Surging and Stalling. Somebody help!!!!!

Rodney · 09-02-2001, 01:35 PM

I have an 89 LX 5.0. I replaced the engine with a 5.0 with the following mods: Cobra upper and lower intake, 75 mm Pro-M (clibrated for the injectors), 65mm t.b., 24 lb injectors, 1.7 roller rockers, ported stock heads, E303 cam, pulleys, equal length headers, hi-flow h-pipe(with cats), and flows. When I replaced the eng. I also replaced sa many sensors as I could including the O2 sensors and the pcv valve.
When I'm driving the car and I put my foot on the clutch to slow down, the idle will shoot up to about 25oo rpm and just hang there. At other times it'll try it's darndest to just shut off, forcing me to rev it to keep it running. The smells coming from the exhaust are all wrong, sometimes super rich, other times lean. I've had someone tell me that the stock computer can't keep up with the air and fuel requirements of this new engine, overcompensating sometimes and backing off too much sometimes. That would seem valid if the car hadn't been doing the same thing when it was stock. I was thinking that maybe the stock computer is bad, but I replaced it with another stock computer and no difference.

Any help would be greatly appreciated. This problem is killin me.

PKRWUD · 09-02-2001, 02:52 PM

How old is the EGR valve?

Take care
~Chris

------------------
Retired Moderator
MustangNet

My site: JimPorterRacing

RACECAR spelled backwards is RACECAR

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SlowStang2 · 09-02-2001, 06:26 PM

My car did the same thing. When I went to slow down the idle would shoot up to your RPM and stay there. It would even do it while I was driving(just let off the gas while it was in gear and it drove it self until 2500). Now I know you said you replaced the sensors, but in my case, it was my TPS. I had it replaced hby Ford, but until I did, I disconnected the clip from the old one and just drove it like that. When I did this, the RPMs would shoot down when I shifted, but it didnt stall and it never went up to 2500 RPMs at idle by itself. If I were you I would go out and disconnect it, if the idle problem goes away, then it is your TPS sensor.

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94' Stang GT Convertible --Cobra upper&lower, GT-40Y Turbo Swirl aluminum heads, Mac cold air w/K&N, BBK equal length shorties, BBK offroad H-pipe, American Thunder cat-back, BBK T/B 65mm, 24lb injectors, Pro-77mm MAM, pulleys, aluminum driveshaft, 3.55s, Steeda Tri-Ax shifter, adjustable fuel regulator 14.4@100 MPH on G-tech;96 at track. (Sad, i know. This is with the stock heads)

HAITHAM · 09-04-2001, 06:42 AM

mine did the opposite way guy's, when I press the clutch the RPM will drop down to around 500 rpm then stall.
Any idea way ??

------------------
94 COBRA # 926/5009
TFS track heat heads (ported), Cobra intake (ported), 24# Injectors, 3/8" Phenolic spacer, E303 Cam, TFS 1.7 rr
BBK 1 5/8" headers, BBK 65mm TB, Pro-M 80mm MAS, PIH kit w/ A9L computer, FMS 3.55 ratio
BBK 190 lph fuel pump, Paxton fpr, MSD'S, March Pulley's, Pro-5 tower power shifter, Autometer shift light (5600),
Intellitronix Air/Fuel gauge, Eibach Sportline Springs, Tokico 5-way adjustable, Granatelli Motorsport Subframe

09-02-2001, 01:35 PM	#1
Rodney Registered Member Join Date: Sep 2001 Location: Souderton, Pennsylvania, United States Posts: 1	Surging and Stalling. Somebody help!!!!! I have an 89 LX 5.0. I replaced the engine with a 5.0 with the following mods: Cobra upper and lower intake, 75 mm Pro-M (clibrated for the injectors), 65mm t.b., 24 lb injectors, 1.7 roller rockers, ported stock heads, E303 cam, pulleys, equal length headers, hi-flow h-pipe(with cats), and flows. When I replaced the eng. I also replaced sa many sensors as I could including the O2 sensors and the pcv valve. When I'm driving the car and I put my foot on the clutch to slow down, the idle will shoot up to about 25oo rpm and just hang there. At other times it'll try it's darndest to just shut off, forcing me to rev it to keep it running. The smells coming from the exhaust are all wrong, sometimes super rich, other times lean. I've had someone tell me that the stock computer can't keep up with the air and fuel requirements of this new engine, overcompensating sometimes and backing off too much sometimes. That would seem valid if the car hadn't been doing the same thing when it was stock. I was thinking that maybe the stock computer is bad, but I replaced it with another stock computer and no difference. Any help would be greatly appreciated. This problem is killin me.

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09-02-2001, 02:52 PM	#2
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	How old is the EGR valve? Take care ~Chris ------------------ Retired Moderator MustangNet My site: JimPorterRacing RACECAR spelled backwards is RACECAR HEY !!! Are you ASE Certified ??? If you are, ask me about iATN. The best tool you'll ever have, and it's free !!!

09-02-2001, 06:26 PM	#3
SlowStang2 Registered Member Join Date: May 2001 Location: Stuart, FL, US Posts: 147	My car did the same thing. When I went to slow down the idle would shoot up to your RPM and stay there. It would even do it while I was driving(just let off the gas while it was in gear and it drove it self until 2500). Now I know you said you replaced the sensors, but in my case, it was my TPS. I had it replaced hby Ford, but until I did, I disconnected the clip from the old one and just drove it like that. When I did this, the RPMs would shoot down when I shifted, but it didnt stall and it never went up to 2500 RPMs at idle by itself. If I were you I would go out and disconnect it, if the idle problem goes away, then it is your TPS sensor. ------------------ 94' Stang GT Convertible --Cobra upper&lower, GT-40Y Turbo Swirl aluminum heads, Mac cold air w/K&N, BBK equal length shorties, BBK offroad H-pipe, American Thunder cat-back, BBK T/B 65mm, 24lb injectors, Pro-77mm MAM, pulleys, aluminum driveshaft, 3.55s, Steeda Tri-Ax shifter, adjustable fuel regulator 14.4@100 MPH on G-tech;96 at track. (Sad, i know. This is with the stock heads)

09-04-2001, 06:42 AM	#4
HAITHAM Registered Member Join Date: Jun 2000 Location: Saudi Arabia Posts: 130	mine did the opposite way guy's, when I press the clutch the RPM will drop down to around 500 rpm then stall. Any idea way ?? ------------------ 94 COBRA # 926/5009 TFS track heat heads (ported), Cobra intake (ported), 24# Injectors, 3/8" Phenolic spacer, E303 Cam, TFS 1.7 rr BBK 1 5/8" headers, BBK 65mm TB, Pro-M 80mm MAS, PIH kit w/ A9L computer, FMS 3.55 ratio BBK 190 lph fuel pump, Paxton fpr, MSD'S, March Pulley's, Pro-5 tower power shifter, Autometer shift light (5600), Intellitronix Air/Fuel gauge, Eibach Sportline Springs, Tokico 5-way adjustable, Granatelli Motorsport Subframe