Help me confirm my engine diagnosis

Before I spend hundreds of dollars on one part. I'm thinking I have a bad MAF. I have the following codes

p1250 - MAF code
p0170
p0173
p1188
p1189

Occasionally I'll get a misfire code. After extensive searching, it seems that these are usually caused by a bad MAF, although not always. After I clear the codes with a scanner, it usually takes a day or two for it to come back on, and it always comes back while I'm idling at a stoplight.

The car starts perfect, idle is completely stable and smooth. Really the only symptom is the car is a bit sluggish. I tried cleaning the MAF with no difference whatsoever. I've replaced the following parts over the past year:

VANOS seals
Precat O2 sensors
fuel filter
air filter
both intake boots

So, is there anything you guys could think of other than a MAF? I'm going to be really pissed if I drop $300 on this part and it doesn't fix the problem.

sounds to me like it could be something as simple as needing fresh oil and/or spark plugs. where r u in indy?

With your car running, unplug the maf. If there is no difference in the way its running,its a bad maf.

Originally Posted by scottswheels

sounds to me like it could be something as simple as needing fresh oil and/or spark plugs. where r u in indy?

I change the oil every 5k and oil isn't going to throw codes. I haven't changed the spark plugs because I figured i'd have an idle or starting issue if they were a problem. They look fine.

I'm in Fishers.

Originally Posted by BodyMan

With your car running, unplug the maf. If there is no difference in the way its running,its a bad maf.

Well this morning I fired the car, disconnected the MAF, the engine RPMs dropped for a second then returned to normal. I drove the car with the MAF disconnected and it felt slightly more responsive for a few minutes, then returned to normal. I cleared the codes before doing this and they didn't return.

I'm not sure if my results with the MAF disconnected really told me anything, because I'm not sure if the car was truly more responsive or it was just in my head.

Anyone have any input?

Where did you get those codes from? An OBII scanner? If so, see my sig. You don't want to guess its the mass air flow sensor (very expensive part).

Originally Posted by Chriztofor

Where did you get those codes from? An OBII scanner? If so, see my sig. You don't want to guess its the mass air flow sensor (very expensive part).

Yes it came from a OBDII scanner.

Anyone else want to help me out?

Originally Posted by Chriztofor

Where did you get those codes from? An OBII scanner? If so, see my sig. You don't want to guess its the mass air flow sensor (very expensive part).

Your signature is misleading. Autozone does not have the manufacturer specific fault code descriptions, but it still does give you the manufacturer specific fault codes for you to look up on your own.

Originally Posted by Hartman

Anyone else want to help me out?

I would say check the wiring. Go through and unplug every sensor and then plug it back in. One of the wires could be shorting out. Take one of the spark plugs out and see if there is any white colored residue on them. Also check for vacuum leaks with preferably a smoke test.

Originally Posted by jayton

Your signature is misleading. Autozone does not have the manufacturer specific fault code descriptions, but it still does give you the manufacturer specific fault codes for you to look up on your own.

This statement is actually more misleading than his signature.

Your BMW generates two codes when a fault is detected - one BMW-Specific, Factory Programmed code that the dealerships use for diagnosis, and one generic version of it that follows protocol established by the government. THIS INCLUDES THE SO-CALLED "MANUFACTURER SPECIFIC" RANGE OF OBDII CODES.

Those "manufacturer specific" codes ARE NOT the BMW Factory codes. The factory codes can only be read with a tool capable of using that protocol - such as the Peake Research R5-FCXIII. The Peake tools are Non-OBDII, BMW Specific, and only read the codes your dealer or BMW tech uses.

I highly recommend you (and the original poster) read the article linked in my signature titled "Is your check engine light on?" You'll find more information about the differences between OBDII and BMW-Specific codes and readers.

Also, you can check out the article I wrote for the home page on www.bimmerfest.com titled "Peake Tool School".

Finally, if you have any questions about the tools, OBDII vs. BMW specific codes, or any of our products, do not hesitate to contact me directly - ken@bimmertools.com.

Ken

Originally Posted by ken@bimmertools

This statement is actually more misleading than his signature.

Your BMW generates two codes when a fault is detected - one BMW-Specific, Factory Programmed code that the dealerships use for diagnosis, and one generic version of it that follows protocol established by the government. THIS INCLUDES THE SO-CALLED "MANUFACTURER SPECIFIC" RANGE OF OBDII CODES.

Those "manufacturer specific" codes ARE NOT the BMW Factory codes. The factory codes can only be read with a tool capable of using that protocol - such as the Peake Research R5-FCXIII. The Peake tools are Non-OBDII, BMW Specific, and only read the codes your dealer or BMW tech uses.

