Problem revving engine. Skips to rev limiter

Rebel79 · 03-07-2001, 02:03 AM

Ok this problem has been happening for a while now. It started after I did my fuel upgrade which consited of 30lb injectors, 6:1 FMU, and a Pro-M 80mm Mass Air Sensor.

Originally this was the problem: When under heavy throttle (3/4 or more) at 5,000 RPMs, the motor will suddenly shoot up to redline (6,250) and then backfire. The backfire was from the factory rev limiter shutting off every other injector.

After a week or so, the problem stopped happening in 1st gear, and continues to happen in every other gear. The only thing I can think of is my throttle spring may be wearing out. I seem to remember feeling the pedal go down when the engine RPM shot up.

Anyone have any other suggestions?

------------------
1994 Mustang Cobra
308ci, Vortech S-trim 11#, ported GT-40 heads, E-303 cam, FMS 1 5/8 headers, BBK Offroad H-pipe, 2-chamber flows, and several other goodies.
Rebel Racing. Home of Bay Area Mustangs

03-07-2001, 02:51 AM

With the motor off,have a friend press the accelerator pedal slowly a few times to the floor while you are looking at the throttle linkage.If it is binding,you should be able to see while it's being depressed.

Also you really should get yourself a MSD Rev control ignition box instead of using the factory rev limiter.The factory rev limiter does the worst thing to a blown motor,it removes the fuel,causing a instant lean condition.The MSD box removes spark instead of fuel..

------------------
Paxton Blown 87GT

Rebel79 · 03-07-2001, 11:10 PM

Rebel79 · 03-08-2001, 02:20 PM

No it does not bind.

Please guys I need help. Anyone else?

Unit 5302 · 03-08-2001, 03:05 PM

Well, if it's shooting up to redline suddenly there has to be a sudden increase in speed to coincide with the rev when you are in gear.

Are the tires breaking loose, are you just getting very rapid acceleration, or is your clutch slipping?

An engine can't just rev while in gear without one of those three things happening. If you are getting a sudden burst of acceleration, I'd be wondering more why the car doesn't always pull like that. If the tires are spinning, you know the S/C is just overwhelming the tires once it's hitting max boost. Dan had a rpm pegging problem in Death Machine, but it turned out his clutch was slipping badly. Maybe your clutch isn't gripping when the boost really gets up there.

If no jump in acceleration, wheelspin problems, or clutch slipping problems occur, then you are not actually revving like that and I'd say something is amiss with your ignition or computer system.

lx mike · 03-08-2001, 08:37 PM

Well since u upgraded your fuel system you are making a bit more power so it could be slipping the clutch once the boost hit in upper r.p.m's. What clutch are you using? Your getting it dyno'd soon aren't you?

------------------
93-LX: 5 Speed, Flow's with H-Pipe, 3.73's Sub's and K&N.

Rebel79 · 03-08-2001, 10:05 PM

Well I highly doubt that its the clutch since it has been replaced after the fuel install and no change. I went with the Centerforce Dual Friction. However it is possible that I need a new clutch quadrant cause the pedal is WAY out of adjustment. That could have something do to with my problem.

I get dynoed on next Saturday so I really need to get the car in working order by then. Hoping for over 400rwhp.

------------------
1994 Mustang Cobra
308ci, Vortech S-trim 11#, ported GT-40 heads, E-303 cam, FMS 1 5/8 headers, BBK Offroad H-pipe, 2-chamber flows, and several other goodies.
Rebel Racing. Home of Bay Area Mustangs

Unit 5302 · 03-09-2001, 05:22 PM

So that thing is spinning the tires then, or is it just suddenly taking off like a bat outta hell. I can't imagine it redlining that fast in a higher gear without something slipping tires/clutch.

I'm gonna have to say your clutch is slipping under high hp application. It's most likely the quadrent. If it slips too much you're gonna have hot spots on the flywheel and pressure plate pretty quick.

You could always find a deserted road if you're nuts. Disconnect the quadrent altogether and see if it still slips. Just start it in gear, it'll roll the whole car forward for a sec. Then give it hell. If it redlines like that again you know it's not the quadrent (now anyway).

When you did the clutch did you put a new flywheel on, or did you just have it resurfaced? If it was resurfaced maybe the shop took too much off and it's not thick enough to hold that much force?

Even if your clutch still slips when the quadrent is disconnected I'd have to say it could still have been the reason for the problem originally and now your flywheel/pressure plate is glazed. The C/F dual friction clutch is a beast, I don't think it's incapable of handling that kind of power, but if the surface areas are glazed it doesn't matter how good your clutch disc is.

I'd recommend the steeda ajustable clutch quadrent. From what I've read they have a knob that goes on the inside of the car you turn to adjust. Nice... No crawling around underneath the thing to reset your adjustments.

