'87 GT idle surge problem

quickfox87 · 06-25-2007, 10:28 PM

I have a '87 GT i just recently put a ford racing F303 cam in it and it idle surges. I have checked for vacuum leaks and found none. It sucks because i have to idle it at 1000 RPM at least where it won't go dead due to the surge, SO I CAN'T HEAR THE CAM!AHHHH! It is drivin' me nuts! I am stumped any advice would be deeply appreciated!

QWKSNKE · 06-26-2007, 05:06 AM

What is the timing, fuel pressure, and tps voltage set at?
What is the rest of your combination?

I have never ran the F cam (several on here have) but it maybe that it is to big for the EEC to compensate for when trying to idle without having a custom EEC tune

04 Mach1 · 06-26-2007, 06:20 AM

The vert has the f cam. Go ahead and check everything Lee has said but most likely you'll have to have it idle around 1000 rpms. That where ours idles.

quickfox87 · 06-26-2007, 07:05 PM

it has 70 mm throttle body, underdrive pulleys, 3:73's, PP intake, CAI, 2400 stall, BBK shorty headers, borla exhaust. timing is around 12 degrees over top dead center, and how do i check tps voltage
could it being a speed density car have anything to do with it?
would it maybe help to carbeurate it?

QWKSNKE · 06-26-2007, 07:55 PM

Quote:

Originally Posted by quickfox87

would it maybe help to carbeurate it?

No!!!!!!!!!!!!!

quickfox87 · 06-26-2007, 09:36 PM

how do i check tps voltage and if i dont need to carbeurate it what about converting to a mass air flow?

QWKSNKE · 06-27-2007, 05:04 AM

MAF conversion would help but when you get into decent size cams whether you are carbed or fuel injected you will have to bump the idle up unless you get a custom tuned chip or EEC tuner

04 Mach1 · 06-27-2007, 06:14 AM

Do a MAF conversion should straighten everything up. I heard on a speed density car you really can't do much other than a set of 1.7 rockers with out killing the ilde quality. Or you could have a chip burnt for it.

Tps voltage is check on the green wire at the tps. Should set around .98 volts.

coupe · 06-27-2007, 10:43 AM

Yes, a MAF conversion is your solution.

The Speed Density computer gets its airflow numbers based on a MAP sensor (Manifold Pressure) and ACT (Air Charge Temperature). So the computer uses temperature and pressure in the manifold to calculate a volume of air present...no airflow measurement.

The cam is drawing more airflow into the motor and causing the O2 sensors to see what it thinks are problems with too much air, so it tries to regulate the Idle-control causing surging. The MAP and ACT don't change with the cam...the pressure and temperature of the air stays the same...this is the defficiency of Speed Density in our application.

Do the MAF conversion (MAF meter, MAF computer, and the wiring swap in the harness). The car will quit making you mad.

No Carb.

Italian LX · 06-27-2007, 10:54 AM

Quote:

Originally Posted by coupe

. . .The car will quit making you mad.

I wouldn't go that far - I've had many MAF cars make me go mad.

. . . hell, ask Marc about his glow-tech issue.

Quote:

Originally Posted by coupe

No Carb.

06-25-2007, 10:28 PM	#1
quickfox87 Junior Member Join Date: Jun 2007 Location: southside,AL Posts: 15	'87 GT idle surge problem I have a '87 GT i just recently put a ford racing F303 cam in it and it idle surges. I have checked for vacuum leaks and found none. It sucks because i have to idle it at 1000 RPM at least where it won't go dead due to the surge, SO I CAN'T HEAR THE CAM!AHHHH! It is drivin' me nuts! I am stumped any advice would be deeply appreciated!

06-26-2007, 05:06 AM	#2
QWKSNKE 3v's are slow Join Date: Dec 2004 Location: Here and There Posts: 17,152	What is the timing, fuel pressure, and tps voltage set at? What is the rest of your combination? I have never ran the F cam (several on here have) but it maybe that it is to big for the EEC to compensate for when trying to idle without having a custom EEC tune __________________ 2009 Porsche Carrera S 2008 ///AMG C63.. Eurocharge Tune. RIP 2019 AMG GLC43..wife's 03 F250 SD.. Edge Evo, AFE Stage 1 CAI 08 GT. JBA axle back, FRPP springs, FRPP swaybars.. daughter's 01 Cobra vert... wife's I need a new toy

06-26-2007, 07:05 PM	#4
quickfox87 Junior Member Join Date: Jun 2007 Location: southside,AL Posts: 15	it has 70 mm throttle body, underdrive pulleys, 3:73's, PP intake, CAI, 2400 stall, BBK shorty headers, borla exhaust. timing is around 12 degrees over top dead center, and how do i check tps voltage could it being a speed density car have anything to do with it? would it maybe help to carbeurate it? Last edited by quickfox87; 06-26-2007 at 07:07 PM. Reason: forgot

06-26-2007, 09:36 PM	#6
quickfox87 Junior Member Join Date: Jun 2007 Location: southside,AL Posts: 15	how do i check tps voltage and if i dont need to carbeurate it what about converting to a mass air flow? __________________ GO FAST OR GO AWAY!!!!!!!!http://forums.stangnet.com/images/smilies/Track.gif

06-27-2007, 05:04 AM	#7
QWKSNKE 3v's are slow Join Date: Dec 2004 Location: Here and There Posts: 17,152	MAF conversion would help but when you get into decent size cams whether you are carbed or fuel injected you will have to bump the idle up unless you get a custom tuned chip or EEC tuner __________________ 2009 Porsche Carrera S 2008 ///AMG C63.. Eurocharge Tune. RIP 2019 AMG GLC43..wife's 03 F250 SD.. Edge Evo, AFE Stage 1 CAI 08 GT. JBA axle back, FRPP springs, FRPP swaybars.. daughter's 01 Cobra vert... wife's I need a new toy

06-26-2007, 06:20 AM	#3
04 Mach1 Bet I red light B4U Join Date: Aug 2005 Location: ANNISTON, AL Posts: 975	The vert has the f cam. Go ahead and check everything Lee has said but most likely you'll have to have it idle around 1000 rpms. That where ours idles.

06-27-2007, 06:14 AM	#8
04 Mach1 Bet I red light B4U Join Date: Aug 2005 Location: ANNISTON, AL Posts: 975	Do a MAF conversion should straighten everything up. I heard on a speed density car you really can't do much other than a set of 1.7 rockers with out killing the ilde quality. Or you could have a chip burnt for it. Tps voltage is check on the green wire at the tps. Should set around .98 volts.

06-27-2007, 10:43 AM	#9
coupe Super Moderator Join Date: Dec 2004 Posts: 6,313	Yes, a MAF conversion is your solution. The Speed Density computer gets its airflow numbers based on a MAP sensor (Manifold Pressure) and ACT (Air Charge Temperature). So the computer uses temperature and pressure in the manifold to calculate a volume of air present...no airflow measurement. The cam is drawing more airflow into the motor and causing the O2 sensors to see what it thinks are problems with too much air, so it tries to regulate the Idle-control causing surging. The MAP and ACT don't change with the cam...the pressure and temperature of the air stays the same...this is the defficiency of Speed Density in our application. Do the MAF conversion (MAF meter, MAF computer, and the wiring swap in the harness). The car will quit making you mad. No Carb. __________________ " If you can't explain it simply, you don't understand it well enough. " - Albert Einstein