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Discussion Starter #1
Last night I was on my way home from dinner with a friend. There's a really nice tunnel that makes the muffler delete sound just wonderful so I decided to open it up a bit (this was well after the car was completely warmed up). I started out at 45 mph in 2nd gear and went to probably 80 in 3rd when I felt a loss of power and the car started running really rough. At that point the SES light came on for a bit and I could still feel it being rough. I slowed down and eventually the light turned off and it smoothed out.

At the next street I pulled off and pulled the codes. I got a bunch of misfires. Here are the codes:


  • Cd - Misfire during warmup, cylinder 1
  • CF - Misfire during warmup, cylinder 3
  • D0 - Misfire during warmup, cylinder 4
  • D1 - Misfire during warmup, cylinder 5
  • D2 - Misfire during warmup, cylinder 6
  • D5 - Misfire during warmup, multiple cylinders
  • C7 - Misfire, cylinder 4

I'm guessing C7 is the one that was causing the problems. So, I cleared the codes and continued on my way home. During the drive home it felt really low on power. So, I parked it and let it sit for a few hours.

Early this morning I took it out for a drive. I did the same thing -- going through 2nd and 3rd. It felt considerably stronger, but it didn't feel like it was exactly 100% (though it's probably hard for me to tell... I've been driving the M5 every evening this week after only driving my Honda for a couple weeks). The LPH cluster test came up with about 127 (after correction) during these pulls. The maximum LPH number I've had with the car was about a month/500 miles ago and I want to say it was around 140. I also noticed that the coolant temperature stayed around 73 to 74 degrees Celsius while cruising at 70 mph on the highway.

In the last 15,000 miles or so my car has had the following parts (that I've found generally lead to trouble) replaced:

  • MAFs
  • Bank 2 exhaust CPS
  • O2 sensors
  • Fuel pump
  • Spark plugs
Based on the recent history, I'm thinking the next steps to take would be just replace the other three CPS and based on the lower coolant temperature, replace the thermostat. What do you guys think?

I've also heard that sometimes our cars just do a random misfire every once in a while but after clearing the codes and letting it run a bit all is well. I just don't want to find out the hard way that I ignored something serious. I've also found that some days my car feels more powerful on the butt dyno than others... That feeling might be inaccurate, though, since I daily drive a slow (but fuel efficient :)) Honda, and the M5 is, of course, going to feel quick after two weeks of driving the Honda.

Thanks.

James
 

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New thermostat first

You definitely need to replace the thermostat, given your 73-74 degree temps. It should never be
below 79-80 degrees at freeway speed.

Start there and report back.

Regards,
Alan
 

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You definitely need to replace the thermostat, given your 73-74 degree temps. It should never be
below 79-80 degrees at freeway speed.

Start there and report back.

Regards,
Alan
I concur with Alan. Replace the T-Stat, clear the codes and see what you have. Where is the needle position on the gauge? if it doesnt get almost vertical 12'o'clock position, I might suggest changing out the sensor in the t-stat housing. Its about $25 from the stealer.

Suggestion*** You DONT need to change the PITA Black metal ring inside the housing. Just change the T-Stat and the O-rings for the pipes. Read up on the DYI so you can get the o-rings in right the 1st time.

Good Luck

Steve
 

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James...

Are you sure that all those things were done to your car? Did you personally replace the MAFs? The reason I ask is this reminds me of my car when first purchased with bad MAFs.

No knowing for sure about the MAFs the three things I would do in order are -

TSTAT
MAFs
CPS
 

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Discussion Starter #5
Thanks for the replies!

The temperature gauge hangs out in between the first hash mark and dead center. If it's particularly warm out, it will sit right in the middle.

Aaron -- I did the CPS and spark plugs myself. The service records that came with the car indicated that the fuel pump, o2 sensors, and MAFs were all changed by BMW shop within the last 15,000 miles... I hope the records aren't lying, haha.

Thanks again.

James
 

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Was the fuel filter done with the pump? Would replace if it's still original and +1 on all the t-stat recommendations.
 

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A little clearer now

Thanks for the replies!

The temperature gauge hangs out in between the first hash mark and dead center. If it's particularly warm out, it will sit
right in the middle.

Aaron -- I did the CPS and spark plugs myself. The service records that came with the car indicated that the fuel pump,
o2 sensors, and MAFs were all changed by BMW shop within the last 15,000 miles... I hope the records aren't lying, haha.

Thanks again.

