Got a problem with my son's 1989 F-150/ 305 FI. The other day it sounded as if it had a dead cylinder. Did a compression check and all cylinders were above a 100 lbs except one wich was about 90 lbs. Went ahead and replaced the plugs and wires because it needed it anyway. Started up and it was the same if not worse. Tried to drive it and it got so bad the dash board would shudder and the truck would hardly pull. It's to the point it's not driveable. With the hood up you crank the throttle up and the engine acts as if it wants to do back flips. Checked the wires to make shur they were not crossed; and their OK. Checked the codes with engine off and through the ignition switch and nothing comes up. Asked my son if he had done anything to it reciently and he said he changed the oil the day before and put a quart of Marvel Mistery Oil in it. I know a quart is a bit much but can't see it being enough to cause a problem like this. Truck has 190000 mls and was running good prior. Replace the module, coil, distributer cap less than a year ago. Any ideas please. Mayby skipped timeing (How do you check that?) Colapsed lifters, plugged injectors. Thanks for any help.

 

What brand plugs did you put in it?
Is the vacuum line still on the MAP sensor?
Any smoke out the back?

Edit:
I think I would get a Fuel Pressure gauge and check the fuel pressure first.

 

My '87 did something similar to that a while back, except that it would only run at WOT. Turns out a rat chew some insulation off of a wire running to my coil and was shorting out but if it was being torqued the motor would pull away from the wire and it wouldn't short.

 

Gets my vote and check for plugged exhaust.

 

The plugs are motercraft. All vacume line are good and no smoke.

 

i got a 300 that just recently skipped timing it did it for a little bit let it sit overnight and it went away by morning so i am gonna agree with the cylinder check cause a skip in timing goes away after a bit but a lost cylinder wont

 

PULL THE DIST CAP AND LINE UP THE TIMING MARK ON FLYWHEEL and see where the rotor is pointing, as to what cylinder on cap should point at either #1 or #6 if i am correct. ill bet on a wasted timing chain, my truck wouldnt even move itself in low range when my chain finially went. Good thing is the chain and gears arent expencive and its not a terrible job to change it. plugs real wet? on a side note try advancing the dist a lil to see if it inproves

 

To check for skipped timing, pull plug number one and hold your thumb over the hole. Have some one you trust with your thumb turn over the engine either with the ignition or with a wrench, when you feel a puff, pressure building, on your thumb, you have TDC. check this position against the marks on your harmonic balancer etc. The quick and dirty test is to rotate the distributor clockwise and or anti clockwise until the thing runs better and then read the timing marks, if they are off much, chances are good your timming has jumped. If rotating the distributor doesn't work, the fuel system is worth a good long look, filters are usually cheaper than the fuel to get you to the store. I'd replace the fuel filter regardless, and follow Chilton's instructions for checking the fuel system: a slug of fuel roughly the size of the line for every so many revs etc.
My 77 ran pretty well with 4 vacuum leaks and the timing out by 25 degrees when I bought it, as long as I ran it hot, if the other options don't turn up anything, try spraying ether gently under the carb/EFI while it runs, if she picks up steam you have a vacuum leak, could be a bad gasket rather than a line.

 

The way I would check the chain (I am guessing you meant 302 and not 305) is to align the TDC timing mark on the Damper with the pointer, take the distributor cap off.
Now put a socket wrench on the crankshaft and rock the engine back and forth a little while watching the rotor and the timing marks. See how much you have to move the engine before the rotor pointer moves.

If the timing marks move less than four degrees (each one is 2 degrees) it has not jumped timing.

If it moves more than 4-6 degrees you need a new chain and gears anyway.
Rotate the engine until the rotor points to #1 position on the cap.
Then replace the timing gear set.

A new timing set the play will be about zero degrees to turn the rotor.

By the way does the fuel pumps run all the time the key is on?

When you put that fuel gauge on it you should get a reading of 32-35 PSI at idle, pulling the vacuum hose off the Fuel Pressure Regulator (FPR) the pressure should jump to 42 PSI.
If you get these readings you know you have the 42 PSI fuel pressure across the fuel injector that you must maintain at all times for the yellow 19 lb. Injectors to work right with the computer.
Do this fuel check with a cold engine.

To set the timing pull the SPOUT shorting bar out and with a timing light on #1 wire with the engine running set the timing mark to 10 degrees BTDC at the pointer by turning the distributor, lock the distributor down at that setting and recheck. Then put the SPOUT back in and check to see if the timing has moved a few degrees. It should move and if it does not you have wiring or computer problems.



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Thanks for the advise. I'll be doing the timeing check this week but I feel shure it has skipped timeing. Thanks again.