How should an M20 idle anyway?

[Vincent Brick]

It goes: mmmmmmphutmmmmmphutphutmmmmmmmm

Pretty much. Mine idles at 1000-1100 though, but I suspect the tach is off (any way to adjust that?), sometimes I get random low dips, random hunting, and lots of hunting when cold (it really runs like shit until it warms up). Good ICV, good valve eccentrics, recent O2, recent smoke test, still idles so rough it rocks the car back and forth. It runs strong so I don't sweat it, tempted to get poly mounts so I have "because racecar" as an excuse. :)

The guys at the local BMW indie shop that have raced a lot of SpecE30 and Lemons say mine idles a little rough compared to their M20s, but not in a way I should be concerned, that it is an unopened ~225k mile motor after all.

[wilholl]

Once I fixed the poor electrical connections in my 88 seta, it idles smooth as butter!
I was really amazed at how smooth. Just the quiet ticking of the injectors pulsing away is all that is noticeable. I did not think that it was ever possible for this engine to idle this smooth! Installing reconditioned injectors (cleaned) helped as well.

[Ether-D]

I'm just another guy saying that the mmmmmmmmphutmmmmmphutphutmmmmm is the hilariously exact phonetic representation of the sound of every m20 I've ever had.

Now can you spell the sound of a massive belch or fart? Cause that shit would make me crap myself.

[crappycoco]

* phrrrrrraaaaaaaat .. phhee

But seriously, I was hoping to see/hear some clips, instead im sitting here at work mumbling strange noises to myself and laughing =D

[estoguy]

I'm still hoping to find someone on the board to corroborate, but I spoke with a few of the older techs at work who had spent time working on E30's and they all agreed that M20's hiccough and stutter when they are idling properly.

One guy said "asking an M20 to not have a goofy idle is like asking it not to sweat oil from the gaskets. It's just part of the character of those engines."

I'd agree... when my Eta is cold, she'll stumble a bit for the first minute or two, especially in the winter. Then she evens out just fine. And the engine should sound like a sewing machine if the valves are properly adjusted.

[EatsHondas]

The stock engine management fires the 6 fuel injectors in two groups of three (called bank injection). This leads to a less-than-ideal distribution of fuel between cylinders, causing varying air fuel ratios and rougher running. The Motronic DME's of that era were designed with only two transistors to drive the injectors, one for each bank, which makes sequential injection impossible. (You would need one transistor per injector).

[15Michaeljoseph]

The stock engine management fires the 6 fuel injectors in two groups of three (called bank injection). This leads to a less-than-ideal distribution of fuel between cylinders, causing varying air fuel ratios and rougher running. The Motronic DME's of that era were designed with only two transistors to drive the injectors, one for each bank, which makes sequential injection impossible. (You would need one transistor per injector).

Well, I guess that's that :)

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[juliancates]

But seriously, I was hoping to see/hear some clips...

Short, but best I've got right now. Right after replacing two rockers with broken pads that made it sound pretty terrible.

https://www.youtube.com/watch?v=amzp5MPfuyc

[crappycoco]

I've always wondered what's causing that background whine (i dont know if i should call it a whine tbh) that you can hear in the video?

"Whooooo-OOO-oooooo-oo-oOOOOooo"

[itsonlygeorge]

I've always wondered what's causing that background whine (i dont know if i should call it a whine tbh) that you can hear in the video?

"Whooooo-OOO-oooooo-oo-oOOOOooo"

My engine makes the same sound and it's been driving me crazy trying to figure out where it's coming from. Sometimes it almost sounds like there's a little mini turbo in there somewhere.

Previous owner I know I did a mild port on the ETA's intake so maybe there's a failing gasket or a result of that modification.


Sent from th

[15Michaeljoseph]

My car makes that noise too... I think it's just another characteristic of the engine.

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[HollywoodDale187]

my engine made a similar "whine" and when i tore it apart the water pump felt like junk, bearings were noisy and had slop. might be worth checking

[Panici]

I think my video shows what you guys are talking about pretty well.

Was running straight pipes right off the stock manifolds, before I got my exhaust on.
It sat for a while before this video (and had old plugs), so it's probably not running perfectly, but you get the idea.

M20B25 with 173 ECU conversion. Dinan Gen3 91 Octane chip.

https://www.youtube.com/watch?v=Hd-QA-AJ2Bc&index=2&list=PLD68RiPVWELXksp6cm4i97XwM6adrVcQo

[crappycoco]

My car makes that noise too... I think it's just another characteristic of the engine.

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Yeah, I've heard it in most m20's. But I'm really curious about which engine component(s) are actually making that sound.

my engine made a similar "whine" and when i tore it apart the water pump felt like junk, bearings were noisy and had slop. might be worth checking

Maybe? I'll be sure to check after a timing belt job =)

[HollywoodDale187]

Yeah, I've heard it in most m20's. But I'm really curious about which engine component(s) are actually making that sound.







Maybe? I'll be sure to check after a timing belt job =)

Yeah. That was just my guess. Or maybe the tensioner??? I dunno. These things are just noisy. Lol.