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Discussion Starter #1
Hey everyone! New Beast owner looking for help (bet that’s the first time you heard that phrase).

Here are the symptoms:

Car will seemingly start fine when cold, but idles very low (no more than 500rpm, or in other words, the needle usually rests on the top of that first little dot on the tach). Car will idle and drive pretty smoothly when cold, but once it reaches temperature it starts misfiring. After that, the idle is rough and there is a severe loss of power.

However, it is somewhat questionable whether the car ever truly reaches temperature because while the oil temp gauge reads about 170F-180F, the water/coolant temp gauge rests around the first dot on the cool side. It never gets close to the 12 o’clock position (maybe my thermostat is stuck open?)

Here are the codes she threw:

08 - “Intake camshaft position sensor, Cyl #5-8”

26 - “PreCat oxygen sensor heater control, Cyl #5-8”

28 - “AfterCat oxygen sensor heater control, Cyl #5-8”

CF - “Misfire during warm-up, Cyl #3”

D0 - “Misfire during warm-up, Cyl #4”

D1 - “Misfire during warm-up, Cyl #5”

D5 - “Misfire during warm-up, multiple cylinders”

Here is what I have done so far:

Code 08 has been taken care of by replacing the driver’s side intake CPS (not fun).

Codes 26 and 28 have also been taken care of because the previous owner plugged the AfterCat O2 Sensor INTO the PreCat O2 Sensor, and plugged the lines leading from the car to the two sensors INTO THEMSELVES!!!! I replaced the PreCat O2 Sensors for both banks and plugged in both driver’s side O2 sensors the right way. The passenger side O2 sensors are fine.

The car had also had a Fuel Pump Relay code earlier on, but I replaced that the day I bought the car.

I have also switched back and forth between the MAFs that came with the car and VW MAFs I bought, but the change in MAFs doesn't change anything. In fact, the car runs slightly "better" with the OEM BMW sensors than the VW ones.

All I am left with are CF, D0, D1 and D5 codes, as well as the likely case of a thermostat that is stuck open. All of you guys here seem knowledgeable…

So my questions to you all are:

Could the thermostat cause all this?

What could I have done wrong in replacing the CPS, O2 sensors and Fuel Pump Relay to keep those replacement from doing the trick?

What are the other likely culprits?

Can any of you who have resolved similar problems share your solution with me?

Should I buy and install OEM BMW MAFs?

…any help would be much appreciated!
 

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My suggestion is to clear the codes and see which ones come back. That's what I did with mine after replacing multiple parts during a preventive maintenance kick.
 

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Discussion Starter #3
ok, I will give that a try and see how it goes.
 

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Discussion Starter #4
Also, could anyone check on their Beast and see if both the passenger and driver side MAF plugs (the female-plugs that run from the engine/car to the MAFs) have all five (5) of the little metal connectors? My passenger side MAF plug only has four (4) of the metal tabs that are supposed to connect the the male-plug end of my passenger side MAF. The MAF itself has five (5) metal tabs though. Could this be a problem?
 

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In fact, the car runs slightly "better" with the OEM BMW sensors than the VW ones.
Now that's a surprise :S

There is usually a code 69 for faulty Thermostat. I am pretty sure this would show up if so.

Yes one wiring loom for the MAFS will have 4 and the other will have 5 (the extra wire is the Intake Air Temperature Sensor feed to the DME)

By the way don't mess around with the VW MAFs, just get the real deal !

So I presume you are getting the misfire codes repeatedly after clearling them right ?

CPS is pretty straightforward, you put in a new Green O Ring right ?

Ever had the engine badly steam cleaned or anything, water ingress into the Spark Plug Cover perhaps....please lift and check. Wiring on the coils can be checked, especially the earthing screws iirc. Might as well take out the plugs to look at their condition and get some more insight.

02 sensors could be incorrectly wired but doubt it as you have considered that obviously. While you recheck them, check for any exhaust leaks around the O2 bungs, unrelated I reckon but always worth a check.

Fuel Pump Relay...what code did you have to make you change that ?

