Ignition timing on 190E 2.0

Another general question about my 1990 190E 2.0

Yesterday I took a look at the ignition timing. The car appears to be fitted with a TSZ type ignition and not the EZL type as everything seems to match the pictures in my Haynes manual, and there's no sign of a EZL resistor pack.

When putting the strobe timing , I see the ignition is right about TDC, or perhaps a few degrees before. The manual tells me I can change the timing the traditional way, by rotating the distributor, but when I try this the engine speed changes (as expected) but the strobe still gives me EXACTLY the same reading.

I did some searching before posting this and came across a couple of posts from a guy with a similar looking problem. One of the posts did mention that the timing simply wasn't modifiable.

My questions are:

1) Do I have a TSZ type ignition?
2) Is the timing reading of around 0 degrees TDC OK?
3) If it's not OK, how can I change it?

Many thanks

Mark

[mbdoc]

Ignition timing isn't adjustable after 1986 on the 190E engine. Base timing should be between 2 & 7 deg at idle.

Thanks for that, it had me a little perplexed for a while.

Do I base my distributor position on the idle speed I obtain? At the moment it's ticking over just under 1,000 rpm (just as a test) whereas before it was at the more normal 800 rpm tickover.

If I don't set it by the idle speed, is there a more 'scientific' way to set it? Again in the manual I have, it states there is a marking on the machined face at the top of the distributor body, and that this should be aligned with the rotor arm. With the metal contact of the rotor arm being about 0.75 or an inch wide, and the marking they refer to being a scribe line, there's plenty of room for error. (I'm also starting to be more than a little sceptical about what the Haynes manual tells me!)

Many thanks

Mark