Stumbling at 4000rpms

[CyberEye]

I'm trying to hunt down this problem, any help would be appreciated. At WOT when the engine reaches around 4000rpms it starts to jerk and stumble all over itself. It only does this at WOT, not partial throttle. When this happens O2 voltage drops to 0.

Plugs are brand new; BPR6ES gapped to .28.
Wires are maybe 6 months old; NGK
Fuel filter was changed today
O2 sensor is brand new

I changed the fuel filter today hoping it would solve the problem, but no luck there. I took it out for a drive after and the problem was still there. This time however when the car started to jerk, I heard a pop. Not a bang type pop, more so a pop like when a high pressure hose blows off. It may have happened before, but if it was I didn't notice it.

Could it just be that one of the clamps on my IC pipes is broken, and under wot and full boost (15psi) the hose is expanding letting all the air out? All the piping is still attatched so nothing blew off. I did a couple of 3rd gear pulls after I put the filter on and both times I heard the pop.

The only mods really done to the car are a 16g turbo, which was on when I bought it, and the fuel pump is re-wired.

Thanks
Mac

 

[oldman]

Sounds like a boost leak test is in order.

 

[swarm]

HaHa, I have the same problem, dude. Good luck finding the problem.
Here's what I know about it:

When I put on a friends bov, the car ran MUCH better, but didn't fix it completely.
I can set my MBC to anything. and it never passes 14psi.

I have replaced the following:
    o2 sensor            (oem)
    boost leak check     (vfaq tutorial)
    fuel filter          (oem)
    plugs/wires          (7es, taylor)
    fuel pump            (255)
    fuel rail            (oem)
    exhaust              (2.5 catback, cat is good)
    tested injectors     (napa tests injectors)
    MDP Sensor           (oem)
    MAS Sensor           (oem)
    Air Filter           (K&N)  

Used code tag for spacing.

I am waiting for my 1g bov to come in, so I will report after I get it installed and tell you if it fixed it. I am also going to try to get I/C piping to see if it is leaking, as you suggested - I had that on my list of things to check, also.

I hope my post can help you, as this problem has been plagueing my car since I bought it.
If you find something out, Please PM me and tell me what fixed it; I will do the same for you.

PM me for phone # if you would like to throw thoughts around.

To anyone else, I am still offering $200 reward for a fix to this.

 

[CyberEye]

I have a dejon tool uic pipe and 1g bov ready to go on.

 

[Defiant]

Plugs are brand new; BPR6ES gapped to .28.

That'll be .028

Are you hitting fuel cut?

 

[swarm]

Defiant,
If his problem is indeed the same as mine, it does not feel like fuel cut, but rather that the car feels boosted until 4k then feels like it's nonturbo. His may be a more severe case if his is jerking or anything.

Cybereye,
Install the uicp and 1g bov and see if it fixes your problem, if you have time. Please report back with your findings

 

[CyberEye]

Defiant,
If his problem is indeed the same as mine, it does not feel like fuel cut, but rather that the car feels boosted until 4k then feels like it's nonturbo. His may be a more severe case if his is jerking or anything.

Cybereye,
Install the uicp and 1g bov and see if it fixes your problem, if you have time. Please report back with your findings

It holds solid at 15psi and pulls strong untill 4000rpms. I'm honestly not too sure what fuel cut feels like so I couldn't realy tell you if thats it. I'm hopefully putting the UICP and BOV on tommorrow, and checking all my other clamps and couplers while I'm at it.

 

[GalantGst]

clamps breaking is very possible. i just broke one onfront of the mall and the pipe blew off

so ####ing embarassing.

or it could be bad wires.

at night disconnect a spark wire 1 at a time and put it next to the cover and see if u see little sparks sparking from the wall of the wire. and check at the coil pack if there is a leak there ana u disconnect the wire from a cylinder u will see it there.


EVERYONE PLEASE DO UR SELF A FAVOR AND BUY TURBO CLAMPS ITS LIKE 2$ EACH.

 

[swarm]

Cybereye, after the car starts feeling wierd, does the boost still hold for the most part?
Mine does.

