Car update with a couple questions...

So my car has been sitting since mid Jan. I hate driving it in the snow. It needs an oil change badly (got approx. 5k miles on the oil). So this weekend I'm going to do all the routine maintence on it, give her a bath and wax it up since the weather is finaly getting a little nicer around here. But the one thing that I'm still concerned about is the problem I've been having since last summer...... I'm not sure what exactly it is. I'm running the hardtop (not the Spyder anymore). Most of you already know the specs. 97 GST, 5spd, K&N filter, poly mounts, SBR FMIC (fucking huge), 16g turbo, Greddy bov, B&M short-throw w/ poly mounts, Autometer Cobalt series (Boost/vac, oil pressure, water temp), NGK plugs (1 heat range colder), Thundervolt 10.4mm wires... Anyway, I'm running around 14-15psi. Now through 2nd-5th gear i have this problem. If i give it WOT, it boosts nicely until the rpms start to get higher (like above 4500) the car starts to hesitate and jerk a bit. The motor sounds like it stuttering. I noticed in cold weather it almost never does it. In hot weather, it does it every time.

Here's what I've done to try and fix the problem.

Boost leak check (passed).
New NGK plugs.
New intercooler pipe couplers (just incase).
Started using 94 octane instead of 93 (doesn't help much).
Used injector/combustion chamber cleaner (made her smoke quite a bit, heh).
Took the MAS out and cleaned it.
Took the downpipe off and ran it (thought maybe a plugged catalytic converter).
Checked for any vacuum leaks. New EGR valve gasket.

All of this and the car still runs jittery under full boost. If i lower the boost to around 11-12 it runs perfect. I thought maybe it wasn't getting enough fuel, but I was told that you can run 16psi on a 16g with the stock fuel system. I believe i'm running lean anyway - last summer me and a few friends kind of had a gumball rally to Pittsburgh. Got there and my header was glowing red.....
So after all of this I temporarily lowered the boost until i pinpoint the problem and was staying off the throttle before I quit driving my car.

One question that i have is this - can a MAS cause this problem? I noticed before winter started, i was driving around one night and suddenly the motor started stumbling and missing REAL bad (wasn't even boosting). Pulled in the garage, popped the hood to see what came disconneced. I smacked the MAS and suddenly the motor came back to life and was idling smoothly.

So any suggestions from anyone?

What gap are your plugs at?

Sounds like fuel cut. Get that fuel system upgraded and fatten her up a big

sounds like you are knocking and losing your timing. I would bet on it. Hook up a logger and take a look. Header/turbo glowing is fine, totally normal if driven for several hours. The heat will raise intake temp significantly and really kill your timing.

97GSTSpyder, every now and again you come completely out of nowhere with these story problems, and then disappear for another 6 months....

I thought maybe it wasn't getting enough fuel, but I was told that you can run 16psi on a 16g with the stock fuel system. I

It's not pressure that you need to look at, it's flow. You really need to take a look at the mass of air you are pushing at 16psi. It could be that you are outflowing what the injectors can handle. Each car is going to flow a different mass of air at a given pressure. It depends on restrictions in the intake and exhaust track. It sounds like you have a pretty unrestriced flow, so that could be the problem.

As suggested above, plug gap is another thing to look at. It should be 0.026 - 0.028". I would also suggest running plugs that are one step colder than stock, if you aren't already.

Without a logger, it's hard to pinpoint your problem. I have see the 2g MAS break up at higher flows, which could be causing your problem. I also had a problem last year similar to yours, but it wasn't boost dependant. It turned out that condensation had formed in my spark plug wells and was arking the spark before it made it to the plug.

Do you have a logger?

97GSTSpyder, every now and again you come completely out of nowhere with these story problems, and then disappear for another 6 months....


yea i live by him and he does the same thing to me he never calls or nothing just like hides or something i dont know

Sorry lol I've been busy lately, hardly ever get on the computer anymore...
I don't have a logger, unfortuneately. The plugs that I have are NGK 1 step colder, gapped at .028. As for the glowing header/turbo, someone told me that was from running too lean, but it makes sense to be normal if running the car at long periods of time with a lot of boosting. One of the other problems i had over the summer was having the car overheat quite a bit. I believe it's because of the gigantic FMIC blocking off the radiator. Normal driving in the summer, the temp was around 200. When i hit full boost through all 5 gears it'd spike right up to 250+. So i'm thinking about saving up for a beefier radiator/fans and maybe turbo wrap. I just need to quit neglecting the poor car and drive it around after i change the oil. Hopefully I'll get around to it within the next few days.