Whats going on with my car????

I've been dealing with my 2003 325i for some time now, its been problem after problem but I still love BMW. This is my third e46 and I really need to finally fix this thing. I've done so much to it in the last 7k miles its not even funny and still got problems.

Codes Im getting
P0171 - Mixture Control System Too Lean
P0185 - Fuel Temperature Sensor B Circuit Malfunction
P0174 - Mixture Control 2 System Too Lean Bank 2


Recently replaced:
6 Ignition coils (Bosch)
6 Spark Plugs (Bosch)
4 Oxygen Sensors (Bosch)
Valve Cover Gasket (if this even matters)

Some of the things i've replaced in the last 7k miles mechanically wise:
Fuel Pump (VDO)
Fuel Filter (Meyle)
Crankcase Ventilation System (BMW)
Fuel Purge Valve (BMW)
MAF (Aftermarket - This could be my problem)
Clean Idle Control Valve
New Intake Manifold Gaskets
New throttle body gasket


I took it to a mechanic a few weeks ago and had him do a compression test, fuel pressure test, and vacuum test and everything checked out good.

Check your vac lines and I'm surprised you didn't list lower intake boot too.

I have no idea what a fuel temp sensor is. Have you searched for your codes in thread titles?

Also, many possibly bad vac lines behind intake mani, I'm sure you know.

I got the service engine soon light for the first time yesterday. This morning the only code I got was P0174. The AutoZone ticket they printed listed the fault as system too lean- bank 2 as you know. Why you have other seemingly related codes is beyond my ability to help. Even though it lists Volkswagon on what AutoZone printed my trusty Haynes manual confirms this definition. I saw your thread before I searched on here.

Under probable cause it listed, in order: faulty oxygen sensor bank 2, large vacuum leak, faulty maf sensor.

You took care of the first option so I would look into the other two. Subscribed to see what others think. Not to hijack your thread but mine starts fine, idles fine, and runs fine in case this helps anyone point me in the right direction.

I'll follow up when I figure it out in case that helps you.

Shaun D.

Follow up- Replaced the DISA. It failed the smoke test.

Originally Posted by dmax

Check your vac lines and I'm surprised you didn't list lower intake boot too.

I have no idea what a fuel temp sensor is. Have you searched for your codes in thread titles?

Also, many possibly bad vac lines behind intake mani, I'm sure you know.

Oops yes I replaced both the intake lower and upper boots. Before I replaced my intake manifold gaskets I took a look at the rubber hoses and all are well. I'm not sure what fuel temp.sensor is either. I tried looking for it but no results. Ill try looking for other threads.

Originally Posted by Hamsocne

I got the service engine soon light for the first time yesterday. This morning the only code I got was P0174. The AutoZone ticket they printed listed the fault as system too lean- bank 2 as you know. Why you have other seemingly related codes is beyond my ability to help. Even though it lists Volkswagon on what AutoZone printed my trusty Haynes manual confirms this definition. I saw your thread before I searched on here.

Under probable cause it listed, in order: faulty oxygen sensor bank 2, large vacuum leak, faulty maf sensor.

You took care of the first option so I would look into the other two. Subscribed to see what others think. Not to hijack your thread but mine starts fine, idles fine, and runs fine in case this helps anyone point me in the right direction.

I'll follow up when I figure it out in case that helps you.

Shaun D.

Same here my car runs good and idles fine. Acceleration is excellent after I replaced the coils. The only problems I'm having is when I start the car and sometimes it would almost lag when I give it gas or feel like its gonna stall but doesn't. When I start the car the rpm needle dips up.and down for like 2 seconds and it sounds bad. Kinda embarrassed to start my car near people.

Could it possibly be the after market Maf?? The only reason I went with aftermarket is cause I didn't have the $400 at the time. But I would hate to spend $400 if that's not the reason you know

Sent from my LG-P990 using Bimmer App

Try unplugging the maf and if the car runs better, it's usually either air leak or maf. Try listening for leaks with a hose/stethoscope or diy smoke testing with a cigar (haven't done it...but it sounds cool!

Assume you have read the first link below in my signature.

Problem was not likely your MAF originally.

If you have your old MAF put it back on the car.

Problem will not be O2 sensors either.

The issue with start up leads me to think you really need to check your DISA, probably need to be replaced.

Hopefully the valve cover is not cracked.

Does the CEL come on and idle or while cruising at 40 MPH or above?

Your P0185 is most likely Fuel Control Mixture Lean (Bank 2 Sensor 1), not fuel temperature.

This is a code triggered before the fuel trim goes to greater than 10% which then triggers P0174.

No help for me jfoj? I have read all your links and printed them out along with Mango's cooling information and his what to do if your just purchased your e46. Also have the Old School BMW Maintenance Schedule v02.11. And, even some of Dmax's jokes.

