CIS and Timing Fun (or "all the things that don't do anything")

[gerryc]

I've been playing around with my CIS getting to know it better before ripping it out to put in carbs. (not interested in a carbs vs CIS debate... already been had. )

So I was playing with the fuel mixture screw in the AFM, and I also tried my hand at timing.

Here's what I have learned:
1) That AFM adjustment really does reqiure the 3mm looong allen wrench. And there is very little feedback while you're turning it - except stalling the engine - so it's a tedious process. I now understand why there's religion around having a wideband o2 sensor. It would be very helpful. Nearly zero chance that I have it right without that.

2) The timing marks on my flywheel are invisible. So my timing light cannot see them. And I cannot see them. So, that has become a guessing game too. I could do the "roll it slowly in fifth gear" thing to find it, then paint the little ball red when I can see it, but I have not done that. Only one of me, and my kids are too short to do either part of that job (wouldn't ask my wife...)

3) I have read all about it and now know what the 02 sensor in my exhaust pipe does. It makes the car surge. So I unplugged it. No more surging.

4) I also know what the vacuum advance on my distributor does - very little. So that line from the intake manifold is plugged with a golf tee.

So, with its modified timing and CIS tweeks my car *really stinks* like emission fumes, runs smoother than it ever has and it GOES LIKE HELL! I guess until i foul my plugs or something...

Who could have guessed.

Ha.

Carbs on the way.

[sunrnr33]

I've been trying to eliminate some rich/idle rough issues and what I have found is a real lack of black and white info. It was very difficult finding the timing info and the info in the bmw manual is pretty vague....which side of the motor are you shining the timing light from, which years have a ball and which have a "z". My car is a 78 and what is the purpose of two vaccum ports on the advance for the dist., do both need to be connected. Plug gaps, .24-.28 or .35 like some say. I've read every FAQ and info I can find on numerous websites and there's a real lack of good updated tech info in one place. I'm a retired master tech and I wasn't wrenchin' on these back in the day, however I can say that the tech info for some of my other rides is more complete and easier to use. Hopefully when I call Bavarian they'll be able to give some good info.

[epmedia]

There is a reason for everything to be in spec. And there is no crime to tinker and experiment .

Some bandaids are helpful, some are not.

The only purpose of my vacuum advance is for 4th gear. The only purpose of my vacuum retard is for more engine torque at lower rpms, and less stink when idling.

The only purpose for my egr system is to burn un-burned fuel when the engine is not idling. The only purpose for my air injection and reactor is to help burn un-burned fuel.

Anyways, I'm just suggesting that there may be something wrong (ie: cat or O2 sensor, or basic tune stuff).

That's all for now, Robert

[gerryc]

ha! for me it's definitely basic tune stuff... just fiddling around before i tear it all out. ;-)

I will say this thing is pretty resillient - it's got to be WAY out of spec and is still going.

G

[g323]

[quote=gerryc;17243202]

2) The timing marks on my flywheel are invisible. So my timing light cannot see them. And I cannot see them. So, that has become a guessing game too. I could do the "roll it slowly in fifth gear" thing to find it, then paint the little ball red when I can see it, but I have not done that. Only one of me, and my kids are too short to do either part of that job (wouldn't ask my wife...)

From your diagnostic Socket cross wires 11 and 14 to jump the starter and turn over the engine.

4) I also know what the vacuum advance on my distributor does - very little. So that line from the intake manifold is plugged with a golf tee.

So, with its modified timing and CIS tweeks my car *really stinks* like emission fumes, runs smoother than it ever has and it GOES LIKE HELL! I guess until i foul my plugs or something...

Who could have guessed.

Ha.

Carbs on the way.

You likely have a vacuum leak and are running rich if your vac advance is not working as stated and the car smells like fumes.

[txmatt]

Roll it in 5th gear? Why not just turn the engine by hand using the fan or crank pulley?

as far as timing marks go, another alternative might be to use the TDC notch on the crank pulley. You could measure and paint a mark for whatever timing setting you need and set it to that. heck of a lot easier to see for me. Of course if you have the stock engine fan it might get in the way, I'm not sure about that. Oh and don't wear a necktie while doing this.

One more thing: go electronic