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What modern BMW uses plugs that aren't pregapped?

by vesrah 9y ago

tsomctl 9y ago
Used spark plugs are going to have a bigger gap.
- mulmen 9y ago
  These were (supposedly) new plugs. The car threw up a service light around 60k miles for new coils and plugs. This is routine maintenance. The problem was not a gap that was too large, the problem was 0 gap.
mulmen 9y ago
I assume the plugs were pre-gapped at time of manufacture. Maybe they dropped this plug, maybe it was a bad batch or a defect, maybe they did it on purpose. For the shop rate at a BMW dealer they can take the time to check the gap. Regardless of the root cause the dealer installed a plug with the ground bent into the electrode which caused a misfire. They misdiagnosed it as a bent valve and told me that I probably missed a shift at freeway speed and slammed the car into second gear, causing the engine to over-rev and skip a tooth on the timing chain. Somehow this bent only one valve and the other 23 are still fine. Oh and it ran fine until they had it in their shop. Also the timing chain is still in the correct timing. I told them to get bent and took it to an independent shop that fixed the problem for $45.00. The BMW dealer claimed there was low compression and a misfire on cylinder 4. My independent mechanic found perfect compression on all six cylinders and a misfire on cylinder 6 (the one with the bent plug). I went back to the BMW dealer and they refunded me the $4,000.00 in unnecessary repairs they did. At this point I think they are either intentionally sabotaging customer cars because they get away with it or the incentives drive them to employ complete idiots. Either way the most dangerous place to take a BMW is the dealer.
- vesrah 9y ago
  That's pretty strange. It's possible for a mis-shift to not skip timing, but to be high enough to float the valves momentarily and allow for a valve (or more) to kiss a piston. This can lead to a very minor bend in valves to cause an idle misfire, until the valve eventually fatigues and drops. Diagnosable through a leakdown. A foreign object through the intake tract would be a more likely case for a 0 gap plug, as it would basically require a broken piston or valve to otherwise close up the gap on the plug and you're not missing this. Either way, absolutely terrible on their behalf and a zero sense diagnosis.
  - mulmen 9y ago
    None of that happened, the head and valves are fine. I never missed a shift. I cut my teeth driving grain trucks so I always heel-toe double clutch. That makes missed shifts highly unlikely as the shifter slips easily from gear to gear, assuming you’re pulling it into the correct gear. Also I’m not an idiot and I have never selected the wrong gate. BMW also puts heavy springs on the shifter to make it unlikely the incorrect gate is selected on accident. There is no internal engine damage as far as my mechanic can see. The dealer did also do an intake cleaning (allegedly) which involves media blasting the intake runners. It is possible there was FOD introduced at that time. I mentioned that to the dealer and they assured me that is “impossible”. The dealer did put about 35 miles on the car while they had it for new plugs, maybe they missed a shift but there’s no apparent damage to the engine. The plug damage appears to be a result of negligent installation. My most generous guess is they dropped it on the floor. I wouldn’t be surprised if they intentionally re-gapped it to cause a misfire but I have no evidence. When they told me I needed a new head I called around all the shops in the area that work on these cars. I asked them how this could happen and if they have seen it before. All the shops I talked to in the Seattle area said they have never had an N54 open. They've never seen engine damage on one and doubted the diagnosis. BMW Seattle was the only place that said they had seen this "several times". I think they just use this as a way to make a quick buck or their mechanics are so incompetent that they routinely grenade engines by installing spark plugs and cleaning intakes incorrectly. What I do know is that the people responsible should be nowhere near a car and probably not allowed outside without close adult supervision.
mikestew 9y ago
EDIT: never mind, as later details indicate, the dealer mechanics should not be allowed anywhere near a car because they bent the electrode, then said the car needed a new head because it wasn't firing on that cylinder. You know that dev at your work for whom getting it simply compile is a major victory? Yeah, BMW dealers apparently have the mechanic version of that. -- I had the same thought. I haven't changed the gap on a spark plug in decades. Oh, I check them before they go in, but they're always spot on. My only theory is that the dealer failed to torque the plug, and engine compression blew the plug out of the head, taking the threads with it. Because at the very worst, if the plug gap is way too big, the electrode might touch the top of the piston. Even then, the piston would just mash it down. I cannot think of a way to ruin a head by improperly gapping a spark plug. But I digress way away from parent's original point...
- deleted 9y ago
  [deleted]

