Stutters at full boost after head gasket replace

[JayB98GST]

I blew my head gasket and a coolant line came loose after hitting a raised manhole a couple of weeks ago and had to drive the car overheated for a couple of minutes till i could find a safe place to pull over. So I had the head milled and rebuilt, and put it all back together. Everything runs fine excpet that when I get to full boost the car kind of stutters, almost like its not getting enough fuel. The car will stutter for a couple of seconds even after i let of the gas a little. Also I noticed that once it starts to stutter, if I put it in neutral and let it coast the vacuum will go close to 0 psi and then after a couple of seconds it will slowly start to go up to normal. I don't know if that means anything though. I have a rewired walbro pump and my fuel pressure is set correct. I replaced the plugs (NGK BPR7ES) and wires (Accel) after the rebuild. First i had the plugs gapped at .028 and that didn't seem to help, so then I regapped them to .026 and that didn't help either. I also noticed that when I took the plugs out, the tips were white... I guesss this means that I was running lean, but I can't figure out why. And I also did a leak test and there are no boost leaks. Anyone have any suggestions? Thanks for any help.

 

[JayB98GST]

I just had the CEL code pulled and it says cylinder #2 missfire. Plugs and wires are brand new and the firing order is correct.

 

[Quasimondo]

Make sure there's no carbon deposits briding the gap on the plugs, and that the boots on the plug and coil are properly seated. I had the same problem with a misfire problem on the #4 cylinder and it was because the plug wasn't seated at the coil even though it looked fine.

 

[tech27]

did you replace the coil pack to, also there is an ignition capacitor module located right under the coil packs that could be an contributing factor to your problem also take a look at your number 2 fuel injector those get clogged and could be not delivering the proper amount of fuel on heavy load hope this helps

 

[ddavisaf]

How long did you hold 20 psi during your boost leak test?
Test your coil pack like tech27, test both primary and secondary coils.
Test your plug wires for ohms and make sure they're not damaged from the factory.
Make sure your air filter isn't dirty or clogged.
Check and make sure your injectors are firing. And easy way to do this is let the car idle and stick a length of hose in your ear and place the other end on the top of the injector. You sure hear it click at a steady pace.

What psi is your boost set to?

 

[JayB98GST]

I didn't really time how long but it did hold pressure for a good 20 to 30 seconds.
And my boost is only set for 15 psi with the stock turbo.

 

[91gsxboosted]

I blew my head gasket and a coolant line came loose after hitting a raised manhole a couple of weeks ago and had to drive the car overheated for a couple of minutes till i could find a safe place to pull over. So I had the head milled and rebuilt, and put it all back together. Everything runs fine excpet that when I get to full boost the car kind of stutters, almost like its not getting enough fuel. The car will stutter for a couple of seconds even after i let of the gas a little. Also I noticed that once it starts to stutter, if I put it in neutral and let it coast the vacuum will go close to 0 psi and then after a couple of seconds it will slowly start to go up to normal. I don't know if that means anything though. I have a rewired walbro pump and my fuel pressure is set correct. I replaced the plugs (NGK BPR7ES) and wires (Accel) after the rebuild. First i had the plugs gapped at .028 and that didn't seem to help, so then I regapped them to .026 and that didn't help either. I also noticed that when I took the plugs out, the tips were white... I guesss this means that I was running lean, but I can't figure out why. And I also did a leak test and there are no boost leaks. Anyone have any suggestions? Thanks for any help.

one thing I would do is check the injector o rings and make sure none of them are leaking. Also, another think i would check if you can not find any vacuum problem is that cat, make sure it is not clogged.

 

[JayB98GST]

I don't have a cat, so that shouldn't be the problem. If the o-rings were leaking, I would be able to see or smell gas on the outside of the fuel rail by the injector that is leaking, right? If so, then its not leaking. But I have noticed that everytime I take the plugs out to check them, the tips are white, even if I only drive it for a coulpe of miles.

 

[JayB98GST]

ok, here's an update... I did another boost leak test and at above 20 psi i can hear a small leak coming from the #2 injector... so i'm guessing the o-ring is bad. Hopefully this is the problem.