Engine running bad after using turn-signal (uhu)

[paul_boivin]

Hi guys & girls?
Short intro: 48, driving a 1991 964 Turbo for about 10 years now, deam come true :-) Been around reading here & on Dutch porsche forum+rennlist and now also this place.

If you like freaky electronic stuff read on...
Since a few years now I've got a weird problem and sofar no specialist has been able to figure it out. They've spent a few hours, not days but maybe someone here had an idea?

Problem is that when I use my signal light the engine starts to run rough and won't pick-up on revs, when getting on boost it feels like normal I think.

To make it even more bizarre, the problem is only in the FRONT signal-lights. If i take out the fuse for the front left (or right) turnsignal light then all is normal and I can use the signal ligt left without the engine going bad. Same for right signal (taking out the right fuse)
And now the funny part ...using the alarm lights gives NO problems at all.

The fuel pumps have been checked for correct voltage when running, no probs there.
I tried to ground the signal light to another point, no cigar
Tried another turn-signal unit (pff not just a little switch, had to take off steering wheel to replace it), no cigar

To me it feels like ignition problems (fire angle gets set too late?) , something causes it to be "late", for me because it feels related to the bad revving, takes forever to speed up & some popping

When driving, if I really need to use the turn-signals, turning the key off/back on again while driving resets it back to normal till the next turn

So anyone dare? Have been doing some reading, faulty turbo control unit that has something to do with the igniton map? Asked at 2 places but they don't have'm lying around so I could test something.

So, anyone out there any clues?
PS everything else (windows/roof/ligt/seats etc) work fine and dont cause the problem
Cheers, Paul

[techman1]

Paul, have you replaced your front main ground from the battery to the body? I know, it may look great, but I have been told it will pick up resistance in the cable and the contact points. Sounds strange, but I have firsthand experience of strange electrical gremlins being banished with this change. You should be able to pick up a close match at a local store at a low price. This would confirm whether it corrects the issue, then if originality is an issue for you, order a "$Porsche$" cable.

[RedCoupe]

+1 on the ground cable. I had a negative battery cable that looked like new yet caused bad running and eventually caused stalling before I replaced it. At least remove the cable and check for resistance while you are moving/shaking it.

[paul_boivin]

Solved...

Tried another groundcable but (to my expectations) didn't solve the problem. (The thing hasn't been replaced or so and *everything* else works fine)

My expert amateur conclusion:
After studying the electric diagrams I'd thought I'd give it a try to use a different powersource for the turn-signals wich comes from the flasher unit located under the dash, this solved the symptoms/problem

So after disconnection the original (black/yellow) powersource and connecting another powerlead (wich always has power) to the flasher it all works again except I lost the "parking light" feature....who cares. Hazzard light also works (that's why I wanted a "constant power" lead to connect)

I think that the real problem is in the ignition switch (the thing you put your key in :-) ) because the problem also occured when flashing high-beam. After some digging I think the problem is caused by using *anything* that is powered/connected via the iginitionswitch, wich makes more sense now. This also explains to me why the problem didn't occur when using the hazzard light switch, that's not routed via the ignition switch wich works without the key in/ignition on! (turn signals only work with ignition turned on!)

What the actual problem is (just fixed the symptom) I don't know, to me it feels like the ignition is beeing retarded/ the EZ69 has some different built in modes I understood so probably it goes wrong there...

Going to replace my ignition thingy in the near future, for now I can use my blinkers again!