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P0174 - what would you check next

3K views 20 replies 8 participants last post by  nike001 
#1 ·
I am trying to do as much as possible before I go to a shop.

So far:
* New CCV System
* New Intake boots
* Fuel filter. vacuum lines on fuel regulator
* Fuel Pump
* Air Filter and spray clean MAF.
* I added some sealant to the DISA gasket, I know I shouldnt but did just to be sure.

Under a load the car has a surge to it, kind of bucking a bit. I notice it increasing throttle on the hwy in 5-6th gear at around 3k rpm. If I hit it hard the car runs fine.

On the highway at about 140-250 miles after clearing the code , P0174 comes back. I have limited time to work on this thing, so what would you check next.
 
#3 ·
Yes, if it is in just one bank, look at everything dealing with just that bank of cylinders rather than things that deal with all of them.

It's good that you did all that other stuff, it probably needed to be done anyway.

As TerraPhantm said, it very well could be the O2 sensor dealing with bank 2. If you're okay with spending the money, you can replace both of them. One other thing you could do is test the O2 sensors and see if they're giving the right values. A shop or BMW Scanner can do this.
 
#4 ·
This sounds familiar...

So, if you get on the highway and put it in top gear, as you're between 2500 RPMs and 3000 RPMs, do you get a repetitive, almost rhythmic stutter/surge/hesitation/bucking? Does it completely go away at 3k? In a headwind, or going up a hill, can you make it happen pretty much at will when going about 75mph?
 
#5 ·
You have to be really careful how you interpret the data here.

P0174 is a lean code. Since you have replaced the fuel pump and filter this is good.

You need to figure out if the lean code is triggered at idle or at cruise.

Do you have any freeze frame data to go along with the P0174?

What is the status on the Pre-cat O2 sensors and do you have anything to graph their behavior?
 
#6 ·
to answer everyone. And thank you all in advance for your time answering these questions.
* It is always P0174 Lean Condition on Bank 2.
* I mainly drive on the highway. It always seems to come on when cruising then maybe backing off the throttle when I come up on a slower car. Not when driving with more throttle and accelerating, you know?
* The car has 126000 miles, so I thought it likely needed a lot of this stuff, along with the waterpump and belts and so on.
* The hesitation issue is just like described by painbreak. It is like , pulse, pulse, pluse, then smooths out. When under some kind of load. I thought maybe the fuel pressure was not good or something so I replaced the pump. Not fixed.
* I don't have any time of tools or software to monitor the engine. That is why I am chasing this a bit. i hate to just buy 02 sensors if they are not needed. I pulled out the DISA and did the vacume check on it and it appeared OK. Even this, I hate to just buy one to see if it was the problem.

Should I just buy 02 sensors or bring it to a shop?
 
#7 ·
Here's the deal, O2 sensors are consumables. They recommend that you change them at 100k miles, I do it at 75k miles assuming they do not have problems before then.

Bosch O2 sensors are the only way to go in my opinion, usually about $50 each on Amazon.

If you are getting these codes while cruising, then not likely a vacuum leak, more likely O2 sensors and could actually be a MAF on top of the problem.

I would only worry about the pre Cat O2 sensors at this point.

If you can put them in, you replace them from under the hood, then you save any an all money you would spend at a shop. Shops just change parts like you do anyway without a lot of deep thought to your problem.
 
#8 · (Edited)
I wouldn't jump into replacing *ANYTHING* at this stage of the game.

Buy a cheap ELM327 device from Amazon ($16) and Torque Pro for Android (and get your hands on an Android device if you don't have one). Pair it, set up codes to log, set up trip logging, turn key to "ON", start logging, start the car, warm it up, then go for a test drive where the stuttering happens. Then, email the .csv to yourself from inside the Torque app, and create a graph in Excel (or send it to me, and I'll do it.) Also, as part of the test drive, do a 2nd gear run to near redline. This will give you a good idea as to whether or not your MAF is functioning correctly.

With this data, you'll know if your O2 sensors are working, if your fuel trims are weird, if the MAF isn't working, if your engine temp is off, etc. It's pretty cheap, and better than just throwing money at the problem.

I don't believe in replacing things that aren't broken. O2 sensors break, and when they break, it's time to fix them...but not until. Sure, O2 sensors are cheap, but not cheaper than free.

