating temperature in Park and any PL file you have.

 

[Chuck Leeper]

The issue I am having is when I first turn it on and drive it around runs great just has a little stutter under super heavy boost.

That's the cyl heads trying to leave contact with the head gaskets.....

 

[Theserg2008]

A "tap test" on the maf. At idle, tap on the mf with a screwdriver handle. Stumble?
Shouldn't quit after unplugging it.
What are the Scanmaster, Powerlogger data readings?

Ok I’ll do that. Unfortunately I do not have a Scanmaster which does make diagnosing a lot more difficult.

 

[Theserg2008]

That's the cyl heads trying to leave contact with the head gaskets.....

But what I find odd is it doesn’t do it all the time. It will run good with very little stumble, then I let it sit turn it back on and it stumbles back to where it’s undrivable. I’ll definitely consider it maybe might have to re torque the heads down

 

[Theserg2008]

Out beating on it when it isn't running right...seems to be an epidemic around here. Like Chuck says, give us your SM reading with the engine at operating temperature in Park and any PL file you have.

I unfortunately dont have a scan master, but once I get payed I will defiantly try to invest in one

 

[Chuck Leeper]

But what I find odd is it doesn’t do it all the time. It will run good with very little stumble, then I let it sit turn it back on and it stumbles back to where it’s undrivable. I’ll definitely consider it maybe might have to re torque the heads down

That was a bit of sarcasm!
Beating on it without knowing WTF is going on is, as explained. a good way to blow the gaskets out.

 

[Theserg2008]

Update: car will run good with a/c off but when I turn a/c on it wont go past 3000, when it hits 3000rpm it pops really loud

 

[Chuck Leeper]

Update: car will run good with a/c off but when I turn a/c on it wont go past 3000, when it hits 3000rpm it pops really loud

Continue on.... You'll find the problem. It'll be in the pile of parts, right next to the crank, when it blows up.
A sure candidate for membership in the DOTCC.

 

[dynoman]

Shouldn't quit after unplugging it.

This ^^^ and what is super high boost ? What plugs ? Close the gap down to .025"

 

[Theserg2008]

This ^^^ and what is super high boost ? What plugs ? Close the gap down to .025"

So it’s a very weird issue now it’s running great no issues. Spark plugs I have them gapped at .32. I also just installed a boost gauge to see at what boost it stutters at but so far it’s running great so I’ll let you know what happens

 

[Theserg2008]

Continue on.... You'll find the problem. It'll be in the pile of parts, right next to the crank, when it blows up.
A sure candidate for membership in the DOTCC.

Dude what’s your problem I just came on here for help cause I’m very lost with this issue. Anyway I wanted to fix this issue cause on the highway cars at like 3200rpm, but the issue is with the a/c turned on at 3,000 rpm it stutters constantly. But when the a/c is turned off it runs fine. Any ideas to this issue would help

 

[Chuck Leeper]

Dude... I don't have a problem. You do.
You don't answer questions from those that have experience with these cars.
You are beating on the car without the least bit of data monitoring gear, even a boost gauge.
I stand by my comments in post # 10....
I'm done.

 

[mblum]

Dude what’s your problem I just came on here for help cause I’m very lost with this issue. Anyway I wanted to fix this issue cause on the highway cars at like 3200rpm, but the issue is with the a/c turned on at 3,000 rpm it stutters constantly. But when the a/c is turned off it runs fine. Any ideas to this issue would help

Chuck is trying to help you.

More information is needed than what you have provided so far to diagnose this issue with out just plain guessing. If the car is back firing that badly you need to stop doing that until you have at least a Scanmaster. Your playing Russian Roulette with your engine every time your doing that. These engines are not cheap to have rebuilt. My advice is to leave the car parked until the Scanmaster is installed and some data from it is provided.

The problem your trying to fix right now probably won't cost much to fix but it needs to be approached correctly with data.

 

[Theserg2008]

Chuck is trying to help you.

More information is needed than what you have provided so far to diagnose this issue with out just plain guessing. If the car is back firing that badly you need to stop doing that until you have at least a Scanmaster. Your playing Russian Roulette with your engine every time your doing that. These engines are not cheap to have rebuilt. My advice is to leave the car parked until the Scanmaster is installed and some data from it is provided.

The problem your trying to fix right now probably won't cost much to fix but it needs to be approached correctly with data.

Yeah understood, ok I’ll try to get one. Once I do get a Scanmaster I’ll let you guys know about the data thank!!