Hesitation off Idle/ Vented BOV the Cause?

[Lil John]

Hey everybody. I'm having trouble with with my 98 Gsx with 6 bolt swap we just did. The problem is theres a slight heastitation when you quickly give gas. If you slowly give it gas its fine, its just when you tap the gas quickly. You can hear it suck in air through the filter when you do it, then it takes off. I haven't been able to really drive it so all I know so far is it does it just off idle, not sure about the driveablilty yet.

The motor is fresh. It has great vacuum. Ive done a boost leak test and there are none at all anywhere. I rebuilt the throttle body. It has new plugs and wires. Timing is set between 5btdc and 7btdc. Fuel pressure is set at 43psi. Changed fuel filter. Swapped out Maf with a know good one. Motor idles really good for most part. It seems like its running a little rich, exhaust burns your nose. Brand new front and rear O2 sensors. My stft and ltft are decent at idle. I'm running out of ideas. I'm wondering if a vented bov will cause that stumble or hestitation just off idle? I know it can cause stalling between shifts.

Mods include full exhaust, evo O2 housing and manifold, 18g turbo, 550cc injectors, afpr, walbro 255, big front mount, safc. I'm just getting frustrated, because everything seems fine except for that and I'm wondering about the vented bov being the cause. I appreciate any help and thanks!

 

[Barracuda]

Err, do you have gm maf as blowthru or some standalone engine management? if not, why do you vent it to athmosphere? I mean, If you have a type of bov that is open under idle/vacuum, it sucks air all the time while off boost making your fuel trims look jerky.

 

[Lil John]

Update.

I just took it up to 2k rpms and held it there at the throttle body, then revved it quick and there wasn't any hesitation. It seems to only do it off of idle which is around 850rpms. Maybe its just normal? I dont know? Thanks.

Err, do you have gm maf as blowthru or some standalone engine management? if not, why do you vent it to athmosphere? I mean, If you have a type of bov that is open under idle/vacuum, it sucks air all the time while off boost making your fuel trims look jerky.

Its a TurboXS RFL BOV. Im not sure it its the type that is open under idle or vacuum. If so that would explain it.

 

[Barracuda]

Well IF the bov is after a maf and IF it's open while on idle -> lean off boost. If you have a wideband o2 and a gauge for it, put your hand on top of the hole(s) where it usually vents out the air. And if AFR changes, it sucks air. Another trick is to hold a piece of toilet paper in front of the hole to see if it draws air. But don't let it in

btw. I have some hesitation too on low throttle->WOT. My setup has 3.5" gm maf as blowthru and bov vented to athmosphere too. The bov is before the the maf so it doesn't matter if it would suck air under idle. I don't worry much about the hesitation.

 

[rEclipserGST]

btw. I have some hesitation too on low throttle->WOT. My setup has 3.5" gm maf as blowthru and bov vented to athmosphere too. The bov is before the the maf so it doesn't matter if it would suck air under idle. I don't worry much about the hesitation.

I also have the Hesitation off of idle. I figured it was because I have an automatic. I have my bov recirculated . Any of you do the EGR block-off yet? I just ordered a plate, so I will let you know if it helps with hesitation. Its known to help with throttle response though, so I think it should definitely help.

 

[Lil John]

I also have the Hesitation off of idle. I figured it was because I have an automatic. I have my bov recirculated . Any of you do the EGR block-off yet? I just ordered a plate, so I will let you know if it helps with hesitation. Its known to help with throttle response though, so I think it should definitely help.

I will try to toilet paper trick. Lol. My egr is blocked off with plate along with the fiav passages are jb welded closed. Maybe its normal.

 

[Barracuda]

I have the egr blocked off too... with a gasket i made from beer can

 

[LandoAWD]

Its a TurboXS RFL BOV. Im not sure it its the type that is open under idle or vacuum. If so that would explain it.

Problem identified.

BLT the car, and update your profile. Report back after that.

 

[Lil John]

Problem identified.

BLT the car, and update your profile. Report back after that.

BLT has been done and there are no leaks anywhere. I checked all vacuum hose connections inside the car as well, all fittings, intercooler piping, fuel injectors insulators, afpr, around gaskets, etc. Everywhere basically. I guess I'm leaning toward the vented BOV being the culprit. Thanks.

 

[mitsu_gst97]

slap a 1g on there and recirculate it.

 

[LandoAWD]

I guess I'm leaning toward the vented BOV being the culprit. Thanks.

I highlighted the LeaksXS valve in my quote.

 

[snowborder714]

How many psi are you using for your boost leak test? I had a TurboXS when I first purchased the car and it leaked at a fairly low psi (I forget exactly).

 

[LandoAWD]

All of the TurboXS valves I've had over the last 10 years, except the one that came welded to my FMIC when I bought it used, leaked. They sound cool, but the design is really poor.