Turbo 5.0 goes to WOT by itself.

nurkvinny · February 27th, 2011, 07:10 PM

I have an 89 5.0 with Cobra intake, GT40 heads, good valvetrain, stock cam and bottom end and a 72mm turbo setup using a C4 trans. Aftermarket throttle body, but unsure of brand or size.

Twice now, once while idling in reverse and once while idling in drive, the car went from idle RPM to 5500-6000rpms by itself. I've seen cables stick open, but I was not revving it beforehand, just idling. Something caused the RPMs to raise and stay at WOT until I killed the ignition.

Any ideas of a possible cause would be appreciated.

Thanks guys.

JTs03v6 · February 27th, 2011, 07:16 PM

idle air control could be the only thing i can think of. clean or replace it

EscortSportage · February 27th, 2011, 07:20 PM

damn thats scary i hope u have an MSD 6AL box or some kind of rev limitor

FastStang91Lx · February 27th, 2011, 07:42 PM

I'm gonna go with a ghost. Did a previous owner die in your car?

BULLET20XD · February 27th, 2011, 07:45 PM

My old 1990 GT did the same thing, it was my cruise control going crazy. I unhooked the CC cable and problem solved. Hope this helps.

nurkvinny · February 27th, 2011, 07:52 PM

Originally Posted by BULLET20XD

My old 1990 GT did the same thing, it was my cruise control going crazy. I unhooked the CC cable and problem solved. Hope this helps.

Thanks. No Cruise Control of any kind in this vehicle.

BULLET20XD · February 27th, 2011, 07:58 PM

Originally Posted by nurkvinny

Thanks. No Cruise Control of any kind in this vehicle.

LOL, sorry i couldnt help. Keep us posted!

nurkvinny · February 27th, 2011, 09:23 PM

Verified gas pedal movement, no binding.

Strong return spring rate, nothing in its way.

The only odd thing I can find is that the inside of the TPS looks all buggered up.

FastStang91Lx · February 27th, 2011, 09:29 PM

Any sign of ghosts?

93hatch · February 27th, 2011, 09:29 PM

tps. My car did the same thing. Yes your tps can pull the car to 6k with the tb closed. Dont ask me how

nurkvinny · February 28th, 2011, 07:40 AM

Originally Posted by 93hatch

tps. My car did the same thing. Yes your tps can pull the car to 6k with the tb closed. Dont ask me how

Odd. I'll ask around for one to plug in and try.

dblzroracin · February 28th, 2011, 08:54 AM

I would check out everything around the throttle body as mentioned 1st. May be far fetched but just a thought here even though I dont think I have heard of this happening but may be a possible cause, if something is causing the blowoff valve to close at idle & starts building boost that forces the TB open & engine to rev.

nurkvinny · February 28th, 2011, 10:00 AM

Originally Posted by dblzroracin

I would check out everything around the throttle body as mentioned 1st. May be far fetched but just a thought here even though I dont think I have heard of this happening but may be a possible cause, if something is causing the blowoff valve to close at idle & starts building boost that forces the TB open & engine to rev.

That is a heck of an interesting thought. I'll double check everything around and connected to it tonight.

Thanks

Trick Tuners · February 28th, 2011, 10:21 AM

It wont rev that high without boost, or an open throttle body. A vacuum leak would be there all time. As suggested watch your boost gauge when it happens to rule out wastegate issues.

nolife · February 28th, 2011, 12:23 PM

My failing TPS caused mine to randomly jump to at least 3-4K with the throttle plate closed. Seems like it could have just as easily went higher. Logically, you do need air from somewhere to support that but it was doing it and seemed like it could have gone higher. My intake on that car is completely stock but a lot of people with boost have a breather and the PCV or some type of seperator, maybe it sucked supporting air through that.

fogged306 · February 28th, 2011, 09:23 PM

Originally Posted by 93hatch

tps. My car did the same thing. Yes your tps can pull the car to 6k with the tb closed. Dont ask me how

Originally Posted by nolife

My failing TPS caused mine to randomly jump to at least 3-4K with the throttle plate closed. Seems like it could have just as easily went higher. Logically, you do need air from somewhere to support that but it was doing it and seemed like it could have gone higher. My intake on that car is completely stock but a lot of people with boost have a breather and the PCV or some type of seperator, maybe it sucked supporting air through that.

