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Thread: P0171 and P0174 codes after changing Valve Cover Gasket

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    P0171 and P0174 codes after changing Valve Cover Gasket

    Recently bought my 2001 BMW Z3 Roadster 2.5L. It had a leaking valve cover gasket so I replaced the gasket with a FelPro one including the bolt rubber grommets.
    After changing the gasket (no more leaks) The Service Engine soon light came on. I pulled the codes and it has the P0171 and P0174 codes (System too Lean Bank 1 and Bank 2 respectively)
    I replaced the vacuum line that runs behind the valve cover as it appeared to be brittle. The oil cap seal was hard so I replaced the oil cap.
    I replaced the O2 sensors (with Bosch sensors) as the wires looked like they had been crimped at some point. I removed the oil cap while the car was idling to see if there was excessive pressure under the valve cover. There wasn't.
    I have focused on the valve cover area as it didn't throw these codes prior to the valve cover removal. I don't hear any obvious leaks and I have sprayed the vacuum lines that I can see with carb cleaner (all I had in my garage) to see if the idle changed.
    Car runs great and idles perfectly. I'm at a loss on what to check next?
    I assume the valve cover gasket could have been pinched somehow but that would show some leakage?

    I did change the spark plugs and the air filter at the same time as both were in need of replacement.

    Any ideas?

    I was told the oil cap test I did above would tell me if the CCV system is stuck (if the cap was hard to remove, it wasn't)

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    dworthy's Avatar
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    Welcome to the Forum!

    Ah the classic P0171 and P0174, they will point to a vacuum leak. Also it isn't a great idea to be spraying a flammable around the motor bay, so please don't. The only way to find said vacuum leaks is to get the intake smoke tested. It can be the CCV line that goes from the valve cover to the CCV is cracked when you replaced the valve cover gasket, or many other things again the best way to find it is having a smoke test completed.
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    As I am an amputee standing around trying to replace the CCV components on my own, even with my prosthetic leg is not desirable option.
    Does anyone have a cost for a shop to replace the CCV components? labor wise as I bought the replacement kit.

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    I tried to look it up for you to give you the official time, and I found nonsense. Every shop I've worked at charged about 3.5 hours to replace the crankcase vent valve/ oil separator, plus the 4 associated hoses/pipes. That's what I would quote at my shop.

    That said, I would likely suggest a smoke test of the intake system, and a crankcase vacuum test first. For a shop with the right tools, these tests together would only take about half an hour.

    Chris Powell
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    Quote Originally Posted by bmwdirtracer View Post
    I tried to look it up for you to give you the official time, and I found nonsense. Every shop I've worked at charged about 3.5 hours to replace the crankcase vent valve/ oil separator, plus the 4 associated hoses/pipes. That's what I would quote at my shop.

    That said, I would likely suggest a smoke test of the intake system, and a crankcase vacuum test first. For a shop with the right tools, these tests together would only take about half an hour.
    I have it scheduled to go into a local German car shop next week.
    I was just trying to get a ball park cause I'll most likely have them change them out at some point since I don't know how old the hoses are.

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    An update in case anyone was curious. Local German car shop ran a smoke test and found a vacuum leak on Cylinder #3 spark plug hole. They are saying the plastic valve cover is warped and to replace it.

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    dworthy's Avatar
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    Thank-you for coming back to close the loop.

    As you performed the work, take a close look to ensure you didn't roll the profile gasket, or see if it got cut or ripped on install. Valve covers tend to be rather expensive if you are looking for an OE one, and gaskets are cheap in comparison.
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    I'd like to mention that on "N" generation engines (beginning in ~2006). no dealerships, and very few good BMW specialist independents, will replace just the valve cover gasket. The fix is to replace the valve cover, complete. These valve covers DO warp, and crack, and no shop wants to have to go back in again to try to fix a recurring leak that's not their fault. At my shop, and the three I've previously worked for, there is no warranty if the customer insists on just replacing the gasket. I worked on a 2007 328i yesterday, that was pissing oil from the valvecover....he'd had the gasket replaced just four months ago at a generic shop.

    The "M" generation plastic valve covers (like yours) didn't seem to be quite as bad, but no plastic cover puts up with ANY error of installation, either. Bolts MUST be snugged together, then tightened together. The grooves of the used cover must be spotlessly clean, and the gaskets need to be glued into the grooves of a used valvecover, so that they don't droop, catch on something, or misalign during install.

    Chris Powell
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    I assume by glued in you mean with high temp Permatex?

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    Yes, and don't forget to put just a touch in the half-moon areas up front. I also like to put just a touch where the VANOS meets the head too, not really needed, but doesn't hurt.
    Darin
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    Actually, what I was referring to was something to keep the gasket in firm contact with the valve cover, if you're re-using the old cover, and after you carefully clean all the oil from the gasket slot. This is not the same function as sealing the couple of places like the half moons. What I use to keep the gasket in place in the valvecover slots of a used valvecover is Gorilla Snot. Yeah, I know, but this slang term is universally recognized at NAPA, Autozoo, etc. The real name is 3M weatherseal adhesive; it comes in amber or black, in a tube. It's pretty much instantly sticky, so you don't have to wait for RTV to harden to install the valvecover. NOTE PLEASE: This is NOT for use between the gasket and the cylinder head, this is ONLY to adhere the new gasket to a used valvecover. (AND, it will not work if the slot isn't completely clean.)

