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Place your bets....What's the cause of the codes?

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Discussion Starter #1 (Edited)
OK folks hope you can help me with my problem on my 14 year old 330ci with 122k miles on the clock.

I've been getting the check engine light with P0171 and P0174 codes, over the last 20-30k miles, with it gradually coming on more frequently. Initially the light only came on in winter and on a cold start and even then not straight away, often after several days of the same conditions. But gradually the light comes on sooner, the colder the weather the sooner it comes on. If temps are above 15 degrees C, although the codes come up, the "check engine" light will not. The car appears to run fine, except for in winter when temps go below 5-7 degrees C, when until its fully warmed up, the idle can bounce up and down a little when I come off the gas to a stop.



http://www.youtube.com/watch?v=9DuAt5p3Wnw&list=UUl4kj0pLPCOfCEdtg6qGWCA&feature=share

My peake tool gives me:

Table 19
E3 is O2 sensor adaptation limit Cyl # 1-3
E4 is O2 sensor adaptation limit Cyl # 4-6

Here's a video of my DISA, yes its long vid, but essentially the pin is fine, the flap doesn't rotate freely, and moves the piston towards the vacuum pot. BUT the vacuum pot doesn't appear to hold position at 45 degrees

http://youtu.be/UWyW5rSCByc

I'm just surprised that all other aspects of my DISA after 122k miles appear fine and that its the vacuum pot that's the cause of my codes and rough idle in cold weather.

I've also done the white mark test, where the arm/piston of the DISA is marked with white dots. It moves and closes the flap on start up, and opens fully when revs go over something like 3k revs. I'll post a video asap as to what i mean by this.

When i first started getting the problem, only P0174 came up, but gradually P0171 started popping up as well. This is what makes me think its O2/Lambda sensors rather than the DISA.

Additionally:
DISA seal has been renewed
MAF has been cleaned
CCV system completely overhauled (this actually decreased the frequency of the codes and engine light coming especially in the warmer weather last summer. And I've been through whole install again to make sure everything was connected up right)
Minor valve cover gasket leak (oil consumption well under 1 litre per 1000 miles)
Fuel Filter changed about 60k miles, and I'll be replacing this shortly as a preventative measure.

So what to ppl think, DISA or lambda/O2 sensor at fault??
 

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I had the same codes plus lean codes on my '01 325Cic (125K miles) and I replaced the VCG, CCV, DISA and throttle body gaskets and vacuum hoses but the codes returned. My auto inspection was coming due, so I took it to an Independent and they told me all four O2 sensors needed replacing. I did the front sensors and I had them do the rear because of my lack of workspace. The codes subsided for a brief time and I finally found the issue when I replaced the ICV gasket last month. I would explore the least expensive fixes and work your way up, not throwing parts at it hoping to solve the problem.
 

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Did you replace the two hoses the goes from the MAF to the ICV? They, and the "F" connector are common leak items.


Sent from BimmerApp mobile app
 

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Not likely your O2 sensors, if they were bad, you would not have lean codes as the sensors could not properly measure the O2 in the exhaust stream.

Read the first link below in my signature.

You have one or more crankcase and/or intake air leaks.

DISA could contribute, but you likely have bigger issues.
 

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Post freeze frame data.
 

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Discussion Starter #6
The codes subsided for a brief time and I finally found the issue when I replaced the ICV gasket last month. I would explore the least expensive fixes and work your way up, not throwing parts at it hoping to solve the problem.
Cool thanks. If that the big thick orange gasket i replaced that at the same time as CCV.

Did you replace the two hoses the goes from the MAF to the ICV? They, and the "F" connector are common leak items.
Yes checked those. but 2 yrs ago when this split, the same codes, check engine light and running issues would happen within minutes of driving. whereas at the moment its more like a few days, apart from rough idle as temps are now above 9 degrees. i suppose this puts weight to jfoj's theory of unmetered air entering the system.
 

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Discussion Starter #7
Just read through "all" of your post jfoj in the 1st link. Very informative, I don't know why I got fixated on DISA? Will be checking over the SAP next.

With regards to freeze frame data, sorry for the stupid Q, I have the OBD tool, but what does that actually mean? Do I just take a snapshot of (which?)values at certain points, rpms?
 

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Just read through "all" of your post jfoj in the 1st link. Very informative, I don't know why I got fixated on DISA? Will be checking over the SAP next.

With regards to freeze frame data, sorry for the stupid Q, I have the OBD tool, but what does that actually mean? Do I just take a snapshot of (which?)values at certain points, rpms?
Your scan tool may not support freeze frame data.

This is a feature that the base line models will not support, but the cost-up models will. If your scan tool supports it, it will tell you that freeze frame data is available, and you press a button to get to it.

The freeze frame data is stuff like the Long and Short Term Fuel Trim at the moment of the fault, the RPM and vehicle speed, and other information that can help in diagnosing the problem. My scan tool only gives the freeze frame data at the moment of the first fault, but as other faults crop pup, there is no new freeze frame data for them.
 

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the flap doesn't rotate freely, and moves the piston towards the vacuum pot. BUT the vacuum pot doesn't appear to hold position at 45 degrees
I had the same 2 codes and my disa had the same symptom as yours. I was also throwing a code for the maf. I replaced just the disa and all codes went away/ses light off as well. With our cars it could be anything though. Good luck.
 

