As mentioned, that is a protection relay to prevent the cat's from overheating and lighting things on fire if part of the ignition system malfunctions.

The issue is this: The ignition system on later cars is split into two halves, 4 cylinders each. Separate ignition amps, separate coils, separate distributors. So a failure of one side of that will leave you with four cylinders dead, four working.

If you are an idiot and drive the car like that, then unburned air/fuel mixture from the four dead cylinders is dumped down the exhaust, causing the cats to get very hot as they burn that fuel, hot enough to potentially start a fire.

Of course the engine is only running on four cylinders in that situation, which is to say very poorly, but it will run. And some folks are idiots, so around 1990 the Porsche engineers designed a protection circuit to detect that only four cylinders were working (by measuring exhaust temperature for one cylinder on each ignition bank) and cut off fuel to those cylinders, to keep idiots from burning up their cars.

The protection circuit itself is troublesome and probably results in more 4-cylinder running than any problems with the ignition system (which is actually quite robust), so many folks remove the protection relay and jumper it. And then they make a solemn promise to not drive the car with only four cylinders working.

Engineers are continually designing bigger and better idiot-proof systems, of which this is only a very small example.
And of course the universe is continually creating bigger and better idiots.

The universe is winning.

Leave it the way it is, make a solemn oath to not drive the car if only four cylinders are working, go find a mountain road and be happy.

 

Well said Jim !! I still maintain that the urge to "just make it home" seems to kick in as people rationalize driving a car that has obvious problems but still is running reasonably well....
When your car is talking to you it is usually best to LISTEN

 

thanks everyone for sharing your feedback. Im spending the winter on the car and going throught everything. It appears (correct me if im wrong) that the ims has been disabled by the ground wire that was spliced into the blue wire? I haven't touched anything with the ims so far (and it was running this way), but i was thinking of purchasing porsches bypass and plugging that in and removing the spliced wire.

any thoughts?

 

The splice is a bypass for your toothed belt tension switch... do you have a Porkensioner on the car? if not there is presumably some issue with the tensioner 'switch' - do you know that the belt is tensioned correctly? - I'd be worried if it has the stock tensioner on there...? (BTW this is a very ugly "splice"...)

This has nothing to do with the IMS. If you don't have jumpers in the white plug that would connect to the relay? - then someone has bypassed it somewhere else.

Alan

 

The ignition monitor relay bypass 928 615 175 00 is $27.41 and we sell a lot of them.

 

But if the car runs without a Porsche IMS bypass and without the IMS relay - someone already bypassed it somehow/somewhere - its certainly not this other "splice"...

Alan

 

IMHO it would have helped to give the plug letter and pin no of the blue wire that's been spliced, then we wouldnt have been guessing what was being jumpered to ground.
jp 83 Euro S AT 55k

 

Hah Indeed!