Hello there. My name is Bill. And I've been reading on this forum. For a couple of days and I'm hoping you guys can help. I have a 93 Ford. Truck with a 5.8. and the other day I drove it home. It was fine. The next morning I started it up. And I had a small Shake. When I tried to take off I got on the freeway. And it was like I lost a couple of cylinders. The next day I put a complete new tune-up on it. And the timing is correct. And it did nothing. It's stayed the same. Now when I plug in the ob one meter At idle it says I have 6 cylinders. If you rev It Up. To about 2,000 RPMs. I get all 8 cylinders and it seems to run a little better. Can't figure it out. Help somebody can help.

 

Exactly what parts did you change as part of the "tune up" and what brands did you use? Have you confirmed the firing order is correct? I think I might do a compression test.

It wouldn't hurt to put some Techron in the gas in case you have dirty injectors.

 

I put plugs wires. New cap rotor and all from Napa the good stuff all brass stay the same. I changed the manifold absolute pressure sensor. No difference. I change the fuel filter. No difference. It still runs. Like I saw it. Six cylinders until you rev it up to about 2,000 RPMs and then it Smooths out a bit. I put some Lucas Fuel Injector Cleaner. Nope change yet.

 

Pull the plugs and do a compression test.

 

Did you recently put any chemicals down the throttle body? If you did, you destroyed the gasket between the upper and lower intake which is what it sounds like happened. At idle the engine doesn't have enough air running thru the intake to seal the leak. Once the volume increases it seals the gasket or seals it enough to get 8 cylinders firing. You cannot run any chemicals down the throttle body in that series of engines. No seacrap, no throttle body cleaner, nothing. To clean the throttle body it MUST come off of the engine. If you didn't run any chemicals down the throttle body, I'd strong suggest removing it and give it a cleaning along with the ports for the IAC. The throttle body on these engines that haven't been cleaned expect an odd idle. If the IAC ports are clogged, you can't get a steady idle.

 

It was running fine. One night and the next morning it just started doing this. After I did all the work I added a little bit. Of Lucas injector cleaner and the tank and it didn't make any difference. I haven't checked the IAC yet. Or the EGR That's my next move. Thank you.

 

check for any fault codes set on the OBD I ?
And did you refuel somewhere just prior to the problem starting?