M6 stalling out, some loosing power at low RPM

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Sixracer1
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M6 stalling out, some loosing power at low RPM

Post by Sixracer1 »

Hi All,
Had a great first drive of the season today. But things went weird about 45 minutes in.

First after 45 mins (admittedly mostly city) driving I parking for 20 mins or so. Battery had not been toppped off by alternator. Fine I always bring my portable booster. Then driving home I got stuck in some nasty stop and go traffic. Not a terribly hot day but engine temp ticked up. I had killed the AC as I approached just to help the engine out. After a few minutes RPMs started dropping dangerously low...so I revved as I knew battery wasnt charged up.

Once past the traffic and rolling for a few minutes another slow down on the highway. Car started losing power briefly and bucking a bit. Few more traffic lights to home. Kept her well revved over about 2-3k to keep her running. Low RPM were not happy, stalled 2-3 times just parking.

Dead or calcified battery causing ignition issues?

Got some travel coming up so figure I will hook up the battery and charge it up, decalcify and see if that helps. Still always nice to get a second opinion!
Last edited by Sixracer1 on Mon Jun 04, 2018 4:03 pm, edited 1 time in total.
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dwcains
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Re: M6 stalling out, some bucking at low RPM

Post by dwcains »

Put a voltmeter across the battery terminals and check the voltage with the engine off, and then running. A fully-charged battery should read 12.7V, and with the engine running, you should see 13.8V or better (at slightly above idle speed). Also check that you belts are tight and not slipping, as a weak battery will put more load on the alternator.

If the car's been sitting for a while it could also be a bunch of sediment has been sucked up by the fuel pumps and is clogging the filter, so if the electricals check out OK, I'd check that.
Dean
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raykoke
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Re: M6 stalling out, some bucking at low RPM

Post by raykoke »

I'd have a look at the AFM as well.

Good luck,

Ray
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Re: M6 stalling out, some bucking at low RPM

Post by 86_6series »

If it was running fine for the first 45 min. Then started acting up with low battery, I'd say it was
low voltage trying to run all the electronics. Charge that battery up and see if that cures it before looking at other faults.

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Re: M6 stalling out, some bucking at low RPM

Post by Brucey »

I agree a freshly charged battery may 'solve' the running issues, but if so, it indicates that the alternator is probably not changing the battery whilst the engine is running.

It isn't unusual for the alternator brushes to wear in such a way as the alternator doesn't reliably produce electricity at low engine rpm; this may or may not be accompanied by the charge warning light coming on....

cheers
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Re: M6 stalling out, some bucking at low RPM

Post by e24mpwr »

dwcains wrote:Put a voltmeter across the battery terminals and check the voltage with the engine off, and then running. A fully-charged battery should read 12.7V, and with the engine running, you should see 13.8V or better (at slightly above idle speed). Also check that you belts are tight and not slipping, as a weak battery will put more load on the alternator.

If the car's been sitting for a while it could also be a bunch of sediment has been sucked up by the fuel pumps and is clogging the filter, so if the electricals check out OK, I'd check that.
Sorry - I've forgotten how many things we've done. We've checked the battery, and it is fine based on measurements at idle and steady RPM of 1500 and 3000. The battery is also fairly new and kept on a nice trickle charger over the winter, etc.

The alternator is also fairly new (~4-5 years max, not lots of miles) and has the solid bushings so it stays in place (after I replaced it the soft bushings failed within a couple of years).

I'll call my mech and see if he checked out the alternator, but I'm pretty sure he would have. There's also the question of why the "trick" would solve that problem (even temporarily)?

Some thoughts have centered around a bad/missing ground somewhere. I know diddly-squat about electricity (I did buy Rob Siegel's book and a decent multimeter recently though :)), but it seems like resistance building up somewhere would be kinda dramatic. I had a bad ground in my headlights soon after I bought the car and it melted some stuff...
Last edited by e24mpwr on Tue May 02, 2017 10:46 am, edited 1 time in total.
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Re: M6 stalling out, some bucking at low RPM

Post by e24mpwr »

raykoke wrote:I'd have a look at the AFM as well.

Good luck,

Ray
We did swap a nearly-new (only a thousand miles and in a car running perfectly) AFM in on the way home last year and it didn't make any difference.

I have considered sending the AFM to Programa along with the ECU to be reflowed/etc. though...
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Re: M6 stalling out, some bucking at low RPM

Post by e24mpwr »

Apologies - I was answering in this thread thinking it was my thread (viewtopic.php?f=2&t=28490). Not sure how that happened...
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Re: M6 stalling out, losing power at low RPM

Post by Sixracer1 »

e24mpwr, very funny.

So new battery and a check of alternator voltage (13.4v at idle). Drove a 20 min highway jaunts and everything seem fine.

Then today issue happened again after another 20 min highway drive. Luckily was close home. Had to keep revs pretty high and sounds like misfires on a few cylinders. The rotor and distributor are only a few thousand miles old but maybe I'll have a look at them. Plan to meter alternator again. Also wondering about fuel pump going.

