Missing engine - help!

[n.a.mccanna]

I have a 94 Mazda B4000. It is the 4.0L, automatic with roughly 278000 miles on it. The only modifications are the alternator, when from the stock 95 amp to a newer models 130 amp. Two 10" JL Audio W0's and a 600 watt JL amp. Other than that the truck is stock. About a week ago the engine started missing. I checked the plugs and didn't see any that are burnt black...they all seem to be the same in that there is kinda this rust color on them. These plugs are roughlt 9 months old along with the wires.

The missing seems to be happening mostly right above idle and at cruising...under full power the truck typically runs fine. But I can't just keep my foot in it all the time (I don't mind but the cops sure would!).

I'm going to swap out the plugs today and run some injector cleaner when I fill up today but any other suggestions would be greatly appreciated!

I'll post after the new plugs are in and I've run it a little bit.

 

[Tbars4]

..In your case, the first thing I would do is park it for one hour and then take a voltage reading at the battery...

..Then I would start the vehicle and take a voltage reading while it is running..

 

[n.a.mccanna]

Voltage while running is 14.6V with the stereo off...it varies while the stereo is running at full tilt. It's right around 12V after sitting all night.

 

[n.a.mccanna]

Engine misses while stereo is off

 

[kkjb4x4.0]

A missfire should trigger a code.Make sure the usual items like plugs and wires are in decent shape,would'nt hurt to do a compression check with that many miles on it.

 

[n.a.mccanna]

The only code that was displayed was a vacuum canister purge but that isn't the problem. When I bought the truck, the lines were all dry rotted. I pulled them off and capped the corresponding place where I pulled them off...that was 10 minutes after buying it. I've put 15K miles on it since then with the lines capped off.

Just finished putting the new plugs in, Bosch Platium +4's, and took the truck out. Also added a can of Sea Foam to this fill up and the truck runs "great". Thanks for the tips and advice guys!

 

[kkjb4x4.0]

Just keep an eye on those Bosch's,,everywhere I"ve read says they don't play well with fords.

 

[n.a.mccanna]

Thanks! I've never heard that before and have run nothing but Borscht in my trucks over the years. This is the first time I've had issues with them, but they were the mid grade plugs...the super plus. I'll definately be keeping my eyes on them tho!