What modern BMW uses plugs that aren't pregapped?

by vesrah 9y ago

What modern BMW uses plugs that aren't pregapped?

tsomctl 9y ago

Used spark plugs are going to have a bigger gap.

mulmen 9y ago
These were (supposedly) new plugs. The car threw up a service light around 60k miles for new coils and plugs. This is routine maintenance. The problem was not a gap that was too large, the problem was 0 gap.

mulmen 9y ago

I assume the plugs were pre-gapped at time of manufacture. Maybe they dropped this plug, maybe it was a bad batch or a defect, maybe they did it on purpose. For the shop rate at a BMW dealer they can take the time to check the gap. Regardless of the root cause the dealer installed a plug with the ground bent into the electrode which caused a misfire. They misdiagnosed it as a bent valve and told me that I probably missed a shift at freeway speed and slammed the car into second gear, causing the engine to over-rev and skip a tooth on the timing chain. Somehow this bent only one valve and the other 23 are still fine. Oh and it ran fine until they had it in their shop. Also the timing chain is still in the correct timing. I told them to get bent and took it to an independent shop that fixed the problem for $45.00. The BMW dealer claimed there was low compression and a misfire on cylinder 4. My independent mechanic found perfect compression on all six cylinders and a misfire on cylinder 6 (the one with the bent plug). I went back to the BMW dealer and they refunded me the $4,000.00 in unnecessary repairs they did. At this point I think they are either intentionally sabotaging customer cars because they get away with it or the incentives drive them to employ complete idiots. Either way the most dangerous place to take a BMW is the dealer.

vesrah 9y ago
That's pretty strange. It's possible for a mis-shift to not skip timing, but to be high enough to float the valves momentarily and allow for a valve (or more) to kiss a piston. This can lead to a very minor bend in valves to cause an idle misfire, until the valve eventually fatigues and drops. Diagnosable through a leakdown. A foreign object through the intake tract would be a more likely case for a 0 gap plug, as it would basically require a broken piston or valve to otherwise close up the gap on the plug and you're not missing this. Either way, absolutely terrible on their behalf and a zero sense diagnosis.
- mulmen 9y ago
  None of that happened, the head and valves are fine. I never missed a shift. I cut my teeth driving grain trucks so I always heel-toe double clutch. That makes missed shifts highly unlikely as the shifter slips easily from gear to gear, assuming you’re pulling it into the correct gear. Also I’m not an idiot and I have never selected the wrong gate. BMW also puts heavy springs on the shifter to make it unlikely the incorrect gate is selected on accident. There is no internal engine damage as far as my mechanic can see. The dealer did also do an intake cleaning (allegedly) which involves media blasting the intake runners. It is possible there was FOD introduced at that time. I mentioned that to the dealer and they assured me that is “impossible”. The dealer did put about 35 miles on the car while they had it for new plugs, maybe they missed a shift but there’s no apparent damage to the engine. The plug damage appears to be a result of negligent installation. My most generous guess is they dropped it on the floor. I wouldn’t be surprised if they intentionally re-gapped it to cause a misfire but I have no evidence. When they told me I needed a new head I called around all the shops in the area that work on these cars. I asked them how this could happen and if they have seen it before. All the shops I talked to in the Seattle area said they have never had an N54 open. They've never seen engine damage on one and doubted the diagnosis. BMW Seattle was the only place that said they had seen this "several times". I think they just use this as a way to make a quick buck or their mechanics are so incompetent that they routinely grenade engines by installing spark plugs and cleaning intakes incorrectly. What I do know is that the people responsible should be nowhere near a car and probably not allowed outside without close adult supervision.

mikestew 9y ago

EDIT: never mind, as later details indicate, the dealer mechanics should not be allowed anywhere near a car because they bent the electrode, then said the car needed a new head because it wasn't firing on that cylinder. You know that dev at your work for whom getting it simply compile is a major victory? Yeah, BMW dealers apparently have the mechanic version of that. -- I had the same thought. I haven't changed the gap on a spark plug in decades. Oh, I check them before they go in, but they're always spot on. My only theory is that the dealer failed to torque the plug, and engine compression blew the plug out of the head, taking the threads with it. Because at the very worst, if the plug gap is way too big, the electrode might touch the top of the piston. Even then, the piston would just mash it down. I cannot think of a way to ruin a head by improperly gapping a spark plug. But I digress way away from parent's original point...

deleted 9y ago
[deleted]