mis firing problem

[jager420]

My 1989 f150 xlt lariat 4.9 straight 6 is having a terrible misfiring problem it can not maintain a constant idle and the engine shakes bad, I just redid the plugs, changed em all with performance plugs and it did nothing to help the problem, what would this problem be, a vacuum leak maybe? I'm an amateur mechanic so any help will be greatly appreciated, I wanna keep the frankenford alive

 

[blacksnapon]

Might I suggest cap and wires? In the dark, while its running, spray a fine mist of water on everything. The fire flying should point you in the right direction.

 

[smokey]

If a cap and rotor doesn't help check for excessive play in the distributor.

 

[jager420]

The distributor cap is in good condition , how much to replace that,caps and wires

 

[73F100Shortbed]

I would suggest replacing the cap, rotor, and wires as well. When you say cap is in good condition did you take it off and check inside?

 

[flareside_thunder]

Check for codes...you can use the paperclip method if you like..... www.fordfuelinjection.com

 

[jager420]

That is onething I didn't do, I figured it wouldn't change anything

 

[flareside_thunder]

Nope, a bad distributor cap can cause all kinds of issues....I had one awhile back in my truck that "tracked" all over the place...my truck ran like crap till i replaced it.

 

[smokey]

There are different grades of caps. the contacts in the cheap ones scale over and cae
use misfire.

 

[jager420]

So I changed my distributor cap and rotar and all new plugs and wires and yet the misfiring still continues, any hints from here?

 

[73F100Shortbed]

Do you have the wires in the right order? Check your firing order. Maybe 2 of the wires are mixed up. I've done it a few times.

 

[jager420]

I did that a few times but I looked up the firing order " 1-5-3-6-2-4, and replaced the wires with deelectric grease and it still does it, could it possibly be the idle air control valve or some thing to do with the vacuum system?or maybe even piston work?

 

[73F100Shortbed]

Possibly a bad fuel injector.

 

[jager420]

I thought of that , I used lucas oil and other injector cleaners to no prevail, idk much about engines I'm kinda learning as I go, is there only one fuel injector and how hard is it to replace?