This is going to be a little long winded so bear with me, but I wanted to provide as much info as I could. 
So don't know if anyone remembers me, but back in maybe 2008-2009 I had a stroker/maf project on here. Long story short I never got it running right and lost motivation and the truck ended up just sitting. I don't think it was smart of me to take on such a big project with what little knowledge I had about cars. ._.
Fast forward to 2013 and I got married, bought a house, and the inop Bronco came with me. Me and my husband got really into motorcycles right after so that's been my focus since then. After over 5.5 years sitting in the driveway my husband implored me to do something with the Bronco or get rid of it. Even though I had barely looked at it in years I still have a deep attachment to my Bronco and it finally regained my focus.
I've been working as a tech at Toyota for the past 6 years now so I consider myself a little more mechanically inclined than before. Lol
So last year I pulled the engine back out, intending to put it back to stock mostly, but still using a few small upgrades for a little extra power. I worked on it off and on over the year and finally got it back in the truck.
Now it has some idling/power issues that I've been trying to figure out, but haven't gotten it quite yet.
This is where you guys come in to hopefully help solve my issues.
First here's what I've done so far:
Got a factory engine harness/ecm from the junkyard and replaced all the broken connectors then repinned my ECM connector back to stock.
SPECS
-1991
-E4OD
-351W bored 0.40 over
-Scat Crankshaft
-SpeedPro Pistons with Factory Rods
-Edelbrock Truck Intake
-BBK 56mm Throttle Body
-Reman. GT40 iron heads with Crane Cams stud conversion kit
-Crane CompuCam and Lifters CRN-444232
-Comp Cams 5/16" Pushrods (8.250")
-Ford Racing Double Roller Timing Chain/Gears
-Gibson Shorty Headers
-Bassani Y-Pipe (3" ID all the way back)
-Walbro 255lph Fuel Pump (about 10 years old, but been sitting in empty fuel tank. Fuel pressure seems ok?)
All engine vacuum lines replaced with thick-walled silicone hoses from siliconeintakes (triple checked for correct routing)
4gauge power and ground wires to battery/alternator.
Factory Distributor and Grey TFI Module
C1Z ECM (F1TF-12A650-ATA) from Junkyard
Factory Fuel Rail
MasterPro Ignition Coil
Timing 13° BTDC (with SPOUT disconnected); jumps to mid-high 20s with SPOUT connected
IAT @~55°F - 3.4V, 51.7K ohms (forgot to check it when warm)
NEW Parts
*Throttle Cable
*Fuel Filter
*Motorcraft PCV
*Waterpump
*Thermostat
*Harmonic Balancer
*Spark Plugs (Motorcraft AGSG32C) - 0.055 Gap
*Ford Racing Spark Plug Wires (routed as per factory tsb to prevent crossfire)
*MSD Cap and Rotor
*Bosch 4 Hole 19lb Injectors
*EGR Valve
*Magnaflow Catalytic Converter
*Engine Coolant Temperature Sensor
*O2 Sensor
*Fuel Pressure Regulator
Fuel Pressure at Rail:
-KOEO 40psi then drops to 34psi
-KOER First starts holds at 34psi, 36-38psi once it's idling a couple minutes.
*Throttle Position Sensor
-5V Ref
-Closed 0.93V
-WOT 4.66V
*Idle Air Control Valve
-9.7ohms
-Drops RPMs to ~450 when unplugged
So my very first starting attempt on the new engine it would crank strongly and sounded like it wanted to start, but wouldn't. After some poking around found the TPS resistance way out of spec.
Replaced TPS (set to 0.93V closed) and engine now starts, but will rev up for a bit and then drop in rpms and die. I usually have to keep my foot on the gas until the engine warms up then it'll idle pretty much on its own. Still will randomly drop idle, and then sometimes die out. Idle isn't that smooth, but is hanging around high 700rpms.
Once warmed up the engine felt ok when giving it throttle in Park. But when I tried driving it around the block it really lacked power and would hardly pick up speed when giving it steady throttle; eventually the pedal will be to the floor and still no change. This is when I decided to replace the FPR to see if there was any improvement (since my readings at the rail were borderline and it's a cheap part; vacuum line smelled a little like fuel also). Didn't seem to change anything. The hose on my fuel pressure gauge isn't very long so I was unable to view my fuel pressure when driving it.
No Check Engine light coming on, but here are the codes I get.
KOEO DTC 11
KOEO CM DTC 11
KOER CM DTC 44
KOER CM DTC 77
The GT40 heads I ordered did not come with thermactor holes (wasn't aware the later model ones didn't have them) so that may be the 44 code. I read the thermactor wasn't crucial for engine performance or to pass smog so I didn't worry too much about it. Tapped holes in the back of the heads though so I could still bolt up the pipe and all the other smog parts to make it look factory. So everything is hooked up as it should be, just no thermactor ports in the heads.
