351W acting up

blk88lx · 01-17-2004, 01:49 PM

hey all, I'm having problems w/my GT.

1st, here's my combo:
Stock 5.8W, GT-40 lower, Cobra upper. 24LBS injectors, Adjustable pressure regulator, 155 LPS Fuel pump. Computer is stock 93 HO, pollution control is hooked up.

Heres what it's doing. I've had this set up in the car for about a year now. At low speeds 35 and below the car will buck. When I down shift it sounds like a big block, rough (sounds cool but not right). It pull hard, and runs great at high speed, car has lots of power.

Here's what Ive done (or had done). Vaccum is good, injectors seem good, alternator has been upgraded to a 94 and up, it's fine. Messing w/the timing doesn't help.

Any ideas? I have a freind who is a mechanic who said it seems lean at mid-range but he cant isolate the problem.

stang_racer20 · 01-18-2004, 01:51 AM

How new is the fuel filter? What pressure is the fuel set at?

blk88lx · 01-18-2004, 11:37 AM

Fuel pressure is about 40 LBS. Timing is 13 degrees. I would think that if the filter was bad, I would be having trouble at Wide Open Throttle.

BilLster · 01-18-2004, 01:27 PM

what type of maf are you using ? and when you change timing your removing the spout and letting the car sit with the battery disconected right ?

mardyn · 01-18-2004, 01:29 PM

Sounds like a cool set up... if it has just started acting up.. it's likely a sensor failure casuing a lean condition at part throttle... Are the O2 sensors working properly? Remember, these babies tell the ECU what to do with the fuel curve... the increased output from the larger injectors may be skewing the exhaust O2 readings and hence the ECU is compensating by trying to lean out the fuel curve... of course it would have been doing this all along.. it all depends on when it started running poorly.

btw... I really need one of those GT40 lower intakes for a 351W... Ford no longer offers it as it has been discontinued..
Any help would be appreciated.

Good Luck
mardyn

mardyn · 01-18-2004, 01:44 PM

If anyone knows of a manifold for sale, please contact me at
mardyn@msn.com or 972-579-7114...

Thanks
David Berry

blk88lx · 01-18-2004, 03:24 PM

Well, It's been doing it since the engine change a year ago, the MAF is a 73mm calibrated for 24 lbs injectors. I haven't thought of the O2 problem...

01-17-2004, 01:49 PM	#1
blk88lx Registered Member Join Date: Jun 2001 Location: Fort Leonard Wood, MO Posts: 179	351W acting up hey all, I'm having problems w/my GT. 1st, here's my combo: Stock 5.8W, GT-40 lower, Cobra upper. 24LBS injectors, Adjustable pressure regulator, 155 LPS Fuel pump. Computer is stock 93 HO, pollution control is hooked up. Heres what it's doing. I've had this set up in the car for about a year now. At low speeds 35 and below the car will buck. When I down shift it sounds like a big block, rough (sounds cool but not right). It pull hard, and runs great at high speed, car has lots of power. Here's what Ive done (or had done). Vaccum is good, injectors seem good, alternator has been upgraded to a 94 and up, it's fine. Messing w/the timing doesn't help. Any ideas? I have a freind who is a mechanic who said it seems lean at mid-range but he cant isolate the problem. __________________ 93 GT, 5.8 EFI usual bolt ons, 3.55's, subs, hurst, K+N 78 F100 Short bed, 5.8, dual pipes 4 bbl 03 Sable

01-18-2004, 01:51 AM	#2
stang_racer20 Registered Member Join Date: Jun 2003 Location: Wisconsin Posts: 348	How new is the fuel filter? What pressure is the fuel set at? __________________ 92 Mustang GT, 347 Stroker(Forged Steel Crank/Rods-Balanced, Forged Aluminum Dished Pistons), Trick Flow Track Heat Intake, Trick Flow Twisted Wedge Heads w/ Stage 3 port/polish, 80mm C&L MAF, FMS 30# Inj., BBK AFPR, Trick Flow Stage 2 Cam, Trick Flow 1.6R Rockers, BBK E.L. Headers, Flowmaster Cat-Back, MAC CAI, FMS Pulleys, Griffin Alum. Radiator, MSD Pro-Billet Distributor; AOD, Dynamic 3300 Lockup Converter, B & M Super Cooler, B&M Ratchet Shifter; 3:73 gears.

01-18-2004, 11:37 AM	#3
blk88lx Registered Member Join Date: Jun 2001 Location: Fort Leonard Wood, MO Posts: 179	Fuel pressure is about 40 LBS. Timing is 13 degrees. I would think that if the filter was bad, I would be having trouble at Wide Open Throttle. __________________ 93 GT, 5.8 EFI usual bolt ons, 3.55's, subs, hurst, K+N 78 F100 Short bed, 5.8, dual pipes 4 bbl 03 Sable

01-18-2004, 01:27 PM	#4
BilLster Registered Member Join Date: Oct 2000 Location: Ontario canada Posts: 446	what type of maf are you using ? and when you change timing your removing the spout and letting the car sit with the battery disconected right ? __________________ 89 with 331 t3'/t4 hybrids. upr Suspention worked out finnaly . 9.89 144 mph .

01-18-2004, 01:29 PM	#5
mardyn Registered Member Join Date: Sep 2003 Location: Irving, Texas Posts: 14	Did it just start doing this? Sounds like a cool set up... if it has just started acting up.. it's likely a sensor failure casuing a lean condition at part throttle... Are the O2 sensors working properly? Remember, these babies tell the ECU what to do with the fuel curve... the increased output from the larger injectors may be skewing the exhaust O2 readings and hence the ECU is compensating by trying to lean out the fuel curve... of course it would have been doing this all along.. it all depends on when it started running poorly. btw... I really need one of those GT40 lower intakes for a 351W... Ford no longer offers it as it has been discontinued.. Any help would be appreciated. Good Luck mardyn

01-18-2004, 01:44 PM	#6
mardyn Registered Member Join Date: Sep 2003 Location: Irving, Texas Posts: 14	Oh yea, I almost forgot... If anyone knows of a manifold for sale, please contact me at mardyn@msn.com or 972-579-7114... Thanks David Berry __________________ '69 Shelby GT350 w/late model EFI 5.0L & T5... Kenne Bell S/C on the shelf now, and then going back to a 5.8L/EFI/S/C & T56 this fall... I hope... Next on the list, Ford GT40

01-18-2004, 03:24 PM	#7
blk88lx Registered Member Join Date: Jun 2001 Location: Fort Leonard Wood, MO Posts: 179	Well, It's been doing it since the engine change a year ago, the MAF is a 73mm calibrated for 24 lbs injectors. I haven't thought of the O2 problem... __________________ 93 GT, 5.8 EFI usual bolt ons, 3.55's, subs, hurst, K+N 78 F100 Short bed, 5.8, dual pipes 4 bbl 03 Sable

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