Go to the FAQ, unlock your secret menu and go to Test 7 and see what KTMP is showing on a highway cruise with low load. Should not be less than 79 Deg C....

Keep us posted !
 

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+1 what Kumaran said, but I'm wondering about the temp sensor on the thermostat housing. Does it ever reach operating temp if you leave it idling? If the t-stat was stuck open then it would still reach temp if the car is not moving. If it NEVER reaches temp then I'm thinking the sensor is the likely culprit. This is in turn confusing the DME, hence all the misfiring.
 

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Maybe from plugging the o2 sensors into the wrong connecters you blow the heater control fuse for the o2 sensors. Although I think your symptoms would be different but it can't hurt to have a look anyway.
 

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Also, could anyone check on their Beast and see if both the passenger and driver side MAF plugs (the female-plugs that run from the engine/car to the MAFs) have all five (5) of the little metal connectors? My passenger side MAF plug only has four (4) of the metal tabs that are supposed to connect the the male-plug end of my passenger side MAF. The MAF itself has five (5) metal tabs though. Could this be a problem?
this is not the problem. the left side has one more pin cause it takes the air intake temp reading from the left maf.
 

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Former owner plugged the O2's into each other? That's classic. Yer car has been totally confused for a while. If I'm not mistaken you might be able to reset all of your cars fuel trim settings by disconnecting your battery and attaching the two batt. cables to each other for a while. Even without that those values should reset over the next 50-100 miles.

That low idle thing is very odd though. Many people here have had misire codes etc. due to bad fueling. Some have needed fuel pumps others just fuel filters. The FF is very easy and cheap to change actually.

How many miles on this car?
 

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Discussion Starter #10
Now that's a surprise :S

There is usually a code 69 for faulty Thermostat. I am pretty sure this would show up if so.

Yes one wiring loom for the MAFS will have 4 and the other will have 5 (the extra wire is the Intake Air Temperature Sensor feed to the DME)

By the way don't mess around with the VW MAFs, just get the real deal !

So I presume you are getting the misfire codes repeatedly after clearling them right ?

CPS is pretty straightforward, you put in a new Green O Ring right ?

Ever had the engine badly steam cleaned or anything, water ingress into the Spark Plug Cover perhaps....please lift and check. Wiring on the coils can be checked, especially the earthing screws iirc. Might as well take out the plugs to look at their condition and get some more insight.

02 sensors could be incorrectly wired but doubt it as you have considered that obviously. While you recheck them, check for any exhaust leaks around the O2 bungs, unrelated I reckon but always worth a check.

Fuel Pump Relay...what code did you have to make you change that ?

Go to the FAQ, unlock your secret menu and go to Test 7 and see what KTMP is showing on a highway cruise with low load. Should not be less than 79 Deg C....

Keep us posted !
Yes, I will clear the codes but they come back. They seem to be on random cylinders. On the second to last code reading I got misfires on cylinders 1, 3, 4, 5, and 6. Then on the last code reading, the one I mentioned in my original post, I got misfires on 3, 4, and 5. Each time I also get multiple misfires on warm up (code D5).

Yes, the CPS came with a new ring and I’m pretty sure it was green. It was such a long frustrating night trying to reach that little monster that it’s all becoming a blur. I call it “the night of the 5-8 cylinder bank intake CPS”…not a flashy name, but it still send chills up my spine. I ordered it from the BMW dealership. Also, that code is now gone.

Yup, checked the spark plugs and there was a little evidence of moisture from what I also though must have been poor engine cleaning. I went ahead and replaced the old crusty plugs with Bosch Platinum +4 plugs, and I carefully cleaned the corrosion from the coils.

I just went to the garage and checked the exhaust for leaks like you said, but don't see any.

I changed the fuel pump relay because I saw Code 01.

+1 what Kumaran said, but I'm wondering about the temp sensor on the thermostat housing. Does it ever reach operating temp if you leave it idling? If the t-stat was stuck open then it would still reach temp if the car is not moving. If it NEVER reaches temp then I'm thinking the sensor is the likely culprit. This is in turn confusing the DME, hence all the misfiring.
I will go ahead and change out the temp sensor today if I can get my hands on one.

