Car Missing Out Bad

bigbadtalontsi · March 26th, 2007, 08:51 PM

So here's the problem. My car has been doing some really funny things lately. About a week ago the car started missing out real bad to the point where it would not let me pull over 3000rpms. If i barely rested my foot on the pedal the car would raise above 3000rpm, but if i went more than 20% throttle it would act like it was running out of fuel. The car in the mean time would idle okay. I replaced the TPS,replaced the fuel pump with a walbro255,new fuel filter, and a new ajustable fuel regulator. I set the base pressure @ 39 psi. The car ran okay for about a day. Then the problem returned. I pulled the cap and rotor and gave them a good cleaning. That returned the rpms, but the car seems to have no power. When i floor it the car will buck real bad as if i am letting off the accelarator then smashing it back down. My mods consist of GT40 heads,explorer intake,b303 w 1.72s,full exhaust,73mm mass,walbro 255,fuel regulator,under drives,cai,65mm t-body,3:55 gears,.040 bottom end. Thats all off the top of my head. Somebody please help me!!!! I am in dire need the track opens up on 4/3. Thanks

Stangzilla · March 26th, 2007, 10:34 PM

What type of fuel regulator do you have? Might be a dumb question but you would be suprised.. You did adjust the new TPS right?

nolife · March 26th, 2007, 11:30 PM

You seemed to have checked everything fuel related so I'd move onto spark.

How about the ignition control module (attached to the side of the distributor). I do not know how to specifically check that but others have posted here in the past with similar issues and that was the problem.

Do you have cats? Could be clogged. Mine are toast right now but I get no real "bucking" but it does sound and feel like a random/bad miss and anything above 3-4 under load is useless. Idles fine. My cats made some awful rattling just before failure so it was easy to diagnose.

Tony_90fox · March 27th, 2007, 12:02 AM

Just a thought, maybe replace the cap and rotor instead of just cleaning. I had the same problem last year...I thought it was fuel related as well. Bought new cheapo accel cap and rotor and bingo, problem solved for me.

Just an idea, might not help at all.

Maybe some kind of vacuum leak.

bigbadtalontsi · March 27th, 2007, 05:16 AM

The regulator is a Professional Products piece. I will shoot and get a new cap and rotor.

dave0970 · March 27th, 2007, 06:22 AM

Same problem here, idling is not steady. The car run great, but when it stop RPM goes high and low. I gave a little gas it stable. Please help!

shurb125 · March 27th, 2007, 08:51 PM

Check the the tiny wires (maybe called diodes?) on the actual MAF sensor inside the actual MAF unit, could have trash on it causing it not to read corrrectly. I had the same problem and that's what it was. Hope this helps

dave0970 · March 28th, 2007, 05:14 AM

Thanks! But, the time that i replaced the original intake with the chrome, I deleted the AMF.

March 26th, 2007, 08:51 PM	#1
bigbadtalontsi Regular Join Date: Jan 2007 Posts: 61	Car Missing Out Bad So here's the problem. My car has been doing some really funny things lately. About a week ago the car started missing out real bad to the point where it would not let me pull over 3000rpms. If i barely rested my foot on the pedal the car would raise above 3000rpm, but if i went more than 20% throttle it would act like it was running out of fuel. The car in the mean time would idle okay. I replaced the TPS,replaced the fuel pump with a walbro255,new fuel filter, and a new ajustable fuel regulator. I set the base pressure @ 39 psi. The car ran okay for about a day. Then the problem returned. I pulled the cap and rotor and gave them a good cleaning. That returned the rpms, but the car seems to have no power. When i floor it the car will buck real bad as if i am letting off the accelarator then smashing it back down. My mods consist of GT40 heads,explorer intake,b303 w 1.72s,full exhaust,73mm mass,walbro 255,fuel regulator,under drives,cai,65mm t-body,3:55 gears,.040 bottom end. Thats all off the top of my head. Somebody please help me!!!! I am in dire need the track opens up on 4/3. Thanks

March 26th, 2007, 10:34 PM	#2
Stangzilla Hardcore Enthusiast Join Date: Aug 2006 Location: On my way to Baines's house!! Posts: 2,992	What type of fuel regulator do you have? Might be a dumb question but you would be suprised.. You did adjust the new TPS right? __________________ Rotating The Earth 1320 Feet At A Time!! The very existence of flamethrowers proves that sometime, somewhere, someone said to themselves, “You know, I want to set those people over there on fire, but I’m just not close enough to get the job done.”

March 26th, 2007, 11:30 PM	#3
nolife Hardcore Enthusiast Join Date: Dec 2006 Posts: 1,028	You seemed to have checked everything fuel related so I'd move onto spark. How about the ignition control module (attached to the side of the distributor). I do not know how to specifically check that but others have posted here in the past with similar issues and that was the problem. Do you have cats? Could be clogged. Mine are toast right now but I get no real "bucking" but it does sound and feel like a random/bad miss and anything above 3-4 under load is useless. Idles fine. My cats made some awful rattling just before failure so it was easy to diagnose. __________________ 1991 GT - Original owner, all stock 1988 GT - The project car

March 27th, 2007, 12:02 AM	#4
Tony_90fox MM Fanatic Join Date: Jun 2006 Location: Bowling Green, KY Posts: 3,445	Just a thought, maybe replace the cap and rotor instead of just cleaning. I had the same problem last year...I thought it was fuel related as well. Bought new cheapo accel cap and rotor and bingo, problem solved for me. Just an idea, might not help at all. Maybe some kind of vacuum leak. __________________ Suck on it Trebek. Suck it long, suck it hard.

March 27th, 2007, 06:22 AM	#6
dave0970 Newbie Join Date: Jan 2007 Posts: 16	Same problem here, idling is not steady. The car run great, but when it stop RPM goes high and low. I gave a little gas it stable. Please help! __________________ 1987 LX 5.0 Coupe AT

March 27th, 2007, 05:16 AM	#5
bigbadtalontsi Regular Join Date: Jan 2007 Posts: 61	The regulator is a Professional Products piece. I will shoot and get a new cap and rotor.

March 27th, 2007, 08:51 PM	#7
shurb125 Regular 1993 Mustang LX Vert Join Date: Nov 2006 Location: South Carolina Posts: 431	Check the the tiny wires (maybe called diodes?) on the actual MAF sensor inside the actual MAF unit, could have trash on it causing it not to read corrrectly. I had the same problem and that's what it was. Hope this helps

March 28th, 2007, 05:14 AM	#8
dave0970 Newbie Join Date: Jan 2007 Posts: 16	Thanks! But, the time that i replaced the original intake with the chrome, I deleted the AMF.

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