Hello,
I have been having persistent problems since before I replaced the lower intake(about 2 months ago) when flooring it in my turbo fox. The first drive out after replacing the intake I discovered my fuel pump was just hanging in the fuel tank, so I fixed that, and the car ran like a bat out of hell for literally one drive. Since then, it started losing power up top(again), at first it just started falling flat, but now it will also misfire and occasionally backfire through the intake, usually around 3500rpms it starts falling flat and by 4000 its backfiring and running so horribly I don't want to give it any more gas, lol. It seems to rev and build boost fine if I am less than 1/2 throttle but once I start getting into it the car stumbles. Sometimes after driving for a while it will start backfiring through the exhaust while idling and stumbling during light acceleration(less than 1/2) in the lower rpm range(1000-2500ish) and then it will clear up unless I give it more gas. Also since replacing the distributor and TFI module, the autometer tachometer has also started jumping around, which I've heard can be from a bad pip? Water temp always reads between 180 and 210 once its warm, boost is at wastegate right now which is 8psi. Battery voltage is good.
Engine Build:
302 bored to 306
Icon Forged Pistons, Ford Racing Z Aluminum Heads, Scorpion roller rockers, trickflow cam,
billet timing set, plasma moly rings, clevite rod and main bearings, pioneer hp street balancer,
arp main and head studs, arp engine bolt kit , mls head gaskets, heads port matched,
trickflow streetburner intake, aluminum fuel rails, 455lph walbro pump,
adjustable fuel regulator, 60lbs? injectors, msd 6al ignition and 2 step,
Hellion turbo kit w/ 61mm precision turbo.
Car was tuned and Dyno'd at 460hp on 11psi of boost
So far what I've done:
Retorqued the lower and upper intake, Gone through the fuel system from the fuel pump to the injectors, gone through the ignition, from the 6al box(also ran it with the stock ignition, didn't seem to help) to the spark plugs. I've also checked all charge pipes, they were all tight. Checked the engine grounds, all battery grounds, ground running to alternator, grounds for computer. Those were all good and the ones that were not on bare metal are now.
Checked timing, set to 10degrees with spout out, also tried it at 7 degrees(result was worse drivability) recently changed and then checked spark plugs(at about 250 miles), #3 plug was rich enough the insulator was black, every other plug was tan and looked good. Checked fuel pressure while revving, at 4k WOT(using 2 step), and at idle, holds steady at 40psi, sits around 33psi with vacuum at idle. Checked Spark plug wires for arcing using a water spray bottle, did not see anything.
The codes I dump:
at first I was dumping a code 64(ACT sensor) and 41(pass side o2 sensor). I replaced both of those and they went away
Now I am getting code 85(canister purge which is deleted) and 95(fuel pump circuit, car has standalone fuel pump wiring) during KOEO, and code 91(drivers side o2 sensor) during KOER. The driver side o2 sensor was replaced when I first got the car about a year ago.
I tried the Engine balance test but the car idles around 1000rpm and I've read it needs to idle around 600-700 to be accurate. Regardless here are the results:
1st time: cyl 6,7 fail 2nd time: cyl 8 fail 3rd time: cyl 8,5 fail
List of parts I have replaced in order since I got the car:
TPS Sensor, Driver side O2 sensor, Header Gasket replaced with copper Permatex, New 255lph fuel pump(switched back to original 455lph), New Cap, rotor, spark plugs x2, spark plug wires and boots, New Trickflow lower intake, new MSD Coil, new fuel tank, new ACT sensor, New starter solenoid, New Motorcraft TFI Module(ended up being dead on arrival), swapped MSD pro billet distributor with used Motorcraft distributor and TFI module, New passenger O2 sensor.
Also I ordered a A/F gauge and Fuel Pressure gauge for the interior so I can get some better data when its under boost. Any help would be greatly appreciated as I'm just about out of ideas on what to throw money at next lol. also I have a few videos of the problems if anyone wants to see them I can post them or send them.