Maybe from plugging the o2 sensors into the wrong connecters you blow the heater control fuse for the o2 sensors. Although I think your symptoms would be different but it can't hurt to have a look anyway.
I will check the fuses again. Last night I was thinking the same thing you are, so I checked through all the glove box fuses, but didn’t see the one labeled for the O2 sensor heaters or anything close to that. I did check them all though and found that one of the fuel pump fuses, no. 22, was missing. I replaced it with a 25A fuse.

this is not the problem. the left side has one more pin cause it takes the air intake temp reading from the left maf.
Thanks nightkrawler. I wanted to be sure. After the whole O2 sensor plug thing I am double-checking EVERY connection on this car!

Former owner plugged the O2's into each other? That's classic. Yer car has been totally confused for a while. If I'm not mistaken you might be able to reset all of your cars fuel trim settings by disconnecting your battery and attaching the two batt. cables to each other for a while. Even without that those values should reset over the next 50-100 miles.

That low idle thing is very odd though. Many people here have had misire codes etc. due to bad fueling. Some have needed fuel pumps others just fuel filters. The FF is very easy and cheap to change actually.

How many miles on this car?
I will try disconnecting the battery and see if that helps before I do anything else. There is no code for the fuel filter is there? You just have to read the symptoms and change it when you think it’s necessary, right? The car has 117,XXX miles on her.
 

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Discussion Starter #11
Oh and before I unplug the battery I need to ask: what else will be reset? Right now the car has the factory programming to automatically lock the doors once you drive off. Will that be lost too? I don't care about OBC, radio settings, or key programming, just my handy little auto-lock feature!
 

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Discussion Starter #12
Disconnected the battery, but that didn't work. I'm going to give the the temp. sensor a try and let you guys know how that goes.
 

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Discussion Starter #14
Ya, just changed out the temp. sensor and no difference. It was easy to change out though and it cost just under $20 from the dealer so no harm no foul. One less thing to worry about in the future.

I will check for vacuum leaks again and I'm going to double-check the spark plugs and coils.
 

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Discussion Starter #15
Were are the common leak points? The two hoses that feed the air plenum on the top-front of the engine to the outside of the air intake tubes? Anywhere else?
 

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Discussion Starter #18
I checked the line from the brake booster to the throttles and it seems fine. I'm still in the process of checking for vacuum leaks by visually inspecting every hose and gasket I can find then wiggling them around while the car is running to see if I can hear or feel any changes.

I have been searching around the site for threads similar to mine and am wondering if maybe the vanos solenoids could be the culprit. I would think the car wouldn't run properly at any time though, even when cold, if those were the problem. What do you guys think?
 

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There is no code for the fuel filter is there? You just have to read the symptoms and change it when you think it’s necessary, right? The car has 117,XXX miles on her.
Now we're getting somewhere! Any service history indicating any fuel filter replacements? Or fuel pump for that matter? 117K on the factory filter is probably the deatth sentence for your fuel pump. BMW decided to try and convince the world their fuel filter could go 100k miles without being swapped. IMHO correlates perfectly to them including free maintenance with their new cars around the time our M5's were new.
So not only is your filter DEFINATELY clogged if it's original, but your pump trying to push through that clogged filter for XX,XXX miles may have weakened it. You may need to change both to see if I'm right, but start w/ the filter. They're real cheap online, but get the new copper crush washer from your dealer because it won't come w/ a new one.
The DIY/FAQ area has a couple filter change threads. 30 mins TOPS with your front end on ramps.

Change it...TODAY!

P.S. No codes for clogged fuel filters, but I've seen at least one person here get a code that pretty much identified the fuel pump as the issue, but he's the only one.
 

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Discussion Starter #20
The fuses I am referring to are under the left hand cabin filter housing in the engine bay compartment. Do a search on the o2 sensor heater fuse.
I will do a search then check it out on the car. Could the previous owner's poor wiring have fried something in the car's electronics?
 
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