EDIT:
Replaced both fuel pumps then discovered loose connection at MAF. Running better than my ‘08 now.
Last edited by Sixracer1 on Thu Jun 27, 2019 2:21 am, edited 2 times in total.
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Re: M6 stalling out, some bucking at low RPM

Post by raykoke »

You might spend 3 bucks on one of these, for real-time viewing...

https://smile.amazon.com/dp/B0092KVYGI/ ... 04328&sr=1

Cheers,

Ray
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Re: M6 stalling out, some bucking at low RPM

Post by dwcains »

Or, one of these, found on eBay for even less:

Image

That's just the test fit, but it's connected now, and works great. LED's are red.
Dean
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Re: M6 stalling out, some bucking at low RPM

Post by hornhospital »

Yup, got one of those in my E30. They were so cheap I bought a bag full of them and gave them away to the club members. Only complain: it's a little bright!
Ken Kanne
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Re: M6 stalling out, some bucking at low RPM

Post by dwcains »

Agreed - I thought about putting a little scrap of window tint film on mine.
Dean
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Re: M6 stalling out, some bucking at low RPM

Post by gte619n »

Too bright LED is a bit of a pet peeve of mine. I throw these LightDims on just about everything:

https://www.amazon.com/gp/product/B009W ... UTF8&psc=1

Might be good for your gauge.
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Re: M6 stalling out, some bucking at low RPM

Post by hornhospital »

Wow, perfect! Thanks Evan. I was going window tint like Dean (which is an excellent idea, too) until you posted that.
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Re: M6 stalling out, some bucking at low RPM

Post by dwcains »

My wife will love these things.
Dean
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'87 Spider Veloce
'92 Spider Veloce
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Re: M6 stalling out, some bucking at low RPM

Post by hornhospital »

Here's the way-too-bright LED voltmeter. Eagerly awaiting the arrival of those Light Dim stickers. Please ignore the horrid blue-lit head unit. That thing is worse than the red voltmeter. It's leaving as soon as I can find one that's red-orange like OEM.
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Re: M6 stalling out, some bucking at low RPM

Post by raykoke »

Is that car running?

:mrgreen:

hornhospital wrote:Here's the way-too-bright LED voltmeter. Eagerly awaiting the arrival of those Light Dim stickers. Please ignore the horrid blue-lit head unit. That thing is worse than the red voltmeter. It's leaving as soon as I can find one that's red-orange like OEM.
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Re: M6 stalling out, some bucking at low RPM

Post by hornhospital »

Yes. The meter reads about 0.4 volts lower than a Fluke DMM. Close enough to be useful.
Ken Kanne
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Re: M6 stalling out, some bucking at low RPM

Post by dwcains »

hornhospital wrote:Here's the way-too-bright LED voltmeter. Eagerly awaiting the arrival of those Light Dim stickers. Please ignore the horrid blue-lit head unit. That thing is worse than the red voltmeter. It's leaving as soon as I can find one that's red-orange like OEM.
The red was becoming annoying to me, so I found what appears to be the only orange LED voltmeter available:

http://www.ebay.com/itm/Mini-DC-0-100V- ... 464177266?

And, I'm just installing a very nice Kenwood headunit, and the display can be adjusted to be an almost perfect match for the OBC display:

https://www1.crutchfield.com/p_113KMBT5 ... 518HD.html

I actually bought it from Amazon for $102, but the Crutchfield site has more detailed info. I'll post some pics in the next day or two when I'm finished. I still need to run the speaker wires and also get the phone mic installed up in the roof header panel.
Dean
Lutz, FL

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'87 Spider Veloce
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Re: M6 stalling out, some bucking at low RPM

Post by hornhospital »

That Kenwood is just what I was looking at. When I have some 'spare money' (hahahaha...what the heck is that???) I'm going to buy one.
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Re: M6 stalling out, some bucking at low RPM

Post by dwcains »

Just got a message from the eBay seller - orange is not currently available. Asked if I could wait, and for how long - awaiting a reply.
Dean
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Re: M6 stalling out, some bucking at low RPM

Post by hornhospital »

I can put up with the red as long as it's not so blasted bright. The LightDim stickers have left the seller's business, but no tracking number. :evil:
Ken Kanne
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Re: M6 stalling out, some bucking at low RPM

Post by dwcains »

Well, the eBay seller must have found an orange one to send, as I just got the shipping details - we'll see what shows up.

The Kenwood install will be finished tonight, and I'll post pics in a new thread. The lighting color looks pretty good in the dash, and I hope the sound is good, too. Spent most of last night taking apart the interior so I could run new speaker wires, and man, that was a bitch in my 100+ degree garage. No fun in Florida this time of year,
Dean
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Re: M6 stalling out, some bucking at low RPM

Post by hornhospital »

Yes, I had saved the listing, and it went from "out of stock" to "5 available" this morning.

I got the Light Dims today, but haven't had time to put one on. Picture and report to come.
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'85 325e "Hazel Ann"; '95 M3 "Ashlyn"
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