Idle speed increases when depressing the clutch

[bmw1racer]

Not sure if this has always been the case, but after I installed my clutch stop, I noticed that when I depress the clutch, my RPMs increase from the normal idle of around 600RPM to about 1000RPM.

Is this abnormal or what?

[Thunderguts]

I would think it's very abnormal. If your RPM increase when you depress the clutch, that means the clutch isn't fully disengaging when you release the pedal. It's very lightly rubbing against the flywheel, pulling your engine RPM down. Basically you're "riding the clutch" all the time. I can't think another explanation, but maybe there's some weird electronic idle control I don't know about.

Have you installed a new clutch recently? Maybe the throwout bearing is seizing?

[WDE82]

Since the clutch stop is easily removed, see if it behaves differently if you remove it again. This is the easiest way to see if it's really the stop.

After doing small things to our cars, we all often become hyper aware when previously we were not. In all likelihood this is somewhat normal behavior you've never noticed before.

[Thunderguts]

It could also be something silly like maybe you loosened a floor mat when you installed it and pressing the clutch is moving the floor mat against the throttle. I did freak myself out once when the throttle pedal on my old 280Z got caught on the top of the mat at WOT.

[Lester]

Try it with your right foot flat on the floor. You might be applying the slightest of pressure on the throttle while pushing on the clutch.

Many years ago, on this forum - someone posted a similar problem when he was applying the brake pedal. Turns out he had wide feet and big shoes.

[bmw1racer]

Pulled the clutch stop and the idle still appears to go up a bit when the clutch is fully depressed... Not sure if it's always been that way or maybe the idle control is starting to fail.

Time to plug my Bluetooth dongle into the OBDII and see if I read any system errors.

[Lester]

You would expect a little increase, especially in cold weather before driving. Pressing down on the clutch pedal disengages the transmission input shaft, and pressure plate. There is a certain amount of energy saved, so the engine is not working quite as hard.
But you probably would not expect a 400 rpm difference.

[b1aze]

Have you redlined the car lately? If you find the engine cuts out at 6500rpm instead of 7000, you likely have an eccentric shaft sensor failure.

[bmw1racer]

Originally Posted by b1aze

Have you redlined the car lately? If you find the engine cuts out at 6500rpm instead of 7000, you likely have an eccentric shaft failure.

Honestly, I can't say that I've ever redlined the engine... Maybe close, but never.

I have noticed lately that the idle stumbles a bit on a cold start in the morning, but not later in the day.

[Esteban]

I never redlined either one of my 1ers. And I think that's a good thing! Am I wrong? lol

[b1aze]

Originally Posted by bmw1racer

Honestly, I can't say that I've ever redlined the engine... Maybe close, but never.

I have noticed lately that the idle stumbles a bit on a cold start in the morning, but not later in the day.

Sounds exactly the symptoms I had with my eccentric shaft sensor failure.

It’s perfectly fine to redline the car sometimes. Don’t do it out of every stoplight.

[Esteban]

Originally Posted by b1aze

It's perfectly fine to redline the car sometimes. Don't do it out of every stoplight.

I do like to wind my cars out a little every so often, it keeps them healthy. I just don't feel the need to go to redline.

[bmw1racer]

Originally Posted by b1aze

Sounds exactly the symptoms I had with my eccentric shaft sensor failure.

Looks like you're spot on: My OBD2 scanner reports a failing eccentric shaft sensor (Code P1006).

Haven't seen a Check Engine light... Yet.

There goes my stimulus money.

[b1aze]

Originally Posted by bmw1racer

Looks like you're spot on: My OBD2 scanner reports a failing eccentric shaft sensor (Code P1006).

Haven't seen a Check Engine light... Yet.

There goes my stimulus money.

You’ll have to do the valve cover gasket and might as well replace the whole valve cover, depending on the mileage.

Might as well also do plugs and coils if they haven’t been done.

And finally, if you’re a glutton for punishment, the OFHG can be done easily while you’re around there.

Mine drove like a brand new car once I did those.

[bmw1racer]

Originally Posted by b1aze

You’ll have to do the valve cover gasket and might as well replace the whole valve cover, depending on the mileage.

Valve cover should be OK, I only have 37k miles on the car. Any possibility it could be the shaft itself and not the sensor? That could really be big bucks.

Might as well also do plugs and coils if they haven’t been done.

