Vacuum Problem?

[dkennedy]

Hey everyone. I'm not sure if I have adequately searched for a simliar problem, but thus far I've not found anything to match it. So ... my 2nd gear synchro issue aside, I've noticed a new problem with my MSP which began about two weeks ago.

As I was merging into traffic from an on-ramp (in 3rd gear) I accelerated & as soon as the RPMs hit 4000 my car completely hesitated for a good second or two before continuing on. To me it seems like a vac problem but I'm not sure. When I baby it the boost is fine. Even if I pull hard through 1st & 2nd into 3rd there is no problem. It seems to be only when I've already built up some speed & start to do a hard pull (as in the example above) where it hits a point right at 4000 RPM & poof ... a delay. I am curious if the wastegate acctuator was dying or its just a vac line starting to wear down & not holding pressure.

Any thoughts? Thanks in advance everyone.

 

[jestermsp]

sounds like you hit fuel cut my friend. what psi are ya running?

 

[smo0f]

i noticed that at 4k rpm the ecu dumps out a lot of fuel. if it feels like you just hit a wall, that's fuel cut. if it just hesitates, it's due to running rich. you should hook up a boost gauge and see what boost you are running at. you shouldn't be hitting fuel cut at stock boost in georgia in november. also you might want to consider getting the flash update to the ecu from the dealership

 

[dkennedy]

Hmm, thank you guys for the input. I was curious about the fuel cut but really haven't experienced it so I really didn't want to even think it could be that. I do in fact drive a stocker so my boost level should be the normal 6ish PSI. Hmm, I'll have to get some cash together & get my gauges installed like I wanted to a few months ago.

Smo0f it does just as you mentioned, feels like it hits a brick wall. I do get the random hesitation around the same RPM but not too often. It just started happening as I mentioned over the past few weeks. I was curious as to whether or not it was the cold weather, but hell I've had it for over a year & last winter it was fine. The thing that caught me off gaurd was that it wasn't with hard pulls through 1st & 2nd, although I disproved that yesterday morning when I throttled hard out of my subdivision while my car was still working on warming up & I found that wall yet again. Yikes!

Any thoughts as to why a stocker would be running such high boost w/o any mods beyond a catback exhaust? Thanks again.

 

[Yellow MSP]

Hmm, thank you guys for the input. I was curious about the fuel cut but really haven't experienced it so I really didn't want to even think it could be that. I do in fact drive a stocker so my boost level should be the normal 6ish PSI. Hmm, I'll have to get some cash together & get my gauges installed like I wanted to a few months ago.

Smo0f it does just as you mentioned, feels like it hits a brick wall. I do get the random hesitation around the same RPM but not too often. It just started happening as I mentioned over the past few weeks. I was curious as to whether or not it was the cold weather, but hell I've had it for over a year & last winter it was fine. The thing that caught me off gaurd was that it wasn't with hard pulls through 1st & 2nd, although I disproved that yesterday morning when I throttled hard out of my subdivision while my car was still working on warming up & I found that wall yet again. Yikes!

Any thoughts as to why a stocker would be running such high boost w/o any mods beyond a catback exhaust? Thanks again.

I would say first, get a mechanical boost gauge to verify what boost you are running (and if it is indeed high). Second, it is also possible that you blew an intercooler pipe off (not likely but I would check them none the less). Third, if you are running too high of a boost level, either the boost control solenoid crapped the bed (not likely), the vacuum line to the wastegate actuator is not on, ripped, etc (possible), or the wastegate actuator is either not attached properly or the wastgate itself crapped the bed (seems to be very likely with these cars).

 

[ChopstickHero]

i would blame the stock ECU for doing something. sounds like hesitation, fuel cut, overly rich condition. i don't think it would be any vacuum problem b/c like you said if you baby it, it will boost fine. get a few gauges, go with some kind of EMS setup to tune it (yeah, even if its stock) and you'll see how much better it runs.