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E85 / E86 Z4 (2003-2008)
E85 Z4 Roadster, E86 Z4 Coupe, E85 Z4 M Roadster, and E86 Z4 M Coupe talk with our BMW gurus here.

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  #1  
Old 04-13-2013, 03:58 AM
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crewdog843 crewdog843 is offline
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Mein Auto: '08 Z4 3.0si Roadie
Z4 (E85) Big stumble

Have any of you E85 owners ever had this happen? You drive on the freeway, the engine is purring....all systems are 'go' with the engine fully warmed. You depart the freeway via the exit ramp and encounter a red light. While waiting for the light to change, the engine stumbles, RPMs drop and it feels like it's gonna die, but then recovers and starts purring like a kitten again. What's going on? No lights, just a big stumble! Second time in about a month...44000+ miles...'08 3.0si. Always fueled with high octane. Filter clean. Oil needs to be changed soon but....
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  #2  
Old 04-13-2013, 10:06 PM
SC2003Z4 SC2003Z4 is online now
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  #3  
Old 04-14-2013, 05:49 AM
tonywintn tonywintn is offline
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Not much information to go on yet so let me ask you a couple of questions. It looks like you are out west, correct? On the days that it happened, were they warm days? Had you just filled your tank? How full was your tank? What is you approx altitude?
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  #4  
Old 04-14-2013, 06:35 AM
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crewdog843 crewdog843 is offline
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Mein Auto: '08 Z4 3.0si Roadie
Location: Las Vegas. Approximate altitude: 2200'. Daytime temperature: 80+, less than 90. Seventy three miles remaining in tank. Injector cleaner, one tank prior to incident. Car at normal operating temperature, departed freeway to gas up at local Costco (no previous history of fuel problems in 1 1/2 years of driving this car and fueling from any Costco location). Waiting for stop light to change, sudden drop in RPMs accompanied by a shake in the engine from which it quickly recovered. RPMs back to normal (idle 650-700). Car runs very, very well with no other problems. As stated, air filter pulled, trapped, blown out, and vacuumed approximately one month ago, air box vacuumed (after dusty trip through Southern California and western Arizona). Coming up on oil change in approximately 1000 more miles. I'm wondering if it might have thrown a code, but no engine check lights or other indicators appeared. Possible MAF malfunction.
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Old 04-14-2013, 10:04 AM
tonywintn tonywintn is offline
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I'm supposing that the engine experienced a momentary disruption in fuel supply. I'm ruling out a hot fuel issue since the tank was nearly empty. (Fresh fuel is much more volatile than old fuel) Based on 73 miles of range left in the tank that would be about 2.5 gallons or somewhere between 20-30mm of fluid height depending on the fuel tank design. Did the previous occurrence happen with a nearly empty tank? If so, another test you can do with a nearly empty tank: do a full throttle acceleration from a stop that lasts 10 seconds or so and see if the engine loses power. If it doesn't, then you can rule out this theory of momentary fuel supply disruption.
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  #6  
Old 04-15-2013, 06:58 AM
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crewdog843 crewdog843 is offline
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Interesting observation. I failed to take note of the fuel state during the first incident, but will keep it in mind should it happen again. If there is a fuel filter on the car (and I suppose there is), it might need to be changed. I will mention it at the next service. Thanks for looking and commenting.
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  #7  
Old 04-15-2013, 09:23 AM
gmushial gmushial is offline
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I'd look for a vacuum leak - maybe a hose has come loose or even fallen off, or maybe a cracked vacuum hose. Beyond that the DIS ? What I see changing btwn running down the interstate and waiting at a light, is the vacuum levels. I don't see the gas changing somehow magically btwn the two situations; likewise the electronics.
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  #8  
Old 04-15-2013, 09:16 PM
jafxdwg jafxdwg is offline
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When I complained about a hesitation just off of idle, the Tech checked my gas and discovered it was 15% ethanol ! I was shocked seeing as I had just filled up with 94 octane at a Petrocan Station.
They recommended Shell Super 91 Octane cause there is no ethanol in that.
That's all I've used since and while the stumble has not completely disappeared, it does run better.
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  #9  
Old 04-15-2013, 09:35 PM
gmushial gmushial is offline
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Quote:
Originally Posted by jafxdwg View Post
When I complained about a hesitation just off of idle, the Tech checked my gas and discovered it was 15% ethanol ! I was shocked seeing as I had just filled up with 94 octane at a Petrocan Station.
They recommended Shell Super 91 Octane cause there is no ethanol in that.
