stumbles at 4000 plus rpm's

[qwkdsm2]

i was wondering if anybody had any answers or soulutions for my problems......here it is..
when i get on my car hard from a stop the car pulls to redline fine in 1st.....but in 2nd,3rd
at about 4000 rpm's or so it'll stumble hard like fuel cut.....but the thing is can i get fuel cut only pushing 15psi......it use to do it once in awhile......for example this past friday i drove the car it ran fine......come sunday.....two days later it starts doing that....i changed the spark plugs but still no change......my vacumm readings are low reading from the boost guage...15 to 18....but one thing is my car surges...and idle's at about 900rpm's..cause of surging.......also i have an egr blockoff...so don't have may vacumm lines........heres my mod list to help out a little more
16g ported clipped
38mm wastegate
3inch turboback
fmic kit
stock uncrushed bov
190lph fuel pump
-8an fuel line from pump to fuel filter
sx fuel filter
-6an from fuel filter to rail to return line
aeromotive afpr
450cc inj
stock mass

what could it be also what should trouble shoot first.....

 

[Defiant]

How old are your ignition wires? Somehow, 4K is the magic stumble number for leakers.

 

[Larry L]

I agree my car was stumbling around 4k and above on occasion and replacing the ignition wires fixed the problem. Also if your running your FPR at too high of psi it could also cause simular problems. Just my opinion though.

 

[guitarXgeek]

Check your plug wires, I had that exact same problem until yesterday when I put some new ones on.

 

[gaddis]

Check intercooler piping

 

[GTK]

I had the same problems with my car. Put new NGK spark plugs (6's) in and that fixed my problem.

 

[doug]

It is possible to hit fuel cut at 15 PSI-- fuel cut is more than just a "stumble" though. It's stronger than that.

 

[blcknspo0ln]

so true doug.. i hit fuel cut and it literally made me shat my pants the first time

do a boost leak tester first [ VFAQ has instructions ] then replace plugs.. then wires..

 

[Larry L]

Good point do whats free before you go spending your change...IMO it is either ignition or a boost leak. Let us know the outcome...

 

[ShzaTurboGSX]

Ok so my car is doing this EXACT same thing, stumbles but at 5000 rpm, instead of 4. I changed my plugs the other day to no avail, so I'm going to be purchasing some new wires. I'll let you all know if it helped or not.

 

[blcknspo0ln]

let us know.. but did you do an intake leak tester first?

you should, cause i spent a solid 40 bucks on 4 sets of NGK's before realizing it wasn't my plugs fouling..

 

[ShzaTurboGSX]

Ok so I went and grabbed some new wires at the local parts store, swapped em in, and they didn't help it. :thumbdown

However, I think my idle smoothed out just a tad. Either way, I don't know if I should try to return them or not, since I shelled out 47 bucks for something I don't need...

So next fixer on the list would be what?? I'll make a leak tester soon and check for leaks, although I've done it before. I can't seem to think that's it either, because it doesn't matter what psi I set my boost controller at (10, 14, 16) it always stumbles at 4-5k.

More fix-it options welcome!

 

[darkness_fallz]

This happened on an old 93 N\T that I had, but around 4k it would stutter really bad. It ended up being an ECU problem. I reset it twice, same thing... would drive fine to 4k, then start bucking like you wouldn't believe. Ended up just replacing the ECU.

Not likely in your case- but I had the same symptoms on the N\T..... just a possibility.

 

[blcknspo0ln]

coil packs?

 

[G_S_X]

Replace Plugs and wires, check for boost leaks. All 3 of those have caused me some bucking at WOT at about 4k.

 

[Sephroth57]

i was having similar problems, changed plugs wires, etc. and then one day it just stopped doing it... so i guess it was a boost leak that stopped leaking. so either way do a leakdown test and i bet you have a leak, 15-18 vaccum isnt really that great btw, i get about 20-21 but im a 2g so it might be different

edit: oh btw, your idle problem is probably your ISC and not related to this... i dont think 1gs give a check engine for it but mine is on its way out and im idleing around 900-1000

 

[laurence riggs]

Ok so my car is doing this EXACT same thing, stumbles but at 5000 rpm, instead of 4. I changed my plugs the other day to no avail, so I'm going to be purchasing some new wires. I'll let you all know if it helped or not.

did the leads fix it, my gst is doing the same thing going to do a leak down test

 

[1990TSIAWDTALON]

Super old thread, probably should start a new one with the issues you are having.