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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. |
Might wanna try a regular plug like an Autolite Double Platinum or NGK vs the E3’s. If the wires/coils aren’t the problem.
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Originally Posted by Best4x4
(Post 638588)
Might wanna try a regular plug like an Autolite Double Platinum or NGK vs the E3’s. If the wires/coils aren’t the problem.
First picture shows the #8 plug on the left and the #6 on the right. The #8 does show some soot. https://cimg0.ibsrv.net/gimg/landrov...ce7fdd18a.jpeg The Second picture shows the #8 on the left and you can see the electrode looks fine but I swapped them and we’ll see if the misfire moves. https://cimg0.ibsrv.net/gimg/landrov...43ef16f5b.jpeg |
So after work today the SES light came on as expected, but it is still on cylinder #8. I’m at a point now that I will neeed to do a compression check and maybe a leak down test too. It’s driving me crazy since I’ve already dumped so much into this rebuild. I also found a post about another member having misfires during SAI pump blowing and it didn’t seem to have been resolved. Does anyone know if the SAI can cause the misfire? Thanks. |
"if" it was it SAI related it wouldn't be the pump, but the valve on that bank.
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I don't want to give any stupid advice here but I had a similar problem a year back. Nothing would fix it. Finally got pissed and just took it out on the highway and put the spurs to it for about 10 miles. Never had a misfire since.
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Had a misfire issue when I changed out the plugs and wires. Changed out my very expensive new plugs for the cheap OEM ones and it fixed the problem |
Originally Posted by Tito19
Had a misfire issue when I changed out the plugs and wires. Changed out my very expensive new plugs for the cheap OEM ones and it fixed the problem |
Just FYI for everybody, I was just on Rock Auto getting plugs, wires, coils, etc and they have 2 promos on spark plugs. The Autolite Iridium and they AC Delco double platinum for about $4.20 apiece with a $3 per plug mail in rebate.
Just sayin. |
Update:
Misfire is still on 8 at start up so I continued to drive the car and on Friday I got misfires on both cylinder 7 and 4 consistently. I think that’s because I used cheap coil packs I had laying around. So I made an order for the oem Bosch units and they are on their way. Also ordered new Magnecor wires and Bosch platinum +4 since I know these work well. On another note I did a compression test and got 155psi on all cylinders seems to be very even. And the truck is all apart awaiting those parts. I also hooked up a vacuum pump and tested the SAI valves and they seem to work. I’ll update once the truck is back together. |
Don't forget the injectors.
I had misfired, bought new ones and no misfires. |
Update:
Replaced wires with Magnecor 8mm wires. Replaced spark plugs to Bosch Platinum+4 plugs. Replaced coil packs with new Bosch oem. Replaced fuel injectors with reconditioned replacements. And..... still cylinder 8 misfire. At this point I’m thinking it’s something not related to anything with ignition or fuel or compression but possibly electrical or worse the engine. I’m so lost now I’m clueless. And again this is only at startup. Anything else I need to check? |
How were the O-rings on the new injectors? Injector wiring look ok?
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All looked brand new. Injector harness looked fine no cracks or broken insulation. After looking into it more and doing more research cars that have this issue have head gasket leaks. So even though it’s all rebuilt, I’m going to pressure test the cooling system. This is becoming a nightmare....
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Please keep us updated on what you fine - I've got the intermittent 308 as well, but I haven't changed coil packs yet.
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You can look into cyl 8 with a cheap ebay boroscope attached to your smartphone. That would at least rule in or out any HG issues there.
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https://cimg0.ibsrv.net/gimg/landrov...375c9ff4f3.png https://cimg1.ibsrv.net/gimg/landrov...190866e483.png https://cimg2.ibsrv.net/gimg/landrov...75010f4e87.png Sorry for the lack of updates. I have done an internal check with a borascope while pressurizing the coolant system with 1.25 bar of pressure. I didn’t find any leaks in the cylinder. This was done at operating temperature. I also discovered if I hold the throttle at 2000rpm during startup SAI the misfire doesn’t happen. I did that for a week until all my monitors were completed to pass smog. Next morning didn’t do that and the SES light came on. So it may also be a vacuum leak on the cylinder maybe the gasket isn’t fully seated. I need to do leak down to see if the valves are fully seating or try a vacuum leak test. |
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