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Discussion Starter #1
So I recently got both these codes and have looked at the common culprits (ccv, intake boots, Disa valve, looked for vacuum leaks) and haven't been able to resolve the issue. One weird thing I should point out is the codes popped up right after I replaced my exterior temperature sensor, could this have anything to do with it? I should also note the codes come up about 50 minutes into a drive. Car is a 2001 330ci.
 

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Could be MAF or fuel pressure related. maybe clogged injectors
 

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Could be MAF or fuel pressure related. maybe clogged injectors
Likely neither of those.

I had the P0171/0174 randomly occurring as well. Advice I received indicated replacing the Intake Boots was in order as this is a common source for a vacuum leak. I replaced the first one off the MAF and the result was just one of the two codes occurring, again, randomly. Replaced the DISA O-Ring, no change. Replaced the Lower Intake Boot and installed an inexpensive EBay MAF and have never seen a code since (500+ miles now). My MAF was original to the car as evidenced by the white sticker still on it. I can't say what cured my codes but I'm not putting the 134k mile MAF back on to find out.

If your Intake Boots are hard and not pliable, just replace them. OEM replacements are less than $50 and although the Lower Intake Boot can be a PITA to change, it can develop cracks that contribute to a vacuum leak. My Intake Boots were original to the car as evidenced by the Clamp on the Lower Boot being pointed down, as if it was installed before the engine went into the car.

I purchased these for the job and without them, I can't see how I could have gotten the Lower Intake Boot off and the new one on:

Angled 1/4 Ratchet
Flexible Extensions
1/4 Drive Socket Set

Good luck.

P.S. I never did a smoke test so I can't say I had a vacuum leak. I can't say I didn't either.

OEM Lower Intake Boot
OEM Upper Intake Boot
 

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OP, your engine has vacuum leaks. Period. Find a reputable indie shop that specializes in BMWs. Have the shop perform a smoke test on the intake. At that age the various rubber and plastic vacuum lines are starting to fail.

Try www.bimrs.org for a local indie shop that specializes in BMWs.
 

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OP, your engine has vacuum leaks. Period. Find a reputable indie shop that specializes in BMWs. Have the shop perform a smoke test on the intake.
Not true. I did a lot of research when I had these codes and although vacuum leaks are the most likely cause, it is not the only cause. MAF failure is rare but not unheard of. A Lexus owner chased these codes for months and only solved his issue after replacing the MAF. If his MAF is original to the car, it may be failing. They don't last forever. He did not indicate his mileage but it could be his MAF if it is the original and has more than 100k miles. If the MAF has never been cleaned, it may not be reading accurately.

It's really not helping when you tell someone what is wrong with their car when you have not seen or tested it yourself.
 

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Not true. I did a lot of research when I had these codes and although vacuum leaks are the most likely cause, it is not the only cause. MAF failure is rare but not unheard of. A Lexus owner chased these codes for months and only solved his issue after replacing the MAF. If his MAF is original to the car, it may be failing. They don't last forever. He did not indicate his mileage but it could be his MAF if it is the original and has more than 100k miles. If the MAF has never been cleaned, it may not be reading accurately.

It's really not helping when you tell someone what is wrong with their car when you have not seen or tested it yourself.
OP, the fastest way to diagnose this problem is to smoke test your car. Even All2kool agrees that those codes are usually from a vacuum leak. This is also a less expensive fix than the MAF, if you just replace the leaky hose.
I had the same codes 3 years ago, I went ahead and did the whole CCV system and hoses as my car was 13 years old with, I believe ancient, if not original hoses. It solved those codes until 2 years later when the MAF finally did go. It was easy to diagnose, as I knew all the rest of the hoses up top were recently replaced.

A VDO (OEM) MAF will run $215-$275 versus an original BMW @ around $415

A genuine BMW complete cold climate CCV kit with the oil separator valve and all the appropriate hoses is about $200. A BavAuto non OE kit is around $130.00

Or use a low pressure smoke test and chase down the specific hose and R&R it, for dirt cheap, but be prepared to do it again, once the other hoses start failing.

Sometimes the cigar smoke test is not quite enough pressure to find a pin hole leak, so you may have to take it to a shop or build your own with a paint can (see youtube).
 

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Why I give a chance to having MAF issues is because it only happens to a warm engine, where the mixture is closer to the ideal ratio. Vacuum leaks are usually more present in cold or when idling where OP doesn't mention the light comes on when idling.

Same thing why I would think it's fuel related
On cold start the mixture is rich, so low fuel pressure or clogged injectors could keep hiding until the engine warms up and the mixture gets closer to ideal.


If the MAF is for example underreporting the air flow, the engine would be fine when cold with a supposedly "rich mixture" that becomes closer to ideal due to the MAF issue. But once the car warms up, the mixture that should be ideal, becomes lean now.
 

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Not true. I did a lot of research when I had these codes and although vacuum leaks are the most likely cause, it is not the only cause. MAF failure is rare but not unheard of. A Lexus owner chased these codes for months and only solved his issue after replacing the MAF. If his MAF is original to the car, it may be failing. They don't last forever. He did not indicate his mileage but it could be his MAF if it is the original and has more than 100k miles. If the MAF has never been cleaned, it may not be reading accurately.