That's all I've used since and while the stumble has not completely disappeared, it does run better.
Ah yes. Here in the states we're just beginning the E15 dance, sadly. And as our collective gas mileages fall... we know we're making the environment cleaner, not; but the corn farmers richer. :-( When we take the Z on our road trips (tending to be 3000-6000mi in length) we are always grateful to find states that still have E0 gas... and enjoy getting those extra 30 or 40 miles per tankful, and the smoother running. Have to love the BigAg lobby in congress which brings us this silliness. [When one looks at the total carbon footprint (honestly), the ethanol gas is a net loser for the environment, but a big win for the corn farmers.]
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  #10  
Old 04-16-2013, 07:56 AM
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crewdog843 crewdog843 is offline
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Fuel consumption has not been a problem with this car in this state. I normally get high 19s/low 20s in spirited driving in town (19 stop signs / stop lights in nine miles one way). Highway mileages is in the 27/28 mile range depending on wind and/or altitude changes. I regularly fuel at Costco and avoid fueling if the tanker is on site. I like to put a bottle of fuel injection cleaner in infrequently (Lubromoly Jectron is a good choice). I do not have a light foot in town or on the open road, and twice recently I have been faced with situations which required quick deviation from planned paths, but I love this car for its aversion to repair facilities.
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  #11  
Old 04-16-2013, 11:17 AM
gmushial gmushial is offline
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Quote:
Originally Posted by crewdog843 View Post
Fuel consumption has not been a problem with this car in this state. I normally get high 19s/low 20s in spirited driving in town (19 stop signs / stop lights in nine miles one way). Highway mileages is in the 27/28 mile range depending on wind and/or altitude changes. I regularly fuel at Costco and avoid fueling if the tanker is on site. I like to put a bottle of fuel injection cleaner in infrequently (Lubromoly Jectron is a good choice). I do not have a light foot in town or on the open road, and twice recently I have been faced with situations which required quick deviation from planned paths, but I love this car for its aversion to repair facilities.
Yes, Nevada is one of the states where it is possible to find E0 gas still - one of those states before crossing the state line one fills the tank and appreciates real gas as long as it lasts. ;-) Arizona is another. And if one looks carefully, one can still find E0 gas in Oregon - but that's becoming less of the norm. :-(
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  #12  
Old 04-20-2013, 06:51 AM
lennium lennium is offline
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What you are describing as a stumble while driving is something that I just fixed in my 98 z3. My z3 would also stall at low idle too but have a hiccup/stumble as I drove, only sometimes and rarely, turned out to be my crank position sensor. No cel light but using inpa I was able to see a shadow code for the crank sensor, shadow codes won't show on some code readers. I thought it was fuel related because that's what it felt like, and went changing fuel filters and cleaning maf,icv, then a plug change. The crank position sensor tells the plugs when to fire, if it fails momentary you have no spark for a split second and your stumble occurs.
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  #13  
Old 04-20-2013, 07:06 AM
gmushial gmushial is offline
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Quote:
Originally Posted by lennium View Post
What you are describing as a stumble while driving is something that I just fixed in my 98 z3. My z3 would also stall at low idle too but have a hiccup/stumble as I drove, only sometimes and rarely, turned out to be my crank position sensor. No cel light but using inpa I was able to see a shadow code for the crank sensor, shadow codes won't show on some code readers. I thought it was fuel related because that's what it felt like, and went changing fuel filters and cleaning maf,icv, then a plug change. The crank position sensor tells the plugs when to fire, if it fails momentary you have no spark for a split second and your stumble occurs.
Might be... but he's seeing this not while driving, but only after a vacuum state transition... but if one can read shadow codes, that would be a real clue/pointer toward where to look/what to do.
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  #14  
Old 04-20-2013, 07:14 AM
lennium lennium is offline
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Mine was mostly at lights, if it didn't stall it would drop then go higher to catch itself then sometimes even go up and down as if finding where it wanted to sit, felt so much like dirty fuel filter I am used to in outback 4x4's that was the first thing I changed. Most of the time it purred!
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  #15  
Old 04-20-2013, 08:27 AM
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Zedfor Zedfor is offline
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Mein Auto: 2003 Z4, 2007 X3
Z4 (E85) Big stumble

Have your codes read. Crank position sensor sounds like the most logical problem otherwise MAF could be the culprit.


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