I have been having persistent problems since before I replaced the lower intake(about 2 months ago) when flooring it in my turbo fox. The first drive out after replacing the intake I discovered my fuel pump was just hanging in the fuel tank, so I fixed that, and the car ran like a bat out of hell for literally one drive. Since then, it started losing power up top(again), at first it just started falling flat, but now it will also misfire and occasionally backfire through the intake, usually around 3500rpms it starts falling flat and by 4000 its backfiring and running so horribly I don't want to give it any more gas, lol. It seems to rev and build boost fine if I am less than 1/2 throttle but once I start getting into it the car stumbles. Sometimes after driving for a while it will start backfiring through the exhaust while idling and stumbling during light acceleration(less than 1/2) in the lower rpm range(1000-2500ish) and then it will clear up unless I give it more gas. Also since replacing the distributor and TFI module, the autometer tachometer has also started jumping around, which I've heard can be from a bad pip? Water temp always reads between 180 and 210 once its warm, boost is at wastegate right now which is 8psi. Battery voltage is good.
Engine Build:
302 bored to 306
Icon Forged Pistons, Ford Racing Z Aluminum Heads, Scorpion roller rockers, trickflow cam,
billet timing set, plasma moly rings, clevite rod and main bearings, pioneer hp street balancer,
arp main and head studs, arp engine bolt kit , mls head gaskets, heads port matched,
trickflow streetburner intake, aluminum fuel rails, 455lph walbro pump,
adjustable fuel regulator, 60lbs? injectors, msd 6al ignition and 2 step,
Hellion turbo kit w/ 61mm precision turbo.
Car was tuned and Dyno'd at 460hp on 11psi of boost
So far what I've done:
Retorqued the lower and upper intake, Gone through the fuel system from the fuel pump to the injectors, gone through the ignition, from the 6al box(also ran it with the stock ignition, didn't seem to help) to the spark plugs. I've also checked all charge pipes, they were all tight. Checked the engine grounds, all battery grounds, ground running to alternator, grounds for computer. Those were all good and the ones that were not on bare metal are now.
Checked timing, set to 10degrees with spout out, also tried it at 7 degrees(result was worse drivability) recently changed and then checked spark plugs(at about 250 miles), #3 plug was rich enough the insulator was black, every other plug was tan and looked good. Checked fuel pressure while revving, at 4k WOT(using 2 step), and at idle, holds steady at 40psi, sits around 33psi with vacuum at idle. Checked Spark plug wires for arcing using a water spray bottle, did not see anything.
The codes I dump:
at first I was dumping a code 64(ACT sensor) and 41(pass side o2 sensor). I replaced both of those and they went away
Now I am getting code 85(canister purge which is deleted) and 95(fuel pump circuit, car has standalone fuel pump wiring) during KOEO, and code 91(drivers side o2 sensor) during KOER. The driver side o2 sensor was replaced when I first got the car about a year ago.
I tried the Engine balance test but the car idles around 1000rpm and I've read it needs to idle around 600-700 to be accurate. Regardless here are the results:
1st time: cyl 6,7 fail 2nd time: cyl 8 fail 3rd time: cyl 8,5 fail
List of parts I have replaced in order since I got the car:
TPS Sensor, Driver side O2 sensor, Header Gasket replaced with copper Permatex, New 255lph fuel pump(switched back to original 455lph), New Cap, rotor, spark plugs x2, spark plug wires and boots, New Trickflow lower intake, new MSD Coil, new fuel tank, new ACT sensor, New starter solenoid, New Motorcraft TFI Module(ended up being dead on arrival), swapped MSD pro billet distributor with used Motorcraft distributor and TFI module, New passenger O2 sensor.
Also I ordered a A/F gauge and Fuel Pressure gauge for the interior so I can get some better data when its under boost. Any help would be greatly appreciated as I'm just about out of ideas on what to throw money at next lol. also I have a few videos of the problems if anyone wants to see them I can post them or send them.
Last edited: