Missfiring cylinder on '99 D2
#1
05-15-2011, 11:51 PM
Missfiring cylinder on '99 D2
Happy ending on this one but thought the problem solving tree might help the next guy:
1999 Disco II 154K miles. 20K on new heads, wires/plugs. Started to idle a little rough, missfire under light acceleration and lost a lot of power in general. OBD2 reader said missfire on cylinder #8.
- Replaced dirty air filter. No improvement, that would have been too easy, but hey try the easy stuff first.
- Replaced worn #8 plug. No improvement.
- Replaced spark plug wire #8 . No improvement. I didn't think to check the spark using a screw driver shoved into the plug wire since at idle it only ran a little rough, not a steady skip. Had I done this I might have been able to isolate a bad coil from the start, posibly. BTW, all the old STI Magancores measures 15K ohms resistance, except for #8, which measured lik 50K ohms. Weird but probably not the show stopper, plus the replace did not fix the missfire.
- Cleaned mass air flow sensor. A very dirty MAF caused a loss of power problem a few years ago and threw O2 sensor codes. It didn't solve the missfire unfortunately and the ODB2 started throwing 'multiple cylinder' missfire codes as well.
- At this point, I'm thinking coil, injector(s), dirty valves/compression, or wiring problem... in that order.
- Removed intake manifold/throttle body, the runners into the engine looked pretty clean. Couldn't see the valves, but guessing the intakes were good since the runners look clean. Simple green and garden hosed out the intake manifold and throttle body. Cleaned all the gunk out, not enough gunk to cause a missfire, but enough to make me feel better that its out.
- Replaced starboard side coil (#8 cylinder). $75 at Napa or Oreilly, can't remember which. No visible issue with the coil, testing with ohm meter told me nothing either. Replacing it was in the hopes the missfire was not wiring harness short or something worse. Whomever decide the backside of the engine underneath the intake manifold was a good place for a coil, curse you! Left the driver side coil alone, think I read a post from discomike or someone who said coils last forever and don't mess with them if they're not busted.
- While the intake manifold was off...
- replaced leaking valve cover gaskets. I also ground .030" off those little
spacers as an experiment to see if I could make the gaskett not leak anymore.
We'll see...
- removed fuel rail and injectors. They looked OK, but clearly had not been touched
ever. Orings were OK but had tiny heat racks on the side facing the motor. Little
bit of carbon coating on the nozzles, but not looking clogged if that is something
you can 'see'. Brought them to the local diesel shop for ultrasonic cleaning, $8/ea.
O'reilly had the orings off the injectors for a Ford Focus, $0.60 each. Good as
new... I'm really glad I did this step.
- cleaned out idle bypass valve, bead blasted/repainted valve covers, replumbed the throttle body heater by-pass, etc. etc etc. Nothing having to do with the missfire.
- All back together with new wires (7mms for now, could get the 8mm ones local) and plugs all round.
Happy endings are the best. She started right up. After a wandering idle for a few minutes to burn off all the dry silicone spray I used liberally as a cleaning/assembly agent, she drives AMAZING, no missfires, no codes, and best of all the amount of power regained simply blows me away. Pulls like a brand new engine. Not sure what fixed the missfire but if I had to guess it was the new coil, with the injector cleaning a distant second and the new wires/plugs, air filter, degunking never hurt anyone. I haven't driven it any distance yet, to the gas station and back, but will report back if it's not fixed good as new.
1999 Disco II 154K miles. 20K on new heads, wires/plugs. Started to idle a little rough, missfire under light acceleration and lost a lot of power in general. OBD2 reader said missfire on cylinder #8.
- Replaced dirty air filter. No improvement, that would have been too easy, but hey try the easy stuff first.
- Replaced worn #8 plug. No improvement.
- Replaced spark plug wire #8 . No improvement. I didn't think to check the spark using a screw driver shoved into the plug wire since at idle it only ran a little rough, not a steady skip. Had I done this I might have been able to isolate a bad coil from the start, posibly. BTW, all the old STI Magancores measures 15K ohms resistance, except for #8, which measured lik 50K ohms. Weird but probably not the show stopper, plus the replace did not fix the missfire.
- Cleaned mass air flow sensor. A very dirty MAF caused a loss of power problem a few years ago and threw O2 sensor codes. It didn't solve the missfire unfortunately and the ODB2 started throwing 'multiple cylinder' missfire codes as well.
- At this point, I'm thinking coil, injector(s), dirty valves/compression, or wiring problem... in that order.
