# Long-term intermittent BMW engine start-up misfire diagnosed as an exhaust valve problem? **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [September 28, 2014, 2:58am UTC](https://community.cartalk.com/t/long-term-intermittent-bmw-engine-start-up-misfire-diagnosed-as-an-exhaust-valve-problem/87401 "2014-09-28T02:58:25Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Tom\_T\_in\_Minneapolis](https://avatars.discourse-cdn.com/v4/letter/t/a88e4f/32.png) [@Tom\_T\_in\_Minneapolis](https://community.cartalk.com/u/Tom_T_in_Minneapolis)\ **Post date:** [September 28, 2014, 2:58am UTC](https://community.cartalk.com/t/long-term-intermittent-bmw-engine-start-up-misfire-diagnosed-as-an-exhaust-valve-problem/87401/1 "2014-09-28T02:58:25Z")
I have an intermittent start-up problem with my 2001 BMW Z-3, 3.0: cylinder 1 misfires on start-up for a few seconds or up to a few minutes under certain conditions. The misfire conditions are consistent: A) OBDII code P0313 (misfire detected with low fuel) or code PO1343 (cylinder 1 misfire with fuel cutoff). Both OBDII codes equate to BMW fault code 238. B) after winter storage it misfires on start–up for 5-10 minutes (I’ve always added a fuel stabilizer before winter storage); C) after a spike in humidity it misfires on start-up for a few seconds or up to a minute after a rain storm or; D) If I don’t run the car for a 3-5 days (always stored in a garage) it misfires for a few seconds (just long enough to turn on the “check engine” light). Otherwise, the car runs flawlessly –plenty of power – smooth as silk - no hesitation, but with the bloody check engine light on 50% of the time. In lieu of black tape over the check engine indicator, I’ve taken the car alternately to both Minneapolis BMW dealers over the years (once if not twice a year), but the intermittent nature of the misfire and the fact that I store the car 5 months the a year has made it difficult to pin down the exact “root cause” of the problem. The dealership mechanics have swapped and/or replaced the cylinder 1 fuel injector, spark plug, cylinder coil and cable, kept it overnight and for days. The last dealership diagnosis was a defective cylinder 1 exhaust valve that could only be fixed with a $2800 valve job! Yes, that’s right, pull the head and do a complete valve job - on all six cylinders. What am I missing here? What about the infamous BMW VANOS valve control system? Thanks for your help and insights, Tom in Minneapolis ---
**Author:** ![circuitsmith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/circuitsmith/32/40376_2.png) [@circuitsmith](https://community.cartalk.com/u/circuitsmith)\ **Post date:** [September 28, 2014, 3:57am UTC](https://community.cartalk.com/t/long-term-intermittent-bmw-engine-start-up-misfire-diagnosed-as-an-exhaust-valve-problem/87401/2 "2014-09-28T03:57:30Z")
I’d take a look at #1 spark plug compared to a couple others, preferably after it’s been sitting for awhile and would misfire. If it’s wet with oil it’s a valve guide seal, wet with coolant it’s the head gasket. Does this have one coil per plug? Try swapping coils. Get a compression test. I really doubt it’s a bad valve. ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [September 28, 2014, 4:27am UTC](https://community.cartalk.com/t/long-term-intermittent-bmw-engine-start-up-misfire-diagnosed-as-an-exhaust-valve-problem/87401/3 "2014-09-28T04:27:50Z")
A leak-down test with #1 cylinder at TDC will verify if there’s a problem with the exhaust valve. If compressed air is injected into the cylinder and air is heard coming out the exhaust pipe that verifies there’s a problem with the exhaust valve. Tester Lakeville, Mn ---
**Author:** ![knfenimore](https://avatars.discourse-cdn.com/v4/letter/k/9fc348/32.png) [@knfenimore](https://community.cartalk.com/u/knfenimore)\ **Post date:** [September 28, 2014, 7:23pm UTC](https://community.cartalk.com/t/long-term-intermittent-bmw-engine-start-up-misfire-diagnosed-as-an-exhaust-valve-problem/87401/4 "2014-09-28T19:23:21Z")
You said when it was damp out you get cylinder 1 fail. Either bad wire or coil on plug 1. ---
**Author:** ![jesmed1](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/jesmed1/32/2097_2.png) [@jesmed1](https://community.cartalk.com/u/jesmed1)\ **Post date:** [September 29, 2014, 8:11pm UTC](https://community.cartalk.com/t/long-term-intermittent-bmw-engine-start-up-misfire-diagnosed-as-an-exhaust-valve-problem/87401/5 "2014-09-29T20:11:00Z")
Here is an extensive troubleshooting list for cold-start misfires on the 5-Series BMW, which I believe shares the 3.0 liter M54 engine with your Z3. [http://www.bimmerfest.com/forums/showthread.php?t=500419](http://www.bimmerfest.com/forums/showthread.php?t=500419) The thread gives a list of 28 possible causes for a misfire, none of which is a bad valve. I highly doubt the “bad valve” diagnosis. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [September 30, 2014, 6:58am UTC](https://community.cartalk.com/t/long-term-intermittent-bmw-engine-start-up-misfire-diagnosed-as-an-exhaust-valve-problem/87401/6 "2014-09-30T06:58:21Z")
Can you describe exactly how the valve problem was diagnosed, and what other items were tested? Do you know if a vacuum gage was used? Sticky valves will show up as an unstable gage at idle, and this could easily cause your symptoms. As to the cost, well, I hate to say it, but that’s part of owning a Z3. A valve job isn’t cheap on any car, a Z3 motor is even more expensive. For one thing, you have 50% more valves than 4-bangers. For another, the market isn’t replete with readily available aftermarket parts. And a dealer is almost always more expensive than a private garage, although even at a private garage the Z3 will be more costly to repair than an econobox. The diagnosis sounds like a very good possibility, but I would like to know more about the diagnosis that went into it.