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Intermittent loss of power, clears immediately after restart

Old 10-10-2018, 08:03 PM
  #1  
Scott Kauffman
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Intermittent loss of power, clears immediately after restart

This has happened twice now on my Q40: just driving along and the car is running smooth but at some point I try and accelerate and it just crawls like a 3 cylinder yugo. Flooring it the car will downshift and RPM's will verrrrrrry slowly raise to 5-6k range and engine still runs smooth but just has no power whatsoever. No check engine light at all.

Both times I turned car off and as soon as I restarted it was 100% back to normal (this morning just turned it off and immediately back on). Limp mode wouldn't let it rev that high would it? Or it would set a CEL? Since when did rebooting your car fix issues like a windows PC lol

I don't have a scanner to see if it has pending codes but it's only done it twice now in about 6 months so maybe it just never repeats enough to trip an active check engine light..

Curious if anyone ever heard of an issue like this?
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Old 10-10-2018, 09:45 PM
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slartibartfast
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Oh, yes, it has occured to others. Infortunately, i don't know what solves the issue.
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Scott Kauffman (10-14-2018)
Old 10-11-2018, 10:53 PM
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Just went through this on a '14 Q60 / Rebadged G37.

I read through multiple threads (G37 and 370Z) that all noted the problem, with the newest threads from around '08 (IIRC), and each ended with a trip to the dealer and silence.

My symptoms were sporadic fits of no power and slow revving that were the same as you mentioned. I will say that this low power symptom is borderline dangerous when it happens as the car does not accelerate, especially at highway speeds. Sometimes it would be this way right after a cold start, (have fun with today's commute...). Sometimes it would go into low power mode while just driving along.

It would go back to normal acceleration if i shut off the car for bit and restarted or did an ECU reset. Regardless, the symptoms always returned during the current drive or on the next drive. I only got the CEL for a MAF issue one time, more on that later. It seems as if the symptoms are some form of a sadistic limp mode.

i used the Torque Pro app while the symptoms were active and noted that the left bank fuel trims were off the scale in the negatives thus adjusting for extremely rich exhaust stream and the timing advance wouldn't move much past 0.

The one time the CEL stayed on, i pulled the code and it indicated a failed left MAF sensor. Instead of changing it, i first tried cleaning it with MAF sensor cleaner and believe it or not, everything worked afterwards. That was a about two weeks / 200 miles ago and all is still well. Not sure what it was all about, but it seems ok now.

I would suggest taking it in to the dealer if it is still under warranty, otherwise, try cleaning the MAF sensors. I used CRC MAF Sensor Cleaner.

Best Regards.
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Old 10-14-2018, 01:36 AM
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Thanks, ordered a Bluetooth obd scanner to see if there's anything weird going on. It's only happened twice in six months so guessing there's not much the dealer could do unless there's something weird in scan results.
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Old 10-30-2018, 12:43 AM
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Jamie Nguyen
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Your car is going into limp mode, there’s a service bulletin for 09+ for an ecu re flash, but it has happened to my 08 so apparently it doesn’t apply, but it only happens on long drives 15min- 7 hours on high speeds and around 40-55 degrees weather for me, I changed out my spark plugs and I have an injen intake, and the intake puts stress on the small plastic oil catch thingy that goes into the driver side valve cover and creates a small crack that will go un noticed so after replacing it three times(having to buy an entire oem intake tubes) I just installed a straight tube and made sure it was sealed and this fall it hasn’t acted up on me but I’m currently doing the water pump and galley, hope this helps

Last edited by Jamie Nguyen; 10-30-2018 at 12:52 AM.
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Old 10-30-2018, 12:50 AM
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And when it happens it’s very rough on the transmission so immediately throw it in neutral bc there’s no point in hitting the gas bc it won’t go anywhere but slow down, emergency’s and pull over safely and kill it to reset, sometimes you have to pull the battery to reset the computer completely to get it to last longer, you have a 10mm in your trunk next to your spare tire tools, it turned my 19hour drive to a 40 hr drive, I bought map sensors for no reason
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Old 01-11-2019, 06:52 PM
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Finally happened again, caught the pending codes with a scan tool. It's both P0101 and P010B - basicly getting weird MAF readings on both MAF's. Just like before immediately clears up after restart the car. Funny there is a repeatable pattern to when it occurs. For sure 2/3 times and I think 3/3 I leave house in morning and drive to local 7-11 for gas, fill up, then moved car to park and grab a soda inside and then come back out and drive away and feel immediate loss of power / lack of acceleration. Shut of car, restart and it's back to normal.

All I can think of is that maybe the short trips starting and stopping interrupts some sort of MAF monitor / calibration operation and leaves the PCM in weird state thinking the voltages are off? Doubt it's dirty sensor as the car runs perfect except for every 3 or 4 months this trips and then goes away just from a restart.

Google shows a TSB for this issue back on 2009 cars, fix was ECM reprogram. Maybe it's just a random software glitch...

OBD scan after restart shows both MAF signals more or less right on top of each other




Last edited by Scott Kauffman; 01-11-2019 at 06:59 PM.
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Old 01-11-2019, 11:00 PM
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Thanks for the info.
this has happened to me on my 07 nismo 350z dual tb and my 13 IPL. Both have aftermarket cold air intakes. Really short commutes. Morning / colder starts. No codes. Just limp mode that clears after a restart. Dangerous indeed.
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