Strange Intermittent Starting Issues

[desertman123]

So I started having issues starting the car and I'm stumped. I bought a new TYC brand starter off Amazon since it was well-rated. All was well for like a week. Started having issues again. Figured it was a faulty aftermarket starter so I dropped the cash on the Bosch, same thing (although it's partially alleviated).

What's happening is the starter will turn strong for a second or two, then stop before the engine has a chance to start. This will happen like 1-5 times before I get a full solid crank and it starts. It's not always consistent though - I can get in and start it with an immediate strong crank 5 times in a row. Then the next 5 times I'll have to let it fail and retry before it starts (but it always does). Sometimes when it fails I can hear the starter continue to turn but it's not engaged with the flywheel

On top of the starting, I hear a relay clicking from the passenger side of the dash when I try and fail to start it, and sometimes on shutdown after a drive. Maybe my CAS relay? I don't know much about that system.

Battery is a relative new (few months) H8 lead acid that was coded and registered. Battery is at 12v and alternator charges fine around 14. Might have O'Reilly's load test them. Maybe looking toward my engine ground straps. It's a Florida car so it never saw salt but I've seen firsthand what the humidity can still do to metal.



edit: found someone describing my exact symptoms and they needed a new CAS module, hmmmm

[NorthernDancer]

85% of these issues are caused by loose or dirty connections. In this case, one of the very many battery or ground cables. The absolute most common is the ground cable very low on drivers side, I think from starter to body. It's a "mesh" cable. PN 12 42 7 578 869.
https://www.fcpeuro.com/products/bmw...nd-12427578869

[Thunderguts]

Sounds like we have some kind of resistance meter for the starter similar to the window regulators. If it detects something outside of its preset parameters it shuts down.

I would definitely check all of your connections and grounds like ND said. That's very often the cause of electrical gremlins.

[NewDaddyDee]

Another vote for check your ground strap

[desertman123]

https://www.e90post.com/forums/showt...3#post28967693

Here's a much more detailed discussion on possible causes and what I've tested, if anyone's curious.

TL;DR I replaced the ground straps (which looked good, I bent them and they didnt split or crack from corrosion or anything) and still no change.

[WrathOTM]

This may be of no help to you, sorry, but my similar experience revolves around the coil-plugs. I replaced 5 of them when I got my 128i last year, as I could see that one was brand-new. Once I did that I started getting really long starts, some of which would fail and I had to hit the start button again. After replacing that sixth coil my car settled down and would start like normal. Just tossing this out in case you maybe replaced only some or one coil sometime in the past.

All that said, I did reset my ecu last week over a brake pad sensor and suddenly I'm getting longish starts now. Sooooo....just German things I guess.

[heyzeus93]

I had these same exact issues on my 128. First my headlights and brake lights would stay on even if the key was out the car. Upon starting, i heard the clicking noise from the passenger footwell. Took it to an Indy shop, said it was the FRM and got it replaced. Was fine for a while then started getting no crank trying to start it, starter went bad so got that replaced. Then the bullshit started again with the headlights. So I took it to BMW and they said my CAS module was fried. Car sat at BMW from Sept. 2022 until Jan. 2023 while they were trying to locate the part. The advisor told me that BMW no longer had any in stock so now it’s sitting at another local repair shop waiting for an aftermarket one which, to no surprise, is on back order. So if you do need a CAS module, I recommend getting it cloned which is what I should have done from the beginning.

[4JawChuck]

Had the same issue, changed starters in summer plus new AGM battery and all was well for a few months. Winter came, hard start on -24C morning and a squeal…sounded like an idler bearing, next day seized solid…rear main bearing bit it.

Went down the CAS module route for a week until I took it in and they found the crank unmovable.

Pics are in the 128i engine forum.

Hope you have better luck.

[WrathOTM]

Bumping this thread, Hey desertman123 did you ever figure this out? I'm seem to be in the same boat as you with most everything you describe.