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Hey I have a 1985 f150 2wd. I bought the truck a year ago not running. Ended up putting the 2 new fuel pumps on it. New filter housing. Cleaned the tank. New injectors. Fuel pressure regulator and iac. Got it running but on first start, through the cold start cycle it would run rough. Idle up and down until it warmed up good. Once warm it was fine. Since then it got new dist, plugs wires map sensor coolant and intake temp sensors. Went to change the thermostat out and ended up replacing the intake due to broken bolt. Ever since then it hasn’t ran right again. Also the distributor fixed the cold idle problem.
now it struggles to start. When it does start it has no power and won’t rev past 3 grand. Put it in drive and it sounds like it’s spark knocking and dies.
there is no shreader valve on my fuel line so I can’t test it. Engine runs better with the aits unplugged and the vacuum line to the map sensor unplugged. I’ve checked timing 3 times each time pulling the dist back out and starting from tdc. With everything hooked up I have 5 pounds of vacuum. With both sensors unhooked I get about 12. I’ve checked for vacuum leaks and can’t find any.
im lost. Took the computer out and replaced the 3 capacitors that “go bad” and got no change. Any help would be appreciated
Did you run the motor after the dist. change but before the intake change?
If so how did it run?
If not and you did all the work, bunch of things at the same time, you will need to find what one of the bunch is the cause.
Also have you pulled the codes from the computer yet?
Dave ----
Congratulations! You own a truck with the most finicky EFI Ford ever assembled. Don't feel alone though, I have a truck with the same configuration.
LIke Dave, I too would be looking at what I did last that changed everything. Seems it would be something big and simple.
With the MAP and temp sensors unplugged, the computer is running on limp home mode. A preprogrammed set of parameters. It's also running at base timing. Should be 10° BTDC. Did you set the timing with the spout (spark output signal to computer) wire unplugged? Is the distributor lined up as shown in pic below, the little notch in the distributor base lines up with the end of that ridge on the opening? Rotor pointing straight back to number one cylinder?
When the vacuum swings like you describe, from decent to a terrible 5", it seems to me that is caused by something that the computer can do. Timing.
Yes, unplugging the spout each time. I will check timing again. I am getting codes 23 31 81 82 11 84 83 one of witch being an egr fault. Could the egr cause this? What would cause the computer to throw off the timing that bad?
The truck ran great for about a week. Then it started slowly losing power and in 4th gear the truck would shake uncontrollably. Then I did the intake job. Now the truck has no power. I can crank it up but it is a hard start. Then with those 2 sensors unplugged it idles and revs great. With those two plugged in it idles rough and won’t rev past about 2,000. Sometimes if I put it in drive it will move under its own power. Most times it just spark knocks and dies. But it never has enough power to go down the road
I should also add I’ve done intake manifolds about 20 times mostly on carbureted fords. Even done a 390 with no vacuum leaks afterword. So I’m confident it wasn’t the intake. I’ve also checked it with carb cleaner
Hey I have a 1985 f150 2wd. I bought the truck a year ago not running. Ended up putting the 2 new fuel pumps on it. New filter housing. Cleaned the tank. New injectors. Fuel pressure regulator and iac. Got it running but on first start, through the cold start cycle it would run rough. Idle up and down until it warmed up good. Once warm it was fine. Since then it got new dist, plugs wires map sensor coolant and intake temp sensors. Went to change the thermostat out and ended up replacing the intake due to broken bolt. Ever since then it hasn’t ran right again. Also the distributor fixed the cold idle problem.
now it struggles to start. When it does start it has no power and won’t rev past 3 grand. Put it in drive and it sounds like it’s spark knocking and dies.
there is no shreader valve on my fuel line so I can’t test it. Engine runs better with the aits unplugged and the vacuum line to the map sensor unplugged. I’ve checked timing 3 times each time pulling the dist back out and starting from tdc. With everything hooked up I have 5 pounds of vacuum. With both sensors unhooked I get about 12. I’ve checked for vacuum leaks and can’t find any.
im lost. Took the computer out and replaced the 3 capacitors that “go bad” and got no change. Any help would be appreciated
Originally Posted by Bronco_man
The truck ran great for about a week. Then it started slowly losing power and in 4th gear the truck would shake uncontrollably. Then I did the intake job. Now the truck has no power. I can crank it up but it is a hard start. Then with those 2 sensors unplugged it idles and revs great. With those two plugged in it idles rough and won’t rev past about 2,000. Sometimes if I put it in drive it will move under its own power. Most times it just spark knocks and dies. But it never has enough power to go down the road
You yourself have identified where you need to go back and revisit, my guess is a vacuum leak or improper assembly of the intake.
The truck was already giving me problems before I put the intake on. Drove it home (about 30 min) and parked it. There is no actual vacuum leak. In fact I gain more vacuum once I creat a vacuum leak(unhooking the vacuum line to the map sensor gives me 10 psi vs the 5 when it’s plugged up) which is why I don’t believe it to be a vacuum leak
Congratulations! You own a truck with the most finicky EFI Ford ever assembled. Don't feel alone though, I have a truck with the same configuration.
LIke Dave, I too would be looking at what I did last that changed everything. Seems it would be something big and simple.
With the MAP and temp sensors unplugged, the computer is running on limp home mode. A preprogrammed set of parameters. It's also running at base timing. Should be 10° BTDC. Did you set the timing with the spout (spark output signal to computer) wire unplugged? Is the distributor lined up as shown in pic below, the little notch in the distributor base lines up with the end of that ridge on the opening? Rotor pointing straight back to number one cylinder?
When the vacuum swings like you describe, from decent to a terrible 5", it seems to me that is caused by something that the computer can do. Timing.
These EFI set ups are very vacuum dependant.
this makes the most sense. The computer overrides any other timing issues and throws it into limp mode, which is why it runs better with less sensors hooked up. Could a faulty egr cause this? Is there a egr delete I can do? I have a code for faulty egr
I'm as confounded as anyone. I am, however, inclined to think it's something mechanical. If the base timing is correct, the ECM is not going to make a drastic change without some RPM.
Vacuum as low as you are reporting is normally a mechanical problem. Late ignition timing can cause lower vacuum but only a little. The ECM only retards timing for spark knock, but again, not that much.
For vacuum in the 5-10" range you are looking at a vacuum leak or late valve timing. Did your truck's engine jump time? One easy way to check is to look at the base of the distributor as instructed above. If it's a leak, it's not small. PCV line attached?
EGR, even with valve stuck wide open isn't going to kill your vacuum.
The ECM can do a lot but that low vacuum is just too low.
Maybe I didn't fully understand your original post. I read it as you had the truck running good (after distributor install) until you went to work on the thermostat housing and that repair snowballed.
