Jerking when lifting the throttle.

[jackalopeTsi]

I recently took a drive over the mountain, and everytime i let off the throttle at higher RPMs it would jerk real bad. like around 4000 RPMs or so.

Could my motor mounts be the problem, as far as i know they have around 170k miles on them. not sure if previous owners ever changed them. and my suspension is completely stock.

I love driving over the mountain, and im gonna try an autocross here in a couple weeks, and i would like to know if there is any way i can fix this cheaply.

 

[v2ner]

are you still runnin the stock clutch n flywheel?

 

[ddavisaf]

If you installed your BOV recently with RTV, that could be your problem.
Trim away the excess RTV so that the airflow path isn't restricted.

Otherwise I would suspect drivetrain.

v2ner
are you still runnin the stock clutch n flywheel?

 

[siceclipse]

i would consider it to be the BOV and a crappy motor mount working together.

 

[jackalopeTsi]

its the stock BOV and i didnt use RTV, i only used a NEW gasket i got from extreme PSI with my uicp. should i have used RTV.

I do have the stock flywheel and clutch, the previous owner said he replaced the clutch right before i bought the car, and its only been a year. but i will try to get a new clutch this winter when i have my tranny rebuilt. damn 3rd gear.

could my stock BOV be a problem, im running 15 psi and its not crushed but modified so its a little sluggish to open than a stock 1g bov.

 

[ddavisaf]

I don't ever use RTV unless I have to. It's too messy.
Your BOV *should* be fine, but run a boost leak test just to make sure.

I would also suspect your transmission mount rather than motor mount, but any of them could be the problem. Take a look at the bolts holding the mounts. Then look at the mounts themselves. You're looking for signs of shearing. Broken bolts/studs etc...
Post back with what ya find.

 

[jackalopeTsi]

ddavisaf ill check that this weekend while im doing some other things to it.

also i was just thinking about it and it feels alot like it did when i vented with my stock mas. but im running a blowthrough setup now so that cant be the problem. just thought i would add this to help diagnose my problem

 

[T2Small]

The same problem for me turned out to be an issue with my BOV. It was modified as well and effectively was "blowing off" fairly slowly AND fluttering when slowly backing off the throttle. If I would really quickly let off the throttle, it would be fine, but even a normal throttle lift would cause some bucking.

I moved from the modified 1G BOV, to a Greddy Type-S, then finally fixed that new Greddy Type-S with a good diaphram and finally solved my problems.

How is your BOV modified?

 

[jackalopeTsi]

i modified it by these instructions. if i go for a new bov i will get either a Turbo XS type H, HKS SSQV(if i can get the money), or a blitz

 

[jackalopeTsi]

i checked my front motor mount and it looks pretty rough, it is ripped pretty bad,

Does anyone make a solid mount to replace this? or do i have to use a new rubber mount with an insert like the ones from prothane?

 

[moparmadd]

is the blow off valve vented to the atmosphere? i just had to hear that thing one day, so i vented it out and capped the intake and it would buck real hard when slowing letting off on the highway. but the sound... so worth it

 

[jackalopeTsi]

i am venting but im doin it the right way, with a GM MAFT setup in blowthrough, and it feels alot like what you felt moparmadd. it feels the exact same way.

could air be rushing back into the maf causing it to read alot of air, its connected to my throttle body elbow(i should have pics on my website), throwing alot of fuel into my engine, like it would with BOV vented? (just thought of this)

 

[jackalopeTsi]

On my way to school this morning i had an intercooler pipe blowoff, i pulled over and put my uicp back together and checked all my couplers and tightened down my clamps(stupid worm gear clamps, no money for t-bolts) i took it easy the rest of the way to school.

on my way home i got onto a semi-curvy country road to do a little "spirited driving" and i let off at around 4000 RPMs and it didnt buck or jerk real hard, a little but thats probably normal.

I have no idea what i could have done, i will see if it is fine later tonight, i have some running around to do.

 

[jackalopeTsi]

The problem still exists, but it is worse in 2nd gear than in 3rd. tranny mounts maybe?

 

[v2ner]

about the motor mount...those prothane mounts will make you feel the engine vibrate a whole lot. in my opinion, just a stock one is good.

 

[jackalopeTsi]

i dont care about a vibration, thats why i asked if anyone makes a good solid motor mount. and i know a solid mount will have MORE vibration than the prothanes
i didnt get this car for its luxury and comfort(AC is broken, Cruise Control is broken, no ABS) i got it so i could make it go fast and i got a good deal on it(not knowing i would have to spend a BUTTLOAD of money on it to get it to run right and fix everything that went bad)