..or at least thats what my codes suggest.

Basic info on the truck.
2001 Dakota Quad cab, 3.9 V6, 5 speed stick. 130,000 miles.
Relatively new Bosch platinum plugs. Clean air filter. No other codes showing on my handheld OBD II tester.


Now the problem...

I read one of the other threads here concerning a misfire under load and changed my distributor cap and rotor button. The electrode posts on top of the distributor were badly corroded with some sort of white calcified type of deposit especially on the #6 post. I was almost happy to see the #6 post was the worst as it made me think I had found the problem. But....no such luck. The inside of the cap was somewhat wore out looking but nothing more than I see on most any high mileage gas engine.

I have a new set of wires which I didn't have time to change tonight. That will be my next move but do you think it could be the Bosch plugs? I recall reading that this engine likes OEM type plugs. Is that true? This misfire on #6 has been developing for about 6 months and now is mifiring under part throttle and frequently. Much more so than the occasional miss in the preceding months. It's also backfiring into the intake occasionally when it misfires under heavier throttle.
What else could it be besides plugs, wires, cap and rotor?

Thanks in advance.
Bill

 

i hate bosch plugs... garabage in my opinion... alot of people like then though.. but i use ngk.. good stuff.... runs smooth... try then and some performance wires.... and make sure you replace the coil wire to the distribtor as well... when i changed that... rust beyond the waazoo... like it ateaway at the wire... still kept the motor running

 

while you may not like them, bosch plugs arent garbage and wouldn't cause a misfire unless they were damaged in some way. i would bet that the problem lies in the cap and rotor area. if the contact area between the cap and rotor has a bad connection the rotor/coil will hold an abnormally large charge if it doesnt discharge when it would and may actually discharge at an angle to the point at the wrong time. this would alter the timing on the affected cylinder and cause misfires and other nasty stuff. moral of the story: keep your truck tuned up and don't use cheap parts. buy the good wires,clean or replace the air filter, replace the cap, rotor and spark plugs. after the tune up clear your codes and see if they come back

 

im pretty sure this wont do much buty... spark plug gap maybe an issue too

 

Guys, I just replaced the #6 wire and the engine is running smooth so far. Gotta go to work and plan to change the rest of the wires this afternoon. I also did another code read this morning when the wife complained the truck was running rough again and the #6 cyl showed another misfire code. Replaced the wire, did a 5 mile test run, rechecked the codes and none were registered.

I hope this was the problem. The plug gaps are right and they are only a few months old. Must be the wires. Least I hope so.

 

get the cap and rotor while your in there, its like $22 to change em both

 

I mentioned that I had in the initial posting. I finished changing the plug wires when I got home. With the 5 original wires it ran pretty good but had a mild miss now and then under part throttle and lower rpms. Nothing near as bad as it was. The other 5 wires were likely almost as bad.

Should be fixed now. I'll post a follow-up for general interest.

Thanks again.
Bill

 

Runs like new now.

There's one thing about todays cars, they run so much better than when I was a kid running leaded gas, having to change plugs, points and condensers every 12,000 miles or so. These newer cars lull you into thinking they will run right forever. It's just not so.