Man, that's crazy. I never would have believed that if you guys didn't actually have that happen to you. I wonder if it limits the injector pulse length so it goes really lean when that happens. That would explain high RPM's with not a lot of air?

93hatch · February 28th, 2011, 11:10 PM

ignore the slow cranking this was when I first got the car back together. This is what my bad tps did

click it its a video

nurkvinny · March 1st, 2011, 12:24 PM

Thanks for posting that. Add 1500-2000rpm and that could have been filmed in my car.

I did find an obvious vacuum leak last night. PCV line was not plugged in. Car is open exhaust and it was too late to fire it up and see what kind of difference that made. I can't believe that the PCV by itself is responsible.

gotn20 · March 1st, 2011, 03:34 PM

tps no doubt. Proofs in the pudding

PsyAbe · March 1st, 2011, 05:11 PM

My fox used to idle at 2k , runs out of breath almost dies then spins up to 2k again. This would happen every time i started her up after a long time parked. Turned out it was a dirty iac. After cleaning it up i saw improvements. I dunno, maybe your iac is seveeerely clogged up or something. as previously stated vacuum leaks should be checked for as well.. Here's a vid i took back when the engine would act silly

YouTube - Video0002

February 27th, 2011, 07:10 PM	#1
nurkvinny Newbie Join Date: Feb 2011 Posts: 13 iTrader: 0 reviews	Turbo 5.0 goes to WOT by itself. I have an 89 5.0 with Cobra intake, GT40 heads, good valvetrain, stock cam and bottom end and a 72mm turbo setup using a C4 trans. Aftermarket throttle body, but unsure of brand or size. Twice now, once while idling in reverse and once while idling in drive, the car went from idle RPM to 5500-6000rpms by itself. I've seen cables stick open, but I was not revving it beforehand, just idling. Something caused the RPMs to raise and stay at WOT until I killed the ignition. Any ideas of a possible cause would be appreciated. Thanks guys.

February 27th, 2011, 07:16 PM	#2
JTs03v6 Hardcore Enthusiast 2003 mustang 7.48x1.56=11.67 Join Date: Sep 2009 Location: East Coast Posts: 2,318 iTrader: 0 reviews	idle air control could be the only thing i can think of. clean or replace it __________________ New combo: Forged SC short Block,280cfm heads, Precision 6262 turbo, cx 31x12x3 fmic http://photobucket.com/JTsTurboBuild http://youtube.com/user/JTsStang

February 27th, 2011, 07:20 PM	#3
EscortSportage Hardcore Enthusiast 1989 Mustang GT 5.0 Join Date: Oct 2007 Location: CT Posts: 2,186 iTrader: 0 reviews	damn thats scary i hope u have an MSD 6AL box or some kind of rev limitor __________________ Cage Maximum Motorsports Sparco QH/BE Nitto "a huge bad azz motor is nice untill you have to turn or stop"

February 27th, 2011, 07:42 PM	#4
FastStang91Lx I Post Entirely Way Too Much 1991 Mustang LX 5.0 Join Date: Jan 2010 Location: Minnesota Posts: 5,572 iTrader: 2 reviews	I'm gonna go with a ghost. Did a previous owner die in your car? __________________ Point made in less than a few hours with minimal response. http://www.moddedmustangs.com/forums...ml#post4465184

February 27th, 2011, 07:45 PM	#5
BULLET20XD Regular Join Date: Jan 2011 Location: Chatsworth,Ga Posts: 158 iTrader: 0 reviews	My old 1990 GT did the same thing, it was my cruise control going crazy. I unhooked the CC cable and problem solved. Hope this helps. __________________ 1990 LX 5.0 2000 Expedition 2002 Honda Accord One tea cup Chihuahua guard dog!!!!!!!

