Electrical problem?

[LOVEHZ]

Hello all, I was out for a long drive in my 86 targa. halfway into the drive the car started missing-like a total shutoff(turing the key off). Power cut out and then it would come on again. This continued off and on. Then close to home I would lose power even tho the engine was running combined with the intermittent total loss. It got to the point that I could hardly get the car into the garage the power was so low. Next day it started up fine but the problem returned within blocks. I replaced the relay under the seat but that didn't help. Any suggestions?

[zippy_gg]

Check for loose battery connection.
How does your ignition switch feel?
It sounds like a cable or wire working its way loose...

[steely]

+1 to the above
Relay was the first thing I would've checked too.
Wires to Coil and from it to the dizzy ok?
DME connector on OK (probably is but throwing that in there)?
Speed and Reference sensors starting to go (insulation crumbling? they can go intermittent before totally bad).

If you can repeat it in the garage, check the ICV for vibration during one of these episodes, bc if it goes off it's a sign that the DME itself lost power.

Is the socket for your new relay looking good?

[LOVEHZ]

Yes, I have had the DME relay fail before so that was my first go to. The socket looks good. The additional problem of loss of power is what's confusing. The engine will be running but almost no power to start moving. I have changed the coil now too. Wires ordered. I haven't been able to get it to fail in the garage just while driving so haven't tested the ICV vibration. Speed and reference sensors were changed a few years ago but will look at them again.

[steely]

Out of curiosity, I looked at some other posts here about 3.2 power loss issues - looks like they can range from the simple to the rare unfortunately - like a cold solder joint in the DME itself or a faulty fuel pressure regulator or damper. Looks like in the cases with the fuel prob, the eng shutdown due to over pressure(!), but it started right back up.

So if you get stuck for clues, a DME swap or a fuel pressure check might be options to try.

[RedCoupe]

I had a bad ground strap from the battery to the chassis cause a similar condition in my 964. The connections looked fine, but the cable had developed internal resistance that would come and go with temperature and vibration. For less than $20 it was all fixed.

[proporsche]

here is a little index to help to all of you.... if need it..
Ivan

[76FJ55]

Sounds to me like classic CHT issue. First thing to check is the connector located on the bracket mounted to the left (driver's) side intake manifold. It is the top yellow connector. The two lower black connectors are for the speed and TDC sensors. Open (Unplugged) or broken will cause cold start enrichment, so it will start cold and then get worse as it warms up.

[76FJ55]

Originally Posted by proporsche

here is a little index to help to all of you.... if need it..
Ivan

This chart is for the older CIS cars and is not applicable to the OPs 86. Good reference for 83 and older though.

[proporsche]

opss sorry .this is the one

Ivan

[76FJ55]

Originally Posted by proporsche

opss sorry .this is the one
Ivan

Sorry Ivan, that came off a little harsh.
Edited: Still not ideal as the cold start and ignition system are different. The 86 is Motronic and doesn't have a cold start valve, thermotime switch...

[RSBob]

Also check that all the multi pin round connectors under the dash are firmly seated. I hit an expansion joint and the car completely died since the plug was just a bit loose.

[sp_cs]

Originally Posted by 76FJ55

Sounds to me like classic CHT issue. First thing to check is the connector located on the bracket mounted to the left (driver's) side intake manifold. It is the top yellow connector. The two lower black connectors are for the speed and TDC sensors. Open (Unplugged) or broken will cause cold start enrichment, so it will start cold and then get worse as it warms up.

CHTS for me too (cylinder head temp sensor)

Check the sensor mentioned above has 2 wires going to it, and not one - the latter is an older design.

[proporsche]

one more index for testing...

[gomezoneill]

Originally Posted by proporsche

one more index for testing...

^^^^^^^
This. Very common intermittent problem. If you test the resistance it may be within specs but still fail at times especially when hot. I would just go ahead and replace them.

[76FJ55]

If you end up needing to replace the Speed or Ref sensors, There is an interchangeable part from a BMW (still genuine Bosch) that has a slightly longer wire that is about 1/2 price compared to the Porsche one. i think the part number is 12-14-1-708-619-M14.