Did you install the bov yet?

 

[GeneralChaos]

you have the car warmed up and everything right?

Have you tried putting a data logger on the car?

do what others said and check all the electricity connections, piping clamps, check for boost leaks, ect.

If its flopping and jerking around it doesnt sound like fuel cut but you never know.

 

[CyberEye]

you have the car warmed up and everything right?

Have you tried putting a data logger on the car?

do what others said and check all the electricity connections, piping clamps, check for boost leaks, ect.

If its flopping and jerking around it doesnt sound like fuel cut but you never know.

Car is warm yes. I had a friend sit beside me with my logger the other day, didn't save the runs, but the 02's were dropping down to 0 whenever it happened. Timing wasn't being pulled and the fuel trims were trying to keep up.
I'll get some actual numbers for you if I can get the damn files onto my computer, can't get the palmnstein transfer thing to work

 

[GeneralChaos]

while your looking over electricity you might want to check all of the grounds on the car, that may be a problem.

Does it get to 4000 and not really go any higher? does it work itself out of it at higher rpms if it gets there?

 

[Big Al 389]

Sounds like you're runing out of fuel!I notice you re-wired the pump but haven't replaced it.Try replacing the pump,it sounds as if the pump may be getting weak and can't keep up.....Just a thought...Al

 

[swarm]

Al,
I am recieving the same problems as him, and I have a 255 non-rewired and a commandflo FPR

 

[Big Al 389]

Swarm,the reason I say to try a pump is that I just had the same prob. on my 2g,I tought it was a boost leak to start with,tested,all was well.Then I went trought the ignition,found nothing.Started with the fuel system,filter,injectors tested...nothing.Replaced the pump and no more bucking and jerking and ran smoother than before the whole problem started.With mine it started out as a mid to high rpm studder then it gradually got worse til the thing was barely drivable....If you don't mind me asking what fuel psi are you running?Also what are you o2 readings when the car is acting up?.....Al

 

[swarm]

40psi@idle

When the car starts misbehaving, o2 drops to 0

Sensor was replaced, so it's good.

I thought fuel pump before, too, but when i replaced it and the problem was still there it made me sad

 

[Cgillies86]

I have a simliar problem, my car backfires, and stumbles at 4k. But, I think it is related to my boost problem, I boost 30 psi at 4k with my boost creep. I went as far as forcing the wastegate completely open; I had no boost until 4k, then the boost shot up to 30 psi. You can read this website maybe it will help: http://members.shaw.ca/costall/1000Q/answers-problems.htm#Mycarstumblesunderboost

Good Luck

 

[Acezwild88]

same exect thing is happening to me i am about to blow up my car. i replaced the fuel pump with a 255 it helped but still dose it. when im looking at my profec gragh it shows the boost and the boost looks like a mountain to me it gose up to 15 then droppes to like 12 or 13. i pressure trested my engein today and i didnt find anything. my friend replaced all of my ignition with his and it didnt help anything. honestly i dont know what the hell is goin on

 

[swarm]

installed 1g bov today, helped a lot but did not completely solve the problem

maybe a failing turbo?

 

[Big Al 389]

Swarm,do you still have the stock t-25 on your car,if so you may want to try boosting around 10-12 psi and see what gives then!
Ace, your boost problem sounds like it's creeping and settling back down.Is your car surging also?
Al

 

[swarm]

when i set my mbc to the lowest setting, it still hits 14psi

 

[Acezwild88]

ya it shoots up to say 14 then gose back down to 12. do you think thats whats up with my car?

 

[Big Al 389]

Swarm,how does the car do at hwy speed if you down shift and nail it?i don't know why you would loose power at 14 psi at highr rpms unless........Do you have or have access to another tp sensor?If so try it and let us know if it helps.
Cyber how does yours act at say 3/4 throttle?..........Al

 

[Big Al 389]

ya it shoots up to say 14 then gose back down to 12. do you think thats whats up with my car?

Ace does the car stumble or is it just the the issue with the boost?.......Al

 

[1grrvalley]

check the ecu