Truck ran fine. High idle until warmed up but not bad. Parked it and now it won’t run. Will start but no idle without feathering the peddle. When giving gas, it revs up but then drops back down. Can keep it running but it is rough and eventually loads up the converter until it starts to smoke. Obviously not burning the fuel in the cylinders. Any suggestions before I replace all of the sensors?

 

Welcome to the forum.
When you start a thread for repair advice please list the year, model, engine and transmission of your vehicle. We can assume it's a Ford but that in itself is not enough information.
Do some diagnostics of sensors and components instead of throwing a lot of money into the engine and still not fix the issue.
Check for error codes, test fuel pressure, look at the spark plugs and do a compression test, check for broken vacuum hoses.
Recently there was a new member on this forum that replaced the engine, wiring harness, two PCM's, all of the sensors and it turned out it was some shorted wires from fog lights that they had installed themselves and by focusing on just the motor they missed the real issue. This forum has more knowledge of Ford trucks than you could find anywhere else.

 

And waste a lot of money. You should do some diagnostics first. Check fuel pressure, does it make the correct pressure(~32psi) and does it hold it or bleed off immediately? If pressure drops immediately one or more injectors could be stuck and leaking fuel into the cylinder, pull the plugs and look for the wet one to confirm.
If you don't find anything wrong there pull codes from the computer, if you don't have a code reader it can be done with a paper clip but a basic code reader(Equus 3145) isn't expensive and will make the job easier. This will tell you a lot even if you don't get any error codes.. it would tell you the electronics aren't the problem, but there are several electronic things that could cause your symptoms too so this isn't wasted time and effort.

 

 

87 F150, 4x4, 5.0 automatic. Ran great the day we parked it.

 

I had a similar situation arise about 2 weeks ago but the vehicle, 1989 F250 7.5L, would only crank. I came here to get some others input just as you did and everyone was just as puzzled and concluded it was electronic AFTER basic diagnostics. Engines are simple before you get to the electronics... you need air and fuel for it to run..... if its running bad you either have too little of fuel, not enough air or no spark. Early fords run on a speed density fuel EFI (meaning its not reading the air like MAF vehicles would to calculate the amount of fuel to inject) It has a curve that relates to speed to determine the amount of fuel to inject. Start by testing your fuel pressure... you can rent the tool from Autozone for like $160 and its fully refunded upon return. I believe the '87 was Fords test years so some of the fuel systems aren't the same as '88 and so forth. For example, your fuel reservoir may have had a fuel filter placed in it that was later deleted due to complications with servicing or it may be one that didn't receive the frame-mounted post high-pressure fuel pump in-line filter. Putting these things aside your system should be very close if not the same.

DIagnostic steps:
Check your air filter and intake lines to make sure it's not obstructed
Test fuel pressure at the fuel rail
Remove the distributor cap and inspect the contacts
Use a multimeter to test the ignition coil for power to the distributor cap
Check spark at all cylinders (while you have the spark plugs out its easy to run a compression test and determine the health of your motor). Clean and regap all spark plugs before replacing them.
Use noid lights and test the pulse rate at the fuel injectors

If everything comes back good we need to check for electronics, bad connectors, possibly a TPS or malfunctioning PCM.

 

Going to tear into it later this afternoon. Trying to hang a garage door right now.

 

Not distributor. Wires cap and rotor all good. Throttle plates moving correctly. No check engine lights. Can make it run buts seems like no air and too much fuel.

 

Had EGR and throttle position codes so replaced both. Still won’t run right. Will start after a few cranks but won’t stay running. Will rev up for a few seconds then drop off even with the pedal to the floor. Will check coil and fuel next.

 

From what I have seen, this issue is usually IAC or EGR and sometimes FPR. Most of the time it is IAC.

 

IAC? Don’t recognize the abbreviation.

 

Idle Air Control valve. Helps keep a steady idle and is supposed to increase RPM for warm-up.

 

Ah, thanks.

 

Now it will fire but lopes badly. Have to rev it up to keep it running. Revs up then falls back off with throttle wide open. Backfired in the intake once in a while. Attached a video.

 

Can’t get the video to load.