Doesn't really matter though. I will hit 70,000 miles soon so just letting an indy shop I trust do a lot of stuff. I have to get the VA inspection so while it is in there... I plan to keep this car forever and learn how to do my own work eventually.

I can't complain. This is my second 2002 Ci and I have been fortunate to have well cared for low mileage cars.

But, this is driving me nuts so any thoughts would be appreciated.

Seriously. Many thanks for those of you that educate and help others. It is appreciated and I don't see people post a thank you a lot.

Edit- that does help. Any ideas why I went to code P0174 without warning? Decent crack in a hose even though it seems fine except for the SES light?

Originally Posted by jfoj

Assume you have read the first link below in my signature.

Problem was not likely your MAF originally.

If you have your old MAF put it back on the car.

Problem will not be O2 sensors either.

The issue with start up leads me to think you really need to check your DISA, probably need to be replaced.

Hopefully the valve cover is not cracked.

Does the CEL come on and idle or while cruising at 40 MPH or above?

No CEL light or anything. I dont have rough idle or misfires, I dont have my old MAF either. IF the Maf was bad im sure the car would idle rough??? I threw that away. Valve cover seemed fine when i replaced the valve cover gaskets. if it was cracked im sure oil would come out???? Can't I just unplug the DISA and see if their is a change in behavior or????

These are the only issues i get

1. When I start the car the RPM needle jumps up and down for 2-3 seconds. It's like the car is trying to catch up on air or something. Pretty much if you run full speed non stop for an hour and you stop and your gasping for air. that's the best way I can explain it.

2. Sometimes the throttle lags for a split second and sometimes feels like the car wants to do but re-catches each other.


Also, I didn't mention this earlier, im pretty sure its a different problem. But if I floor it my transmission acts weird as if it doesn't know what to do at first and than a yellow COG light comes up by the transmission. BTW its an Auto, car has 85k miles on it. The only way to get the light to go away is if I pull over, run through all the gears and than restart the car. I'm going to do a transmission fluid change in the coming weeks so hopefully that fixes that issue.

ham, did you search for 174 in title search? I think you have the list of possibles. Lower intake boot is a common issue.

Tony, did you clean tb along with icv...also, there's a throttle adaptation or something guys do. I have the vastly superior throttle cable, old school TB, so don't have that issue afaik. I know I've read of similar trans issues like yours before. Try searching for that light in thread titles.

Here is what everyone needs to understand -

P1083 Fuel Control Mixture Lean (Bank 1 Sensor 1)
P1085 Fuel Control Mixture Lean (Bank 2 Sensor 1)

Codes are usually triggered when the fuel mixture/trim is consistently between 5-10% high. Smaller vacuum leak or lack of fuel.

P0171 - Mixture Control System Too Lean Bank 1
P0174 - Mixture Control System Too Lean Bank 2

Codes are usually triggered when the fuel mixture/trim is consistently over 10% high as I recall. Larger vacuum leak or lack of fuel.

You also need to pay attention when the CEL comes on. Most often these codes appear at idle. If they happen at idle, you most likely are dealing with a vacuum leak. If the codes appear at a cruise of 40 MPH or higher, then you are likely dealing with a problem MAF and/or a fuel delivery issue.

Keep in mind on all of these cars a vacuum leak as they are referred to are not always just leaks into the air intake path, they can also be crankcase air leaks as well.

Many times if you take a car into a shop for a smoke test they only test the air intake path of the engine. The problem is many times they fail to smoke test the crankcase and the Evap system. So this is something that you as the customer need to fully inquire about and make sure they understand what they need to do as far as testing.

But again, another problem with smoke tests is they are usually under very low pressure and sometimes you will not see smoke leaks where vacuum leaks would occur. So this leave you, the customer, with a situation where the shop charges and performs a smoke test, but fails to locate the problem.

Based upon my major thread, I have outlined a basic visual inspection of many of the common failure points so a smoke test may not be required. The next useful tool is a can of brake cleaner that can beed carefully spray around intake gaskets areas, injectors, vacuum connections, DISA and so forth. Many times the brake cleaner will cause the engine RPM to increase and then once you find this type behavior you can easily pinpoint any leaks closer with a spray of the brake cleaner.

Other ways to identify leaks is with a hose or many times I use a $15 mechanics stethoscope with the transducer removed to find air leaks.

You also really need a scan tool that will display fuel trims so you can watch the trims at both idle and cruise and then determine if any changes you make will reduce the fuel time closer back to "0". A scan tool with the fuel trim displayed and then using the spray brake clean method you will be able to see the fuel trim move toward "0" if you cannot hear the engine RPM change.

If you are getting any sort of lean code, you have a problem and you need to find the source of an air leak into the intake path, the crankcase or the Evap system.

Originally Posted by dmax

ham, did you search for 174 in title search? I think you have the list of possibles. Lower intake boot is a common issue.

