Intermittent misfire under acceleration S Coupe
#1
Intermittent misfire under acceleration S Coupe
Please forgive me if this is a frequently repeated question. I have extremely little time for the next week, and this freaking Mini is about to give me an infarction.
I replaced the battery, which resolved my intermittent rough non-start issue, on Sunday. Monday, on my drive home from work, I started getting an intermittent misfire under acceleration--specifically under boost. This is a hard cut that comes and goes in a fraction of a second. What are common problems causing misfires like this on the R56?
2012 Mini Cooper S coupe, 65k miles, stock, driven daily on a 100 mile round trip commute that is virtually all freeway with lots of acceleration. Original ignition consumables.
I replaced the battery, which resolved my intermittent rough non-start issue, on Sunday. Monday, on my drive home from work, I started getting an intermittent misfire under acceleration--specifically under boost. This is a hard cut that comes and goes in a fraction of a second. What are common problems causing misfires like this on the R56?
2012 Mini Cooper S coupe, 65k miles, stock, driven daily on a 100 mile round trip commute that is virtually all freeway with lots of acceleration. Original ignition consumables.
Last edited by Longitudinal; 09-12-2017 at 10:01 AM.
#4
When a power stroke is lost, that is a misfire. A misfire can have one or more of numerous causes. I am missing the occasional power stroke under load.
Accelerate gradually? I can't accelerate instantly. Do you mean accelerate at a slower rate? If so, no, it seems to be tied to boost.
I should also note that I have not yet detected a misfire with a cold engine. I first noticed it last night at the end of my 50 mile return commute from work. I could not detect a misfire this morning until I had reached the freeway. I can't say for sure that engine temp has anything to do with the problem, but that is the correlation I have observed so far.
Accelerate gradually? I can't accelerate instantly. Do you mean accelerate at a slower rate? If so, no, it seems to be tied to boost.
I should also note that I have not yet detected a misfire with a cold engine. I first noticed it last night at the end of my 50 mile return commute from work. I could not detect a misfire this morning until I had reached the freeway. I can't say for sure that engine temp has anything to do with the problem, but that is the correlation I have observed so far.
#7
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Correct. I don't mind replacing the plugs, but my second general rule of engine diagnostics is "its' not the plugs." That's right behind "it's not the thermostat." YMMV, but I have seen some pretty heinous looking spark plugs in my life on cars whose behavior didn't change even a little after replacement.
#12
Correct. I don't mind replacing the plugs, but my second general rule of engine diagnostics is "its' not the plugs." That's right behind "it's not the thermostat." YMMV, but I have seen some pretty heinous looking spark plugs in my life on cars whose behavior didn't change even a little after replacement.
I stick to oil changes 4,000 miles and plugs every summer. The coils I did at 25k and again at 60k. A fresh battery every few years and the above and the car is reliable and much better to drive. Milage may vary, I average 29 mpg according to gauge and I drive it. Little trips, errands and long trips.
#16
6th Gear
iTrader: (4)
My 2011 MCS is doing what seems to be the same thing, I am at almost 80k miles. A big "jolt" of no power for a split second, then back to normal. Usually happens between 2500 and 3500 RPM's or so, and 80-100% throttle. Very intermittent! I change my plugs every 20k and use NGK Iridiums. These have maybe 10k on them. No CEL, no codes. I used this same scan tool to pull codes when I had a CEL and misfires previously when the HPFP was going out. This scan tool read all the misfire codes, as well as the fuel pressure codes at that time. Very interested to find out what the issue is with your ride, Longitudinal. Keep us/me posted, please!
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#18
What scan tool are you referring to?
My misfire has become significantly less intermittent in the last week. It now regularly stutters at anything more than half throttle and anything above let
s say 2000 RPM.
My misfire has become significantly less intermittent in the last week. It now regularly stutters at anything more than half throttle and anything above let
s say 2000 RPM.
My 2011 MCS is doing what seems to be the same thing, I am at almost 80k miles. A big "jolt" of no power for a split second, then back to normal. Usually happens between 2500 and 3500 RPM's or so, and 80-100% throttle. Very intermittent! I change my plugs every 20k and use NGK Iridiums. These have maybe 10k on them. No CEL, no codes. I used this same scan tool to pull codes when I had a CEL and misfires previously when the HPFP was going out. This scan tool read all the misfire codes, as well as the fuel pressure codes at that time. Very interested to find out what the issue is with your ride, Longitudinal. Keep us/me posted, please!
#19
My German car experience tells me to start with the most expensive solution and work backward toward the cheapest. So I will start with the apparently trash ignition coils and add plugs. What brands of coil and plug should I seek out/avoid?
**EDIT** Oops, the most expensive appears to be the fuel pump. It's on back order at Autohaus. What is the best source for the fuel pump?
**EDIT** Oops, the most expensive appears to be the fuel pump. It's on back order at Autohaus. What is the best source for the fuel pump?
#22
N O !!!!
By no means ever use them. Their ring seal does not compress at nm torque specs for the MINI and back out....Whatever the metallurgy they are made from is not proper for MINI.
Every person I have seen at the shop needing a helicoil and many in this forum has had them back out.....
Use OEM.
By no means ever use them. Their ring seal does not compress at nm torque specs for the MINI and back out....Whatever the metallurgy they are made from is not proper for MINI.
Every person I have seen at the shop needing a helicoil and many in this forum has had them back out.....
Use OEM.
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R56devotion (09-26-2017)
#23
Correct. I don't mind replacing the plugs, but my second general rule of engine diagnostics is "its' not the plugs." That's right behind "it's not the thermostat." YMMV, but I have seen some pretty heinous looking spark plugs in my life on cars whose behavior didn't change even a little after replacement.
#24
I'll ask again for the better choice in plug and coil.
#25