Free revving after a pull

Novadude

Novadude

New Member
Jul 21, 2013
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Murfreesboro, TN, United States
Ok so I just got her running good today, after a new MAF and rewiring the O2 sensor correctly (the PO has a lot of stuff hard wired and didnt do the O2 sensor correctly). I went for a cruise down the interstate and a BMW wanted to run (naturally) so I couldn't resist.
When we started I was in 4th gear, ran up to 5.5krpm at 15psi and tried to shift but after I let off the gas, pressed the clutch, and had it in neutral, it was still revving at around 6k and it took about 8-10 seconds for it to calm down enough to get it into 5th. Needless to say I lost the race (the least of my worries) but I cant for the life of me figure out what happened.
After all this I went to eat with some friends and in the parking lot waiting for them, I checked the throttle linkages to make sure there was no binding or sticking. None whatsoever so I figured id look at it later since my friends had just pulled up. Going to leave, I start it up (didnt touch the throttle) and it starts and revs to around 3.2k for a few seconds then idles fine. Has anyone ever had this issue?

List of mods
Lex/550
3" turbo back
DM intercooler
Bosch bpv
1.7mm mls hg


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supraguy@aol

supraguy@aol

Well-Known Member
Dec 30, 2005
4,231
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Atlanta
I used to have a problem with my floor mat, that when I went WOT, the pedal would get stuck under the front edge of the mat, and my car would bounce off redline.
Dunno if that's a possibility in your case. Otherwise, I can't imagine the car being able to rev above 3000 without some sort of additional air entering the manifold. What is the position of the bypass screw in your Lex maf?
 
supraguy@aol

supraguy@aol

Well-Known Member
Dec 30, 2005
4,231
36
48
Atlanta
And no other possible sources of air improperly entering the manifold?
I know you checked the throttle linkage, but is there any chance of binding at the throttle plate shaft itself?
 
Novadude

Novadude

New Member
Jul 21, 2013
104
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Murfreesboro, TN, United States
Update: only happens after hitting boost, is it possible if the bpv is reacting slow it could be pushing the pressurized air through the iacv into the intake?

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supraguy@aol

supraguy@aol

Well-Known Member
Dec 30, 2005
4,231
36
48
Atlanta
Edit- not sure i a leaking bpv would cause this because the air is pre throttlebody, either way. I'd check the iacv.
 
hvyman

hvyman

Dang Dude! No Way Man.
Staff member
Apr 17, 2007
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Fullerton,CA
A bypass valve should not cause those problems. Its purpose to to remove pressure out of the charge pipes for turbo life. once the throttle plate is closed very little to no air should be entering.
 
hvyman

hvyman

Dang Dude! No Way Man.
Staff member
Apr 17, 2007
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Fullerton,CA
yes but the bov and piping are both before the throttle plate. once the throttle plate is closed it blocks all the pressurized air from going in.

If the throttle return spring was weak and the bov wasnt opening then i could see that.
 
Poodles

Poodles

I play with fire
Jul 22, 2006
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Fort Worth, TX
The more likely culprit is a sticky throttle linkage... I know you've checked, but it's not uncommon. Also check the throttlebody.
 
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