Tony, did you clean tb along with icv...also, there's a throttle adaptation or something guys do. I have the vastly superior throttle cable, old school TB, so don't have that issue afaik. I know I've read of similar trans issues like yours before. Try searching for that light in thread titles.

The throttle body looks brand new, i inspected it after i replaced the tb gasket cause i thought that could be the problem. I've only had the car for around 7k miles. I bought it at the beginning of this year. Yes, I cleaned the ICV, three times actually before it started working good.

I'm literally out of ideas on what the heck is going on, ive went as far as removing the intake manifold just to change the gaskets incase their was a leak. I already replaced the the lower and upper intake boot so that can't be the problem.

I've removed the DISA as well before and just put the orange gasket creme around it and let it dry incase it was letting air in. I'm literally thinking about takeing it to the stealership and paying $165 to diagnose my problems.

I haven't done to much research on the tranny cog icon but again it only comes on during hard acceleration but first im going to do a trany fluid change because i know the car needs it anyway. This is the only BMW ive had thats been like this, and i gotta figure this out. I'll do some research on the throttle adaptation you speak of. My throttle body didnt have a cable so I dont have one of the ones you got

PRDTony,

You should not have put gasket sealer on the DISA, this will not work. You need to use the replacement O-ring due to the way the DISA is installed. You also need to make sure the DISA vacuum diaphram is not leaking vacuum.

You need to make sure the valve cover is not cracked. You can have amleaking or cracked valve cover with no oil leak.

You also need to make sure your vacuum hose to the fuel filter is in good shape. Not sure if you personally did the repairs on yourself?? But you have something with an air leak that you need to locate.

Was the flap on your DISA loose at all, making a noise when you moved the unit, or was it solid when you were fixing the seal?

Originally Posted by jfoj

PRDTony,

You should not have put gasket sealer on the DISA, this will not work. You need to use the replacement O-ring due to the way the DISA is installed. You also need to make sure the DISA vacuum diaphram is not leaking vacuum.

You need to make sure the valve cover is not cracked. You can have amleaking or cracked valve cover with no oil leak.

You also need to make sure your vacuum hose to the fuel filter is in good shape. Not sure if you personally did the repairs on yourself?? But you have something with an air leak that you need to locate.

All repairs have been done by me. The hose from the upper intake boot to the pressure regulator on the fuel filter is fine. again when i had the manifold removed i inspected all the rubber hoses/tubes and everything was fine. The hose from the EGR valve that runs behind the Valve cover into the manifold is perfect.

I'll check around the valve cover and see if I can find something. Could you possibly link me to a gasket for the DISA???

Originally Posted by Andy2108

Was the flap on your DISA loose at all, making a noise when you moved the unit, or was it solid when you were fixing the seal?

The flap seemed pretty solid, the unit looks brand new, I dont remember seeing a bmw logo on it so it might be aftermarket. When i moved the flap their was a noise.

When i took it to a mechanic for a vacuum test, fuel pressure and compression test he said everything was good.

Obviously everything isnt good. Your car should not be experiencing idle surges or stuttering when you apply throttle.

When you had your VCG off, did you inspect your vanos unit for signs of failure such as loose bolts or separated hub tabs?

Originally Posted by Andy2108

Obviously everything isnt good. Your car should not be experiencing idle surges or stuttering when you apply throttle.

When you had your VCG off, did you inspect your vanos unit for signs of failure such as loose bolts or separated hub tabs?

the idle surge is only for 2-3 seconds when i start the car, not constant. The vanos looked fine, i was thinking about replacing the seals. The time chain was nice and tight.

The car smells like its running a little lean when i first start it and if i keep it on in the same spot for a min or 2.

Tony,

You need to read the first link below in my signature.

Let me repeat, you need to read the first link below in my signature.

If you are using anything other than a computer to access this web site, you need to use a computer.

There is more information about the DISA gasket in the first link below in my signature than you will care to read!!

Good luck.

The problem doesn't seem to be vacuum related, which makes me wonder if it could be a timing or a sensor thing. I'm pretty sure my 2004 330Ci ran lean for the whole time I owned it.

Next time its running weird try unplugging the MAF or the DISA and see if it helps anything. You could replace them with new oem parts to be sure they weren't the problem...

Are you using the OEM intake or do you have an aftermarket cold air intake installed?

I got an OEM intake with a dry K&N filter, the filter is new. I think if I had a vacuum leak the car would drive bad and feel like crap??? It drives fine, it doesn't always stutter when i give it some throttle, im just saying it sometimes happens. maybe like every 1-3 times out of 20 throttles. I fill it up with 93 every time. I'm going to read up on that link jfoj right now. I might end up getting the MAF from ECS for $360 shipped and see how that goes. or should i get a new DISA first?