Hello, and a question about false "rev limit" on M44

[Paul_M]

Hi guys

Just joined the site, looks like a great resource. I am in the UK and own a 96 E36 318is with the 1.9 M44 engine. I bought the car partly to use as a work hack, and partly as a track toy. Wanted a 4-pot for the handling and fun factor, rather than a 6-pot.

My other car which I've owned for 3.5 years is a BMW 840Ci 6-speed manual, a pretty rare beast. It's obviously loads more powerful than the 318, and you can't beat the sound of a V8 through a full stainless system. But it's a lot heavier which makes the driving experience very different. It's much easier to get the back end out on the 8 due to the power, but it's not as composed on tight twisty roads due to the weight.

I also have an R1 for when I want to go quickly :cool:

I've just bought a 25% lock LSD for the 318, which I plan to get fitted in the next few weeks, and I'll probably uprate the clutch too as I expect the one fitted is pretty old (although it doesn't slip -- yet). May also tweak the suspension a little, as it's all pretty standard at the moment (with recent dampers all round and new front wishbones & bushes).

I have one issue with the engine at the moment. When I'm driving it hard and using all of the rev range, it hits what feels like a rev limiter at around 5500 RPM. It just bounces off, and if I change up it will again pull strongly until around 5500 RPM again.

I have access to a MODIC so have performed a diagnostic, which has revealed the only stored fault is the lambda sensor. I intend to replace this, but I doubt it's the cause of the "false rev limit". I also checked the RPM read out from the ECU using live data via MODIC to make sure the rev counter is giving the correct reading, and it is correct.

My primamry suspect is the MAF sensor, but this is just a guess really being that I'm not getting any definite pointers from the ECU diagnostic. Other suspects are crank and cam sensors.

Has anyone experienced anything similar, or have suggestions?

Thanks
Paul

[NitroJunkie]

This happens when car ECU goes to safe mode..

It changes the AFR,makes the engine to work rich and limits revs to 5500..

Same thing happened when i changed my muffler for some reason

Reseting fault codes works only for a limited time, than ECU goes to safe mode again..

MAF sensor would  be my starting point if i were in your shoes..

[doitover]

There was another thread recently about a similar situation. I don't think the original poster came back with the results but, if I remember correctly, people suggested either the crank position sensor or that a 6 cylinder gauge set had been swapped in.

[Paul_M]

Thanks guys. Could the faulty lambda (oxygen) sensor be causing the ECU to go into limp mode? This is the only fault stored, and I'm using a BMW MODIC diagnostic system so I'm confident it's giving me an accurate diagnosis (unlike cheap stuff like Carsoft).

Of course, it's possible that a component is faulty but isn't picked up as such by the ECU, therefore no fault code. I had a car before that couldn't detect crank sensor faults, but it would cause the engine to cut out if it did fail.

I can rule out the possibility of a 6-cylinder cluster, as I checked the live data from the ECU using MODIC, and it matches what is being displayed on the rev counter. I also performed the cluster test, and the VIN digits match those of my car, so it's an original cluster.

I may try replacing the lambda first, although I'm sceptical that it'll solve the issue. Then I'll look at the MAF and crank sensors. Ideally I'll try and find a donor car that I can swap bits from to try, rather than just replacing components which may get expensive.