I have a 1992 F150 XLT 5.8
The second cylinder is not firing at all. So far I have changed Plugs, Wires, fuel filter. Also had the oil and filter changed.
Any ideas?

RodgerDodger

 

I have a number of ideas, I don't think you will like them.

OK, here goes. burnt valve, bent valve, pushrod/rocker arm issue?.

Pull the valve cover and watch the rocker arms while cranking the motor. If there is a problem with the valve train, you will find it there.

If nothing jumps out at you, Run a compression test.

 

was the plug from the second cylinder fouled?
occasionally when a cylinder has been miss firing for a long time it gets full of oil and gas residue and plain won't fire. try putting in a hotter plug in that cyclinder. if it fires run it for a few miles to clean out the cylinder.

On point ignition cars I used to pull the wire off the plug and pullit back about a 1/4". if the cylinder began firing i used a hotter plug for a while.

 

The valve issues is something to follow, but you should also check if you're getting fuel to that cylinder as well.

You're on the same vintage truck as me, but bigger engine. How did you track it down to that cylinder, did you disconnect plugs one by one?

Unfortunately the EEC-IV/OBD-I system we have, doesn't produce computer codes for misfires, but the KOEO (key on engine on) will test cylinders one by one, I guess when you hear NO difference, that's your lazy cylinder.

If you remove the spark plug after it's been run a bit, what condition is the plug? Is it wet, oily or what? If it's not wet with fuel, then I guess you have a broken part in the valve system, or a totally blocked injector.

 

Ok, I checked the spark plugs. The one I took out was clean and dry. I also noticed that the engine runs rougher once it gets hot.
RogerDodger

 

Hey Roger,

My '92 sometimes runs rougher when it's hot..or seems to have less power but I imagine it's for much different reasons, so let's worry about #2 at the moment, it could be serious (or not)

You didn't mention how you tracked it down to #2? If you can run through exactly everything you've done, there may be an omission there someone here will pick up on...

If you're sure it's the no.2 plug you checked which was clean and dry, that might perhaps suggest that there's no fuel getting to that cylinder, OR that it's not that cylinder that's missing (sorry, humour me here)

Have you had any check engine lights coming on? Do you have a Ford engine code reader, or is there somewhere you can get them read? As a '92 even if your engine is bigger/different from mine (302) you should have an EEC-IV computer which means with time, patience and a voltmeter (or you can watch the CEL) you can translate the codes without much gear at all,(if you search the forum there's instructions there) but it's important that you check it NOW if you haven't - it'll tell us what else might be going on....

The other question is, is there definitely spark to that plug? You haven't changed the distributor cap or rotor so both must be checked. You also need to ascertain whether fuel is getting to, and through the injector. I'm not up with the best ways of checking this without replacing them or having the injectors all cleaned (which wouldn't hurt) so hopefully others will make suggestions for that.

Meanwhile, you're not giving us a lot to go on, can you tell us more?

 

I noticed that something was wrong when it started running rough. I was driving it, and it ran fine. I shut it down for about 5 hours I started it again and it was running rough. When I got home I pulled all of the wires and tested the spark. On the #2 cylinder there was no spark at all, but before I did any of that I changed the fuel filter and it was still doing it. I changed the air filter, oil filter, and the oil and it was still doing it. So that is where i'm at. This engine has 170,000 miles so I guess it could be anything. I hope it isnt anything major.

 

uhhh, if there's no spark on #2, isn't that your problem??????

You changed the plug and the cable, but did you replace the distributor cap?

These items are consumable and don't last forever.

Since the '92 has a single coil and other cylinders are firing, and there's no spark to #2, it has to be the plug, wire or cap - where the rotor goes to the #2 position - or even the rotor itself (it is still rotor based in the '92?)

So as I read it, one of those should solve your problem - but you did mention that the plug was dry, so maybe you have no spark and no fuel there, so you need to clean the injector...

If all this is (understandably) a bit too complicated or time consuming, why not just take it to a garage? Could be cheaper in the long run.