Runaway throttle....hellllllp
Thread Starter
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Joined: Nov 2011
Posts: 916
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From: Las Vegas, NV
Runaway throttle....hellllllp Hi guys,
Looking for some help here. So the other day, I finally get my setup running pretty good, I thought.
Setup:
2002 Convertible Z28, A4
Stock bottom, LS9 Cam, Stock Heads, etc
Rear Mount Turbo, 76mm, Intercooler, Snow Methanol, NO BOV (Automatic).
I just rearranged my charge pipe (went SD, removed 85mm MAF, removed BOV).
So I'm driving, and I notice that the throttle stays open when the car gets into boost when at WOT. I take my foot off gas, pedal stays down, I **** pants.
This happened at the track on Friday during burnout, I'm standing on brake with both feet, car wont stop. To say the least, I did an NHRA Top Fuel burnout... put in in reverse.... back up 30 ft... then do my run. Have to put car in neutral to get throttle to disengage.
Today, I swapped throttle body with friend, stock TB. No change.
Is it possible that because I am not running a BOV, my turbo is overpowering the TB spring and not allowing it to close? Lots of built up compressed air between the rear mount turbo and the TB.
The only way to get the car to stop is to bump it into neutral.
I'm freaked... my first thought is to get a damn BOV back on. Was hoping to hear from someone who may have heard of something like this happening before. (Side notes: its not the floor mat, that's been taken out and it still happens. It does not do this when in park or when the engine is off. The throttle cable feels fine, smooth. Unable to reproduce when not in boost. Feels like cruise control kicking in. Happens when boost hits 2psi or more. My max boost is set to 8psi.)
Open to ideas... Thanks!
Looking for some help here. So the other day, I finally get my setup running pretty good, I thought.
Setup:
2002 Convertible Z28, A4
Stock bottom, LS9 Cam, Stock Heads, etc
Rear Mount Turbo, 76mm, Intercooler, Snow Methanol, NO BOV (Automatic).
I just rearranged my charge pipe (went SD, removed 85mm MAF, removed BOV).
So I'm driving, and I notice that the throttle stays open when the car gets into boost when at WOT. I take my foot off gas, pedal stays down, I **** pants.
This happened at the track on Friday during burnout, I'm standing on brake with both feet, car wont stop. To say the least, I did an NHRA Top Fuel burnout... put in in reverse.... back up 30 ft... then do my run. Have to put car in neutral to get throttle to disengage.
Today, I swapped throttle body with friend, stock TB. No change.
Is it possible that because I am not running a BOV, my turbo is overpowering the TB spring and not allowing it to close? Lots of built up compressed air between the rear mount turbo and the TB.
The only way to get the car to stop is to bump it into neutral.
I'm freaked... my first thought is to get a damn BOV back on. Was hoping to hear from someone who may have heard of something like this happening before. (Side notes: its not the floor mat, that's been taken out and it still happens. It does not do this when in park or when the engine is off. The throttle cable feels fine, smooth. Unable to reproduce when not in boost. Feels like cruise control kicking in. Happens when boost hits 2psi or more. My max boost is set to 8psi.)
Open to ideas... Thanks!
Thread Starter
TECH Resident
Joined: Nov 2011
Posts: 916
Likes: 5
From: Las Vegas, NV
When you say, "small motors and 25lbs boost..." did they have BOV? I'm thinking my system is flowing so much air and no place to go, its pushing TB open.
Rationale: 8lbs boost > TB spring tension.
Ever heard of such a thing?
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Put a bov on it, even with a auto your killing you turbo everytime you come out of boost (compressor surge) as far as your sticking throttle I'd say thats related to having no bov too.
Thread Starter
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Joined: Nov 2011
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From: Las Vegas, NV
Interesting...Can you elaborate a little? What am I checking for? Never heard of a "foot pedal sensor". Do we have them on '02 Camaro? What's it look like, where is it? How did you know yours was bad? Why would this happen only in boost?
Thanks!
Thanks!
Thread Starter
TECH Resident
Joined: Nov 2011
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From: Las Vegas, NV
Right now, I'm just trying to connect the dots and (for educational purposes) understand why the throttle was staying open. Would like to know if that is the actual cause (no BOV) or not.
Tell that to Denmah, 10k on that $200 ebay GT45 and was still going strong without a BOV!