I did the WOT part of the KOER test when instructed, but still get that 77 code on multiple attempts. Don't know what that's about.
I was getting a KOER CM DTC 41 at first, but then I put in a new O2 sensor and I haven't seen that code come back yet.
So pretty much no codes to go off of.
A few other observations:
MAP may still be factory part (don't recall ever replacing it), but I've read they're not usually suspect for failure? Was thinking of grabbing a couple from the junkyard to see if anything changes.
My brake booster hisses when you press the pedal, but I'm not sure it's leaking. I tried pinching off the hose to it when the engine was running and didn't see any change on the vacuum gauge.
Keep forgetting so haven't checked my transmission fluid yet, but the pan has been leaking all these years so it's probably low. Not sure if that would cause any idle issues.
I don't have a lot of experience with vacuum gauges so I took a video for reference. At idle it's around 18-19hg, but the needle is quivering between. Blip the throttle and it drops to about 5hg then jumps to about 22-23hg. Again, I've replaced all the engine vacuum lines with thick-walled silicone lines.
EDIT: Videos still kinda aren't working, but if you go to the links and click 'Download Original Movie File' right below the player on the page you can view them.
Here's the other day when I first tried to start it; just cranks and cranks.
www.supermotors.net
Then immediately after that I crank it again and it starts and will idle for a little bit then die (fuel pressure was holding at 34 even when it died). A lot of times though when it starts it will stumble bad and I'll have to give it some throttle to help keep it running.
www.supermotors.net
A couple mins after it was running here's the fuel pressure up until it dies.
www.supermotors.net
When warmed up it seems to idle ok for the most part, but still occasionally stumbles.
Let me know if the videos don't work! I just uploaded them.
I've been searching for days on the internet trying to figure out something, but no luck this far. I'm wondering if my fuel pump just isn't cutting it anymore? Or maybe I'm having some kind of ignition problem (factory distributor and factory TFI module). I checked spark coming directly from the coil and it was bright blue.
Thank you everyone who has read this far! Any help will be greatly appreciated!! Please help me get my Bronco back on the road! I really miss driving it.
So don't know if anyone remembers me, but back in maybe 2008-2009 I had a stroker/maf project on here. Long story short I never got it running right and lost motivation and the truck ended up just sitting. I don't think it was smart of me to take on such a big project with what little knowledge I had about cars. ._.
Fast forward to 2013 and I got married, bought a house, and the inop Bronco came with me. Me and my husband got really into motorcycles right after so that's been my focus since then. After over 5.5 years sitting in the driveway my husband implored me to do something with the Bronco or get rid of it. Even though I had barely looked at it in years I still have a deep attachment to my Bronco and it finally regained my focus.
I've been working as a tech at Toyota for the past 6 years now so I consider myself a little more mechanically inclined than before. Lol
So last year I pulled the engine back out, intending to put it back to stock mostly, but still using a few small upgrades for a little extra power. I worked on it off and on over the year and finally got it back in the truck.
Now it has some idling/power issues that I've been trying to figure out, but haven't gotten it quite yet.
This is where you guys come in to hopefully help solve my issues.
First here's what I've done so far:
Got a factory engine harness/ecm from the junkyard and replaced all the broken connectors then repinned my ECM connector back to stock.
SPECS
-1991
-E4OD
-351W bored 0.40 over
-Scat Crankshaft
-SpeedPro Pistons with Factory Rods
-Edelbrock Truck Intake
-BBK 56mm Throttle Body
-Reman. GT40 iron heads with Crane Cams stud conversion kit
-Crane CompuCam and Lifters CRN-444232
-Comp Cams 5/16" Pushrods (8.250")
-Ford Racing Double Roller Timing Chain/Gears
-Gibson Shorty Headers
-Bassani Y-Pipe (3" ID all the way back)
-Walbro 255lph Fuel Pump (about 10 years old, but been sitting in empty fuel tank. Fuel pressure seems ok?)
All engine vacuum lines replaced with thick-walled silicone hoses from siliconeintakes (triple checked for correct routing)
4gauge power and ground wires to battery/alternator.
