Simutaneous cyl 1 & Cly 4 misfire. What could be problem?

[tpeerson]

I was on a short trip away from home the other day when my check engine light came while on the highway. A stop at Autozone revealed codes 0301 & 0304... cyl 1 & 4 misfiring.

What would cause the simutaneous misfire of these two cylinders?

I had traveled about 100 miles @ 70 mph pulling an empty trailer when the light went on. It first flashed on and off and then remained on constantly. It seemed to start flashing when I was "pushing it"... like passing someone at 70mph or accelerating while going up.

Any ideas?
Thanks!

 

[Southern3.0]

What year truck?

and whens the last time the plugs and wires have been changed?

 

[tpeerson]

It's a '96. As a matter of fact, I was just heading out for plugs and wires!
Thanks.

 

[martin]

Does it have a distributor or is it edis?

 

[tpeerson]

edis

 

[Southern3.0]

If the plugs in wires dont help, id look at the coil pack. That would kinda make sence to because the edis uses a wasted spark setup and I think the 1 & 4 cylinders fire at the same time

 

[tpeerson]

Well it turned out that the #4 plug was loose! I was shocked to find a piece of the electrode missing along with some of the white ceramic that surrounds it. It seemed to run a little better with new plugs. I went ahead and installed new wires since I had no idea how long ago those were replaced. I've only had the truck a couple years. I drove it about 75 miles today, and it's running even smoother. I figured the computer needed a little mileage to adjust.

Thanks everyone!

 

[Southern3.0]

Glad you got it figured out.