Hi guys. I'm in need of some help. I bought a 94 f150 flair side with a 5.0. It needed valve cover gaskets and water pump gasket. I changed those and all the other gaskets that I took off. Slapped it all back in place and it would start, idle hi, and then drop and die. If I keep my foot on the gas it will stay running. But the rims won't stay steady. Go's up and down. I thought it was a idle air problem so I replaced the idle sensor and the throtle sensor. The throtle cable that needed replacing anyways and check the vacuume I lines. (I plan on replacing them) but they all seem right. I replaced the distibutor cap and rotor. My father in law said it sounded like the firing order was off. I checked and rechecked to the sticker. It was right. Then I checked other sources. The sticker differs from the books and all online sources. Something about Ford changing the order. Then I remembered that it's was a crate engine. Made in 2011. So I changed the order but didn't seem to help much. Also I cleaned the o2 sensor pig tail that was full of oil. This seamed to help because it ran real low for a few seconds but still died. Not sure what else could cause my problems. Any advice would be great seeing how this is my first Ford and I'm used to working on cars with halve the cylinders lol.

 

The motor should use the 13726548 firing order and just for reference cyl #1 is passenger side front and the cylinders are numbered 1-4 front to back on the pass side and 5-8 front to back on the drivers side.

If you do have the plug wires arranged correctly, next step is to pull the codes. On this vintage truck that can be done without any special tools.. you put a jumper(paper clip) between the Sig_Rtn and Self_Test_In pins of the EEC Test connectors, turn the key to run and count the flashes on the check engine light. Or you can by an inexpensive code reader like the Equus/Innova 3145 and take all the guess work out of it. The EEC Test connectors are on the drivers side inner fender right below the hood hinge.

 

I don't know how well a test will work because the only time the engine light comes on is when it dies. But I order on anyways. Can anyone tell me what the symptoms are for a vacuum leak and for a bad o2

 

The test will over-ride normal light operations and blink the error codes through them.

A bad O2 sensor will usually cause rich running condition, which may not be noticeable when driving. But the self-test should throw error codes that point to that.

A vacuum leak can cause the engine to backfire or buck, depending on how bad the leak is. The self-test will also throw codes that point to that.

The error codes won't be quite explicit as "BAD O2 SENSOR", but things like "TOO LEAN" or "TOO RICH" conditions. Interpreting all the codes you receive will help you arrive at the actual problems.