I highly recommend you (and the original poster) read the article linked in my signature titled "Is your check engine light on?" You'll find more information about the differences between OBDII and BMW-Specific codes and readers.

Also, you can check out the article I wrote for the home page on www.bimmerfest.com titled "Peake Tool School".

Finally, if you have any questions about the tools, OBDII vs. BMW specific codes, or any of our products, do not hesitate to contact me directly - ken@bimmertools.com.

Ken

OK, go with what Ken says. He definitely knows what he is talking about. However, in my experience, I have yet to ever come across a check engine light problem that I was unable to determine the fix for with anything more than an Autozone scan.

Ken, what are some of the other things that you can learn from a BMW specific scan when someone pulls the type of codes the OP has? Is a BMW specific scan going to tell him exactly what he needs to replace?

Thanks

Originally Posted by jayton

OK, go with what Ken says. He definitely knows what he is talking about. However, in my experience, I have yet to ever come across a check engine light problem that I was unable to determine the fix for with anything more than an Autozone scan.

Ken, what are some of the other things that you can learn from a BMW specific scan when someone pulls the type of codes the OP has? Is a BMW specific scan going to tell him exactly what he needs to replace?

Thanks

No tool will tell you exactly what to replace. Your best bet is to start with the most accurate codes for your car as the basis for further diagnosis.

The factory codes are specific to each chassis/ECU combination. Each of those is represented by a table of codes that corresponds to your car. So, if there are systems, sensors, or other monitors that apply to your car only, the corresponding codes will be pretty specific. As you might imagine, the triggered OBDII code may or may not be remotely close to those faults.

You'll see in my article(s) mentions of factory codes that are simply not represented at all in the OBDII range. A generic tool will present "unknown code" in those cases.

There have definitely been instances of this reported on this and other boards.

Beyond that brief explanation, I have no specifics to offer as far as codes that might be missing or incorrect.

Ken

Still trying to figure this out unfortunately. I checked my fuel pressure at idle and it was right around 54 psi, within spec, so I'm kind of at a loss here.

Every single thread about 0170, 0171, 1188, 1189 people suggest checking intake boots for a vacuum leak. I have replaced both intake boots so that isn't the problem. I do get a "chugging" sound from time to time that sounds like a vac leak, but I'm not sure if that's related or not. I have sprayed the DISA valve, CCV, emissions parts, etc. with carb cleaner and nothing seems to be leaking.

At this point I'm not sure I'll ever get this resolved.

A smoke test is a better diagnostic than spraying carb/brake cleaner. Spraying carb cleaner did nothing for me when I had a big-ass hole in the lower intake boot. It could be a leak elsewhere such as the CCV. Seth (jbeurotech) has posted a basic layout for building your own smoke-test machine, or a decent shop should be able to hook it up to a real smoke machine for about an hour's labor (still cheaper than a MAF).

Could also be running lean not due to excess air, but due to inadequate fuel. Depending on your mileage, a replacement fuel filter is good preventive/scheduled maintenance, but for this specific problem it's still a throwing-parts sort of diagnostic.

Did you take the DISA off and look at it?

Originally Posted by nathancarter

A smoke test is a better diagnostic than spraying carb/brake cleaner. Spraying carb cleaner did nothing for me when I had a big-ass hole in the lower intake boot. It could be a leak elsewhere such as the CCV. Seth (jbeurotech) has posted a basic layout for building your own smoke-test machine, or a decent shop should be able to hook it up to a real smoke machine for about an hour's labor (still cheaper than a MAF).

Could also be running lean not due to excess air, but due to inadequate fuel. Depending on your mileage, a replacement fuel filter is good preventive/scheduled maintenance, but for this specific problem it's still a throwing-parts sort of diagnostic.

I mentioned in my original post that I've replaced the fuel filter already. I definitely think it's a fuel delivery problem but everyone keeps telling me to look for vac leaks, that's why I mentioned that.

Franz, I have not removed the DISA and inspected it yet. However, I'm skeptical as to how that would throw fuel trim codes. I will inspect it though.

Sorry, I missed the fuel filter part in your first post.
The lean condition can only really be a handful of things:
- Too much air (vac leak - for instance, the intake boots, leaks around the DISA, leaking CCV hoses, bad MAF)
- Not enough fuel (clogged filter, bad fuel pump, bad MAF)
- Not really a lean condition (bad O2 sensors)

Since you've tested fuel pressure, I'd keep chasing the vacuum/air leak. Try this:
With the car idling, carefully remove the oil filler cap. There should be very slight suction and the engine should continue to idle. If there is a strong suction and the engine sputters, then you may have an intake leak at your CCV (aka oil separator, crankcase vent valve, PCV) or related hoses.

The orange seal around the DISA isn't great; if you remove and reinstall the DISA then it's possible that you have a very small intake leak around it.