e46 codes P0174 P0171

[Tigerweld]

I was driving home today and my car started stalling and jerking at 2500 rpms so I pushed the pedal down a little more. This only caused it to jerk more so I let off the gas a little and it calm down. I shifted thru the gears noting to stay away from 2500. I went about 1/4 of a mile and had to stop at a traffic light. I left the light and got about another 1/4 mile before I had to stop because it was obvious at this point I was going to be on the side of the road so I choose my own stopping place. It got where I could not even make it to 2000 rpm, then 1000. I pulled off the road and it shut off and never cranked again. I happen to have my OBD 2 with me so I pulled it up and checked my codes. I had the beloved P0171 and P0174 codes. I've read the other post people are posting, but I think mine is a little different in that it would not crank, as if it was out of gas. (I had over half tank) I've had a idle issue with this car for years. 5 yrs ago I took it to one of those Euro Fix places that kept it weeks at a time trying this, trying that. I remember they "re-coded" my car, changed the plugs, wires, cleaned the fuel injectors, etc, and never found the issue.

Recently I took the DISA valve off of it and checked it from the steps I've learned online. It checked out ok, but I noticed the O-Ring wasn't tight when I took it out so I bought a new O-Ring and replaced it. I cranked it up and it seem to run fine for a day or two, then started the rough idle again. I think I was just wishing that was the problem. What it will do is when I pull to a stop at a light or stop sign (5 speed) and idle it will 'chase' up and down the rpm's, sometimes settling on its own. Most of the time I have to give the gas a quick stomp to 2000 rpm and release before it settles down without going up and down. There have been times where it would shut off as soon as I crank it and it would take MINUTES of spinning before it will crank again. Those Germans know how to make a starter if nothing else! When this happens it acts like it was starving for fuel. I can smell it and it stinks. I always run 93 octane gas. weird. I often wondered if it could be the catalytic converter, but it runs like a rocket when I hit 3000 rpms.

I'm at a loss and pretty discouraged at the moment. It acts like it isn't getting any fuel. Could a faulty fuel pump, regulator, fuel filter be the issue since it won't crank? I

would love to hear your related stories or experiences or if you have any ideas to try first. I don't want to be one of those that replaces everything from the front of the car to the exhaust pipe and still have the issue. Thanks for reading.

[dodge408]

How is the upper intake hose? Mine completely ripped open the other day and gave me these exact symptoms.
Disconnect the MAF sensor and try to crank it. I was able to get mine started and running for a day with no MAF sensor until I installed the new hose.

[Tigerweld]

Took the MAF completely out, same result.

[SilverSaloon69]

I have cured many cars with the same symptoms. Try a new fuel pump and filter if you don't have the means to test it. These pumps in the e46 typically start to give out after 10 years. Buy a good one or just go with OEM and you'll be giving your car a fresh fuel system tune-up. HTH

[MarcoZandrini]

These codes indicate that the engine has air (vacuum) leaks downstream from the maf. The usual suspects are the 2 large hoses that run from the maf to the icv, and the "F" vacuum connector.

[Chris212]

p0171 should be system to lean/fuel related... p0174 should be maf related... you have herky jerky condition cause the maf circuit is tied into trans circuit... you may have a gear type light illuminated on cluster... basically limp mode due to either to much air and or not enough fuel... cure is replace maf with oem and intake boots upper and lower... upper boot has a vacuum line (venturi effect) type hose attached to it that aids fuel pull and if this part of the boot is compromised your not pulling enough fuel and letting in "un-metered air"... lower part of boot has air bypass line to throttle again "un-metered"... common issue... you need to replace these items perform battery reset to clear adaptation values and drive 10 miles like that old lady that pisses you off every other morning when you dont leave for work at the right time

[stephenkirsch]

I have cured many cars with the same symptoms. Try a new fuel pump and filter if you don't have the means to test it. These pumps in the e46 typically start to give out after 10 years. Buy a good one or just go with OEM and you'll be giving your car a fresh fuel system tune-up. HTH

+1 on the fuel pump and filter. I didn't see that mentioned in the write up; when was the last time those were changed?

[Tigerweld]

I replaced the fuel filter about a year ago. I haven't replaced the pump since I've own it and that's about 7 yrs. For all I know it has the original pump. I rented a fuel pressure tester today only to find that it doesn't have an adapter that fits my car so I'm searching for one to fit. Any ideas where to find one?

[snipez4664]

My money would be on the fuel pump. Like others have said, also make sure that none of your hoses are torn.

[Tigerweld]

I took the fuel pressure tester back to O'Reilly auto parts and picked one up from Auto Zone that has the adapter that fits Schrader valve. Got home and realized it lacked something to press in the valve. Rats. Anyways, I turned the ignition on and pressed the valve in with a small screw driver and I found no pressure at all. Shouldn't there be pressure with just the ignition on?

[dodge408]

You should have pressure at the Schrader valve since your pump primes every time the ignition is turned on. Pop out the back seat and try the ignition again you should hear it hum for a couple seconds

[Tigerweld]

I will try that tonight.

[snipez4664]

I know some fuel pumps dont prime in position 2. They use the crank position sensor and only turn on when the car is cranking. I would turn the engine over a few times to see if it has build pressure to rule that out.
Also, it sounds like the tool you had was correct to screw on to the fuel rail but it just didnt have something to press down on the center of the valve. If that is the car, you may be able to get a standard Schrader(SP?) valve tool and just take out the valve while you do that test.

[Tigerweld]

Ah, didn't think to take the valve out. Turns out it was the fuel pump. I ordered one next day and installed it this afternoon. It crank immediately and has been running great. I don't think it's ever ran this good. A big thank you to all that replied and offered advice. Now off to smoke test for a possible vacuum leak.

[Tigerweld]

Update: it still chases the idle so I don't have a lie what's causing that. It does, however, no longer shut off when taking off from a stop light.

[marvinstockman]

If your car runs good at high speed, and has good acceleration, where fuel needs are greatest, it is not the fuel pump or fuel filter.