[JPIZZLE52]

ok fellas im kinda new to the ford performance game but anyways heres my problem. i just got an 86 mustang 5.0. It supposedly has a fresh rebuild and a cam. It also has been converted to mass air with the ford racing mass air conversion kit. The car has a rough idle and what seems like a cylinder or two missing. The firing order is supposed to be 1-3-7-2-6-5-4-8. The firing order on my car is 1-5-4-2-6-3-7-8. Is there any reason why someone would change the firing order this way? The car seems to run pretty strong off idle, but has a real crappy idle. I've replaced a few sensors like the ECT and the ACT and both o2 sensors. All of the smog and EGR have been removed along with the catalytic converters. You all seem to know your stuff about these 5.0 motors. Any help you can offer will be greatly appreciated!

[95fiveoh]

It could be the cam if it is mild. I believe the older mustangs without the MAF originally equipped has the firing order that you have now. I think they went to the 1-3-7... firing order in 87.

[JPIZZLE52]

would i need to change the firing order now that it is running with the mass air computer? I changed it to the 13726548 firing order once and it seemed to run worse. It was popping and running rougher. It is also running with about 35 degrees of timing which seems about right compared to others ive seen on this forum.

[5SpeedGT]

First off, pull all the plug wires, and the dizzy. Rotate the engine so that #1 cyl. is at TDC on the compression stroke (I stick my finger in the plug hole, you know you're at the right stroke when the air is trying to force it out), and re-stab the dizzy with the rotor on #1 cy.

Put the wires back on using the 1-3-7 firing order (All HO engines since 1982 use this one), disconnect the spout connecter, and start it up. Set the timing to 10* as a baseline. Plug the spout back in, and see how she runs.

It IS possible that whoever rebuilt the engine used a cam ground with the base 1-5-4-2 firing order, but if it's a roller, it most likely uses the HO/351W firing order.

[JPIZZLE52]

This is why I hate having a car with someone elses rebuild. Thanks alot I'll give that a try as soon as possible.