I have a misfire in the #1 cylinder of my Rodeo with 160k that comes and goes. I have an on-board scanner so I can check the code while I drive, always P0301. I drove it from Chicago to Rapid City SD and it misfired all the way there, driving 60-65 mph. A week later I drove it home at 75-80 mph and it ran on all 6 all the way. I thought perhaps if I kept the RPM's up it wouldn't be under a load when it dropped into OD.

When the problem started (Ottawa, IL) I switched the coil packs between #1 to #2, no change. I put a new spark plug in #1 (Des Moines, IA) and it ran perfectly for about 5 minutes. Now that I'm back home and it's running fine it's pointless to switch fuel injectors. It's been using more oil between changes but no blue smoke; don't know if that's relevant.

If you've had an intermittent problem like this I would be curious to know how you solved it!

Thanks!

 

There's too many variables to list any one "fix" even for a common P0301 misfire.

Does your scanner have live data capture; 'Freeze Frame'? This will help pinpoint when the code sets. Check the sensors for appropriate readings. Make SURE the 02 sensors are balanced and not going lean. A WOT test should show 900mv, if it's not close, it's running lean. B1S1 and B2S1 sensors; not the post cat 02's, as they should read netural (appx 500mv). The P0301 and B1S1 are on the same side, so look for differences side to side.

The isolated codes indicates a specific cylinder problem, which makes it easier to figure out. It's probably safe to rule out the EGR and other related sensors. Swapping coil packs is a good test, as done. No mention of spark plug brand/quality, but would recommend premium plugs (no el'cheapo's). Possibly a new plug temporarily helped.

There could be a lean/rich out condition due to poor fuel atomization, which can cause the misfire; OBD uses the crank sensor to measure time between sequences to calculate a Misfire.

Lastly, excessive oil useage could be isolated from that cylinder. Excessive valve stem seal or piston ring wear. Rings will quickly become damaged from injector problems- usually from leakage; causes cyl. wall "washdown"; results in rough idling or hard starting; fuel in oil which will cause excessive oil useage (viscosity breakdown).

If it were me, I'd also check the compression, both cold, hot and wet, or performa Leak Down test, which is the ultimate to verify mechanical issues. At about 100PSI combustion cannot be supported. Last i recall my Trooper was in the 185+ psi range, a lot of carbon buildup could push this, or any engine, higher. Alway test at WOT for max PSI readings.

A cheap help: I've had GREAT luck using Amsoil P.I fuel treatment, but of course won't fix a bad injector, much better than ANY other producte I've used. Not many companies recommend NOT to over use, or frequently use, their product.

Also, a better quality oil will help seal the piston rings, and could help some on worn valve seals and guides. I used Amsoil 15-40 Diesel in my 3.5L Trooper. My Trooper started burning oil (at cold startup) at just 30K miles.

These engines are a nightmare to rebuild, as a close auto tech friend of mine attested to.

If you want more info about anything send me a PM.

Best of luck!

 

You have a 14 year old vehicle, and you know for sure you have a misfire on the number 6. That could be plug or wire. Tick and knock is never a good sign, and is usually an indication that you are about to have severe problems with the engine, tick equals a problem with the values, and knock usually indicates a bearing about to fail.

 

Well i have joined this forum newly.So i have no idea on this.I would suggest you to go to your dealer and ask him about this problem.

 

After many months of frustrating intermittent misfire issues, the problem was the injector pigtail. Unfortunately the unburned fuel caused the catalytic converter to fail, but found Smith Brothers Converters of Crestwood IL that sells rebuilt converters (smithcat.com) $250 with a one year guarantee. Just passing this along!