Retard ignition timing by moving CPS?

[George Davis]

Couldn't find anything on this when I searched. My car (1994 525i auto, M50TU) pings on most upshifts. I've seen some discussions on decarbonizing methods, but wonder if retarding the ignition a couple of degrees by moving the CPS pickup has ever been done?

I had a '95 Mustang for a while that pinged a lot. It had an "octane plug" in the engine wiring harness. Pulling the plug retarded timing 2 degrees throughout the operating range. Eliminated the pinging instantly and it ran better, too. I was told by techs that this was done a lot here in Portland because we get low quality gas. Wonder if something similar can be done to the bimmer.

Thanks for any thoughts!

[ryan roopnarine]

Couldn't find anything on this when I searched. My car (1994 525i auto, M50TU) pings on most upshifts. I've seen some discussions on decarbonizing methods, but wonder if retarding the ignition a couple of degrees by moving the CPS pickup has ever been done?

I had a '95 Mustang for a while that pinged a lot. It had an "octane plug" in the engine wiring harness. Pulling the plug retarded timing 2 degrees throughout the operating range. Eliminated the pinging instantly and it ran better, too. I was told by techs that this was done a lot here in Portland because we get low quality gas. Wonder if something similar can be done to the bimmer.

Thanks for any thoughts!

i asked here about 1.5 years ago, i think that the answer is no. iirc, the octane bar is located on the distribution point for the plug wires in the ford? as you probably know, you have coil on plug in your 525....i have a 525i complete wire harness in the shed at my mother's house.....didn't see anything analguous to the ford "feature" on it. you probably have a proble that a retard couldn't fix anyway, as you don't indicate that your knock sensor is doing anything (is it?). i know i have a carbon problem, because when my motor was put back into my car last aug. or so, i looked at the valves, which were spotless at the time....don't know where this heavy a build up is, just know that getting rid of it is imparting a notable, positive change.

[632 Regal]

you always fight this **** over the principle and I'm not going to say you should stop. I find it tremendously entertaining to hear you running around in circles but I have to ask a couple things.

Did YOU replace your knock sensor?

What grade fuel are you using?

Do you have a chip in it?

WHy are you like the ONLY one i have read about with this problem?

[ryan roopnarine]

you always fight this **** over the principle and I'm not going to say you should stop. I find it tremendously entertaining to hear you running around in circles but I have to ask a couple things.

Did YOU replace your knock sensor?

What grade fuel are you using?

Do you have a chip in it?

WHy are you like the ONLY one i have read about with this problem?

i'm not sure what your concern is right now jeff........
i was simply telling the gentleman that i have a complete m50 electrical harness (ie, computer to FI rail to plug on coil ) octopus in my mother's shed, and i didn't see anything like the ford retard plug on it. my mother drives a ford taurus, so i know what the retard switch looks like. he did relate his question to a ford......

q1......No i did not replace my knock sensor, my car does not have the variable valve timing. VVT with the knock sensor came about in the 1993 model year 525i with bosch motronic 3.3, i have a 1992. i'd care a lot less about my problem if it did have one.

2.....i've used mobil, shell, citgo, and chevron supreme gas in there, they all knock the same, so i use the citgo (car likes it)

3.....i'm using the EAT chip. i'd rather not pull it right now, as gas is kind of expensive, and if i'm going to knock, id rather get decent gas mileage doing it.

[George Davis]

Thanks Ryan,

but I guess I wasn't real clear on what I was asking. The CPS tone ring is external (at least I think I saw it!), so I figured physically moving the CPS pick-up to alter base timing might be feasible. Doesn't sound like anyone has done this, though.

I'll look into the knock sensors before doing anything.

[ryan roopnarine]

you mean like shimming the CPS out? i tried that once, and with my elementary experiment, the car began to run real crappy.

[winfred]

that would require something like sliceing the mount off of the front cover of the motor and fabbing up a adjustable mount, then finding out if this does any good or does moving the pick up point piss anything else off, it'd be cheeper to figure out why it's getting pre ignition

Thanks Ryan,

but I guess I wasn't real clear on what I was asking. The CPS tone ring is external (at least I think I saw it!), so I figured physically moving the CPS pick-up to alter base timing might be feasible. Doesn't sound like anyone has done this, though.

I'll look into the knock sensors before doing anything.

[winfred]

it wasn't getting a good reffrence of where tdc was to set the timing properly

you mean like shimming the CPS out? i tried that once, and with my elementary experiment, the car began to run real crappy.

[Bellicose Right Winger]

No, he means moving the CPS clockwise, looking at front of engine, a few degrees relative to center of crankshaft to fool the DME into believing TDC is really a few degrees after TDC. This will reduce spark advance.

I think it will work. Whether it's worth the time an effort as is a different matter as Winfred has pointed out.

Paul Shovestul

you mean like shimming the CPS out? i tried that once, and with my elementary experiment, the car began to run real crappy.

[MarkD]

Couldn't find anything on this when I searched. My car (1994 525i auto, M50TU) pings on most upshifts. I've seen some discussions on decarbonizing methods, but wonder if retarding the ignition a couple of degrees by moving the CPS pickup has ever been done?

I had a '95 Mustang for a while that pinged a lot. It had an "octane plug" in the engine wiring harness. Pulling the plug retarded timing 2 degrees throughout the operating range. Eliminated the pinging instantly and it ran better, too. I was told by techs that this was done a lot here in Portland because we get low quality gas. Wonder if something similar can be done to the bimmer.

Thanks for any thoughts!

Quite a few M50tu's have the same problem you mention. Are you hearing pinging between roughly 2200 and 2700 rpm? My theory is that the MAF sensor or knock sensors are bad. Do you know if you have a stock EPROM (chip ) in the DME? I can make a chip where I would retard the timing in certain rpm and load ranges if you can describe where the problem is. But, it would be better to find out what is casuing the problem. What octane fuel are you using?

MarkD