It's really not helping when you tell someone what is wrong with their car when you have not seen or tested it yourself.
Those codes are classic indications of vacuum leaks. Now, you are correct that a bad MAF can cause the ECU to throw those codes. But, a bad MAF will cause the ECU to throw other related codes. The best way to check the MAF is to use OBDFusion and check the MAF's operation. If it shows erratic flow at idle the MAF is bad. Also, a bad MAF will prevent the cruise control from being enabled when you push the button on the steering wheel. Also, the MAF's electrical connector's pins can widen and cause erratic operation issues.
 

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Those codes are classic indications of vacuum leaks. Now, you are correct that a bad MAF can cause the ECU to throw those codes. But, a bad MAF will cause the ECU to throw other related codes. The best way to check the MAF is to use OBDFusion and check the MAF's operation. If it shows erratic flow at idle the MAF is bad. Also, a bad MAF will prevent the cruise control from being enabled when you push the button on the steering wheel. Also, the MAF's electrical connector's pins can widen and cause erratic operation issues.
If a person has ODB Fusion, this is a great suggestion. Another suggestion is to swap the MAF from a car that is not having any issue, if that is an available option.
 

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If a person has ODB Fusion, this is a great suggestion. Another suggestion is to swap the MAF from a car that is not having any issue, if that is an available option.
It should be mandatory to have an OBD2 Connector and OBD fusion to post on the site (LOL).
For less than $20 you become an automotive genius.
 

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Discussion Starter #11
Short update
I took off the MAF, Cleaned it, changed my air filter and looked as best I could for any vacuum leaks. After about a 60 mile drive the same codes are pending. I might also note that my cruise control doesn't seem to work but that may be because the radio on the car is not original. I also discovered that these codes came up after I finally was able to fix my secondary air pump system (previously it wouldn't turn to ready no matter how much I drove the car). Maybe this is connected? I am really starting to suspect it might be that my MAF has gone bad. I don't want to just throw parts at the car hoping I will fix it so im considering just taking it over to a shop.
 

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If the cruise control enabled light won't come on then the MAF is suspect. The ECU won't enable cruise control if the MAF is having issues. I just went through this with my car. Bought a Siemens/VDO MAF from FCPEuro for $215. Get OBDFusion and check the MAF operation.
 

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If the cruise control enabled light won't come on then the MAF is suspect. The ECU won't enable cruise control if the MAF is having issues. I just went through this with my car. Bought a Siemens/VDO MAF from FCPEuro for $215. Get OBDFusion and check the MAF operation.
Very interesting. While driving down the interstate a few days ago with the CC on at 60mph, CD playing (from the trunk changer), Heat on and out of nowhere - the CC cuts off and the EML/DSC/Brake (parking) lights all come on. Made it the next 2 miles to my destination just fine, turned the car off, then back on and all appears fine. Car sits for two hours, I drive it home another 12 miles without issue. Plug in the code reader and nothing, no codes, none pending. Have driven the car a few more times without issue.

My current MAF is a cheapo EBay one I put in a few months ago. I still have the OEM MAF which I believe is original to the car. If I get the EML/DSC/Brake lighs again with the CC on, maybe I'll put it back in.
 

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Short update
I took off the MAF, Cleaned it, changed my air filter and looked as best I could for any vacuum leaks. After about a 60 mile drive the same codes are pending. I might also note that my cruise control doesn't seem to work but that may be because the radio on the car is not original. I also discovered that these codes came up after I finally was able to fix my secondary air pump system (previously it wouldn't turn to ready no matter how much I drove the car). Maybe this is connected? I am really starting to suspect it might be that my MAF has gone bad. I don't want to just throw parts at the car hoping I will fix it so im considering just taking it over to a shop.
I am sure someone will correct me but I don't think these codes will clear themselves. If you clear them and they return, then a smoke test is in order.
 

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Very interesting. While driving down the interstate a few days ago with the CC on at 60mph, CD playing (from the trunk changer), Heat on and out of nowhere - the CC cuts off and the EML/DSC/Brake (parking) lights all come on. Made it the next 2 miles to my destination just fine, turned the car off, then back on and all appears fine. Car sits for two hours, I drive it home another 12 miles without issue. Plug in the code reader and nothing, no codes, none pending. Have driven the car a few more times without issue.

My current MAF is a cheapo EBay one I put in a few months ago. I still have the OEM MAF which I believe is original to the car. If I get the EML/DSC/Brake lighs again with the CC on, maybe I'll put it back in.
In your case the CC got turned off due to the DSC error which I don't know what it was.
 

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marcozandrini,
what is the fastest speed the OBD fusion can do? for example precat O2 sensor voltage sample rate?
 

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In your case the CC got turned off due to the DSC error which I don't know what it was.
Unless the car's DSC lamp flashed it won't be a DSC error. I'm betting the ebay MAF is the problem. Use OBDFusion to sample the MAF flow rate. Set it to "grams per second (g/sec) reading.
 
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