Greetings all;
I have a 1996 f-150 extended cab 4x4 with 225k on the origional drive train. Engine has some issues but nothing major, small exhaust leak at the drivers side manifold and some oil coming from the front of the pan. The engine is the 5.0. I did a tune up, nothing major plugs, wires, cap, rotor, oil, air filter pcv, coolant all with OEM (Castrol high mileage oil and castrol anti freeze). I ran each wire independantly to ensure no miswire issuse, I gapped the plugs to 0.54, applied some anti-seze started the plugs by hand and tightened with a deep well plug socket, set the wires by hand and put everything back together. She's running rough now she was only sluggish before, thought maybe it could be a timing issue (checked and it was a little off but not now). I checked all my work again, plugs are gapped properly and none of them are chipped, wires are 8mm duralast and ohmed them to 20 +/- ohms each, routed the wires as recomended by ford to avoid crossfire, cap only goes on one way and again double checked to ensure it was on right and tight. Put it all back together and same issue. I sprayed some starter fluid around all the vaccum hoses with no change at idle. No check engine light or trouble codes with scan tool.
Ideas and questions please guys/gals tell me what you think???

 

well... did you change the fuel filter?

is this fuel injected or carb?

 

You OHMed the plug wires so all should be well there. Maybe you got a bad spark plug. I would pull the spark plug wires off one at a time with the engine running
and listen for a change in engine sound. I would pull all the plug wires loose from the spark plugs on one side with the engine off and set the wire loosely on top of the plug. Get a plastic plug wire holder and start the engine and pull the wire far enough away one at a time so the spark plug can't fire. Listen for a change in sound to determine which cylinder is misfirng and go from there.

 

What brand of spark plugs did you replace with? Fords don't run good on some brands of plugs. Recommend Motorcraft only for the plugs.

 

302's run fine with Autolite copper plugs.

I would suspect those Duralast wires, even though they ohm okay. An ohmmeter doesn't test them under load.

 

I'm going to guess you have a fuel injected 5.0 from the year. To determine without a doubt which cylinder is missing I would suggest putting a vacuum gauge on one of the constant vacuum lines and then pulling the plug for the injector one at a time. The fuel rail vacuum line is normally the one I use to check. You will notice a drop on the gauge far easier then trying to catch it by ear.

After you figure out which cylinder is missing you can go from there on checking possible causes. I have had plugs be an issue, so I like to keep a couple extra laying around. With the milage and saying it's all original it could be a worn cam, valves, lifters...

I like to start at the easy fix and then work up to the bigger problems after isolating the issue. My wifes explorer just recently went back to the dealer for warranty work for lifters collapsing and a valve job with only 68k on the thing.

 

I had a crossfire issue... I looked into some common issues and apparently if cylinders 1&3 5&6 are not seperated properly they will cross. The 8mm sciliconized wires should have prevented this but once they were seperated and put in that seperating lock that is suppled by FORD the issue went away. Now there is another problem that I'm wondering about.
The engine now has a rattle under load (esp going uphill) sounds like a valve tap, the engine is a bit sluggish but nothing I'm worried about given the history of the truck a little bogging down is "normal". I used castrol 10w30 high mileage oil. I'm wondering if I want a 40 weight or even a 5/20 weight. Anyone have an opinion?
PS
Thanks for all your ideas

 

This! Use a vacuum gauge on the engine and see what it's doing. Also run a compression check on each cylinder and see what you find there. Thse tests should be the first thing that a mechainic does when checking an engine. They will find basic mechanical problems in an engine indepedent of ignition, carburation, etc. Vacuum test will also find difficult to diagnose problems such as low compression, vacuum leaks, mis-adjusted idle air mix, sticking valves, etc.

 

As to the oil weight question I have found using a slightly heavier oil helps quiet the engines down once they start to show some age and get high milage. I'm not sure if it hurts the oil pump pushing a thicker viscosity or helps or hinders in any way. I do know it does make them run a little quieter and helps with boosting weaker oil pressures.

It should be 5 quarts for a 302, you might try using 2 quarts of 10w-40 and see if that helps. I have gone with 3 quarts of 20w-50 on one old motor just because I am lazy and didn't want to rebuild her. She still runs fine today and I've used that ratio for the last 8 years on her.