Sputtering under full boost

[91gst]

Ok well I have a 91 GST with about 69xxx miles on it. I just changed the valve seals because it was burning oil, and I put a new headgasket in. The car is still burning a little oil on start up but then it goes away. It passed the emissions test which surprised me too. But anyway, under full throttle the car will sputter and buck. I checked for boost leaks and Im pretty positive that thats not what it is. I eliminated emission lines when I changed the seals on the head, could that have anything to do with it? Also at partial throttle maybe around 7 or 8 psi the car pulls hard and doesnt sputter at all. Its only when I really get on it. Does anyone know what it could be? Thanks in advance.

 

[TSIfreek]

I have the same problem but I think I have a boost leak somewere. I would make sure all your ignition components are in good shape. High Boost puts alot of pressure on the ignition system and can make the engine miss under boost. Very common problem on this board.

 

[quiXilver]

I have the same thing going on right now, exactly. I just changed my valve cover gasket also and put a bigger hose going to the BOV->Intake manifold. That's when mine started. I think it's the wires 'cause they are in bad shape. I'm gonna try that and see what happends. I'll let you know if it fixes it.

 

[1fast97gsx]

I had some corrosion on my ignition module and my car would miss under high boost. Cleaned the terminals and all was well.

 

[quiXilver]

I had some corrosion on my ignition module and my car would miss under high boost. Cleaned the terminals and all was well.

Oo..where's that?

 

[pianoman]

I have the same problem although it studders once at 5500 and then goes boom at 6k, was thinking its possible the 02 sensor since it was dead, or the coil pack, which is in the worst possible spot.

 

[TurbochargedJt]

I also have this problem once I past 11psi it will start to buck and sputter...It really sucks. People have tried changing fuel pumps, rails, filters, etc. Different things seem to work for different people. I guess the ignition is the next thing I'll be looking at.

 

[91gst]

Yeah, im kind of leaning toward it being the turbo because its the original turbo, it smokes a bit on start up, and is especially "whiney" when the car is still warming up and Im driving. I let the car warm up until it gets to the first line on the thermostat gauge and then I start driving and building any boost pressure it whines quite a bit, but once its warmed up it goes away. Ill check my ignition components first and then Ill check the turbo for freeplay. Thanks for the replies guys and good luck with your own cars.

 

[JwUoNoG]

Have you changed your plugs recently? Bad plugs caused my car to sputter under boost.

 

[quiXilver]

Have you changed your plugs recently? Bad plugs caused my car to sputter under boost.

Funny you say that. That's when my problem started! I replaced my plugs/valve cover gasket and that's when I started having the problem...

 

[RiffRaff]

what plugs/wires were you using before the problem occured?

 

[quiXilver]

Well, I just replaced my wires, and it still does it.

The only other thing I did was make the hose going from the BOV to the intake larger. Would that have anything to do with it?

 

[mrgsdsjg]

I'm having a very similar problem, i'll try cleaning the ignition thing, but mine just started, i have 5k old bosch (platinum?) plugs and new wires. Mine does not always sputter and buck though, sometimes it does it under full load and sometimes it doesnt. Another thing mine will do it at partial throttle, (just enough throttle to spool to 9-10 psi. I originally thought this was fuel cut but my air/fuel guage says im running rich. Another thing, its been getting worse, i use to run 13-14 psi, then i had to start decreasing it cause of this problem. I'd lower my boost and it would go away for a few weeks, turn up boost and it would act like crap. Any body got any more advice other than that ignition cleaning?

 

[andymoraitis]

I'm having a very similar problem, i'll try cleaning the ignition thing, but mine just started, i have 5k old bosch (platinum?) plugs and new wires. Mine does not always sputter and buck though, sometimes it does it under full load and sometimes it doesnt. Another thing mine will do it at partial throttle, (just enough throttle to spool to 9-10 psi. I originally thought this was fuel cut but my air/fuel guage says im running rich. Another thing, its been getting worse, i use to run 13-14 psi, then i had to start decreasing it cause of this problem. I'd lower my boost and it would go away for a few weeks, turn up boost and it would act like crap. Any body got any more advice other than that ignition cleaning?

Get those platinum plugs out and replace with a set of NGK's. 4G63's HATE platinum plugs.That should solve your problem.

 

[Goobdog]

Mine just starting doing this as well. It does it at partial throttle sometimes and full throttle it seems like right when it gets to 15-16psi. It just started doing it out of nowhere. It has new plugs, wires and 0 boost leaks. I checked for boost leaks earlier and came up with nothing.