Engine stutters hard

[RacerX03]

Ok here we go. car works great and at 100k miles it seems like it falls to pieces. anyway here is my problem. when easing on the throttle the car will run fine but when any extra throttle is given to make the boost go up the engine starts to stutter hard. Really Hard. and it seems to backfire. so far i've replaced the fuel filter (made it a little better), replaced the ignition coils. also helped very little so i went to put the old coil back on the car and test drove it and it seemed to run a lot worse with the old coil so i put the new on back on. the plug wires are on their way i had to order them and i'll get to test them out. Also i tried to bypass the fuel pressure regulator by unplugging the hose and making it run full open. For 2 runs around the highway this seemed to almost completely eliminate the problem (thats when i put the old coil back on after that cause i thought it was the pressure regulator, but that made it worse) anyway to make a long and frustrating story short the car still runs horrible and stutters very hard under any acceleration, 75% OF THE TIME, there is a chance that there is no effect and it will do perfect.

anyways if the plug wires don't help i have no idea what to do next. and i hate playing the guessing game with my money. so any suggestions would be greatly appreciated thanks.

p.s. i forgot to mention i have replaced the spark plugs and by the time the car hits around 5500 rpm it straightens out and its hard to start. or was i'll know in the morning if the coil helped there.

 

[Gromit]

Ok here we go. car works great and at 100k miles it seems like it falls to pieces. anyway here is my problem. when easing on the throttle the car will run fine but when any extra throttle is given to make the boost go up the engine starts to stutter hard. Really Hard. and it seems to backfire. so far i've replaced the fuel filter (made it a little better), replaced the ignition coils. also helped very little so i went to put the old coil back on the car and test drove it and it seemed to run a lot worse with the old coil so i put the new on back on. the plug wires are on their way i had to order them and i'll get to test them out. Also i tried to bypass the fuel pressure regulator by unplugging the hose and making it run full open. For 2 runs around the highway this seemed to almost completely eliminate the problem (thats when i put the old coil back on after that cause i thought it was the pressure regulator, but that made it worse) anyway to make a long and frustrating story short the car still runs horrible and stutters very hard under any acceleration, 75% OF THE TIME, there is a chance that there is no effect and it will do perfect.

anyways if the plug wires don't help i have no idea what to do next. and i hate playing the guessing game with my money. so any suggestions would be greatly appreciated thanks.

p.s. i forgot to mention i have replaced the spark plugs and by the time the car hits around 5500 rpm it straightens out and its hard to start. or was i'll know in the morning if the coil helped there.

When was your last boost leak test done?

 

[gsxtacy]

After the answer regarding the boost leak test....

Post up a pic of all four spark plugs, as clear as possible on the electrode end....
labeled 1-2-3-4 in corresponding order so we can see which cylinder IF NOT all cylinders are experiencing the same miss.

Do you have any CEL's?

 

[RacerX03]

ok i'll do my best to get a pic of the plugs on here but i will examine them again when i change out the plug wires as soon as they arive. On a good, well i guess its good in narrowing it down, my check engine light came on after it stuttered as i pulled onto the highway, so i'm going to hook up the handheld to it and see what it says. also about it being hard to start, this morning i went out to start the car and it fired up on the first try so i guess replacing the coils helped a little on that end. and as far as the boost leak test goes i haven't had one done in a while so i should stop by the mitsu place and get that done. does anyone know right off hand how much it costs?

Anyway thanks for the help so far guys i will keep u all posted on the situation.

 

[Skunked tsi]

I would be willing to bet your awaited plug wires will fix your issue. Also I am willing to bet that the code you will end up pulling will be something on the lines of Cylinder 1 2 3 or 4 miss fire.
Tyler

 

[RacerX03]

and the winner is skunked TSI i just came back from getting the cel code read and sure enough its a miss fire on cylinder one and my plug wires are in the mail. also i do believe the coils had something to do with it also since my car starts on the first try no matter what now.
well soon as they come in i'll let u know whats up

thanks for all the support guys

p.s. i downloaded the page on how to make your own boost leak test thing and i'll be trying that out this weekend just for the heck of it.

