I just got my 89 F350 going on the road, and Ive come across my first issue. Under hard acceleration, it feels like it only runs on some of the cylinders and it has very little power. If you rev it up in neutral, it doesnt seem to have this loss of power. Im going to pull codes, but what should I check for? Keep in mind that it had about a 1/4 tank of gas that was at least 5 years old in it and the truck wouldnt even idle until I ran some fresh gas and some fuel injector cleaner through it.

 

Run the motor in the dark and look for arcing at the plug wires when you rev it, you can also try misting some water into the engine bay sometimes this exposes a weakness. Also check the fuel pressure, should be 35psi idle and it should jump to 40psi when the throttle is cracked.

 

I agree with Conanski. I was having a similar problem in my 89. I replaced the wires and plugs and its all back to normal. #5 was arcing and #2 was badly worn from rubbing on something. $20 for wires from autozone.

 

I am having a similar problem with my 89 5.8 L. I replaced the plugs and wires, still the same. I am getting a code 12. Do you have any codes?
My truck had sat for 7 years.

Brian

 

I just started to have this problem as well.
The changes that I made was a new Cap and rotor, cleaned the IAC and new filter. The miles on the plugs and wires was low so I did not replace them, but I did not have this problem before the new parts.
I also installed a new 190* heavy duty thermostat and the truck is running at 210* all the time now. Ran a bottle of sea foam in the front tank (it does not seem to matter if running on the front or rear tank).
Truck runs good and pulls nice if I am not wide open on it. When I am, it has a miss.
If I keep it on the floor, it will run good up to about 4K RPM and then start to miss and stumble, then when it grabs 2nd gear it runs ok again till about 4K again.

I am going to take a closer look at it this weekend and see if I can get a better idea of what is going on here. Since I have a crack in the Ex manifold, I am starting to think maybe my o2 sensor is ready to be replaced?

John

 

It's not impossible that one of the new wires is faulty, these can be measured with a multimeter and should be about 5000-8000 ohms, shorter wires will be less than the longer ones, but all should be in the range.

 

ok, so i will replace the wires. I already took the garbage bosch platinum plugs out of it and replaced with motorcraft oe ones.

 

Okay, I did the wires, cap, and rotor and the truck runs much better. however, it still feels as though it loses all power at full throttle. It almost feels like the truck accelerates faster at 3/4 throttle ten at WOT. I also got a code 33 which seems to point towards my EGR. could this be associated ?

 

Im having the same problem with my 89 F-250 351 C6 trans I have no power at WOT but if I back off the throttle some it seems okay but when I hold it to the floor going up a hill I acually lose speed also my trans will ot kickdown thats also a problem please help

 

EGR problems will affect the way the engine runs under load, the computer commands it to open a certain amount proportional to load and rpm and if the valve isn't reacting properly the engine may run too lean and loose power. Both you guys need to check base timing and also that it advances correctly when the spout plug is reinstalled. Also check fuel pressure under these conditions, if that is dropping at higher rpm then it's possible the high pressure fuel pump is failing, the wiring is bad and it's not getting full voltage, or the fuel filter or selector valve is partially clogged.

 

I check fuel pressure its ok, the egr valve on the side of the throttle body is there supposed to be something coming out the bottom like a vacuum line i cant find a diagram also I have never checked the timing on a vehicle what kind of steps are involved I no you need a timing light but what are the next steps thanks so much for your help so far

 

I have a 1994 f350 5.8L e4od trans that dose the same thing u guys ar talking about have I'm lost on this i have check every thing I can think of fuel / timing / plugs wires the olny not shur how to check the egr system

 

Robert this is an ancient post you should have just started your own.

In any case the most common causes of this are plugged exhaust or low fuel pressure, an exhaust problem should be obvious but you need a gauge to test fuel pressure it's not good enough to just do a squirt test on the fuel rail, the system should make and hold 32-35psi when the engine is running and that should increase to 40-45psi under load, if you never get more than 30psi or it falls under load you have a weak pump and/or clogged filter.

 

Well I delited the cat and changed the fuel filter but have yet to check the fuel preacher but I will do that thanx for your help kinda new to this kinda problem and all the shops I have Ben to doesn't want to mess with it