Motronic 3.1 Doesn't Like Wot?

[brian j 31]

So now the car is running I have a driving issue.

 

The test drive was short due to the cam seal failing, but in the time I had:

 

The car starts, idles, and goes well. It seems happy to rev and pull, but if I push the throttle all the way to the floor, it is like I have just sidestepped the throttle peddle (Engine doesn't miss or complain, the power just disappears)

 

My setup is:

 

Standard XU9JA bottom end

Longmans head (10.5:1CR, 1mm oversize inlets)

Piper 270 Cam

Motronic 3.1 from a ZX volcane (ecu, inlet, throttle body, tps, flywheel, crank sensors etc.)

Lambda fitted and wired in.

 

It feels like the throttle travel is too much for the TPS, but it's position isn't adjustable on this setup.

 

Any other ideas?

 

Thanks

[pug_ham 240 3 Cars]

This was the same on mine & cured by Wayne at chipwizards, the TPS switch is wired incorrectly & the order of the wires at the TPS plug need changing as when you floor it, the ecu thinks its at idle due to the signal from the TPS.

 

I'll have a look at my loom & let you know the new order to change them too.

 

I thought it was a 405 loom issue but I've just checked the ecu pin order on autodata again & the 405 ecu uses the same pinout as the ZX ecu we are using so shouldn't be an issue.

 

 

 

It must be the internal TPS switching due to its position on the TB is different, at least thats all I can think it is & at WOT you are managing to travel back to the idle map switch point.

 

Graham.

[brian j 31]

I was just thinking that a wire swap sounded easy too... I'll try having a play after I change the cam seal an put a new set of belts on it...

 

Thanks Graham

 

(null)

[peter 20]

This is exactly what happened when I fitted a gti6 throttle body to my 8v turbo! Tried unplugging it but didn't help at all!

[pug_ham 240 3 Cars]

Ok, just checked my loom.

• Ecu pin 9 to pin one on tps plug
  
• ecu pin 3 to tps plug 2
  
• ecu pin 6 to tps plug pin 3
  

Hopefully that'll fix yours.

 

g

[brian j 31]

Thanks Graham, Next time I'm in your part of the world, a drink on me is definitely in order...

[pug_ham 240 3 Cars]

Thanks, lets see if it fixes yours first.

 

g

[peter 20]

Don't mean to hijack, I didn't want to start a new topic that is so similar, the mp3.2 I'm using with gti6 throttle body the wiring is correct but has the same symptoms. Possibly the gti6 tsp is in a different place but I don't think it is. Or the wiring has broken, must check that now!

[pug_ham 240 3 Cars]

It could be the same as with Brians & mine, wiring rings out as it should but tps internals don't match what signals the ecu expects to see at WOT so order needs changing.

 

g

[peter 20]

After measuring the resistance between pins 1 and 3 the gti6 tps is the reverse of the 8v giving a low resistance at low throttle and a higher resistance at full throttle 1k ohm an 3k ohm respectively, the 8v is 3k ohm at closed throttle an 1k ohm full throttle. Also it's not as simple as just using the 8v tps as the gti6 one is mounted on the other side of the throttle spindle so it opens anticlockwise.

 

however drill a hole in the 8v one and mount backwards should work, well it gives the correct signals for throttle position.

 

Will test tomorrow to make sure.

[pug_ham 240 3 Cars]

A GTI-6 tps is completely different to the original jetronic tps which is a basic open closed switch unlike the TPS from one such as the MP3.1, what 8v tps were you testing it against?

 

g

[brian j 31]

OK, Thanks to Graham, all is working.

 

For future reference, on my 405 loom and ZX tps, the original pinout was:

 

Pin 1 --> Wire M43 (earth, ECU Pin 6)

Pin 2 --> Wire 9 (+5V, ECU Pin 9)

Pin 3 --> Wire 3 (Signal, ECU Pin 3)

 

Swapping them as Graham advised above:

 

 

Pin 1 --> Wire 9 (+5V, ECU Pin 9)

Pin 2 --> Wire 3 (Signal, ECU Pin 3)

Pin 3 --> Wire M43 (earth, ECU Pin 6)

 

It now behaves as I would hope.

[pug_ham 240 3 Cars]

Good work Brian, interesting that the order is different at the tps plug end for the same system that normally uses a different style of tps.

 

g