- Removed intake manifold/throttle body, the runners into the engine looked pretty clean. Couldn't see the valves, but guessing the intakes were good since the runners look clean. Simple green and garden hosed out the intake manifold and throttle body. Cleaned all the gunk out, not enough gunk to cause a missfire, but enough to make me feel better that its out.
- Replaced starboard side coil (#8 cylinder). $75 at Napa or Oreilly, can't remember which. No visible issue with the coil, testing with ohm meter told me nothing either. Replacing it was in the hopes the missfire was not wiring harness short or something worse. Whomever decide the backside of the engine underneath the intake manifold was a good place for a coil, curse you! Left the driver side coil alone, think I read a post from discomike or someone who said coils last forever and don't mess with them if they're not busted.
- While the intake manifold was off...
- replaced leaking valve cover gaskets. I also ground .030" off those little
spacers as an experiment to see if I could make the gaskett not leak anymore.
We'll see...
- removed fuel rail and injectors. They looked OK, but clearly had not been touched
ever. Orings were OK but had tiny heat racks on the side facing the motor. Little
bit of carbon coating on the nozzles, but not looking clogged if that is something
you can 'see'. Brought them to the local diesel shop for ultrasonic cleaning, $8/ea.
O'reilly had the orings off the injectors for a Ford Focus, $0.60 each. Good as
new... I'm really glad I did this step.
- cleaned out idle bypass valve, bead blasted/repainted valve covers, replumbed the throttle body heater by-pass, etc. etc etc. Nothing having to do with the missfire.
- All back together with new wires (7mms for now, could get the 8mm ones local) and plugs all round.
Happy endings are the best. She started right up. After a wandering idle for a few minutes to burn off all the dry silicone spray I used liberally as a cleaning/assembly agent, she drives AMAZING, no missfires, no codes, and best of all the amount of power regained simply blows me away. Pulls like a brand new engine. Not sure what fixed the missfire but if I had to guess it was the new coil, with the injector cleaning a distant second and the new wires/plugs, air filter, degunking never hurt anyone. I haven't driven it any distance yet, to the gas station and back, but will report back if it's not fixed good as new.
Last edited by phatduc; 05-15-2011 at 11:57 PM.
#2
05-19-2011, 02:51 AM
Hi there i had the same problem on my 96 discovery se7 and a buddy of mine told me to run the tank empty and put some lucaz fuel injector cleaner in there. and change my fuel filter as well. i try it and my misfiring was gone. honestly i don't know what is got to do with the fuel system but it worked. by the way u did a lots if cleaning and i bet u Ur problem is not coming back. and if it does u can feel free to try the same thing i did. by the way i used almost ( 4 oz for every 5 gallons) not 3oz for every 5gallons like it says on the bottle directions. good luck with ur truck.
#3
05-19-2011, 07:36 AM
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That mechanic is the stupidest one out there, you NEVER run a fuel tank empty. First of all you can burn up your pump, pick up a lot of junk from the bottom of the tank and plug up your filter.
Second Lucas, as much as I like it, is not for a quick clean up, rather to maintain s system that has been cleaned out already. If you want to clean out a system put 1 can of B&G's 44K on a full tank of 91 Plus and drive it out.
Second Lucas, as much as I like it, is not for a quick clean up, rather to maintain s system that has been cleaned out already. If you want to clean out a system put 1 can of B&G's 44K on a full tank of 91 Plus and drive it out.
#4
05-19-2011, 11:40 AM
That mechanic is the stupidest one out there, you NEVER run a fuel tank empty. First of all you can burn up your pump, pick up a lot of junk from the bottom of the tank and plug up your filter.
Second Lucas, as much as I like it, is not for a quick clean up, rather to maintain s system that has been cleaned out already. If you want to clean out a system put 1 can of B&G's 44K on a full tank of 91 Plus and drive it out.
Second Lucas, as much as I like it, is not for a quick clean up, rather to maintain s system that has been cleaned out already. If you want to clean out a system put 1 can of B&G's 44K on a full tank of 91 Plus and drive it out.
#5
05-19-2011, 03:34 PM
hey Disco Mike I'm not trying to be an *** but why don't we stop using big words and be civilized people. I just passed on what my friend told me to do simple as that. i never reply back telling phatduc that that is what his got to do to his truck. and ofcourse that u can not drive it all the way empty you have tu use commun sence. and for the record i never said that i was a certify mechanic.
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