    Chris Powell
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    So I replaced the valve cover with a new one, new gasket etc. last week. Have driven the car several times since. All good.
    Today I replaced my coolant reservoir tank as it had a hairline crack that the shop I took it to had noticed. I changed it out, bled the cooling system and took it out for a long test drive (about 20 miles) Still all good code wise.
    When I got back from the test drive I had it idling in my driveway after about 30 minutes while I verified that there were no leaks from the new coolant tank and the hoses connecting to it the service engine light came on again.

    It only pulled one code, the p0171 code. No p0174 this time.
    Any ideas. If I take it back to the shop they want another $150 to check it again.
    Should I clear the code and see if it stays away?
    As I had previously mentioned I have replaced both upper and lower intake boots plus the spark plugs, O2 sensors above the cat.

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    Clear the code and see if it does indeed come back. I would take a look at the oil cap gasket, and make sure it tight.
    Darin
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    91 316i euro Tizianrot/Gray cloth - E-36 w/M-40 RIP, but great on gas! Best was 38 MPG
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    Quote Originally Posted by dworthy View Post
    Clear the code and see if it does indeed come back. I would take a look at the oil cap gasket, and make sure it tight.
    So took the car out today for the first time in a while as it was actually dry and sunny in January.
    Drove it about 30 miles and it popped the code again.
    So it took quite some time for the code to pop up again. I drove it several times since my last post. It has been sitting since November however.

    I cleared the code again. Any ideas what else I could check. Find it hard to believe it would be the valve cover gasket again. I replaced the Oil cap with an OEM one after your response in August.

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    Somewhere at the beginning of all this, I recommended a smoke test of the intake / ccv system. THIS is the way to find leaks, not throwing parts. A good BMW/Euro repair shop will have a smoke machine.

    Chris Powell
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    Quote Originally Posted by bmwdirtracer View Post
    Somewhere at the beginning of all this, I recommended a smoke test of the intake / ccv system. THIS is the way to find leaks, not throwing parts. A good BMW/Euro repair shop will have a smoke machine.
    I indicated that I had a local shop do a smoke test in a previous post.
    Quote Originally Posted by Majorbimmer View Post
    An update in case anyone was curious. Local German car shop ran a smoke test and found a vacuum leak on Cylinder #3 spark plug hole. They are saying the plastic valve cover is warped and to replace it.
    That's how the warped valve cover was discovered. I replaced it last summer.
    Last edited by Majorbimmer; 01-18-2022 at 07:38 PM.

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    Because they discovered a leak at the valvecover doesn't mean there's not another leak at, say, the oil return tube to the dipstick tube (or somewhere else). While there's an "upstream" leak, you can't find the "downstream" one. A smoke test still needs to be done, until the system remains leak free for ~7 to 10 minutes under pressure.

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    Quote Originally Posted by bmwdirtracer View Post
    Because they discovered a leak at the valvecover doesn't mean there's not another leak at, say, the oil return tube to the dipstick tube (or somewhere else). While there's an "upstream" leak, you can't find the "downstream" one. A smoke test still needs to be done, until the system remains leak free for ~7 to 10 minutes under pressure.
    Puzzling part is the car has been driven several times since summer. The code popped after a 30 mile drive yesterday.
    Was hoping to avoid yet another $150 test. But if there is no alternative.

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    On ebay, you can buy a smoke machine for about $140.

    EDIT:
    https://www.ebay.com/itm/25507724524...UAAOSwcjdhp426
    Last edited by bmwdirtracer; 01-19-2022 at 07:13 PM.

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    Quote Originally Posted by bmwdirtracer View Post
    On ebay, you can buy a smoke machine for about $140.

    EDIT:
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    Another update. Had the CCV valve and the hoses changed out by a local shop. Car is still pulling the two lean codes p071 and p074.
    Valve cover and gasket were replaced originally as the previous smoke test showed a problem with the original valve cover.
    Anyone have any other ideas what could cause it?

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    I know it's easy for me to say, since I own a smoke machine, but I would ALWAYS have to do a smoke test before any other chasing of a lean code, even if you had one done before the latest work. I can't tell you how common it is to cause other leaks in the system while fixing an intake/ccv leak.

    After that...fuel pressure, O2 sensors, etc.

    But chasing this issue using P-codes, instead of BMW diagnostic codes, is highly counterproductive. Use a better , BMW-specific, scan tool.

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    I'm using A Foxwell elite scanner. It has BMW software on it etc. I was looking for more of the "odd" things to check. The CCV and hoses are new, the vacuum lines to the intake are new, intake boots are new. Vacuum line to the secondary air pump is new. Valve cover and gasket is new, Oil cap it new.
    As the intake was removed to do the CCV stuff there is a new intake manifold gasket as well. I get the smoke test idea. As I can't bring the car back to them until next week, I was simply seeking anything that I could look over or try until then.
    Last edited by Majorbimmer; 05-13-2022 at 06:46 AM.

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    what do the BMW codes say?

    You can test fuel pressure, if you have a gauge. I usually tape mine to the windshield and drive the car hard, then monitor the gauge while flat out in third or fourth gear.

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    20220513_183906.jpg

    These are the codes from the BMW specific part of the Foxwell scanner that I pulled.

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