Hey,

I need some help, badly. I've got a 87 F150 w/302 motor. I've posted before and got a lot of good help, thinking I may have a crossfire issue with my wires. I've got all the wires seperated nicely now, with about 10 seperators, haha. No more spark show at night when I mist it with water. I've added dielectric grease to the connections as well to ensure good connection.

Anyway, I've still got a misfire, and it seems to be getting progressively worse. When I first bought the truck 6 months ago, it had a misfire while cruising about every 10 minutes, and none at idle. Now, it has it almost all the time, even at idle. While accelerating it will buck pretty bad. If I continue to hold down the accelerator when it's missing and going up hill, I hear almost like a snapping sound on the passenger side of the engine bay. My accelerating is great until it misfires, no feeling of bogged down or anything like that. Happens seemingly randomly at any RPM. Some days it seems to not really have an issue.

I've done a full tune up, plugs, wires, cap, rotor, ignition coil, as well as TPS (due to TPS code) and IAC. Also did a seafoam treatment. I still have an EGR Vent Fault code with KOEO, and another EGR code and HEGO sensor code with KOER. I figured the KOEO code might have to do with the KOER codes, so I didn't jump ahead and replace the HEGO sensor. All the vacuum lines seem to be ok, sprayed with TB cleaner with no effect. Battery connections are good and tight.

I didn't think the EGR would cause this issue at idle and while cruising, am I right? Where do I go from here? I am about ready to sell this thing, so I don't want to sink any more money into it. My turn signals also just stopped working, this thing is falling apart. Any help is appreciated. Thanks.

 

You might have a valve that's not sealing properly. Do a compression test and see what it turns up.

 

Ditto the compression test. If it's done correctly, you can determine what cylinder is giving you the problem and whether it's a valve that's not behaveing or it's a piston ring. If it turns out that it's a valve issue, remember that it clould be a sticky valve, sticky lifter or worn cam lobe all of which can be diagnosed and fixed with the engine still in the truck.

 

Is it a miss-fire or mpossibly an intermittent miss or hesitation (Something like turning the ignition off and quickly back on?)
I had a similiar issue that I finally traced to a faulty Ignition module (Mounted to Distributor)
https://www.f150forum.com/f10/help-1...ng-out-107456/

 

It's like a strong misfire. I can see the rpms drop when it happens. I started going the sticky valve route, so I added a quart of lucas. Seems to have helped, but it could be a coincidence because the weather has been cooler here.

One thing I didn't mention is that every morning, I have to rev it up after I start for about 10 seconds or it will die. If it dies, it will start right up just fine the next time.

Ill see if the problem stays improved. The ignition module does seem possible too, just so hard to tell. If I had compression testing equipment, I would have tested like you guys said, but $ is tight right now.

 

Its more of a bucking, or stumble. Its usially a couple in a row, not just one stumble. If I hit the gas when this starts, it obviously bucks harder. If I let off the gas, it might resolve temporarily, or it might not.

 

Does it happen at a consistent rpm range? A similar problem drove me nuts for months. I had a miss in my '95 302 at certain rpm levels, so after a process of elimination I bought a rebuilt distributor for it. Still had the same problem and was pulling my hair out. Finally took it to Ford and they determined the replacement distributor was bad. They replaced it and it did ok until recently and it started the same old miss routine. Bought a NEW distributor and stuck it in last night. The miss at idle is gone now, but haven't had a chance to drive it yet as the right front wheel is torn down for wheel bearing and brake caliper replacement

 

Hey out there!
Had a similar prob with my brandnew MSD distributor, after having it installed together with ignition coil and wires it started bucking and misbehaving at all kind of rpm, idling, coasting,accelerating, you name it, sometimes more often, sometimes no probs on a 10 mls ride...
Pulled the new distributor and had to find out that the rotor did cut the black wire coming from the ignition module connector to the pick up, shaved off the insulation and got contact with the copper core, this producing a short...wires simply were too long...
Maybe you`ll find something there...?!
Good luck, this drove me nuts!