Artifically Low Redline

[unevolved]

Since I've bought my car, it has been rev limited at 5800 RPM. Other than that, it has no electrical problems. The only thing I could think of was an incorrect/modified ECU, but it's a blue label 0 261 200 175, which I believe is correct, and it hasn't been opened. It's not original to the car, for some reason, as it has writing in sharpie on the back "1/91 318is E30 #175".

Anyone have any ideas, or heard of similar things happening? I searched all over and couldn't find anything.

[LJ851]

A bad crank sensor will do this.

[unevolved]

Interesting. Would it cause any other symptoms?

[AndrewBird]

My guess is the wrong coding plug in the cluster. Assuming it's an M42, it might have an M20 coding plug in it.

[unevolved]

My guess is the wrong coding plug in the cluster. Assuming it's an M42, it might have an M20 coding plug in it.

Possible. I know the cluster was replaced before I bought the car. The owner was pretty knowledgeable about BMWs, and M42s in particular, but I suppose it's something he could have overlooked. How would I check that? I'll start doing some research as well.

[5Toes]

OP did you ever solve this? my m42 is exhibiting an identical problem.

going to get my hands on another crank pulley and see what happens. will update this thread if it is the cure.

[MVincken]

Check your fuel pressure regulator, should give 3Bar.

[5Toes]

my car has loads of work done, including but not limited to:

-rebuilt head with 180psi cold on all 4 cylinders
-new bosch coil packs
-new NGK silicon plug wires + ngk bkr6ek plugs
-new fuel pump, and have driven with a fuel pressure gauge installed, its always rock solid at 3 bar especially while my "low redline" is happening
-rebuilt air flow meter from bavrest.com with new air filter
-rebuilt 21.5lb pink top injectors
-brand new BMW OE crank sensor
-brand new FACET brand camshaft sensor
-new BMW OE main relay
... probably a few more things I cant remember :)

I need to install my sssquid chip but Im pretty sure thats not really going to help as far as this problem goes. I am likely running slightly rich at the moment but this is only temporary until I can get this spark cut problem sorted. the e36 crank pulley carries the same part # so I am gonna stop by the picknpull this weekend to get the nicest one they have (they have two m42 e36s at the moment).

Hoping it will solve my issue. This problem has plagued multiple e30 owners online so Im hoping to post a solution that will truly work for future drivers. The problem is very obvious to be ignition related, but the tach does not drop off as in the case of a DME losing power or a crappy main relay.

[Dj Buttchug]

A wrong cluster swap will also do this. causes you to think the revs are 1k to low at all times pretty much.

[5Toes]

the cluster in my car is good, it idles at 850-900 and I can just tell the engine can wrap out more, Ive driven one other m42 that was really healthy. swapping this pulley on tonight in the dark, fingers crossed!!! I remember my old one's rubber surround being much more cracked than this new e36 one I got at picknpull

[5Toes]

SOLVED:

new crank pulley fixed my m42 redline problem!!! did it in the dark with a flashlight, such an easy job :) Im totally stoked hooray!!! the old one did not look that damaged but the problem is certainly fixed now, the car will goto 6500 no problem.

the old pulley the rubber looked kind of cracked but not enough to be damaged looking. oh well, its a CHEAP and EASY part to swap so Id recommend giving it a try if your car is acting up like this. what happens is the crank signal is getting corrupted from the centrifugal force at high rpms.

and yes e36 crank pulley is the same and works great.