Well the ol' 1994 f-150 is missing when the engine is lugging under light throttle. The truck is a 302, 2wd with e4od. It has 115k miles, and everything is original except for the autolite plugs and pcv valve, both of which were replaced about 10k miles ago.

The miss started about 1000 miles ago when I had a new catalytic converter and y-pipe put on because the old one got gunked up by the previous owner driving the truck with an oil soaked oxygen sensor from a leaking oil pan. Luckily, this was all repaired right when I bought the truck.

The miss started about 300 miles after the new cat and had gotten progressively worse since (about 1000 miles). It usually happens about 1600 rpm under light throttle.

I run fuel injector cleaner from the store in it about every other tank or so for the 10k I have owned it. I also sprayed some intake cleaner into the throttle body while someone else goosed the throttle about 5-6k ago.

This morning I grabbed all of the spark plug wires to see if I could get my self electrocuted and find a bad wire (I hate reaching for those things)... but no shocks...

I did hear what sounded kind of like a light buzz from the passenger's side I thought... could have been nothing though - maybe the belt or something.

Two questions: is it safe to drive with a miss (sounds like one cylinder is missing...) I don't want unburnt fuel to gunk up the brand new catalytic converter... would this be a problem?

Second: What order would you suggest checking for the miss to get it fixed? I already low on cash from forking out money for the catalytic converter.

I am planning on doing a tune up (new distributor cap, rotor, plug wires, coil) next weekend when the goodies from jegs get in.
I'll try to check the EGR at the same time... but where should I go from there? How could I fix the EGR... could I shoot some carb cleaner through there?

Thanks for the pointers!

Matt

 

sorry for the long post before... here's some more info - the fuel filter is new (5k old) and the air filter is fine too.

 

I'd be inclined to get rid of the Autolite plugs and install some Motorcraft plugs. No they arent the same
You can check for a miss by pulling off one plug wire at a time with plastic pliers made for doing that. if you pull a wire off and it makes no difference in the rpm and smoothness of the engine you've found your miss. Or another way to do it, seeing that you're replacing your plug wires anyway, is to take a test light, ground the ground wire like if you were checking something for power and then carefully probe the top of each plug wire on the distributor cap. This will ground the spark to each cylinder and again if you find one that makes no difference you've found what cylinder is missing.
Running too long with a miss isnt a good idea but for a short time it shouldn't hurt much.

 

Hi there,
I just went through a similiar problem on my 95 Bronco 5.8L and finally found it. I started doing the typical tune up stuff and found 2 bad spark wires. The best way to test them is with an OHM meter. Grabbing the wire and hoping not to get electricuted is not the best method. You really need to measure the resisitance in the wire. It could be completely broken internally but if the sheild is still good you won't get shocked. But, this didn't fix it completely for me. I then found a clogged fuel filter and that helped also but didn't fix it completly. Yesterday I replaced the O2 sensor and she is running like new again. If your plugs are old enough look for a whiter burn on all 4 plugs on 1 side. That may provide you a clue to check the O2 sensor. If its missing regularly, run a diag on the computer. Some shops do it really cheap and most Autozones will do it for free. Good luck.