Past stock boost levels, Car shudders

[Cool Mr Steve]

Anything past 9-10 psi, the car stutters while building boost. I have run it for a very long time at about 15-16 psi, but in the midst of a 2nd gear pull, it started stuttering past 9 psi. When I try to build up any boost past that, it moves up very slowly (only actually did it up to about 12 psi) while making the car shudder, and causes it to accelerate very slowly. Some issue with the wastegate maybe??? I have a hallman manual boost controller, if that makes any difference. Check my profile if you need to know my other mods.

 

[its3much]

check for boost leaks and your t2small could be dieing on ya

 

[90GSXDan]

It could be the turbo dying, fuel cut, or what happened to me... Blowing spark... Pull the plugs and check if they are foul and check their gap. I have mine set to .028 from .030 because it blew spark at 5k.

 

[oldman]

Definitely check for boost leak and eyeballing it don't count.

 

[Eclipsemblue]

I have the same problem, but i dont have my turbo boosting above stock. whenever i decided to want to boost hard at like 3,400rpms i step on the gas and the car goes no were it just shakes violently and studders and i get no boost and i dont gain any speed. but yet when i step on the gas progressivly it will boost fine but i cant just step on the gas hard to boost hard and fast.

 

[PieEyedPiper]

It could be the turbo dying, fuel cut, or what happened to me... Blowing spark... Pull the plugs and check if they are foul and check their gap. I have mine set to .028 from .030 because it blew spark at 5k.

what does blowing spark mean?

 

[PaleDSM]

It could be the turbo dying, fuel cut, or what happened to me... Blowing spark... Pull the plugs and check if they are foul and check their gap. I have mine set to .028 from .030 because it blew spark at 5k.

Same advice I was going to give.

 

[90GSXDan]

Blowing spark is when the gap in your spark plugs is too big or it is fouled. They dont spark as fast or when they are supposed to, causing your car to shudder. Mine sounded like a supra hitting the rev limiter when I was blowing spark. Made me lose some races...

 

[Cool Mr Steve]

I found a few boost leaks, 2 at my HKS SSQV, one at my UICP to throttle body gasket, and one at my BISS screw. I'm in the process of fixing these up, but while I'm waiting, do these relatively small leaks sound as though they could be causing my car to shudder and not be able to boost past stock boost levels. BTW, these leaks were present below 5 psi, as that was all I could get my little cigarette lighter air compressor to do.

 

[Cool Mr Steve]

Well, did a half-assed job of patching up some of the boost leaks just to see if it would help, but I can still see and hear a leak at the throttle body gaskets that I will try to fix tomorrow. Before I test drove the car, I re-gapped my plugs, as most of them were at about .031, back to .028. The car drove better and didnt sputter until about 14-15 psi, but it sucks that now I'm not quite sure which fix made it better. I am going to get some non-platinum plugs tomorrow, some NGK BPR7ES's or 6ES's as well as the gaskets, and we'll see how it does. Should've test drove it before I did the plugs... Balls... Oh, well, it's gotta be one of the two...

 

[Defiant]

Change your plugs to NGK BPR6ES at .028".

 

[Cool Mr Steve]

Change your plugs to NGK BPR6ES at .028".

Yeah, I'm going to try that tomorrow. What makes me less inclined to assume that the problem is in the spark plugs, though, is the fact that it was sudden and I couldn't boost past 9-10 psi, whereas I was able to boost to 15-16 not 5 minutes before. It seems like it had to be the throttle body gasket, or am I just being stupid? Can spark plug's go out like they did that quickly? I mean, when I checked them, the gaps were too wide, then I re-gapped them and the problem got better. It seems like if it were the plugs, it would have gradually escalated to that level.

 

[Cool Mr Steve]

BTW, and don't jump on me for this, but just FYI, I am using platinum plugs, if that helps any.

 

[dave99gst]

BTW, and don't jump on me for this, but just FYI, I am using platinum plugs, if that helps any.

U allready said that --- tis why defiant said change em'

 

[oldman]

Get yourself a real compressor, some leaks don't show up until higher boost and 5psi is not going to do it. Fix the leaks at 5psi and pump it up again until you can reach 20psi at least, I'm sure there are others.

 

[Cool Mr Steve]

I changed my plugs to BPR6ES's, and the throttle body gasket is coming tomorrow (if Mitsubishi keeps them in stock), followed by another boost leak test to put it up to 20 psi. After I changed my plugs, the car boosted to 15-16 with no problem for about 30-40 miles. After a few hours, I drove it another 20 or so miles and the problem started rearing its ugly head again. The problem is not at all as prominent, but it does it, nonetheless. It seems as though if I boost high, it does it initially, then as I go through the gears the problem seems to die down. I pulled my new plugs and saw some pretty nice black carbon buildup. Could the problem be that it is just running too rich??? I have an aftermarket fuel pressure regulator, installed by the last owner, but I'm not sure at what pressure it should be operating or how to adjust it. It is coupled with a Walboro 255lph fuel pump on stock injectors. Could it just be the carbon build-up on the plugs???