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Freeze frame data helps diagnose.
If the light came on at idle, it's probably vacuum leaks.

If the light came on at speed, low fuel pressure, or faulty MAF is more likely.
 

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I had the same lean codes (19 E3 E4) which would only show up at an autocross. I replaced the valve cover, the rubber boot behind the MAF, and was still getting the code. Did a little research and upon the suggestion of a shop, swapped in a new fuel filter based on the guess of low fuel pressure. No problems since even though I've had three more autocrosses since but I'll admit I have not run the fuel below 1/4 tank.
 

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Discussion Starter #12
z3papa, thanks and yes I'm hoping to replace the fuel filter as part of routine maintenance, its now 60k miles old. And of course sods law, daytime temps are consistently above 15 deg C, so no check engine light yet on a mixture of city and 200 miles of highway driving. Will have to go on some night drives.

I have a question about testing the DISA, from a post I saw over at Bimmerfest (pic below isn't mine)

Can someone confirm that covering up the hole shown in the picture should result in the flap NOT moving at all? When I cover up this hole, the flap immediately springs back :hmm:

The usual test is to place the finger on the hole on the underside of the DISA (0.53 secs in video below) and even it results in the flap opening to 45 degrees.


http://youtu.be/cglRUWQ46uU"]http://youtu.be/cglRUWQ46uU
 

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Discussion Starter #13 (Edited)
The plot thickens, i did some idle tests and heres what happened:

Cold start at 10 deg C, car not driven, Engine left to warm up at idle. Within a few mins, idle became very rough, like misfiring (assume this happened after the cars automatic choke cuts out,). Engine left to warm up to normal temps, then shut down and codes read.

Peake tool, BMW specific
E3: O2 sensor adaption limit Cyl # 1-3
E4: O2 sensor adaption limit Cyl # 4-6
CA: O2 sensor control limit Cyl 1-3
EE: Misfire Cyl # 1
FO: Misfire Cyl # 3
EF: Misfire Cyl # 4
C6: Catalytic convertor efficiency Cyl # 1-3

Genereic OBD codes:
P0171 & P0174 ***8211; lean banks 1&2
Crankshaft position sensor code
Misfires on numerous cylinders


Tested again like above. Car not driven, cold start but at 17 deg C. Engine left to warm up at idle on petrol. Within a few mins, idle became like above, perhaps not as severe. Codes as follows:

E3: O2 sensor adaption limit Cyl # 1-3
E4: O2 sensor adaption limit Cyl # 4-6
CA:
FO:
EF:
C6:

Generic OBD codes as above.

The day before this test, heres how it ran:

6 miles city driving from cold start, at 10 deg C:
Check Engine Light came DID NOT COME ON, car drove fine, But following codes pulled at the end of drive:
E3: O2 sensor adaption limit Cyl # 1-3
E4: O2 sensor adaption limit Cyl # 4-6

P0171 & P0174 ***8211; lean banks 1&2


And 1 week prior to this i did 200-250 miles on petrol of mixed city and motorway driving, with outside temps > 12 deg C and there was no CEL or codes.

The idle tests really had me stumped, but then i guess I've never started the car up from cold and just sat there, I'm usually rushing to work!!

Anyway spark plugs and fuel filter getting changed today
 

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Vacuum leaks, smoke test to find the problem(s).
 

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Discussion Starter #15 (Edited)
Vacuum leaks, smoke test to find the problem(s).
thanks, yes going in tomorrow to get checked.

I swapped out the plugs and changed the fuel filter, however the vacuum return hose (return fuel vapour?) looked perished somewhat and there was a small hole. I've temporarily put some self adhesive/amalgamating tape over the hole, see attached pics, sorry best pic is out of focus.

So after chaged the plugs and fuel fiter, I started her up at 14 deg C, from cold, and it idled fine, no CEL. But i still got E3 & E4 after letting it warm up and then check for codes. I then cleared codes, started it back up again from warm, let it idle a few mins and then went for the a short drive to get car washed. Came back, no CEL, no codes.

I wonder if the fuel filter vacuum pipe could have been part of the issue?
 

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I've had this issue in both my current 330Ci and my now sold 01 330Ci also on my friend's 330i and it was always caused by these two issues. Cracked intake pipe which caused a vacuum leak or the MAF sensor was bad and needed replacing. Now I'm not saying these 2 issues will always be the issues. There are many other reasons you can get the 171 & 174 but these are the 2 issues that were the reasons why and it always happened during the cold season. I'm assuming for the cold season the intake pipe would get hot from the engine being on. Then during the cold night it would cause the pipe to crack. MAF sensors just got bad sometimes especially aftermarket ones.
 

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Discussion Starter #17
Just an update, at 128k my car was due replacement of its precat oxygen sensors, and this seems to have resolved the problem. Longterm fuel trim are both approx at -6%. The ultimate test will be to see how the car runs when temps drop below 0 deg C, currently temps haven't dipped below 9 deg C. I managed to get a used DISA in better condition than the original one currently installed on my car. If codes appear again as temps fall, I'll install it and see if that further improves things.

It seems to me that given the age and miles on most of our cars, the lean trouble codes can often be due to a number of issues.
 
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