car runs lean under boost - 2003-04 Mach 1 Registry Owners Club

jv7 · 06-03-2017, 05:18 PM

Car runs fine cruising around idles fine but above 3lbs of boost seems to run extremely lean it will start to backfire and sputter I think thats about the time the boost a pump is suppose to kick in other than than on fuel I'm running 80lb inj and Aeromotive 325lph fuel pump. I can rev it up to redline if I keep the boost at 3lbs or less but above that regardless of rpms seems lean. Could it be a bad bov? I have the vortech mondo. Thanks.

littlemags · 06-03-2017, 05:23 PM

definitely not getting fuel for sure. I switched to full return style because of such issues with boost a pump. I would make sure that is working but with seeing some data log it would be hard to self diag

TKat13 · 06-05-2017, 11:20 PM

overly simple, but check your fuel filter.

jv7 · 06-09-2017, 03:29 PM

Already did that. Cleaned maf and kn filter no change.

DSG2003Mach1 · 06-09-2017, 03:55 PM

Is it lean or is it bad spark blow out?

Sounds like you need to get a wideband on there

Cooldbz12 · 06-10-2017, 12:48 PM

Id get a wideband right away to see how lean your going, then adjust from there with a handheld tuner. also check all the hoses for cracks and such, maybe there is air getting in there past the MAF. A fuel pressure gauge would help alot to to diagnose stuff too. At 3 psi i think the pump your running should be fine even without the BAP. If your running a off the shelf tune, id get it to a tuner and get a custom tune right away.

Gauges you should always have if your boosted.

A/F gauge
Fuel Press Gauge
Oil Press gauge
Boost/ Vac Gauge
Water temp gauge ( even if not boosted )

06-03-2017, 05:18 PM	#1
jv7 Registered User Join Date: Jan 2004 Location: Round Rock, TX Posts: 950	car runs lean under boost Car runs fine cruising around idles fine but above 3lbs of boost seems to run extremely lean it will start to backfire and sputter I think thats about the time the boost a pump is suppose to kick in other than than on fuel I'm running 80lb inj and Aeromotive 325lph fuel pump. I can rev it up to redline if I keep the boost at 3lbs or less but above that regardless of rpms seems lean. Could it be a bad bov? I have the vortech mondo. Thanks. Last edited by jv7; 06-03-2017 at 06:50 PM.

06-03-2017, 05:23 PM	#2
littlemags finally paid for Join Date: Nov 2004 Location: Ypsilanti Twp, Mi Posts: 4,077	Re: car runs lean under boost definitely not getting fuel for sure. I switched to full return style because of such issues with boost a pump. I would make sure that is working but with seeing some data log it would be hard to self diag __________________ 2004 mach 1-turbo build in progress.. Fast xfi 2.0 OLD combo- 826rwhp/720 trq -100 shot NX 9.13@154 on 100 shot NEW- in progress...

06-05-2017, 11:20 PM	#3
TKat13 Mach-T Join Date: Jun 2004 Location: DFW Posts: 2,865	Re: car runs lean under boost overly simple, but check your fuel filter. __________________ Darrell Black '04 Mach 1 Track Times (bone-stock w/drs):60 ft - 1.90 \| 1/8 - 8.67 (100 shot,E85,4:10s,Street tire):60 ft - 1.67 \| 1/8 - 7.88 New build - 750rwhp; not track tested (yet) Mods: Build Log Paint&Body Tuned by Manny @ HPP

06-09-2017, 03:29 PM	#4
jv7 Registered User Join Date: Jan 2004 Location: Round Rock, TX Posts: 950	Re: car runs lean under boost Already did that. Cleaned maf and kn filter no change.

06-09-2017, 03:55 PM	#5
DSG2003Mach1 700 HP Mach Join Date: Nov 2003 Location: Orlando, FL Posts: 8,384	Re: car runs lean under boost Is it lean or is it bad spark blow out? Sounds like you need to get a wideband on there __________________ 03 dsg mach1 - MPR built 9.5:1 motor, D1, cams, ported intake, full exhaust, magnum t56, built rear, E85 etc... '12 F150 FX2 Supercrew with Ecoboost daily beater

06-10-2017, 12:48 PM	#6
Cooldbz12 Registered User Join Date: May 2007 Location: FS, TX Posts: 796	Re: car runs lean under boost Id get a wideband right away to see how lean your going, then adjust from there with a handheld tuner. also check all the hoses for cracks and such, maybe there is air getting in there past the MAF. A fuel pressure gauge would help alot to to diagnose stuff too. At 3 psi i think the pump your running should be fine even without the BAP. If your running a off the shelf tune, id get it to a tuner and get a custom tune right away. Gauges you should always have if your boosted. A/F gauge Fuel Press Gauge Oil Press gauge Boost/ Vac Gauge Water temp gauge ( even if not boosted ) __________________ 2003 Mustang Mach 1 (Bought 11/16/2005) Eaton Swapped @7psi (On 10/24/15) 13.2@107 (Bone Stock Run) 2000 3.8 Mustang Sold But Will Never Be Forgotten

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