High Reving Upon Startup

06-01-2001, 04:13 PM

I'm new to the EFI scene, up until now, I ran a carbereted 69 stang. I got an 88 GT a couple of months ago, and whenever I start it up (hot or cold), it revs up to about 2000 rpm's for about 2 seconds, then it settles down to an idle. I've searched for vaccum leaks and found none. Can anyone shed some light on this? Thanks in advance.
Dave

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Dave & Robin 88 GT, T5
306, polished crank, TRW pistons, underdrive pulleys, cold air induction, 73mm MAF, Xtreme Energy Cam, 3.73's

egiap's 5.0 · 06-01-2001, 04:53 PM

I think at start up the idle air bypass valve opens up father to bring up idle speed to get other sensors to working tempature. Some one correct me if I'm wrong.

------------------
Independent Amsoil dealer. For needs or information about amsoil synthetic products leave a message. Ask about preffered customer program.

06-01-2001, 05:08 PM

I can understand that, but 2,000 RPM's seems way too high to me. I've talked to some of my local stangers and none of them know what's going on. Theirs don't do it and they don't know of anyone elses stang that does. I'm lost!?!?

Casper5.0 · 06-01-2001, 05:26 PM

cleaning you IAB on the side of the throttle body can sometimes help that, because at times it can stick open. the IAB is the cyclinder lookin' deal on the side of the throttle body, it comes off and unscrews and you can clean it with carb cleaner, hope this helps, a couple of buddies of mine had the same trouble, good luck!!

RYAN

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94 cobra, steeda tri-ax, ultra flo's

14.2 @ 99 (stock)

jimberg · 06-01-2001, 09:23 PM

Yeah, mine only goes up to about 1400 or so. What do you consider to be a normal idle? 900? 650?

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351W 89 Mustang GT Convertible

06-01-2001, 10:17 PM

My normal idle is about 750-800. I'll try to clean the IAB out and see if that helps. Thanks again.
Dave

------------------
Dave & Robin 88 GT, T5
306, polished crank, TRW pistons, underdrive pulleys, cold air induction, 73mm MAF, Xtreme Energy Cam, 3.73's, 5 5/8 unequal length headers, MAC H-pipe, 2 chamber flowmasters, turn-downs, King Cobra Clutch

jimberg · 06-01-2001, 10:54 PM

One thing you could do is do the engine running test with a code reader. Idle control is one of the tests. It should let you know if it's the IAB.

------------------
351W 89 Mustang GT Convertible

vande97 · 06-02-2001, 09:42 PM

mine is doing the same thing, i cleaned everthing! TB,EGR...etc and it still does it some times! i cant figure it out either.. hum

QuantumMotorsports · 06-03-2001, 11:43 AM

You guys should try setting your TPS voltage. It could possibly be the problem. Also, a lot of problems like that in my honest opinion are caused by fords crappy wiring and electronic design. I have an intermittent idle problem that I can only figure is a bad connection or a prob with my computer. My idle changes every time I start the car, it will be 1500 one day, 800 the next, then 1200. I'm convinced it is an electrical problem (most likely a bad ground for the TPS or a bad voltage regulator in the computer for signal voltages) because when it is idling high I can press both window switches at the same time to draw current off of the battery and the idle drops 50 rpm or so. Anyway, as long as your car idles low while driving around town, I'd be happy, it's better than having it sit at 1500 RPM at stop lights.

------------------
Michael Black
Quantum Motorsports
Norman, Oklahoma

1988 Merc Cougar 5.0 HO, Ported and Polished E7TEs, 2.25" offroad H pipe w/ 2 chamber flowmasters, T5 tranny
New E/T!!!
14.626 @ 94.94mph, 2.194 60' time, a little better than last time. Keep in mind this thang is heavy (3590lbs) Finally 14s!!!!

