RE: 75 ts misfire.

[Anders.l.Nilsson@xxxxxxxxxx]

> Can anyone help?..
I can at least give it a try.

> 
> My 75 ts has been suffering from a misfire which occurs 
> between 2000-2500
> rpm when under load. It started off at around 2400 rpm but 
> now does it in
> this whole range. However, it works fine when just running on 
> the front set
> of plugs. It won't even start when I try and run it off just 
> the rear set.
> I've checked both coils and they're fine, it's got new 
> ignition leads and
> new distributor caps, and I'm pretty sure the V.V.T. device is working
> alright, so I'm stumped now. Is there any way the ignition 
> timing could
> have gone out or anything?
It doesn't sound like a timing problem to me ( at least it's not the only
culprit).
On a TS, you can only change the static timing. All dynamic timing advance
is performed by the Motronic box. Both ignition systems should have exactly
the same timing and advance.

You should be able to run the car on each plug set independantly. Since this
is not the case, I would assume that you have a problem somewhere in this
region.
Debugging list (if you haven't done all of this yet):

*1 Disconnect the rear lead low power connection and verify that the car
runs well on front plug set.

*2 Connect the rear set low power to the front set lead and try it out. If
it runs well you know that the low power side (signals from Motronic and
power supply) is working for both sets, continue at *3. If it doesn't run,
you have to find out whic signal(s) are missing in the faulty low power
connection. Easiest to check would be power supply to the lead. The
ingnition timeing signal could be harder to check, maybe you need an
oscilloscope for that, I'm really not sure.

*3 Switch High voltage cable from the front lead, so that you run on the
rear plug set with the front lead. Now you know if ther's something wrong
with the distributor or set of cables.

*4 Are you sure that both dists are set equal. I read somwehere that it is
pretty common nowadays that garages/shops puts one of them 90 or 180 deg off
(can't remeber which) since that's how they should be on newer TS engines
(155 and 156). On the 75 TS they should ignite simultaneously.


I've this way verified my ignition, runs on each set independantly, but I
still have some misfiring problem under load in the mid range ( 2000 - 3500
rpm ).
The search continues.

Please let me know if this helps you out, or if you need some more help.


Reagrds
Anders Nilsson
- -90 75 2.0TS with 173.000km   and rolling (without rear muffler, pipe rusted
off last week)

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