Also, I've added you as a member of the club, in my signature. You should stop by sometime. :)
 
#9 ·
I don't believe in replacing things that aren't broken. O2 sensors break, and when they break, it's time to fix them...but not until.
O2 sensors generally do not break, they go soft and get lazy. O2 sensors are not lifetime devices, same as MAF, spark plugs, fuel filter and many other things.

You may have a specific way of doing things, but you are expecting a 10 year old car to perform like a new car with 10 year old parts, you are expecting WAY too much.

Maintenance is needed and required to keep any vehicle in top shape.

So just be careful how you convey your philosophy.

For those who do not have a Droid, here is another low cost software option that may be helpful, not the greatest, but the price is right for gathering
data.

http://www.amazon.com/ScanTool-4230...ie=UTF8&qid=1358734819&sr=1-1&keywords=obdwiz
 
#13 ·
Check the Plug on the end of the secondary air pump. It is a little rubber cap that goes with the vacuum lines . I would replace all the vacuum lines and also change the throttle body gasket and the manifold gasket
While youre at it I would check the line that connects under the manifold to the purge valve and check the vacuum line that goes to the fuel filter.
 
#14 ·
Will get that Scan tool "JFoj" suggested, I still have the old blackberry. I sometimes spend more money on parts than I need to because of time. If I am going to have to take a weekend to work on a car, well then while there I might as well do X-Y-Z. Because I don't have time to button up the whole thing just to take it apart the next weekend.
* Buy the tool and see what comes back.
* Check the vacuum lines off the secondary pump. Purge valve lines, I need to look this up not sure what it is. I did do the fuel filter vacuum lines.
* I think the throttle body was an O-Ring? When I did the CCV I think I added some non-hardening sealant to it. I don't think I replaced the o-ring though. I never did the intake gasket, I think this will be the last resort.
* Because of the work and time issue, while out there I will likely put in the 02 sensors. Just because of Murphy's law. While pulling stuff checking vacuum I will be right there and with 126000, I may need to do it in the next year anyway.

As for this hesitation. It does seem to be between 2000 and 3000. The best example is cruising down the highway, 3000+ rpm, around 70? If I get off the gas and it slows, maybe 2500 to 2800. then jump on the gas to pull out and pass or something, I get this hesitation in acceleration. It seems like two short ones, a third a little longer, then I start hitting 3000 and it goes away. I am not sure if it 3000 or just that there is less load on the motor at 3000. But over 3000 and winding it up, I can't notice or as much. Not sure if this is related to my P0174 or not. As mentioned earlier, I thought it was some sort of fuel pressure issue, but I guess not.
 
#17 ·
There are iPhone/iPad apps, however, they are a bit more expensive and some require an expensive interface. Search around and see what you can find, however, I recall one program had a cable that was required that cost over $100 plus the cost of the App.

The other problem if it is your wife's phone, you will have a hard time getting it when you need to use it, trust me, no amount of money is worth trying to take the wife's phone.
 
#18 ·
I actually have identical issue... I though it was a vacumm leak but this is hard to find at this point. Ive done all ccv, tb, intake hoses, fuel filter, all the little rubber hoses... issue is same as before i began my search... I did spray the intake manifold with carb cleaner to see if I get some kind of response but nothing is happening..

As im hitting about 2700 in 6th, it begins to make pulsating hesitation till it hits 3000 and then it pulls very hard and steady... I do have the O2s, wideband, so they are more expensive then the <04 e46. I have them sitting in my garage and because I havn't gotten any codes yet I didn't put them in. Ive scanned my dme with 1.4 scanner but it only shows me shadows for bank 2... nothing in red.
 
#19 ·
Pawelgawel - what is good is that you are not getting a code. So that means I can clear the code at some point. Then try to figure out this hesitation. When I ran the car with Techcron fuel cleaner I did not seem to have the problem, maybe just a coincidence. I think a good thread should be how much of these parts can be removed or bypassed to end it forever.
 
#20 ·
#21 ·
I work at a dealer, and wasn't planning on having it scanned but a buddy did it for free. Found the same code and inspected my engine bay.

I have a hole in my lower intake boot and a seal on my disa has a good leak as well. Don't know which one tripped the code though. I'll be fixing both anyways
 
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