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09-30-2010, 08:02 AM | #1 |
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RPM dip on startup?
I noticed this a few times in the past week or so and thought I'd post to see if anyone had any thoughts about it. On starting the car in the morning, the RPMs will typically hover at around 1100-1200 RPM for maybe 15-20 seconds, which is normal from my experience. However, in the last week I noticed that a few seconds after starting up the RPMs will suddenly dip below 1000 and then kick back up to 1200, for seemingly no reason. The car doesn't stall or anything but it's definitely a new behavior. Also I don't notice anything amiss during normal driving.
A few things that changed recently: I installed a fresh OEM air filter (Thursday), I used a bottle of Techron (Friday), and I had my first track weekend (Saturday-Sunday). As for gas, I have always used Shell V-Power 93. I didn't think it was a problem, but wanted to check to see if anyone had any ideas. |
09-30-2010, 08:07 AM | #2 |
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Is the weather starting to cool down a bit? It may have something to do with that, as the car adjusts its operation for different ambient temperatures.
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09-30-2010, 08:07 AM | #3 |
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I don't know what's the problem, if there is one, but mine does the same thing once in a while. I use the same gasoline, old air filter, recently used techron in the last 1700 miles. I don't think those things would make it do that. It doesn't happen often. Perhaps it's something kicking on? Perhaps a bubble in the fuel line? i don't know.
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09-30-2010, 12:40 PM | #4 | |
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I've thought about having the shop look at it, but of course they won't be able to replicate it, after I've driven it over there. <g> Bruce |
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09-30-2010, 12:51 PM | #5 |
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My 06 will also do it once in a while. It usually lasts for no more than a few seconds and doesn't appear to be a problem. Mine started doing it after the lifters then head assembly was replaced. I am totally retentive about my car, but it doesn't seem to be a problem.
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09-30-2010, 12:55 PM | #6 |
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Yes, the weather is cooling down a bit so in the morning it's in the high 50s/low 60s in my garage vs. 70+ as it has been.
I doubt it's the Techron since I put it in on Friday in the middle of a 3.5 hr drive and have since gone through 2 complete tanks of gas over the course of the weekend. I'm not too worried about it. Mostly I just wanted to get a sense of whether this was pretty normal or if it's a sign of some larger issue. That was one of my thoughts as well. That was another thing that changed for me. Since I got the ZHP 2 months ago, I only drive the M coupe on weekends or at most once or twice during the week. Today was the first time I drove it since Sunday. Maybe stagnant fuel in the lines or something? |
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09-30-2010, 01:04 PM | #7 |
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mine just started doing this too. I drive it daily. The temp has gotten a LOT cooler in the mornings. It's just a cold engine start. notice your tach has the rpm lit up al lthe way to like 5K then once it warms up it's settles down to 7500?
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09-30-2010, 02:45 PM | #8 |
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i've only just recently started experiencing these same symptoms, and it has indeed gotten a lot cooler in the mornings. i do notice that the dip in rpm occurs after a slightly longer than normal crank for engine start and after having sat overnight in approximately 60 degree temperatures.
btw, i've started leaving my air conditioning completely off when i start the car to help with getting it to start better. maybe i'm getting paranoid? |
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09-30-2010, 03:54 PM | #9 |
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It's most likely the gas and ethanol in your area that are causing the cold start issue. It used to happen everyday to my '04 3.0i, even when I was filling up at Chevrons and Shells. Then I moved to a different area and started filling up at different gas stations and the problem went away instantly.
These days I fill up with Chevron 94 with 0.0% of ethanol and have never experienced the cold start issue again. The engine just fires up effortlessly with a really clean sound and stable idle.
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09-30-2010, 04:36 PM | #10 |
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Incidentally, I was just reading about ethanol-free gas this morning because I had noticed the 10% max ethanol content stickers on the Shells around here for a little while. I wonder if the ethanol in the gas does something after sitting for more than a few days. Unfortunately, I don't think ethanol-free gas exists anymore in the Chicagoland area.
For me, the behavior always manifests as a sudden drop in RPMs within the first 10 seconds or so that goes back up right away. The dip never lasts longer than a half second or second. |
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09-30-2010, 07:35 PM | #12 |
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You can add me to that list of people experiencing the same symptoms. My 2003 3.0i has even had the RPM dip so low that the engine died and I had to restart. I would have guessed it was an ECU issue, like it has a hard time adapting to cold starts with different gas. It's something I would think software could fix, rather than forcing the driver to change the variables (use different gas, etc).
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09-30-2010, 07:53 PM | #13 |
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My 06 Z4MR experiences the 'blip' on startup too, after it has sat for a while or when it gets cooler. First time it happened, my heart sank, but it seems to be a pretty normal thing, judging by responses here and in another thread on this site. A lot of guys seem to eliminate it with 0% ethanol gas.
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10-01-2010, 01:46 PM | #14 |
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i had the same issue a while back, started in the spring to it in and they acutally found the same problem. they changed my idle rpm a little lower and solved the problem, before i was idling around 12 now it around 9 just my $.02
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10-01-2010, 02:04 PM | #15 |
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One thing worth a try (works for me) is to turn the key to the point just prior to the engine cranking but allowing the fuel pump to start and prime for about 5-10 seconds then turn to start. Having the fuel pump started and primed gets rid of most of the dip for me
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10-01-2010, 05:16 PM | #16 | |
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10-01-2010, 06:47 PM | #17 |
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my 06 MC does this too
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10-01-2010, 09:06 PM | #18 |
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as per the few suggestions concerning ethanol as a constituent of gas, i have been regularly filling up with shell v-power, which contains 'up to 10% ethanol'. i only experience the rpm dip symptom sporadically and cannot recreate it on demand. it does seem to be related to fuel/fuel pump somehow.
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10-01-2010, 09:45 PM | #19 |
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Normal...
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10-02-2010, 11:12 AM | #20 |
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I had the same issue while my car was under warranty. Since I could never recreate it while at the dealer, I took a video of it doing the rev drop for a few days and showed it to my service advisor. They performed some kind of software update and it hasn't happened since. The receipt for the service just says "Fault stored. Need to program DME."
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10-02-2010, 04:55 PM | #21 |
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Is anyone else experiencing this problem at some other time besides starting the car? This happens to me sometimes after I've driven the car for a few minutes (not after I've driven it longer than 5 minutes though). I've experienced the dip on startup where the engine has shut off and I've had to turn the car back on, but the last time that happened was over a year ago. Just last week, however, maybe 5 minutes after starting the car and driving, I was at a red light and I got the dip along with vibrations (not violent). The vibrations I'm talking about are the ones that happen when your engine turns off. Any ideas?
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10-02-2010, 09:27 PM | #22 |
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i get an rpm dip on a cold start about a few seconds after it cranks
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