3B misfire/cutout

[dkw_dude]

Hi
My -91 S2 3B has suddenly developed a misfire. the car has been running good with RS2 setup for a long time but not anymore.

From cold it starts as normal, and runs normal at warmup (running little or no boost). When warm it misfires/cuts out when it boosts, and after a short while off boost too. But runs mostly ok when light on the throttle. If I blip the throttle it sounds like it runs on 3 or 4 cylinders!

If I let it cool down and take it for another test run it will repeat this behavior.

I have checked the following:
MAF: ok
Pressure test: ok
Fuel pressure: ok
Rotor: measured resistance, ~17kohm. Changed it for a new correct one. No change.
Plugs looked ok, but will replace them anyway I think.
Rotor cap/cables looks ok. HT cables not to old so they were in good condition.
VAGcom: No fault codes.

Next is ignition amplifier/coil I think.
If anyone has a good suggestion on what to next I would be thankful.

[archiboy24]

Try the O2 sensor?

[dkw_dude]

No, have WB gauge w narrowband output tapped into the Motronic. It shows ok values, except when misfiring of course, goes lean then (unburnt O2). Thanks for the input though
I'm going to pull of distributor cap and HT leads and inspect more thorough and see if I can find anything..

[dkw_dude]

Have discovered sparks jumping off the centre lead on the distributor cap. Cap is chipped where the coil lead connects to it. So I think I am on to something Will get new cap and see.

[dkw_dude]

New distributor cap (Beru) in place, and haven't missed a beat (spark) since . It feels like it's running better than before, the resistance in the old rotor was ~17k ohm instead of 1 k ohm in the new, I guess that has something to do with it.
Now it's soon time to install the stuff I got from pnanassy

[DJones]

New distributor cap (Beru) in place, and haven't missed a beat (spark) since . It feels like it's running better than before, the resistance in the old rotor was ~17k ohm instead of 1 k ohm in the new, I guess that has something to do with it.
Now it's soon time to install the stuff I got from pnanassy

Its good to know what fixed it, thanks for letting us know.

There is nothing worse than following a thread that has similar symptoms to your own with no mention at the end as to what fixed it...

[dkw_dude]

Thanks, I also like to see a conclusion on a thread. Here's a pic of the distributor cap, the chip of the center piece is NOT ok A slight leak from the distributor axle too, had to clean that up as well.

[rsmaku]

Yup, same is the story with cheap caps, they misfire alot. Had the same problem. The misfire came almost at maximum boost usually.

[rsmaku]

And the misfire result was this, with original setup.

[dkw_dude]

Ouch. I hope my rods are a bit straighter than that.. Still runs ok but I'll do a compression test later I think..

[rs200]

the misfire killed my engine too.

now when I started my new engine I want to check everything what included ignition, before I go on the road. how to check ignition angle of spark?

thanks. igor

and here is my result of misfire:

[pnanassy]

Nice fingernails