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Another P0308 Misfire Post
Hi everyone, there has been a ton of information regarding this topic and yes I have read through them all. Well almost all. I have a 2003 Land Rover Discovery 4.6 with SAI. Long story short I rebuilt the entire engine including new top hat sleeves, ARP head studs and rebuilt heads. The truck is running great with no overheating, leaks or hesitation. One morning when I was starting the truck to go to work the SES light came on and it was the P0308 code. No other code just the single misfire. I cleared it thinking it was random and today this morning the same thing. Its been cold these past few days getting close to 40° F (cold for LA) in the mornings when I get to work, and that’s the only time it comes on. Does not come on in the afternoon and doesn’t flash when the SES light comes on in the morning at startup. (Only happened 2 times in past 2 weeks) Current specs: 200miles on the rebuild 91 octane premium only 8mm STI wires E3 iridium spark plugs No coolant leaks and plugs are normal and dry If anyone has gone through this with success please share your knowledge, as I need to pass smog so I can finally register my late fathers Discovery. Thanks |
Did you check the plug / plug wire / coil?
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Originally Posted by Saturnine
(Post 638024)
Did you check the plug / plug wire / coil?
Wires have low miles like 1000miles max coils are original, could that be the culprit? |
Its possible. My understanding is that a single misfire is probably plug / wire related but if you were having a pair of misfires from the same coil that the coil is probably toast.
:dunno: Like you actually unplugged the wire and inspected it or you just looked at it? |
I’ve experienced a single misfire from one cylinder = bad coil on two different D2’s now. My personal 02 Kalahari was cylinder #7. Friends 03 D2 was cylinder #5. Both cases the coil was the culprit and it had spark from the coil on my friends D2, but it was very very weak & it caused misfires. Slapped a spare coil in and no more issues!
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Well, there you go.
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Originally Posted by Saturnine
(Post 638027)
Its possible. My understanding is that a single misfire is probably plug / wire related but if you were having a pair of misfires from the same coil that the coil is probably toast.
:dunno: Like you actually unplugged the wire and inspected it or you just looked at it?
Originally Posted by Best4x4
(Post 638028)
I’ve experienced a single misfire from one cylinder = bad coil on two different D2’s now. My personal 02 Kalahari was cylinder #7. Friends 03 D2 was cylinder #5. Both cases the coil was the culprit and it had spark from the coil on my friends D2, but it was very very weak & it caused misfires. Slapped a spare coil in and no more issues!
Originally Posted by Saturnine
(Post 638029)
Well, there you go.
Thank you both for your advice. I’ll return on here if it solved the issue. |
Replace the plug first. I have a 2003 and issues occur same cylinder, plug looked good, replaced it just 2 days ago and now runs great. Go from there.
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If it's the OEM coil packs I'm going to almost safely say age is now a huge factor as well. D2's are getting up there in age, and coil packs over time will eventually loose their Hot Spark and will need replacing. It can happen to just one bank on the coil or the entire coil itself (just depends).
I've replaced 4 D2's worth of coil packs lately and all were still OEM units. Owners had done their own diagnostics and they all claimed they had spark. However the spark was so weak it caused misfire faults. If you're replacing the wires/plugs the coil packs are cheap enough now days to just replace them while you have it all torn down. Just doesn't make sense to upgrade the wires/plugs and leave the nearly 20 year old coil packs in place. |
Originally Posted by Best4x4
(Post 638169)
If it's the OEM coil packs I'm going to almost safely say age is now a huge factor as well. D2's are getting up there in age, and coil packs over time will eventually loose their Hot Spark and will need replacing. It can happen to just one bank on the coil or the entire coil itself (just depends).
I've replaced 4 D2's worth of coil packs lately and all were still OEM units. Owners had done their own diagnostics and they all claimed they had spark. However the spark was so weak it caused misfire faults. If you're replacing the wires/plugs the coil packs are cheap enough now days to just replace them while you have it all torn down. Just doesn't make sense to upgrade the wires/plugs and leave the nearly 20 year old coil packs in place. On Sunday I replaced both coil packs with new units. They looked to be original, but one seems to have been replaced with a used unit in the past(not the bank that was misfiring). Finished up the job and drove it last night with no issues. This morning started right up no issues. Then after work light came on and as the dreaded misfire is back. It seems to come on when the SAI is blowing at its maximum during start up. Could it be that the SAI is blowing out the spark? I am about to remove cylinder 6 spark plug and swap it with #8 to rule that out. I have already swapped wires from cylinder 7 and 8 still misfired on Saturday. I’ll take a picture of cylinder 8 plugs with cylinder 6 plugs side by side to compare and share it here later tonight. Thanks for the diagnostic advice. |
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