06-01-2001, 04:13 PM	#1
D&R Stang Guest Posts: n/a	High Reving Upon Startup I'm new to the EFI scene, up until now, I ran a carbereted 69 stang. I got an 88 GT a couple of months ago, and whenever I start it up (hot or cold), it revs up to about 2000 rpm's for about 2 seconds, then it settles down to an idle. I've searched for vaccum leaks and found none. Can anyone shed some light on this? Thanks in advance. Dave ------------------ Dave & Robin 88 GT, T5 306, polished crank, TRW pistons, underdrive pulleys, cold air induction, 73mm MAF, Xtreme Energy Cam, 3.73's

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06-01-2001, 04:53 PM	#2
egiap's 5.0 Registered Member Join Date: Apr 2001 Location: Mansfield, OH. Posts: 113	I think at start up the idle air bypass valve opens up father to bring up idle speed to get other sensors to working tempature. Some one correct me if I'm wrong. ------------------ Independent Amsoil dealer. For needs or information about amsoil synthetic products leave a message. Ask about preffered customer program.

06-01-2001, 05:08 PM	#3
D&R Stang Guest Posts: n/a	I can understand that, but 2,000 RPM's seems way too high to me. I've talked to some of my local stangers and none of them know what's going on. Theirs don't do it and they don't know of anyone elses stang that does. I'm lost!?!?

06-01-2001, 05:26 PM	#4
Casper5.0 Registered Member Join Date: Jun 2000 Location: Stillwater, OK Posts: 107	cleaning you IAB on the side of the throttle body can sometimes help that, because at times it can stick open. the IAB is the cyclinder lookin' deal on the side of the throttle body, it comes off and unscrews and you can clean it with carb cleaner, hope this helps, a couple of buddies of mine had the same trouble, good luck!! RYAN ------------------ 94 cobra, steeda tri-ax, ultra flo's 14.2 @ 99 (stock)

06-01-2001, 09:23 PM	#5
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	Yeah, mine only goes up to about 1400 or so. What do you consider to be a normal idle? 900? 650? ------------------ 351W 89 Mustang GT Convertible

06-01-2001, 10:17 PM	#6
D&R Stang Guest Posts: n/a	My normal idle is about 750-800. I'll try to clean the IAB out and see if that helps. Thanks again. Dave ------------------ Dave & Robin 88 GT, T5 306, polished crank, TRW pistons, underdrive pulleys, cold air induction, 73mm MAF, Xtreme Energy Cam, 3.73's, 5 5/8 unequal length headers, MAC H-pipe, 2 chamber flowmasters, turn-downs, King Cobra Clutch

06-01-2001, 10:54 PM	#7
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	One thing you could do is do the engine running test with a code reader. Idle control is one of the tests. It should let you know if it's the IAB. ------------------ 351W 89 Mustang GT Convertible

06-02-2001, 09:42 PM	#8
vande97 Registered Member Join Date: Jan 2001 Location: okemos Posts: 205	mine is doing the same thing, i cleaned everthing! TB,EGR...etc and it still does it some times! i cant figure it out either.. hum

06-03-2001, 11:43 AM	#9
QuantumMotorsports Registered Member Join Date: Jul 2000 Location: Norman, Oklahoma, USA Posts: 597	You guys should try setting your TPS voltage. It could possibly be the problem. Also, a lot of problems like that in my honest opinion are caused by fords crappy wiring and electronic design. I have an intermittent idle problem that I can only figure is a bad connection or a prob with my computer. My idle changes every time I start the car, it will be 1500 one day, 800 the next, then 1200. I'm convinced it is an electrical problem (most likely a bad ground for the TPS or a bad voltage regulator in the computer for signal voltages) because when it is idling high I can press both window switches at the same time to draw current off of the battery and the idle drops 50 rpm or so. Anyway, as long as your car idles low while driving around town, I'd be happy, it's better than having it sit at 1500 RPM at stop lights. ------------------ Michael Black Quantum Motorsports Norman, Oklahoma 1988 Merc Cougar 5.0 HO, Ported and Polished E7TEs, 2.25" offroad H pipe w/ 2 chamber flowmasters, T5 tranny New E/T!!! 14.626 @ 94.94mph, 2.194 60' time, a little better than last time. Keep in mind this thang is heavy (3590lbs) Finally 14s!!!!