This seems to be a new one, or at least an old one that is as of yet unsolved in the history of the internet (though I certainly hope I just missed it).
2004 D2 with ~78k on it. I have the check engine light on, and no symptoms whatsoever. This happened when I was on a group outing about 200 miles from home (in the last 30 minutes of the last day thankfully), so with no symptoms I took 'er easy and drove the rest of the way home. There were still no symptoms on the trip home, the truck has sat parked since Sunday waiting for my scanner which showed up today, when I fired it up tonight to check the codes there were still no symptoms (a total of about 15 minutes idling peacefully).
There was only one code stored, P1170, which comes up again right away when cleared. I have not been able to find any definite data anywhere as to what this might be, but I have seen much speculation about O2 sensors and $230 MAF sensors. Since I have zero symptoms in about 200 miles of driving on it I lean towards the latter... but I'd like some sort of confirmation before I start throwing mod monies at an undomesticated anser.
Also, the scanner shows the MAF sending data just fine. While I am not familliar with the unit of measurement or what it "should" be reading, it seems to be right in line with the RPMs, and is steady/consistent at various throttle positions (including idle).
Recently performed mods/maintenance which might cause a code:
- 200 miles ago - CEL with code P1170 - no symptoms
- 400 miles ago - removed resonater from exhaust and replaced with turn-down tip so as to never have rock/exhaust contact again
- 500 miles ago - changed the oil/filter - K&N filter with Valvoline MaxLife 10/30
- 1200 miles ago - installed aluminum fuel tank skid - tank changed vertical position no more than one inch during install
- 4000 miles ago - custom exhaust (straight pipe after the cats) courtesy of a rock in Swansea - patched up after about 500 miles (happened mid-trip)
Oh, and there was a long water crossing about 80 miles before the light came on, though it was not terribly deep... up to about 8" below the intake, and I took it s l o w (rocky bottom).
Here is the landrover specific definition for P1170:
P1170 Land Rover Lambda sensor aging tv bank 1 Drive cycle C:Signal out of range - above maximum / below minimum
means you front O2 sensor is not responding to changing conditions as fast as your ECU thinks it should be. The ecu is getting the dats just out of sync with the rest of the system. probably time to replace
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1999 discovery 11, some new cars, 1988 xj40, 1976 deville 8.2l, 1974 450sl, 1969 lotus 7, 1961 austin mini
the best view is always from the point of no return
I add to this error P0306 (misfire in cylinder 6) and running really rough with any throttle. Fortunately I've been able to park it and use another vehicle while I was waiting for the O2s to get here (arrived this morning). I still have no other trouble codes, but my understanding from other searches is that the misfire may be being caused by teh bad O2s, and it is possible nothing else is wrong?
Ok, new O2s are installed (all 4). I started it up, noted it was idling perfect again, cleared the codes, left it to idle for about 10 minutes before checking everything again. All seemed well so I took it out for a short drive. I got about half a mile down the road (light load, doing about 30) and the CEL came on again (flashing) and everything got rough again. It is back to idling rough, and rumbling/shaking under any load. The error code P0306 is still coming up, no other errors.
So why/how out of the blue would cylinder 6 start misfiring?
I reset the computer again, and again it seemed to be running fine. Took it out for a drive, got about half a block again, ilght came on again, same codes (P0300 and P0306), and it immediately started running like crap again. I was a little heavier on the throttle this time out and let it wind up to about 4k RPMs, the engine sounded beautiful until AFTER the codes were thrown, which makes me think this is a sensor/computer issue (which only enrages me further as that means there is NOTHING WRONG WITH THE ENGINE YOU STUPID COMPUTER!!!)
generally speaking if you are getting misfire codes then the plug is not firing because its not getting spark. there are a myriad of other causes with it not getting fuel (which will also send a fuel injector fault unless its a mechanical fault) or not getting enough air (which generally throws all sorts of codes). if you are getting the misfire fault after a slow O2 sensor fault code my logic would go opposite to yours! I would say you have had deteriorating spark plugs or leads which have been giving you less than the 22Kv minimum spark to do a full burn on your fuel, but enough to overcome the +/- 5Kv minimum that would throw a misfire code. that would lead to fast sooting of the o2 sensor and slow responses.
given your new codes I would change out my plugs or plug leads before I worried about the O2 sensor (replace it if you have a new one but do the leads and plugs first). even pull spark plug 6 and see what it looks like or post a picture.
cheers
barri
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1999 discovery 11, some new cars, 1988 xj40, 1976 deville 8.2l, 1974 450sl, 1969 lotus 7, 1961 austin mini
the best view is always from the point of no return
With your mileage, you need to replace your factory wires with some good 8 mm wire and plugs, if they haven't been changed yet.
# 6 misfire is the most common one on our engines and is always wire related, #6 is causing your 300 misfire code also.
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Mike
Retired service manager, member of Solihull Society, SCLR, NCLR and the Santa Barbara 4Wheelers clubs.
99 D2, 3" lift, CDL with Detroit,T.T. lockers, 4:11's,H.D. axles, custom ft/rear bumpers with sliders, a 9500 HSI Warn winch and 5 HID's.
generally speaking if you are getting misfire codes then the plug is not firing because its not getting spark.
Good call. I just got back from my elk trip (took a friend's truck) and did a more detailed inspection. Turns out the wire for #6 was resting on one of the tubes for secondary air, which had melted through it. It hasn't been driven more than maybe 20 miles since this problem started so I'm hopeful I can replace the wire and be done. Guess the computer was right afterall...
Quote:
Originally Posted by Disco Mike
With your mileage, you need to replace your factory wires with some good 8 mm wire and plugs, if they haven't been changed yet.
# 6 misfire is the most common one on our engines and is always wire related, #6 is causing your 300 misfire code also.
Thanks Mike, I took your adivce from another thread already and did the Magnecor 8mm set when I did plugs about 5k ago.
I hope I can order JUST the #6 replacement wire...
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P1170
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