91 with new motor issues
#1
10-13-2018, 10:35 PM
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91 with new motor issues
Hey folks,
purchased a 91 f150 lariet with no motor awhile back. Later, found an 85 block, had it completely rebuilt, .040 overbore, new pistons, bearings, etc. two weeks ago dropped the motor in and it started up! Woohoo! First time putting an engine in a truck. Ran like crap, but had enough fuel/air to idle. Seemed to have a vacuum leak of sorts that lead to a wavy idle. Two days ago, started up the truck to move from driveway to garage and it would barely move. Super rough idle, felt like it wouldn’t go into gear. Now it won’t stay running at all. Starts right up, idles high for 30 seconds and dies. Attached is a list of things I’ve attempted, as well as some odd ball parts as this is a bit of a craigslist special on the engine build.
85 block, rebuilt
double roller tuning chain
comp cam 31-255-5
top end from a 94 f150 - intake manifold, throttle body, coil, egr, tab, tag(?)
new ngq plugs, ford wires
new o2 sensor
new throttle position sensor
when I say it was running, it was running well enough to do a few laps around the block. No highway cruising.
Is is there some sort of issue with the 94 top end being plugged into the 91 wiring harness?
Also, i did the paperclip test the night before it stopped running and was able to pull a code 41 for running lean.
Will rent ob1 scanner tomorrow and report any findings.
Thanks in advance.
purchased a 91 f150 lariet with no motor awhile back. Later, found an 85 block, had it completely rebuilt, .040 overbore, new pistons, bearings, etc. two weeks ago dropped the motor in and it started up! Woohoo! First time putting an engine in a truck. Ran like crap, but had enough fuel/air to idle. Seemed to have a vacuum leak of sorts that lead to a wavy idle. Two days ago, started up the truck to move from driveway to garage and it would barely move. Super rough idle, felt like it wouldn’t go into gear. Now it won’t stay running at all. Starts right up, idles high for 30 seconds and dies. Attached is a list of things I’ve attempted, as well as some odd ball parts as this is a bit of a craigslist special on the engine build.
85 block, rebuilt
double roller tuning chain
comp cam 31-255-5
top end from a 94 f150 - intake manifold, throttle body, coil, egr, tab, tag(?)
new ngq plugs, ford wires
new o2 sensor
new throttle position sensor
when I say it was running, it was running well enough to do a few laps around the block. No highway cruising.
Is is there some sort of issue with the 94 top end being plugged into the 91 wiring harness?
Also, i did the paperclip test the night before it stopped running and was able to pull a code 41 for running lean.
Will rent ob1 scanner tomorrow and report any findings.
Thanks in advance.
#2
10-13-2018, 11:35 PM
Elder User
Is the motor you dropped in the same size as what was in it? If not the PCM is gonna give ya fits and if the engine is, and it has a lot of variance from factory specs (cam,etc) then the PCM will constantly try to adjust within it's parameters . What you have done so far is change a LOT of things so I really do not know where to start.
#3
10-14-2018, 08:09 AM
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Is the motor you dropped in the same size as what was in it? If not the PCM is gonna give ya fits and if the engine is, and it has a lot of variance from factory specs (cam,etc) then the PCM will constantly try to adjust within it's parameters . What you have done so far is change a LOT of things so I really do not know where to start.
I guess my my real question is, does the pcm wildly differ year to year when it comes to sensors for the truck?
#4
10-14-2018, 08:16 AM
Elder User
ahhhhh.. I think I see the problem, or at least part of it. You have a MAF intake when you need Map. The 91 I believe uses a MAP sensor.
https://www.ford-trucks.com/forums/6...d-density.html
https://www.ford-trucks.com/forums/6...d-density.html
#5
10-14-2018, 08:39 AM
We need more info. When you say no motor, what was originally in it?
Where did you source the ignition and fuel injection components?
Was there an engine harness in your truck? Never swapped computers?
You likely have more than one issue here that is causing your problems. Then there are the normal kinks that need to be ironed out after an engine swap or rebuild like timing, or timing, and timing.
Where did you source the ignition and fuel injection components?
Was there an engine harness in your truck? Never swapped computers?
You likely have more than one issue here that is causing your problems. Then there are the normal kinks that need to be ironed out after an engine swap or rebuild like timing, or timing, and timing.
#6
10-14-2018, 09:45 AM
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We need more info. When you say no motor, what was originally in it?
Where did you source the ignition and fuel injection components?
Was there an engine harness in your truck? Never swapped computers?
You likely have more than one issue here that is causing your problems. Then there are the normal kinks that need to be ironed out after an engine swap or rebuild like timing, or timing, and timing.
Where did you source the ignition and fuel injection components?
Was there an engine harness in your truck? Never swapped computers?
You likely have more than one issue here that is causing your problems. Then there are the normal kinks that need to be ironed out after an engine swap or rebuild like timing, or timing, and timing.
if it helps, the truck remains set up with a sd system, map sensor, etc.
#7
10-14-2018, 09:54 AM
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ahhhhh.. I think I see the problem, or at least part of it. You have a MAF intake when you need Map. The 91 I believe uses a MAP sensor.
https://www.ford-trucks.com/forums/6...d-density.html
https://www.ford-trucks.com/forums/6...d-density.html
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#8
10-14-2018, 10:59 AM
What fuel pressure do you have?
Do you still have the plugs wired for the old 15426378 firing order? You should.
Does the truck have a full exhaust system on it?
#9
10-14-2018, 11:47 AM
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There is no such thing as a MAF or MAP specific intake for these trucks, they are functionally the same except for minor differences like the air temp sensor location so this isn't your proiblem.
What fuel pressure do you have?
Do you still have the plugs wired for the old 15426378 firing order? You should.
Does the truck have a full exhaust system on it?
What fuel pressure do you have?
Do you still have the plugs wired for the old 15426378 firing order? You should.
Does the truck have a full exhaust system on it?
currently working on fuel pressure as I think that’s my issue. Will run for a min with starting fluid I’ve just found out.
The exahaust has been converted to some sort of duel set up. However it splits after the cat.
Im not exactly sure how to check fuel pressure without the truck running.
One of my rookie mistakes was running old gas at the very start before adding fresh fuel. Well, I say old gas, I have no idea how long the truck sat for. I’m leaning more and more towards a clogged fuel filter or sorts.
#10
10-14-2018, 12:05 PM
#11
10-14-2018, 01:01 PM
Elder User
There is no such thing as a MAF or MAP specific intake for these trucks, they are functionally the same except for minor differences like the air temp sensor location so this isn't your proiblem.
What fuel pressure do you have?
Do you still have the plugs wired for the old 15426378 firing order? You should.
Does the truck have a full exhaust system on it?
What fuel pressure do you have?
Do you still have the plugs wired for the old 15426378 firing order? You should.
Does the truck have a full exhaust system on it?
)edit) just saw where he kept the MAP system. My bad,carry on.
#12
10-14-2018, 01:06 PM
#13
10-14-2018, 03:56 PM
#14
10-14-2018, 04:00 PM
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#15
10-14-2018, 04:10 PM
The most likely cause is a failing pump.. especially if the truck has been sitting for some time, it's possible but I have never seen a regulator fail with low pressure they usually either leak into the vacuum line or cause extremely high pressure.