Factory Distributor and Grey TFI Module
C1Z ECM (F1TF-12A650-ATA) from Junkyard
Factory Fuel Rail
MasterPro Ignition Coil
Timing 13° BTDC (with SPOUT disconnected); jumps to mid-high 20s with SPOUT connected
IAT @~55°F - 3.4V, 51.7K ohms (forgot to check it when warm)
NEW Parts
*Throttle Cable
*Fuel Filter
*Motorcraft PCV
*Waterpump
*Thermostat
*Harmonic Balancer
*Spark Plugs (Motorcraft AGSG32C) - 0.055 Gap
*Ford Racing Spark Plug Wires (routed as per factory tsb to prevent crossfire)
*MSD Cap and Rotor
*Bosch 4 Hole 19lb Injectors
*EGR Valve
*Magnaflow Catalytic Converter
*Engine Coolant Temperature Sensor
*O2 Sensor
*Fuel Pressure Regulator
Fuel Pressure at Rail:
-KOEO 40psi then drops to 34psi
-KOER First starts holds at 34psi, 36-38psi once it's idling a couple minutes.
*Throttle Position Sensor
-5V Ref
-Closed 0.93V
-WOT 4.66V
*Idle Air Control Valve
-9.7ohms
-Drops RPMs to ~450 when unplugged
So my very first starting attempt on the new engine it would crank strongly and sounded like it wanted to start, but wouldn't. After some poking around found the TPS resistance way out of spec.
Replaced TPS (set to 0.93V closed) and engine now starts, but will rev up for a bit and then drop in rpms and die. I usually have to keep my foot on the gas until the engine warms up then it'll idle pretty much on its own. Still will randomly drop idle, and then sometimes die out. Idle isn't that smooth, but is hanging around high 700rpms.
Once warmed up the engine felt ok when giving it throttle in Park. But when I tried driving it around the block it really lacked power and would hardly pick up speed when giving it steady throttle; eventually the pedal will be to the floor and still no change. This is when I decided to replace the FPR to see if there was any improvement (since my readings at the rail were borderline and it's a cheap part; vacuum line smelled a little like fuel also). Didn't seem to change anything. The hose on my fuel pressure gauge isn't very long so I was unable to view my fuel pressure when driving it.
No Check Engine light coming on, but here are the codes I get.
KOEO DTC 11
KOEO CM DTC 11
KOER CM DTC 44
KOER CM DTC 77
The GT40 heads I ordered did not come with thermactor holes (wasn't aware the later model ones didn't have them) so that may be the 44 code. I read the thermactor wasn't crucial for engine performance or to pass smog so I didn't worry too much about it. Tapped holes in the back of the heads though so I could still bolt up the pipe and all the other smog parts to make it look factory. So everything is hooked up as it should be, just no thermactor ports in the heads.
I did the WOT part of the KOER test when instructed, but still get that 77 code on multiple attempts. Don't know what that's about.
I was getting a KOER CM DTC 41 at first, but then I put in a new O2 sensor and I haven't seen that code come back yet.
So pretty much no codes to go off of.
A few other observations:
MAP may still be factory part (don't recall ever replacing it), but I've read they're not usually suspect for failure? Was thinking of grabbing a couple from the junkyard to see if anything changes.
My brake booster hisses when you press the pedal, but I'm not sure it's leaking. I tried pinching off the hose to it when the engine was running and didn't see any change on the vacuum gauge.
Keep forgetting so haven't checked my transmission fluid yet, but the pan has been leaking all these years so it's probably low. Not sure if that would cause any idle issues.
I don't have a lot of experience with vacuum gauges so I took a video for reference. At idle it's around 18-19hg, but the needle is quivering between. Blip the throttle and it drops to about 5hg then jumps to about 22-23hg. Again, I've replaced all the engine vacuum lines with thick-walled silicone lines.
EDIT: Videos still kinda aren't working, but if you go to the links and click 'Download Original Movie File' right below the player on the page you can view them.
Here's the other day when I first tried to start it; just cranks and cranks.
1991 Ford Bronco Help video | SuperMotors.net
20200322_183909.mp4 First start, Long crank
Then immediately after that I crank it again and it starts and will idle for a little bit then die (fuel pressure was holding at 34 even when it died). A lot of times though when it starts it will stumble bad and I'll have to give it some throttle to help keep it running.
1991 Ford Bronco Help video | SuperMotors.net
20200322_183920.mp4 2nd attempts; starts; dies
A couple mins after it was running here's the fuel pressure up until it dies.
1991 Ford Bronco Help video | SuperMotors.net
20200322_184230.mp4 Cold idle fuel pressure; dies
When warmed up it seems to idle ok for the most part, but still occasionally stumbles.
Let me know if the videos don't work! I just uploaded them.
I've been searching for days on the internet trying to figure out something, but no luck this far. I'm wondering if my fuel pump just isn't cutting it anymore? Or maybe I'm having some kind of ignition problem (factory distributor and factory TFI module). I checked spark coming directly from the coil and it was bright blue.
Thank you everyone who has read this far! Any help will be greatly appreciated!! Please help me get my Bronco back on the road! I really miss driving it.