I changed those out in August of last year.

[Thunderguts]

Originally Posted by bmw1racer

Valve cover should be OK, I only have 37k miles on the car. Any possibility it could be the shaft itself and not the sensor? That could really be big bucks.

It's very unlikely that your eccentric shaft is damaged unless you have reason to suspect engine damage. The sensor is very prone to oil contamination and failure.

I just replaced my valve cover seals and ESS over the weekend. It's a pain, but it can be done. Technically you could lift the front of the valve cover to replace the ESS without removing the valve cover from the engine, but you'd be a fool to do so unless your seals were less than a year old. I wouldn't replace your valve cover yet. I'll replace mine in another 80k miles when I replace the seals again.

Just be glad that it's a perfectly flat mating surface. I can't imagine trying to keep gasket sealant in place with all the manipulation you need to do.

I'll say this, the next time I do a valve cover on this car, I'm removing the windshield wipers so I can take out the cowling. It's maybe an extra 30 minutes of work and a special tool, but it will save you infinite levels of frustration.

[jlc45]

"I do like to wind my cars out a little every so often, it keeps them healthy."

What is the basis for this assertion? What does "healthy" mean with respect to an engine. I was a professional mechanic and I have no idea what you are saying.

[Thunderguts]

Originally Posted by jlc45

"What is the basis for this assertion? What does "healthy" mean with respect to an engine. I was a professional mechanic and I have no idea what you are saying.

Italian tune up?

It certainly held true in the "old days." I imagine it still clears out a little carbon build-up. I don't do it because it's healthy, but I do like to wind my engine out a couple times a week just for the thrill of it.

[Esteban]

Originally Posted by Thunderguts

Italian tune up?

It certainly held true in the "old days." I imagine it still clears out a little carbon build-up. I don't do it because it's healthy, but I do like to wind my engine out a couple times a week just for the thrill of it.

Haha, ok, then maybe it just keeps me healthy, and happy.

[Esteban]

Originally Posted by Thunderguts

Italian tune up?

Never heard of an Italian tune-up before. Guess I haven't been around much. lol

"Italian tuneup is a slang automotive term for attempting to restore engine performance by driving a car at high engine speed and load. The term originated from Italian mechanics in the 1950s using this practice to burn off carbon deposits from the spark plugs of sports cars." (Wiki)

Saw a funny video about it:

https://www.youtube.com/watch?app=desktop&v=EhtXdrrSrq4

[bmw1racer]

Originally Posted by Thunderguts

It's very unlikely that your eccentric shaft is damaged unless you have reason to suspect engine damage. The sensor is very prone to oil contamination and failure.

I just replaced my valve cover seals and ESS over the weekend. It's a pain, but it can be done. Technically you could lift the front of the valve cover to replace the ESS without removing the valve cover from the engine, but you'd be a fool to do so unless your seals were less than a year old. I wouldn't replace your valve cover yet. I'll replace mine in another 80k miles when I replace the seals again.

Just be glad that it's a perfectly flat mating surface. I can't imagine trying to keep gasket sealant in place with all the manipulation you need to do.

I'll say this, the next time I do a valve cover on this car, I'm removing the windshield wipers so I can take out the cowling. It's maybe an extra 30 minutes of work and a special tool, but it will save you infinite levels of frustration.

Not sure I want to tackle this on my own... Looks pretty involved.

That said, how is this related to the issue with the clutch? Or do I have an separate clutch problem as well?

[Thunderguts]

Originally Posted by bmw1racer

Not sure I want to tackle this on my own... Looks pretty involved.

That said, how is this related to the issue with the clutch? Or do I have an separate clutch problem as well?

You probably don't have any clutch problems because your issue can be traced to a faulty ESS. A faulty clutch could also explain the drop, but since you already have proof of an equally likely scenario, there's no need to suspect anything else.

The valve cover isn't that difficult, just annoying. There is really only one difficult part and that's getting the rear of the valve cover off and on underneath the cowl. More importantly, you do need a good set of tools. You're average tool kit is not going to have the picks, extensions, wobble drives, and U-joints necessary to get at everything. You also need a nice, precise low-range torque wrench. I basically bought a 1/4" Gedore torque wrench for two jobs, this and the oil pan gasket. I already had four other torque wrenches, but I didn't trust them with that level of precision.