OP i hope you figure out the issue, best bet is to stay out of boost until you get another BOV welded back on and see if it changes!
10 Second Club
Joined: Jul 2011
Posts: 176
Likes: 1
From: Seattle
My first inclination was to say "yeah of course it is the BOV because that is what you changed." But the more I think about it the more I would lean towards how is the BOV going to activate if the throttle plate is not closing and creating vacuum in the manifold and a boost spike in the charge pipe? or am I completely out to lunch on my BOV theroy.
You could always build\use a boost leak tester. Pressurize the manifold and snap the throttle by hand to see if you can reproduce. If you can reproduce try disconnecting the cable and see if it goes away. The fact that two TB's did the same thing makes me lean towards bind in the cable.
You could always build\use a boost leak tester. Pressurize the manifold and snap the throttle by hand to see if you can reproduce. If you can reproduce try disconnecting the cable and see if it goes away. The fact that two TB's did the same thing makes me lean towards bind in the cable.
Last edited by jtotheizzo; Sep 10, 2012 at 01:44 PM.
So your issues are coming up AFTER you deleted the MAF, went SD and removed the BOV? Who tuned it for you? Perhaps its in the tune.... there are a few tables that can help fix that issue if in fact it is nothing mechanical.
Thread Starter
TECH Resident
Joined: Nov 2011
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From: Las Vegas, NV
My first inclination was to say "yeah of course it is the BOV because that is what you changed." But the more I think about it the more I would lean towards how is the BOV going to activate if the throttle plate is not closing and creating vacuum in the manifold and a boost spike in the charge pipe? or am I completely out to lunch on my BOV theroy.
You could always build\use a boost leak tester. Pressurize the manifold and snap the throttle by hand to see if you can reproduce. If you can reproduce try disconnecting the cable and see if it goes away. The fact that two TB's did the same thing makes me lean towards bind in the cable.
You could always build\use a boost leak tester. Pressurize the manifold and snap the throttle by hand to see if you can reproduce. If you can reproduce try disconnecting the cable and see if it goes away. The fact that two TB's did the same thing makes me lean towards bind in the cable.
Cable TB.
Can't understand why it would bind under boost and not any other time. Next step is to disconnect a coupler and see if it happens N/A at WOT.
The other thing I can't understand is why is it when I put it into neutral, the pedal pops back up and releases. ??? Haven't had to switch off the ign yet, just bump it into N....
Last edited by HRHohio; Sep 10, 2012 at 04:40 PM. Reason: Added last line.
Thread Starter
TECH Resident
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From: Las Vegas, NV
Actually, I went from MAF to SD before I removed the BOV. Ran fine. Then a couple weeks later, when I got the time to do it, I pulled off the MAF and BOV, put a straight 3" in place with 2 90 elbows, tapped in the IAT and Meth/Water inj. (no change to the tune, was already running SD for about 2 weeks with the MAF still inline but not connected). After all that, that's when the problems started. (Local tuner)
FormerVendor
Joined: Feb 2011
Posts: 547
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You are 100% correct, The BOV can not have any affect on this, it only works when the throttle is closed.
Check and make sure that your throttle body only opens 80-85 degrees.
I have seen this more than once.
Every time it was because someone tweaked the throttle bracket until the
throttle blade was dead flat at WOT.
10 Second Club
Joined: Jul 2011
Posts: 176
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From: Seattle
I am assuming that when you say the pedal sticks to the floor that means it is physically lying on the floor. This says to me it is a mechanical problem. not an issue with the tune.
This makes a lot of sense to me because if the blade is only at 80-85% then the air rushing in does in fact help it close. If it were 100% open you lost that effect.
My thought on this if it were in fact the boost holding it open is it is possible that the spring has the gumption to overcome the bind without the added stress of the boost but lacks the gumption with the boost.
Assuming it has cruise control just for grins disconnect the cruise control motor and see if it still happens. It would be probably one of the weirdest things I have seen but hey its order of elimination here. But with that said I don't recall if my pedal moves with the cruise control. Anyone else on that?
Can't understand why it would bind under boost and not any other time.
The other thing I can't understand is why is it when I put it into neutral, the pedal pops back up and releases. ??? Haven't had to switch off the ign yet, just bump it into N....