Part-throttle bucking problems

[jmv]

I took my car out on a 'moutain run' if you will today, and noticed a particular problem. The car seems to do fine at small throttle openings, and seems okay at WOT (if perhaps a little less responsive than it should be... its like it takes a second to 'kick in', aside from just the turbo spooling). When i do part throttle/part boost, ie if i wanted to keep it at a consistant 80% throttle opening which would keep around, for example, 4 psi of boost, it tends to start bucking alot. Its fairly annoying when trying to run the car near its limits, and i either have the choice of running poorly, not having enough power, or trying to cope with putting down more power than i'd want for the situation. Can anybody make any suggestions for what to do about this??

If its just a fuel delivery/ecu type problem, i've been working with unichip for months now trying to get that figured out....

[mikeski]

i have a problem similar to that and I think it is due to the a/f ecu problem. im looking for a fix also.

[MSP #167]

your wastegate actuator may be fucked.

[jmv]

i haven't checked it any time recently, but i have done a replacement ATP wga, and i'm not having any unusual vac or peak boost issues....

[mikeski]

your wastegate actuator may be fucked.

i dont think its the wastegate. he didnt say he was only boosting 4 lbs, thats just when it starts bucking.

[mikeski]

so u have a unichip?

[jmv]

i have one, its not installed, its not been working properly even after sending it to get 'fixed'. So the car is running on stock ECU, stock boost. I've got a catted midpipe, short ram intake, fmic, upgraded bpv, new wga, thats about it.

[mikeski]

who did u send it to? i know JDM SAM is great at tuning the unichip to customize for the mods you have. did u buy it used?

[jmv]

well thats another topic.... i tried to get it tuned by sam he basically said it was fubared, sent it to unichip and paid alot to get it fixed, still doesn't work.....


but its not involved with the car at all right now, its in a box, so its in no way contributing to the problem.

[junya1985]

I had the same problem awhile back and i got it tuned and it tottaly fixed the problem but i dont have the unichip but it sounds like it just needs to be tuned



well thats another topic.... i tried to get it tuned by sam he basically said it was fubared, sent it to unichip and paid alot to get it fixed, still doesn't work.....


but its not involved with the car at all right now, its in a box, so its in no way contributing to the problem.

[mikeski]

I had the same problem awhile back and i got it tuned and it tottaly fixed the problem but i dont have the unichip but it sounds like it just needs to be tuned

thats what im saying, i need mine tuned and it sounds like the same issue i have now

[SeR_Cyclops]

my car does the same thing but at WOT. my car had been running really good pulling like it should ect, then one day i noticed the vac was only at 13. so i started looking for a vac leak and i found one, and replaced the hose. now i hold more boost and the car seems faster but mayn it will buck for a second right when you go to WOT then it will go away pull hard all the way to redline. but when i have to shift in to the next gear it does the same thing agian it will start bucking when i first shift and then it will work its self out. the bucking is also worse during the night. so i think im getting a mild fuel cut. the bucks are not violent like they were when my WGA went bad and i was hitting 15psi. any ideas?

[Nickson]

Mine is bucking when I try to go and hold a 70MPH on highway:(

need to accelerate or decelerate a little. What's this problem?

[slo03.5msp]

You need a tune. On a side note how come everytime people have a problem everyone always say wga? You all do know there are other parts on these cars beside a wga right?

[cmahlig]

afr

[jmv]

i think my problem actually did turn out to be the wga... you can check my other thread "leak, possible BPV problem" to see the whole episode.

I'm still amazed at how crappy the wga's are.... the stocker lasted maybe 36,000 miles, and stayed on for a while when i was trying to figure out what was wrong with it, and the replacement lasted 25,000 and is done.... i dunno, seems like it just doesn't hold up as well as it should. Hopefully i have better luck with the forge motorsport unit than the ATP, but we'll see...

[ND4MSP]

so you have the forge on there now? i have an atp and I am starting to wonder.

[jmv]

No, currently the leaking ATP is still on, but i ordered a forge from Ken @ protegegarage straight away, hopefully it gets here soon, and holds up better than the ATP did. It really only has been 25,000 miles since i replaced it. I went for the extra $$ for the forge because it says they're rebuildable. I don't know how hard it is to source the rebuilding parts, but i suppose i'll tackle that if and when it comes to it.

[SeR_Cyclops]

i am going to check my WGA i cant belive that yours went bad in 25000 miles. i am getting this bucking also and i have had my wga on for about 23000 miles so im going to check it.

[Nima_What]

im having the same problems too, im gonna check my wastegate. but what shows that wastegate is no longer good?

[SeR_Cyclops]

if the WGA will no longer hold vac pressure then it is bad. or if it holds and leaks off.

[jmv]

you can check by blowing into the vac line going to it... if it lets air out its bad. Thats how i diagnosed my stocker going bad. But, as i more recently discovered, even if it holds air in that situation, if it doesn't hold vacuum it also causes problems. I figured the diaphragm tore and i'm not sure what would make it not hold vacuum but be fine to hold boost... but regardless, you need to check for both.