James
James,

With the added info above, I suspect more may be going on here. Just to restate sensor dual-element function, one of the
sensor elements is for the analog gauge and the other to the DME. When you are viewing KTEMP in test #7 of the "hidden
menu", that value is what the DME is seeing. Have you checked KTEMP values while the analog gauge is "right in the
middle", as you mentioned above? With analog gauge at the 12:00 position, KTEMP values should be approximately
85-95 degrees C if both sensor elements are reporting accurately. Again, these are approximate values, but it does give
reasonable correlation between the two.

It's likely you may have some or all of the conditions below:

1- Debris, trapped on the front of the radiator, that is reducing airflow. The only way to check, is by removing all of the
retaining pins for the fan shroud so that you can move it far enough aft to view the front of radiator. this is something
that needs checking periodically, since it really tends to accumulate trash there.

2- Primary cooling fan viscous clutch is not coupling sufficiently at higher temps. If you have no record of replacement
of the clutch, replace it now. In addition, be sure you replace the plastic fan as well since it becomes brittle with age
and one or more of the blades could fracture.

3- Auxiliary (pusher) fan is not coming online early enough at elevated temps, due to failure of the sensor in the lower
radiator hose. This sensor is primarily used by the DME to regulate the fan speed during A/C operation, but it also turns
on the fan if radiator outlet temps get too high.

Both of these sensors are not very expensive. Replacement of both is cheap insurance.

Regards,
Alan
 

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How are you guys able to provide the digital read out for the Temperature?
Is it via Peake reader or is there a menu in computer that I am unaware of?
 

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Discussion Starter #12 (Edited)
Thanks again for the input.

I took my car for a little drive tonight and kept track of coolant temperatures as I was driving around. If I'm just going around the city normally, I'll see 78-79 C. If I drive a bit hard, it sometimes pops up to 80. But when I get on the highway and start cruising, it goes down to 72-74.

The gauge needle moves a little bit. It's around the first hash mark when the DME reading is 72-74. It is much closer to the middle at 80 C, but not quite there. I took a couple pictures and tried to get as close to the same angle as I could. Here they are:



 

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Discussion Starter #13
One more thing. I've noticed my auxiliary fan goes on much earlier than it did in my old M5. During the summer I ignored it and thought it might because of warm temperatures, but it's still turning on more often than it did in the old car and it's a little bit more chilly outside now.
 

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Your readings look just like mine pre-T-stat replacement. On the way home tonight in 30 degree weather, I was at about 11:45 on the gauge and during warmer weather I am dead on at 12:00.
 

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Thanks again for the input.

I took my car for a little drive tonight and kept track of coolant temperatures as I was driving around. If I'm just going
around the city normally, I'll see 78-79 C. If I drive a bit hard, it sometimes pops up to 80. But when I get on the highway
and start cruising, it goes down to 72-74.

The gauge needle moves a little bit. It's around the first hash mark when the DME reading is 72-74. It is much closer to
the middle at 80 C, but not quite there. I took a couple pictures and tried to get as close to the same angle as I could.

Here they are:



Providing the duel element sensor is providing accurate temps, the true test as to whether the thermostat
is regulating properly, is the reading at freeway speeds with outside temps of 60-70 degrees maximum.

As with any thermistor, this sensor is subject to calibration drift over time. You might try replacing the
sensor and see if the temps stay at 79-80 degrees as per above. However, it is more likely that the
thermostat itself is the culprit.

If my call, I would just go ahead with thermostat replacement and also replace the dual-element sensor,
as well as the outlet temp sensor (in lower radiator hose). Maintaining proper coolant temps is not the
area for leaving to chance. In addition, if your primary cooling fan viscous clutch has over 50 K miles, I
would give consideration to replacing it, as well.

Regards,
Alan
 

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I wasnt aware of the "secret" menu until couple of days ago but here is the instrument picture of my car. I took the picture when I had been driving straight for 6 hours cruising at 75+ MPh. My car has just had the T-Stat done but now I am worried that it wasn't done properly.
I will pull the KTEMP this weekend (since my work commute is city roads and only 9 miles total) on the hwy and see if I am ok. Anything above 76-77 is a good sign at hwy speeds, from what I have read.

 

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Latest Reading from this morning

Here is my latest reading from this morning.

I have a 9-10 mile commute, ALL city driving, highest speed is 55-57 and highest rpm this morning was 3100 in 2nd gear, rest of the commute was below 3000 rpm.

The outside temp was between 21-24 and even them the KTEMP stayed at 78 throughout.


 

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James, I've had the $25 temp sensor sitting in my trunk forever, just haven't had time to install. If you want to try that and don't want to wait for it to ship, you can have mine and just order me another one since I won't have time to do it until January anyway. I also have the same misfire codes during warm-up, but not the last misfire code you have and power/sound is fine.
 
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