 

[Spyder4g64]

Same thing happened to me this morning. I was leaking air at the throttle body & the map sensor (bad O-Ring). ...made a world of difference. Try the boost leak test, it can't hurt.

 

[OTDlifer]

i have almost the same problem. i have a 97 GS-T auto, and it drives fine under normal driving, but as soon as i get any boost 5psi or higher, it just sputters and dosent want to do anything. should i change out my wires too??? my 255 pump, 550 injectors, fuel rail, coil packs are all new. i could change the wires and plugs just dont wanna buy anything untill i know

 

[Skunked tsi]

i have almost the same problem. i have a 97 GS-T auto, and it drives fine under normal driving, but as soon as i get any boost 5psi or higher, it just sputters and dosent want to do anything. should i change out my wires too??? my 255 pump, 550 injectors, fuel rail, coil packs are all new. i could change the wires and plugs just dont wanna buy anything untill i know

Thats what I would suggest, along with plugs.
Tyler

 

[RacerX03]

update:
Well my plug wires came in and i installed them. The unit idles good, BUT the stuttering still persists. When i unhooked the hose controlling the fuel pressure regulator and drove it like that it almost ALMOST got rid of the problem, and it got worse when i put it back on, so i plan on doing the boost leak test this weekend to see if there are leaks. Also the manual says that i will have to start replacing the fuel system components next if the boost pressure test doesn't fix it so here is my next question to you.

I was wondering if it would be ok to go with a walboro 255 fuel pump with the injectors stock, i know i will need to upgrade the fuel pressure regulator to one that can cut back on fuel pressure as well as increase so if you could recommend one i'd greatly appreciate it. Oh yea, is it true that if i put the 255 on there that it has to have more power run to it cause the wiring harness there looks just fine.

And sorry to ask yet another question in one post but i've searched and i'm not sure what its called cause boost creep doesn't sound like it, but sometimes "rarely" when i gas it the boost pressure goes up fast but the car doesn't really have any power and it just gets loud. any takes on that would be appreciated also.

I just want to thank everyone also for putting up with me being a pain in the ass but i just want my baby to run good again.

 

[Gromit]

update:

And sorry to ask yet another question in one post but i've searched and i'm not sure what its called cause boost creep doesn't sound like it, but sometimes "rarely" when i gas it the boost pressure goes up fast but the car doesn't really have any power and it just gets loud. any takes on that would be appreciated also.

Definitely do the boost leak test next before buying any more parts. Your description points directly to a leak. Fix any you find & then look at what you want to upgrade next. The Walbro 255 (rewired) + an Import Evolution Aeromotive AFPR kit is a great upgrade, if your goals warrant it. First & foremost, get your basic maintenance taken care of & then you can look at upgrading.

 

[OTDlifer]

well my plugs and wires are on order. but if my car drives fine under normal conditions, why would it studder only once the turbo boosts 5psi and higher?? and i found out the other day that when i rev the engine high to where the turbo would start to boost, it studders again. so would the plugs and wires work fine normally and not under high boost??

 

[gsxtacy]

boost leak test
new NGK BPR6ES plugs gapped at .028"
new plug wires

and update us...

 

[kazzam]

I think that your problem is in your tuning. I think that your stock FPR is overran when you start hitting boost which results in too much fuel, which results in your car doing the rodeo. I suggest you run lowest boost possible and start cutting back your fuel to see if it changes. I am pretty sure it will. Have you loged your car and looked at the front o2 readings when this bucking starts?

Just to test it out and make sure that it is in the tunning, you can either disconnect your afc or zero it out and throw some stock injectors in there. See if the same problem persists.

Oh yes, and make sure you have no boost leaks!