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  #1  
Old 10-11-2019, 07:45 PM
spawnoflard spawnoflard is offline
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P0171 and P0174 wont quit

Once again another thread on the dreaded P0171 P0174 fault codes and proving elusive to fix.
I've read numerous threads on exactly these fault codes on exactly this model and other M54 engines and this is where I am now but rather than just flipping out parts I've tried to approach from a position of knowledge so here goes.

Smoke tested and put new O' rings on DISA and Dipstick tube after 100 miles it came back.
Smoke tested and noticed the exhaust manifold had a leak so fixed and reset but returned after 120 miles.

Removed the OIL filler cap when running but there's no suction.

Cleaned MAF, problem persisted.
Tried another MAF from an X3 with no fault and still problem persisted.

Changed both upstream oxygen sensors and still problem persisted.

It seems intermittent but I can reproduce the fault codes at idle but not generally when driving except idling in Drive.

If I start the engine from cold and let it idle sometimes the short term lean will be at 0-2% and other times I start the engine and it will go to between 8-12%.
Idling in gear at traffic lights sometimes it stays between 0-2% then after a couple of minutes creeps up to between 8-12% or other times I'll come to a stop at the lights and it'll stay at 8-12%. in those situations sometimes if I tap the gas peddle a couple of times gently it'll drop back to 0-2% and stay there for a minute before starting to climb again.

Sometimes it does also go negative by around -10% at the most

I've found I can stave off the CEL as long as I intervene when idle by taping the gas peddle either to keep the short term lean on both banks subdued.

I don't think there's a vacuum leak, however I believe the purge valve has a hose going into the intake manifold from underneath so possibly was smoking unnoticed.

Of all the ECU monitors, after a reset only the Evaporate Monitor doesn't go into a Passed state with the CEL on.

My next steps are :-
1: Get a fuel pressure tester, when ignition key is turned it should be at 50-51Psi and a stead 45psi when running, although I'll need to do some more googling to get a reliable source of info.
2: Connect a voltmeter to the purge valve terminal set to 200ohms I believe it should read around 30ohms if working and higher if not, again not 100% certain of the values.
3: Clean the throttle body and inspect the intake boot again for leaks.

I hope to hell it's not the fuel filter as this is an in-tank not in-line filter so I'm not looking forward to opening the gas tank up.

Any other suggestions before I flambe my X3?
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  #2  
Old 10-11-2019, 08:48 PM
abscate abscate is offline
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Quote:
I don't think there's a vacuum leak, however I believe the purge valve has a hose going into the intake manifold from underneath so possibly was smoking unnoticed.
The STFT is telling you you have a vacuum leak.
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Old 10-11-2019, 09:25 PM
spawnoflard spawnoflard is offline
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Thanks, It's just hard to nail down exactly where the leak is, I was thinking perhaps instead the fuel pressure was to low either a problem with the filter or pump and that could be causing the disparity with the fuel air ratio.

Interestingly I just got back from a 10 mile drive, P0171 p0174 both pending within 3 miles at the end they were pending with a UF300 but interestingly for the first time I have a P0440 pending too.
Will check the seal on the gas cap and replace it anyway but I have more than half a tank and filled it up 5 days ago.
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Old 10-11-2019, 09:27 PM
dukedkt442 dukedkt442 is online now
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Hook up a quality scanner and obtain a misfire count.


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Old 10-12-2019, 09:06 AM
spawnoflard spawnoflard is offline
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I've been using an ELM327 tool and the 'Car Scanner ELM OBD2'
I'll see if I can get to autozone and see if I can borrow theirs.

I tested the Purge valve and ir read 25.1ohms, I'm not going to rule it out as I got the P0440 code but most commonly people say it's the filler cap.

Off to Harbour freight to get a fuel pressure tester.
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Old 10-13-2019, 07:24 AM
spawnoflard spawnoflard is offline
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Tested the fuel pressure, before start it was 48psi and when running was 51psi so don't think there's an issue there.
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Old 10-13-2019, 08:39 AM
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Attacking Mid Attacking Mid is offline
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Sounds like you need to smoke test it.

AM.
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Old 10-13-2019, 11:25 AM
dukedkt442 dukedkt442 is online now
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Quote:
Originally Posted by Attacking Mid View Post
Sounds like you need to smoke test it.

