some hesitation under normal acceleration, 2 stumbles?

[Korndogg]

hello all
wednesday i was cruisin up a hill in 2nd, probably at 2700-2900 rpm or so, and maybe 7-8 psi of boost (not sure on that, just a guess) and all of a sudden my car jerked very noticeably. i don't know if it was fuel cut (how noticeable would that be if i weren't racing it?) or something else, but it was that type of jerk. not bad enough to make the car buck forward too much, but enough to get your attention right away when you're just kind of zoning out.
then thursday the car did the same exact thing, except i was accelerating just a bit up a lesser incline. probably 3k rpm and 8-9 psi of boost.

my car feels like it hesitates quite a bit under these sort of conditions, but it has done this since i bought it so i really have no idea if it's normal or not. but it's only jerked like this the past 2 days.

i'm thinking fuel filter. and i figured i might replace the o2 sensor also.

does anyone else have any other ideas? is a boost leak possible?

let me know
thanks a lot!


96 TSI FWD
95k miles

T25 @ 17PSI
2.5" catback, reamed-out cat
K&N FIPK
NGK BPR6ES spark plugs - only 8 weeks old or so (replaced wires at same time - Accel)

i think that's all of the relavent information
thanks a lot


edit:
oh, and 1G BOV with dave brode UICP

i have also checked the turbo for play, and there is absolutely no play at all in any direction, and the blades spin freely

thanks again

 

[R3dR]

#1 change to the NGK BPR7ES ( is one range colder plug and will help with the slight hesitations you have)

#2 Lower that boost on the T25


How does the car perform under wot?

I do not think its the O2 or the fuel filter.


Do a boost leak test to be sure its not a leak that is hidden by the over boosting you do at wot, that turbo is not really meant to run that high of boost you know.

 

[CurtTSI]

The problem you are experiencing could also be caused by a dead spot on the throttle position sensor. This will cause the engine to momentarily just shut off for a second or less, while your driving. It produces a bucking sensation.

 

[Korndogg]

i looked around on here for a long time deciding between the 6's and 7's and decided on the 6's as i found that many people had problems with the 7's running too cool and becoming dirty...

how come? i'm not trying to be a pain in the ass.. i've seen several times that above 15psi the T25 just blows hot air, but it really does help my car a lot to be above that....

and the car performs very well under WOT... nothing unusal.



curtTSI:
so you're suggesting just replacing the tps?


thanks

 

[Korndogg]

happened again today. 3k rpm, ~0PSI boost

so i guess the best plan right now is to replace the TPS... anyone have any other sugestions?

thanks a lot

 

[CurtTSI]

Don't know about the 2G, but on my 1G a bad TPS would set a code on the computer. Have any codes read before replacing the TPS. Also, in order to further check the ISC, I tapped into the output from the TPS and measured the voltage going to the ECU. Attached the digital volt meter to the outside of the windshield so that I could observe it while driving the car. I found that every time the engine lost power, the voltage went to zero, indicating a dead spot on the TPS. Replaced it and everything was OK.

 

[Korndogg]

wouldn't there be a CEL if a code was set? or not necessarily...

(i have no CEL)

 

[CurtTSI]

wouldn't there be a CEL if a code was set? or not necessarily...

(i have no CEL)

I did get a CEL with mine.

 

[Korndogg]

this has happened several times since my last posting, but it happened yesterday at WOT as i was passing someone...

does that blow a hole in the TPS theory or no?

if anyone has any other ideas please let me know.

thanks a lot


edit: it's also much more noticeable than suddenly letting off the gas (i don't know if that's what a bad TPS would feel like?). but it's a very quick very noticeable jerk.

random thought: how often should injectors be replaced? i've got almost 96 k on my car.. (and i have no way of knowing what was done to it before i bought it around 90k)
thanks again

 

[jen_cairo]

did u do a vacuum leak test yet?? i had the same problem.