03-07-2001, 02:03 AM	#1
Rebel79 News Editor Join Date: Apr 1999 Location: Concord, CA Posts: 2,101	Problem revving engine. Skips to rev limiter Ok this problem has been happening for a while now. It started after I did my fuel upgrade which consited of 30lb injectors, 6:1 FMU, and a Pro-M 80mm Mass Air Sensor. Originally this was the problem: When under heavy throttle (3/4 or more) at 5,000 RPMs, the motor will suddenly shoot up to redline (6,250) and then backfire. The backfire was from the factory rev limiter shutting off every other injector. After a week or so, the problem stopped happening in 1st gear, and continues to happen in every other gear. The only thing I can think of is my throttle spring may be wearing out. I seem to remember feeling the pedal go down when the engine RPM shot up. Anyone have any other suggestions? ------------------ 1994 Mustang Cobra 308ci, Vortech S-trim 11#, ported GT-40 heads, E-303 cam, FMS 1 5/8 headers, BBK Offroad H-pipe, 2-chamber flows, and several other goodies. Rebel Racing. Home of Bay Area Mustangs

03-07-2001, 11:10 PM	#3
Rebel79 News Editor Join Date: Apr 1999 Location: Concord, CA Posts: 2,101	ttt

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
hesitation when revving engine!	Wikkd GT	Modular Madness	9	06-12-2003 04:22 PM
Please help stutering problem	Just me	Windsor Power	10	10-18-2002 02:37 PM
Surging Problem - Help	Lawless	Windsor Power	32	08-19-2001 10:57 PM
New engine running HOT...is the problem the pulleys?	Stang_ROTY	Windsor Power	3	07-30-2001 08:18 AM
3.8 engine questions	MY PRIZE	Modular Madness	2	01-19-2001 07:28 AM

03-07-2001, 02:51 AM	#2
Mustanguy Guest Posts: n/a	With the motor off,have a friend press the accelerator pedal slowly a few times to the floor while you are looking at the throttle linkage.If it is binding,you should be able to see while it's being depressed. Also you really should get yourself a MSD Rev control ignition box instead of using the factory rev limiter.The factory rev limiter does the worst thing to a blown motor,it removes the fuel,causing a instant lean condition.The MSD box removes spark instead of fuel.. ------------------ Paxton Blown 87GT

03-08-2001, 02:20 PM	#4
Rebel79 News Editor Join Date: Apr 1999 Location: Concord, CA Posts: 2,101	No it does not bind. Please guys I need help. Anyone else?

03-08-2001, 03:05 PM	#5
Unit 5302 Registered Member Join Date: May 1999 Posts: 5,246	Well, if it's shooting up to redline suddenly there has to be a sudden increase in speed to coincide with the rev when you are in gear. Are the tires breaking loose, are you just getting very rapid acceleration, or is your clutch slipping? An engine can't just rev while in gear without one of those three things happening. If you are getting a sudden burst of acceleration, I'd be wondering more why the car doesn't always pull like that. If the tires are spinning, you know the S/C is just overwhelming the tires once it's hitting max boost. Dan had a rpm pegging problem in Death Machine, but it turned out his clutch was slipping badly. Maybe your clutch isn't gripping when the boost really gets up there. If no jump in acceleration, wheelspin problems, or clutch slipping problems occur, then you are not actually revving like that and I'd say something is amiss with your ignition or computer system.

03-08-2001, 08:37 PM	#6
lx mike Undescribable Join Date: Sep 1998 Location: Ft Myers Fla Posts: 1,539	Well since u upgraded your fuel system you are making a bit more power so it could be slipping the clutch once the boost hit in upper r.p.m's. What clutch are you using? Your getting it dyno'd soon aren't you? ------------------ 93-LX: 5 Speed, Flow's with H-Pipe, 3.73's Sub's and K&N.

03-08-2001, 10:05 PM	#7
Rebel79 News Editor Join Date: Apr 1999 Location: Concord, CA Posts: 2,101	Well I highly doubt that its the clutch since it has been replaced after the fuel install and no change. I went with the Centerforce Dual Friction. However it is possible that I need a new clutch quadrant cause the pedal is WAY out of adjustment. That could have something do to with my problem. I get dynoed on next Saturday so I really need to get the car in working order by then. Hoping for over 400rwhp. ------------------ 1994 Mustang Cobra 308ci, Vortech S-trim 11#, ported GT-40 heads, E-303 cam, FMS 1 5/8 headers, BBK Offroad H-pipe, 2-chamber flows, and several other goodies. Rebel Racing. Home of Bay Area Mustangs

03-09-2001, 05:22 PM	#8
Unit 5302 Registered Member Join Date: May 1999 Posts: 5,246	So that thing is spinning the tires then, or is it just suddenly taking off like a bat outta hell. I can't imagine it redlining that fast in a higher gear without something slipping tires/clutch. I'm gonna have to say your clutch is slipping under high hp application. It's most likely the quadrent. If it slips too much you're gonna have hot spots on the flywheel and pressure plate pretty quick. You could always find a deserted road if you're nuts. Disconnect the quadrent altogether and see if it still slips. Just start it in gear, it'll roll the whole car forward for a sec. Then give it hell. If it redlines like that again you know it's not the quadrent (now anyway). When you did the clutch did you put a new flywheel on, or did you just have it resurfaced? If it was resurfaced maybe the shop took too much off and it's not thick enough to hold that much force? Even if your clutch still slips when the quadrent is disconnected I'd have to say it could still have been the reason for the problem originally and now your flywheel/pressure plate is glazed. The C/F dual friction clutch is a beast, I don't think it's incapable of handling that kind of power, but if the surface areas are glazed it doesn't matter how good your clutch disc is. I'd recommend the steeda ajustable clutch quadrent. From what I've read they have a knob that goes on the inside of the car you turn to adjust. Nice... No crawling around underneath the thing to reset your adjustments.