Studder @ WOT

C

Cakes

Guest
I just bought a 1986 Grand National two weeks ago and I am having a problem with studdering at WOT. The engine is a stock rebuild with ATR Stage 3A turbo, 2.5 inch stainless downpipe, 2.25 inch crossover, ATR ram air, ATR pitbull chip, 40 lb injectors, Bosch "237" FP regulator (TTA), hollowed cat, 2.5 inch Hooker exhaust, hard MAF tube, high flow fuel pump, high flow oil pump, Cloyes Double Roller timing chain. Under normal accelration there is no studder or even at 1/2-3/4 throttle there is none. When its matted from dead stop or matted while moving there is a studder like it is hitting a rev limiter. I do not have a boost gauge besides the factory one but I will say the stock one gets pegged very easily. I have not played with the adjustable waste gate at all. I know the ATR chip is pretty aggressive so I dont know if its overboost, lean condition, or bad ignition parts. Any help would be greatly appreciated. Also if and when I get it running healthy any idea of what it would run in the 1/4? Thanks again!
 
Stop now. First thing you need before attempting to mat it is a scan tool and a boost gauge or you will be looking at big $$ in repairs. If you have 40's and a decent amount of boost it could be your fuel pump since I see nothing listed. Get these before you venture on.
 
What you are experiencing is likely knock and massive timing retard. If your boost gage shows any red with a pit bull chip and you are running 93 octane, you are definately getting knock. Like intercooler said, stop now before you blow it up.
 
UNGN....I do see the boost gauge go to red when wide open. Does this mean I should lower my boost. I have been using 93 octane since I bought the car. The previous owner told me he used Sunoco Ultra 94 and there was some in the car when I bought it and it did not studder as bad but it did studder. My next mods, when I get some money, are aftermarket gauges so I can monitor my engine with more accuracy. Thanks again and and any more help is greatly appreciated. Thanks guys
 
Going into the red means nothing. I have seen stock boost gauges that pegged out at 20psi and stock boost gauges that pegged out at 10psi. First get a decent boost gauge, then get a scantool. Then replace the fuel pump with a 255lph if you haven't already.
 
put 3 gallons of 93 and 1 gallon of xylene in the tank and try that ,,ca be bought a Ace hardware for $8
 
Also might be your coil pack. UNGN and intercooler are right. You definitely need a scan tool. If you continue to drive it DO NOT beat on it. You will surely blow a head gasket or worse and you don't want to do the "worse".

As intercooler stated it sounds like your not getting enough fuel. A fuel pump and adjustable fuel pressure regulator may be in order. I see that you said you have both of these but I noticed that the fuel pressure regualtor is a 237. I'm not sure but still don't think that is an adjustable unit.

I had run the pitbull a long time ago (may be different now) and there was alot of timing in that chip for the street. You may want switch chips. I run the J Carter 3 bar map chip on the street and like it but it's expensive with the other items(3 bar MAP sensor and cable for T-Link) you need to buy. I also liked the Red Armstrong 93 chip for the street. Cost on his chips is $50 to $75 I think.
 
You realize one of the biggest Turbo Buick Vendors/Shops in the country is less then 10 minutes from your house right? :)

Sure sounds like you're overboosting if it got worse when you went down to 93 octane. Temporarily what I'd do is take the boost way down until you can get at least real boost gauge and probably a Scanmaster. Better safe then buying a new motor. What you're describing as studdering is the computer pulling timing most likely because its knocking like the police at OJ simpson's house.

If you have no clue what you're doing feel free to email me and we can meet up. Spending money on mods instead of repairs is much more fun believe me.
 
Thanks RealFastV6...and yes I do know that Jack Cotton's place is about 5 minutes from my house. I have yet to go see him but I know a lot of people who are very good friends with him. I graduated with his son from Agawam High in 2000. I am pretty good with cars so I will play with my boost when I get home from school for easter this weekend. Thanks again

PS Do you go to Mark's Auto Parts on Mondays for their car shows?? You may not know me but before I bought the GN I had a Green 1969 Firebird 400 w/ white stripes. Thanks again!
 
Originally posted by Cakes
Thanks RealFastV6...and yes I do know that Jack Cotton's place is about 5 minutes from my house. I have yet to go see him but I know a lot of people who are very good friends with him. I graduated with his son from Agawam High in 2000. I am pretty good with cars so I will play with my boost when I get home from school for easter this weekend. Thanks again

PS Do you go to Mark's Auto Parts on Mondays for their car shows?? You may not know me but before I bought the GN I had a Green 1969 Firebird 400 w/ white stripes. Thanks again!

I just had a flashback, you were on Jacks board a few weeks ago asking about the High Idle too.

Anyhow, does the car have a boost controller on it or is it using the stock solinoid?

Ive been at Marks pretty regularly for years yeah, but I have a horrible memory.
 
I am pretty sure that is has a stock solenoid(it has a electrical plug on one end and 2 vacuum ports on the other....one has vacuum hose to a "Y" that goes to turbo and somewhere else and the other is wide open) Could this be bad or....what?

Maybe we will see each other at Marks this year. I always go and I love showing my car. Just look for MA plates. Thanks again Keep in touch.
 
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