I DARE you to figure out this problem!

mccurdy · Dec 19, 2003

Ok...I JUST put a new 2.5 inch o2 sensor housing with a dump tube in tonight. I disconnected the o2 sensor from its plug, unbolted the coolant hard line, drained the coolant. Disconnected the o2 stock housing. Rebolted the new o2 dump housing. Reconnected the o2 sensor in the new o2 housing. Reconnected the coolant line, refed coolant into the car. I took off the bottom heat shield, but left the top mani heat shield on.

I ran the car for like 10 minutes, and it ran incredable. It sounded mean as hell, and flowed great! Then i tried launching it and max psi (about 21 lbs of boost) on my profec-b with the balance set at maximum. I hit about the middle of 2nd at full boost and BAM. car buckles HARDCORE. i slow way down, and try to accelerate again. It goes from -24 vacuum to 0 psi perfectly normal, almost instantly like it should. But from 0 to 5 i noticed it was slower. then anything after 5 psi, the car starts Hesitating big time, and actually starts slowing down the higher the PSI i go! It also makes a really wierd noise.

I have no white/black smoke i can tell from the tailpipe. Im still using the origional o2 sensor, i have no check engine lights, no visual signs of any leaks anywhere.

I CANNOT FIGURE IT OUT!!! What would make the car hesitate and slow down under boost, yet it goes from vacuum to 0 psi perfectly normal! I can drive it fine under boost and get it up to 90 MPH and drive it on the freeway just fine, yet if i try to mash on it, it just bucks/hesitates and slows WAY down!

Please help guys, i have till monday to figure out this problem!

turboholic · Dec 19, 2003

-did you check the ic pipe for leak?

1badtsi · Dec 19, 2003

yup, BOOST LEAK

Boostin16gGSX · Dec 19, 2003

that sounds like a big boost leak somewhere on ur intercooler piping....

TheCrazyDSM'r · Dec 19, 2003

Yup that is definately a boost leak problem there.

mccurdy · Dec 19, 2003

but if it was a boost leak, then i wouldnt go from -24 vacuum to 0 psi instantly. it would slowly build up wouldnt it? and i can hold 5 psi. Usually boost leaks take awhile to build up the initial boost, then once u get going it over powers it. this, i get to 5 psi just fine, then after that it slows down...boost leaks dont slow your car down the faster you go. it feels like something is blocking the actual air pathway or something

LandoAWD · Dec 19, 2003

Originally posted by mccurdy
but if it was a boost leak, then i wouldnt go from -24 vacuum to 0 psi instantly. it would slowly build up wouldnt it? and i can hold 5 psi. Usually boost leaks take awhile to build up the initial boost, then once u get going it over powers it. this, i get to 5 psi just fine, then after that it slows down...boost leaks dont slow your car down the faster you go. it feels like something is blocking the actual air pathway or something

I'm with the rest. You can still build boost, sometimes rather quickly, but your turbo is working exponentially harder which you can't see on a gauge.

whamazoom · Dec 19, 2003

Im pretty sure the vacuum draw from the turbo will not be affected if there is a intercooler piping leak, the vacuum doesn't get drawn from the turbos outpit hoses.

mccurdy · Dec 19, 2003

Heres something to stump u guroo's. I was driving today to test it out. I disconnected the Profec-b to see if it was that. nope.

so im driving down the street, and i can WOT in first until redline, but once the WG and dump tube opens, the car boggs way down and slows.

then if i shift into second, and give it like 15% throttle up until say, 4500 rpm, the car jerks violently and sputters like no other. it feels like fuel cut once i get to that point its so bad.

what could cause it to sputter that bad (feels like when your in first gear and accelerating and you take your foot off the gas, and the car jerks back, then you accelerate again, and do that repeatidly..thats what the sputtering feels like) at only 15% throttle at 4,500 rpm in second gear????

91awd · Dec 19, 2003

TPS could be going out. Mine did exactly what you said about the first gear thing. If I drove under without boosting it would drive ok so my friend hooked it up to his logger and once in a while the tps would read 0 replaced it with a used one for $30 problem solved.

Sk8er07999 · Dec 19, 2003

Same exact thing happend to me, blew the upper intercooler pipe apart. Major boost leak. felt like fuel cut. car bogged any time it started to boost. Check for boost leaks, vfaq.com has a pretty cool way to check and see if you have a boost leak. Haven't tried it but it looks like it would do the job. Check it out good luck.

Defiant · Dec 19, 2003

Originally posted by mccurdy
but if it was a boost leak, then i wouldnt go from -24 vacuum to 0 psi instantly. it would slowly build up wouldnt it?

No, vacuum is measured in the plenum after the throttle plate and is a mechanical absolute. Boost is measured with the throttle plate open to the compressor. If you had no intake piping, but were supplying fuel to let it idle, you'd still show vacuum with the throttle closed.

mccurdy · Dec 20, 2003

what would cause the car to buck and jerk like it does once i start making boost? can a boost leak even DO that? i have no I/C pipes blown off, everything looks intact. i cant figure out the problem. im gonna check my plugs tomorrow to see if they're fouled, because this is pissing me off. The jerkin motion occurs just as i begin to boost when the WG starts to pop open and dump to the atmosphere.

can u guys list all the shit it possibly could be, besides a boost leak or plugs, and ill just go down the list and start checkin every single one of them.

mccurdy · Dec 20, 2003

whats TPS?

mccurdy · Dec 20, 2003

Ok, well i figured out the problem. It was bad plugs AND i had a lower I/C piping hose crack 90% of the way around, and it was at a crease in the hose where it went from 3 inch to 2 inch (lower greddy piping). I boosted so hard it cracked the whole thing off, and would only start leaking above 5 psi of boost. under 5 psi it sealed itself up.

we fixed it using a leak tester i had made 2 months ago. i cut apart the hose, took off the top of it, and hose clamped the ####er.

Me and my buddy went out cruising later to test it. Some trans am revved on us, i just threw it into 2nd and hit WOT and the o2 dump kicked in and my wheels just spun and almost went across a full lane from tire spin. Once we cought traction we smoked the trans am.

OMG

i cant believe how much power difference it is, especially off the line opposed to the stock o2 housing. Just imagine if i beat a WRX by the end of 2nd gear without the o2 dump, wonder what i could do now....

Thank you everyone who gave me tips, and my advice to you all is to keep some extra 3inch or 2.5 inch hose in your car at ALL times just in case. always have 2 spare hose clamps and try to carry automotive adhesive too.

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