BMW E46 Fanatics Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
302 Posts
Discussion Starter #1
hey guys..
so yes its been a year since ive been able to solve my misfires, codes etc..

symptoms include

hesitation , intake *popping upon startup (cold starts) unless I REV the engine right after the engine fires, misfiring, had a phase of limp home modes on rpms above 4k.

p1189
p1188
p0173
p0170
p1250
misfires on all cyclinders, (p0301,p0302 etc..)
random misfires.

Fixes(or attempts)
-spark plugs professionally changed and gapped
-fuel filter changed
-air filter

I ended up unplugging the MAF, and the car runs perfect, with the exception of running on open loop, there are only slight intake pops in the morning on a cold start.

Now i have taken apart the boots, throttle body, icv etc, disa, and all seems good.

any ideas??? CCV? MAF? I also have a gas cap that is incorrectly sealed. (doesnt fit. some idiot gave me the wrong one)
I have to get my car tested for emmissions this week and i not think ill pass under these conditions..
 

·
Registered
Joined
·
1,599 Posts
Get the correct gas cap as well since if it is not sealed properly - it will cause the SES light to come on and that is an instant fail in many places.
 

·
Registered
Joined
·
10,207 Posts
The Gas Cap is not the problem. It can be a problem, but you have none of the codes that come from a gas cap. None. Not any.

P0170 and P1188 are the same thing. P0173 and P1189 are also the same thing. P0170 and P0173 are also the same thing, but one is on the front three cylinders, and the other is on the back three. P0nnn is a generic definition that all cars can make, P1nnn is a unique definition for the same problem that only BMW uses. I'm not clear on why BMWs have a unique code for a generic condition, but they do. I am not sure what P1250 is, but I'm inclined to ignore it because there is no definition on any of the look-up tables.

Your assorted misfires arise from the same condition that causes P0170, P0173, P1188 & P1189. These codes translate to FUEL TRIM (CONTROL) MALFUNCTION, where trim and control are the difference in P0 and P1. You need a new MAF.

THE JOB OF THE MAF
The MAF looks at the air coming into the intake and evaluates it for quality, temp and density mostly. If the temp and density are X, then a certain amount of fuel is needed. If the quality is Y, then a different amount of fuel is needed. The computer wants to maintain a mixture of 14.7 parts of air to each part of fuel. If the air is X, then the computer sets the injector timing to attain the desired ratio, if the air is Y, then a different injector timing scheme is needed. Under any kind of normal conditions, the air temp and density are a constant -- that is, the air does not change much in any given drive cycle although it can change radically from one day to the next. So, the input from the MAF should be relatively stable during any given trip, unless you are going from the desert to the top of Pikes Peak in the same trip.

When the MAF fails, it sends the computer into a tailspin because the fuel injector timing will be wrong, and the magical 14.7:1 will not happen. The actual air quality of Y will sometimes be reported by the MAF as X, and other times as Z. The fuel delivery will be up and down as the computer constantly tries to keep up with X, Y, & Z.

The O2 Sensors look at the resulting exhaust stream and report back to the computer what the exhaust looks like, and the computer then fine tunes the injector timing. So, the O2s see the exhaust as okay, too rich, or too lean. Your O2s are reporting MALFUNCTION, which means BOTH too rich and too lean. The intake air is a constant, but the MAF is reading it as all over the place, so the fuel delivery is also all over the place. Eventually the O2s tell the computer, no matter what I(we) say, the mixture in the exhaust is never right. It is lean one minute and rich the next.

If you took the car to a service center that uses the data link connector and the BMW diagnostic software, they could look specifically at the MAF and tell you within a minute, literally, if it is working, and in my case the diagnostic pointed to a specific transistor packed inside the MAF as the problem, and it knew that the gate (one of three pins on the transistor) was shorted to ground.
 

·
Registered
Joined
·
302 Posts
Discussion Starter #11
Jdstrickland,

Thanks for the information.
I will be looking into that more detailed this week, good thing the shop is down the road from my place
 

·
Registered
Joined
·
10,207 Posts
You will NOT pass the smog test with your car in this condition. Indeed, the very existance of the codes you are having is why we have to do the Smog Test in the first place. Your codes mean that your car is making smog.
 

·
Registered
Joined
·
302 Posts
Discussion Starter #13
You will NOT pass the smog test with your car in this condition. Indeed, the very existance of the codes you are having is why we have to do the Smog Test in the first place. Your codes mean that your car is making smog.
Yah... That's ubforutanelty my urgency to get it fixed..


I did notice my maf is actually backwards.... If that is the fix Iam going to slap myself... I remember changing around a few things and checking it out when I bought it an that's around the time it starting having problems
 
1 - 13 of 13 Posts
Top