AM.


Or propane test it while watching those STFTs.

Is still want to see a misfire count. A misfire is a vacuum leak.


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Old 10-14-2019, 02:51 PM
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My bet is a crack in the pigtail coming off the intake boot between the MAF and throttle body. I believe it connects to the idle air control valve. The crack is usually on the back/underside and very hard to spot without removing the boot. A smoke test should make it show though.
Next guess would be a cracked or broken oil return line coming off the CCV valve that goes to the dipstick.

My first experience with the P0171 / P0174 codes was the broken oil return line.
Second time it was the intake boot.
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Last edited by Ishniknork; 10-14-2019 at 02:53 PM.
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Old 10-14-2019, 03:53 PM
dukedkt442 dukedkt442 is online now
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That spot is a very common M54 location. Removing the boot to look is easier than a smoke test ImO.


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Old 10-16-2019, 02:45 PM
spawnoflard spawnoflard is offline
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Did remove the boot before and couldn't find a leak.
Fuel pressure 51psi and purge valve read 25.1 ohms.

Used a probe as well to get under he intake to follow the purge valve hose and no leaks there.
Smoke tested the hell out of it and the only smoke was what came out of the exhaust.
checked the harness every single wire not a single break in the loom.

When connected to my elm327 monitoring the shirt term lean on both banks intermittently it would drop to zero or freeze, ditto with new o2 sensors, also the telemetry coming back from them seems very slow.

Mechanic seems to think that the odd behaviour might be a problem with the DME.
Expensive to swap and still not guaranteed to fix the problem.

I think it's time to send this X3 out to pasture.
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Old 10-16-2019, 03:48 PM
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Have you checked all the CCV hoses? The CCV itself? The thing is plastic and could have cracked somewhere.
Like I said before, my first experience with those codes was a cracked/broken oil return line that runs from the bottom of the CCV to the dipstick.
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Old 10-16-2019, 06:50 PM
dukedkt442 dukedkt442 is online now
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Quote:
Originally Posted by spawnoflard View Post
Removed the OIL filler cap when running but there's no suction.
I had to go back and re-read your original post to catch this: if there is NO suction when you remove the oil filler cap, and/or the engine idle doesn't change, you likely have either a completely plugged CCV system or a large intake leak. A little suction is normal, and to be expected.

Smoke tests are great until they aren't.

You need to obtain a misfire count on every cylinder. If you can read that (Torque Pro does), let propane run from a tank directly into the throttle body or intake tube. STFTs will dive negative. Play with the tank until you get the STFTs stabilizing back around 0+/- (with LTFT accounting for the extra fuel) and check the misfire history. If the misfires (if any) have reduced, you have a lean misfire, further adding to your lean codes. This relates back the large intake leak above accounting for no oil cap suction. Repeat the propane procedure ebove and intake boots, intake gaskets, DISA gaskets, MAF gaskets... pretty much any place air can leak. Or, just skip straight to that step.
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Old 10-19-2019, 11:01 AM
spawnoflard spawnoflard is offline
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I'll try and get that misfire count.
But the CEL comes on very sporadically, sometimes I've had 130+ miles on the clock and no CEL.

However after I noticed it went pending I put my hand on top of the Control Unit Box it felt pretty hot.
My suspicion is that the reason the metrics from the sensors are a bit sporadic could be the DME is over heating.

So far I've not found a sensor that reports temperature on it.

Before I pull it apart I want to check if there is a fan in there.
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Old 10-19-2019, 12:43 PM
spawnoflard spawnoflard is offline
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Found the fan in the drivers footwell, drove about 20 minutes but the fan never kicked in even though the top of the controller case felt hot.
Not sure if it's supposed to run continually or only if the dme gets hot.
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  #16  
Old 10-30-2019, 11:56 AM
jlex jlex is offline
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You say you fixed a vacuum leak at the intake manifold based on what your smoke test revealed. I did the same thing on my '05 X3 about 3 years ago and it was okay until this summer... did another smoke test, and found a hose had become disconnected on the CCV system. Has been good once again. When I removed my manifold, though, I replaced the CCV system at the same time. Was easy to do with the manifold out of the car. I'd drag out the smoke machine and give it another go.
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