Car is cutting out top end!!

boosted89 · November 16th, 2006, 11:36 PM

I have an 89 ford mustang with a procharger on it!! It runs good prretty much all the time but when i mash the gas to the floor at about 4500 the motor cuts out pretty much completely!!! Its also only full throttle. If i mash it about 3/4 itll sing to 6000 but as soon as i hit full throttle it cuts out!! Can you help me??

Darrell · November 16th, 2006, 11:48 PM

Have you had it on a dyno to see what the fuel curve looks like? That is where I'd start.

TENGRAM · November 16th, 2006, 11:51 PM

Originally Posted by boosted89

I have an 89 ford mustang with a procharger on it!! It runs good prretty much all the time but when i mash the gas to the floor at about 4500 the motor cuts out pretty much completely!!! Its also only full throttle. If i mash it about 3/4 itll sing to 6000 but as soon as i hit full throttle it cuts out!! Can you help me??

what have you got your spark plugs gapped at? could be a coil or other ignition issue (TFI, cap/rotor, plug wires). could also be fuel related.
have you Checked for Codes?

Tony_90fox · November 17th, 2006, 12:23 AM

definately check the plugs, wires, cap and rotor.

boosted89 · November 17th, 2006, 12:42 AM

i Know the fuel pressure is good but the only thing im curious about is when my fuel pressure raises for the supercharger the pressure jumps up and down for 40 to about 75! And yes i checked for codes but didnt get any!! I also have my plugs gapped at .035 thousandths! 2 steps colder

Darrell · November 17th, 2006, 02:35 AM

Does the pressure jump up to 75 or does it fluctuate while you are wide open. If it just jumps to 75 at wide open throttle that is normal. If the pressure is fluctuating, you have a big problem.

stang fanatic · November 18th, 2006, 09:05 PM

Think of it this way....at 3/4 throttle, your fuel demand is 75% approx., and so your average fuel pressure between 40 and 75 is nominal since air pressure is lower. At full throttle, your supercharger is giving it s all, fuel demand is 100% and so your average fuel psi is now not adequate enough to support the demand and air being fed into the motor. Remeber, the air is still there, but sufficient fuel isnt, find out where the presure loss is from...pump, filter, collapsing line, etc.

IcantDo55 · November 19th, 2006, 08:15 PM

LOOSE THE FMU! Thay suck!

Could also be pinging, mine did that whe I first put on the S-trim. Back down the timing and see if that helps. What injectors you rinning? With 42's and a calibrated MAF you can loose the FMU.

November 16th, 2006, 11:36 PM	#1
boosted89 Newbie Join Date: Nov 2006 Posts: 2	Car is cutting out top end!! I have an 89 ford mustang with a procharger on it!! It runs good prretty much all the time but when i mash the gas to the floor at about 4500 the motor cuts out pretty much completely!!! Its also only full throttle. If i mash it about 3/4 itll sing to 6000 but as soon as i hit full throttle it cuts out!! Can you help me??

November 16th, 2006, 11:48 PM	#2
Darrell Asshole™ 1990 Mustang LX 9.36@143 mph Join Date: Jan 2006 Location: Fond du Lac, Wisconsin Posts: 7,762	Have you had it on a dyno to see what the fuel curve looks like? That is where I'd start. __________________ Racing in memory of Dave Bandt 11/19/69 - 3/23/08 "he's traded his wheels for wings" Professor of Natural Aspiration Thanks to: Artie at Trick Flow, Dave at Team Z Motorsports, Brian at Total Engine Airflow and Harold at Furo Racecraft

November 17th, 2006, 02:35 AM	#6
Darrell Asshole™ 1990 Mustang LX 9.36@143 mph Join Date: Jan 2006 Location: Fond du Lac, Wisconsin Posts: 7,762	Does the pressure jump up to 75 or does it fluctuate while you are wide open. If it just jumps to 75 at wide open throttle that is normal. If the pressure is fluctuating, you have a big problem. __________________ Racing in memory of Dave Bandt 11/19/69 - 3/23/08 "he's traded his wheels for wings" Professor of Natural Aspiration Thanks to: Artie at Trick Flow, Dave at Team Z Motorsports, Brian at Total Engine Airflow and Harold at Furo Racecraft

November 18th, 2006, 09:05 PM	#7
stang fanatic Enthusiast Join Date: May 2006 Location: El Paso, Tx Posts: 855	Think of it this way....at 3/4 throttle, your fuel demand is 75% approx., and so your average fuel pressure between 40 and 75 is nominal since air pressure is lower. At full throttle, your supercharger is giving it s all, fuel demand is 100% and so your average fuel psi is now not adequate enough to support the demand and air being fed into the motor. Remeber, the air is still there, but sufficient fuel isnt, find out where the presure loss is from...pump, filter, collapsing line, etc. __________________ "The gods too are fond of a joke." "If I had only known, I would have been a locksmith. "

November 19th, 2006, 08:15 PM	#8
IcantDo55 Enthusiast Join Date: Aug 2005 Location: Va Beach VA Posts: 586	LOOSE THE FMU! Thay suck! Could also be pinging, mine did that whe I first put on the S-trim. Back down the timing and see if that helps. What injectors you rinning? With 42's and a calibrated MAF you can loose the FMU. __________________ -Mike Link to My Site Want to Play Some Pool??? http://img29.photobucket.com/albums/...utsigtest2.jpg Soon to be stroked and blown!

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November 17th, 2006, 12:42 AM	#5
boosted89 Newbie Join Date: Nov 2006 Posts: 2	i Know the fuel pressure is good but the only thing im curious about is when my fuel pressure raises for the supercharger the pressure jumps up and down for 40 to about 75! And yes i checked for codes but didnt get any!! I also have my plugs gapped at .035 thousandths! 2 steps colder

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Car is cutting out top end!!

Car is cutting out top end!!

Re: Car is cutting out top end!!