February 27th, 2011, 09:23 PM	#8
nurkvinny Newbie Join Date: Feb 2011 Posts: 13 iTrader: 0 reviews	Verified gas pedal movement, no binding. Strong return spring rate, nothing in its way. The only odd thing I can find is that the inside of the TPS looks all buggered up.

February 27th, 2011, 09:29 PM	#9
FastStang91Lx I Post Entirely Way Too Much 1991 Mustang LX 5.0 Join Date: Jan 2010 Location: Minnesota Posts: 5,572 iTrader: 2 reviews	Any sign of ghosts? __________________ Point made in less than a few hours with minimal response. http://www.moddedmustangs.com/forums...ml#post4465184

February 27th, 2011, 09:29 PM	#10
93hatch Banned 1992 Lx 11.39@119.24 Join Date: Jan 2008 Location: Az Posts: 11,644 iTrader: 0 reviews	tps. My car did the same thing. Yes your tps can pull the car to 6k with the tb closed. Dont ask me how __________________ [QUOTE=93mustank;2577445]We speed tested my right arm for quickness in shifts... So he could design the cam for proper shift recovery.[/QUOTE]

February 28th, 2011, 08:54 AM	#12
dblzroracin Regular 92 Mustang GT vert Join Date: Aug 2005 Location: Memphis, TN Posts: 151 iTrader: 0 reviews	I would check out everything around the throttle body as mentioned 1st. May be far fetched but just a thought here even though I dont think I have heard of this happening but may be a possible cause, if something is causing the blowoff valve to close at idle & starts building boost that forces the TB open & engine to rev. __________________ www.bbandtracing.com

February 28th, 2011, 10:21 AM	#14
Trick Tuners MM Fanatic KB'd GT Join Date: Nov 2006 Location: San Diego Posts: 4,467 iTrader: 3 reviews	It wont rev that high without boost, or an open throttle body. A vacuum leak would be there all time. As suggested watch your boost gauge when it happens to rule out wastegate issues. __________________ Check out my forums for stuff on troubleshooting, tuning, etc We teamed up with Socal Performance Racing to bring dyno tuning to San Diego. Be friends with us on FB

February 28th, 2011, 12:23 PM	#15
nolife MM Fanatic 91GT, 88GT, 02GT Join Date: Dec 2006 Posts: 3,057 Blog Entries: 3 iTrader: 0 reviews	My failing TPS caused mine to randomly jump to at least 3-4K with the throttle plate closed. Seems like it could have just as easily went higher. Logically, you do need air from somewhere to support that but it was doing it and seemed like it could have gone higher. My intake on that car is completely stock but a lot of people with boost have a breather and the PCV or some type of seperator, maybe it sucked supporting air through that. __________________

February 28th, 2011, 11:10 PM	#17
93hatch Banned 1992 Lx 11.39@119.24 Join Date: Jan 2008 Location: Az Posts: 11,644 iTrader: 0 reviews	ignore the slow cranking this was when I first got the car back together. This is what my bad tps did click it its a video __________________ [QUOTE=93mustank;2577445]We speed tested my right arm for quickness in shifts... So he could design the cam for proper shift recovery.[/QUOTE]

March 1st, 2011, 12:24 PM	#18
nurkvinny Newbie Join Date: Feb 2011 Posts: 13 iTrader: 0 reviews	Thanks for posting that. Add 1500-2000rpm and that could have been filmed in my car. I did find an obvious vacuum leak last night. PCV line was not plugged in. Car is open exhaust and it was too late to fire it up and see what kind of difference that made. I can't believe that the PCV by itself is responsible.

March 1st, 2011, 03:34 PM	#19
gotn20 Atomized Join Date: Feb 2008 Posts: 1,370 iTrader: 0 reviews	tps no doubt. Proofs in the pudding __________________ spray and pray

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