Like a Christopher Nolan movie, I'm gonna start at the end, and then work back to the beginning. Oh yes...that's right.
Now, as we ponder the sequence of events that led to this shocking discovery, I'll have to take you back....to three weeks ago. The 964 has always had an unsteady idle, and for a 3.6L engine with a 20kg flywheel, is surprisingly easy to stall. Now there is a thing that you can do with these Bosch ecus, which is called an idle-adaptation. It's basically like a hard-reset for the idle function, and can only be done via a diagnostic tester. So I'd asked Autohaus Hamilton to have a go at this, at the recent major service. But their tester couldn't talk to the ecu, and Hamiltons suggested that maybe there's an aftermarket chip in there (which might also explain the poor idling).
So, out comes the ecu, to see what's in there. Firstly, it lives under the passenger seat, where it's secured by 4 easily-reached nuts.
Undo the nuts, and the ecu slides out, and you can unclip the plug.
Interestingly...the ecu doesn't look like it's been tampered with.
And the clips that crimp onto the ecu cover don't look likt they've ever been prised apart.
But just to be sure...let's have a look.
First you notice that the ecu is of a double-decker configuration. And the first step it to separate the pillar-shaped clips on the left side.
Then prise these clips in the plug iself...
Whereupon the top deck slides back, and opens like a book.
...where the main chi is held in with a plastic clip...
..where underneath, the chip doesn't look aftermarket, but I google that number on the chip, and find a few links to euro chip tuning joints: http://www.prorace.cl/autossoportado...1-carrera2.htm and http://www.tecnosport.to/mappe/tabella010.htm
But I dunno if those sites are just referencing the stock Porsche chip number though. Anyway, I put the ecu back together. But that's not all...the ecu in the car is part number 964.618.124.03, which is consistent with my car being a later 964 with the plastic inlet manifold.
However...I do have a spare ecu, which came with an early, alloy 964 manifold, and that has an older part number of 911.618.124.04. At first I thought that the 911 prefix might mean that this is actually a Carrera 3.2 ecu, but it turns out that this is simply the strange numbering that Porsche used for the first year of production.
And interestingly...this DOES look like it's been tampered with!
I take it apart...to reveal its dark secret within :D
So. What do we know now. Well, I think I probably don't have an aftermarket chip, and maybe the poor idling is just the result of all the exhaust and intake mods I've done. We also know that I DO have a Powerderpchup...but at least it's not in the car (and to my knowledge hasn't been in the car). I guess someone owned an early 964, invested in a Powerchip, then met some sort of sticky end which resulted in that car being parted-out, and 20 yrs later bits of that engine are sitting on my shelf.
But oh yes. Hamiltons also said that the cruise control is borked. It hasn't worked for years, and the penny dropped when a few guys mentioned that my brake lights flickered on and off, even though it didn't look like I was braking. So I think that narrows it down quite a bit
The brake light switch is a plunger which operates off the brake pedal, and the freeplay in the pedal was enough to go past the click-point of the switch. So the natural wobbling of the brake pedal would trigger the brake lights as you drove over bumps and stuff...which would then disengage the cruise control. I guess I've take the pedal cluster apart so many times, maybe something's out of alignment, but the switch doesn't look adjustable.
So I backed out the pushrod for the brake pedal half a turn, which moved the pedal forward a few mm, enough to close the brake light switch. So now it won't switch on the brake lights until you actually press the pedal, and the cruise control works again!
Hmm...anyone wanna buy a Porsche ecu?
Now, as we ponder the sequence of events that led to this shocking discovery, I'll have to take you back....to three weeks ago. The 964 has always had an unsteady idle, and for a 3.6L engine with a 20kg flywheel, is surprisingly easy to stall. Now there is a thing that you can do with these Bosch ecus, which is called an idle-adaptation. It's basically like a hard-reset for the idle function, and can only be done via a diagnostic tester. So I'd asked Autohaus Hamilton to have a go at this, at the recent major service. But their tester couldn't talk to the ecu, and Hamiltons suggested that maybe there's an aftermarket chip in there (which might also explain the poor idling).
So, out comes the ecu, to see what's in there. Firstly, it lives under the passenger seat, where it's secured by 4 easily-reached nuts.
Undo the nuts, and the ecu slides out, and you can unclip the plug.
Interestingly...the ecu doesn't look like it's been tampered with.
And the clips that crimp onto the ecu cover don't look likt they've ever been prised apart.
But just to be sure...let's have a look.
First you notice that the ecu is of a double-decker configuration. And the first step it to separate the pillar-shaped clips on the left side.
Then prise these clips in the plug iself...
Whereupon the top deck slides back, and opens like a book.
...where the main chi is held in with a plastic clip...
..where underneath, the chip doesn't look aftermarket, but I google that number on the chip, and find a few links to euro chip tuning joints: http://www.prorace.cl/autossoportado...1-carrera2.htm and http://www.tecnosport.to/mappe/tabella010.htm
But I dunno if those sites are just referencing the stock Porsche chip number though. Anyway, I put the ecu back together. But that's not all...the ecu in the car is part number 964.618.124.03, which is consistent with my car being a later 964 with the plastic inlet manifold.
However...I do have a spare ecu, which came with an early, alloy 964 manifold, and that has an older part number of 911.618.124.04. At first I thought that the 911 prefix might mean that this is actually a Carrera 3.2 ecu, but it turns out that this is simply the strange numbering that Porsche used for the first year of production.
And interestingly...this DOES look like it's been tampered with!
I take it apart...to reveal its dark secret within :D
So. What do we know now. Well, I think I probably don't have an aftermarket chip, and maybe the poor idling is just the result of all the exhaust and intake mods I've done. We also know that I DO have a Powerderpchup...but at least it's not in the car (and to my knowledge hasn't been in the car). I guess someone owned an early 964, invested in a Powerchip, then met some sort of sticky end which resulted in that car being parted-out, and 20 yrs later bits of that engine are sitting on my shelf.
But oh yes. Hamiltons also said that the cruise control is borked. It hasn't worked for years, and the penny dropped when a few guys mentioned that my brake lights flickered on and off, even though it didn't look like I was braking. So I think that narrows it down quite a bit
The brake light switch is a plunger which operates off the brake pedal, and the freeplay in the pedal was enough to go past the click-point of the switch. So the natural wobbling of the brake pedal would trigger the brake lights as you drove over bumps and stuff...which would then disengage the cruise control. I guess I've take the pedal cluster apart so many times, maybe something's out of alignment, but the switch doesn't look adjustable.
So I backed out the pushrod for the brake pedal half a turn, which moved the pedal forward a few mm, enough to close the brake light switch. So now it won't switch on the brake lights until you actually press the pedal, and the cruise control works again!
Hmm...anyone wanna buy a Porsche ecu?
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