Engine has major stumbling at 1/3 throttle and above

[Sockethead]

My engine has major stumbling at 1/3 throttle and above.. it just started out of the blue one day. I replaced the pre cat O2 sensors which I had laying around anyway and I cleaned the MAF sensor but I still have the problem. In DIS I am getting lean codes on the POST cat O2 sensors.... very strange.
I have a fuel pressor tester on order with a long enough hose to get to the windshield so I can test under load but in the meantime, anybody heard of this code and any possible solution?

[telijah]

Weird indeed. Have you tried simply pulling the post cat sensors and maybe just give them a once over?

[Sockethead]

Not yet. The post cat sensors aren't supposed to have any affect on the mixture from what I understand. I think that the error is a result of another problem. I'm going to test the fuel delivery as soon as my fuel pressure tester arrives.

[llll1l1ll]

Maybe your fuel filter is clogged?

[Sockethead]

Maybe your fuel filter is clogged?
Heh, yea... I'm hoping LOL

[Sockethead]

Well I got my pressure tester, hooked it up and drove around. The fuel pressure is dropping to 15 PSI under load. I'm having Kpro bring me a fuel filter even though she thinks it's the pump.... I'm hoping it's just the filter but you know, women are always right...:shift

BTW the only pressure tester I could find with a long enough hose was an Actron Proffesional CP7838. I got it on Amazon. http://www.amazon.com/gp/product/images/B0009XQUKC/ref=dp_image_0?ie=UTF8&n=15684181&s=automotive

http://i424.photobucket.com/albums/pp325/r_powell123/IMG_1131.jpg

[ryankokesh]

my money's on the pump :(

[SoCalZman]

my money's on the pump :(

Do we have finicky fuel pumps? That would be a bummer. Another item to save my pennies for, haha. The ones in my old Turbo Z were bulletproof. Even with the boost turned up.

[S85FTW]

fuel pump or cats, I would bet on cats since I had the same exact problem on my E36 years back when I didnt use BMW approved Gas stations.

[ryankokesh]

...I didnt use BMW approved Gas stations.

wait, wut?

[S85FTW]

wait, wut?
BMW specifically states in their manuals to use only top tier gas stations. The list can be found in the link below. I used to use Getty 93 or cumberland farms 93 (gulf gas) in my E36 and my cats were clogged by 50,000 miles.

http://www.toptiergas.com/retailers.html

[danewilson77]

Do we have finicky fuel pumps? That would be a bummer. Another item to save my pennies for, haha. The ones in my old Turbo Z were bulletproof. Even with the boost turned up.

They are a common failure part on E46. I additionally had to change mine out at about 120k miles. Went with VDO.

[Sockethead]

Yea, Kpro is probably right but since I'd put a new fuel filter in with a new pump anyway, I'm going to try that first.

Dane, curiously, what were your symptoms?

[danewilson77]

Yea, Kpro is probably right but since I'd put a new fuel filter in with a new pump anyway, I'm going to try that first.

Dane, curiously, what were your symptoms?

Read the initial post then post then post #24 :)

http://www.zhpmafia.com/forums/showthread.php?5148-E46-BMW-330i-ZHP-P0172-amp-P0175/page3

[Sockethead]

Hmm, interesting... so that was your second fuel pump?
Looks like every one's bad fuel pump symptoms are different...

[danewilson77]

That was my first (and only).

[Sockethead]

oh, ok, I was confused, the 1st post in that link you posted said that you replaced the fuel pump and post #24 siad that replacing the fuel pump fixed it.

Kris brought home a fuel filter and a fuel pump for me so I'm covered either way.. It's great having a GF that works at BMW :headbang

[danewilson77]

Yup. I just edited the OP so people didn't have to wade through the bullshit.

[Johnmadd]

Haha, I remember the moment that it died forever... and we pushed that mofo a mile and a half back in 100 degree temps with no power after the tropical storm/hurricane.

Rob, it had a muffled type sound and bogging down when he wasn't babying the throttle.

[Sockethead]

Rob, it had a muffled type sound and bogging down when he wasn't babying the throttle.
Yea, mine definitley doing that and the fuel pressure is dying off at 15 psi.... Hmm maybe I should just replace both at the same time and be done with it since I already have the fuel pump... I got over 120k miles on it....

[Johnmadd]

Yea, mine definitley doing that and the fuel pressure is dying off at 15 psi.... Hmm maybe I should just replace both at the same time and be done with it since I already have the fuel pump... I got over 120k miles on it....

Mine died in the 110,00 -115,000 range I believe, it's documented somewhere on the forum... mine was fine and I parked it and no start after that.

[Sockethead]

Mine died in the 110,00 -115,000 range I believe, it's documented somewhere on the forum... mine was fine and I parked it and no start after that.
Yea that's how Kristen's died in her 325

[SoCalZman]

Yea, mine definitley doing that and the fuel pressure is dying off at 15 psi.... Hmm maybe I should just replace both at the same time and be done with it since I already have the fuel pump... I got over 120k miles on it....

I would say that is very prudent of you. 2 birds one stone. And even if it isnt the pump it sounds like its only a matter of time type of thing.

[Sockethead]

I would say that is very prudent of you. 2 birds one stone. And even if it isnt the pump it sounds like its only a matter of time type of thing.
That's what I'm thinking... I've always been big on preventative maintenance after being a fleet mechanic back in the day...

[johnrando]

Of course if you change both at the same time and the problem goes away, you won't REALLY know which one it was. Not that it matters, but I'd be curious as to what it was.

[Sockethead]

Of course if you change both at the same time and the problem goes away, you won't REALLY know which one it was. Not that it matters, but I'd be curious as to what it was.
You know, if it was summer, I'd probably do one at a time but since I'll be freezing my ass off and laying on the ground. I'll be just wanting to get it over with

[telijah]

You know, if it was summer, I'd probably do one at a time but since I'll be freezing my ass off and laying on the ground. I'll be just wanting to get it over with

Move to Florida and this will reverse. I hope and pray I have nothing to do but oil changes on my car in the summer. Otherwise, my fat ass loses 20lbs in water weight every DIY job I perform.

[Sockethead]

Haha ! Ironically, we are on our way to Florida right now... Lol
Fuel pump will have to wait until Monday now:-)

[Sockethead]

I replaced the fuel pump only and tested the pressure under load. It stays constant ~50 psi and once again, the car had good power. Now I'll swap out the fuel filter and put this thread to rest :thumbsup

[Johnmadd]

:thumbsup

[Hornung418]

Yay!

From a GS3, this was sent.