Cheers everyone,

today was driving and got off the Autobahn on a slight descent, so off the throttle and the car rolling.
Gearbox was in "D" for sure when suddenly the engine went completely off!
Managed to stop it and after a few tries it started over, but went out again.
Tried 3 or 4 times then it stayed on and I could drive home the remaining 1 mile.
Checked at home with the Diablosport Predator and only had the P0688 code there that has been there quite a while now.

The only thing I did before was swapping some of the relais in the relais box ("IPM") (2 days ago).
Could it be that there is a bad relais somewhere?

Thanks for any help guys!!

 

Could be a bad relay, bad wiring, or bad PCM..... The code can refer to the PCM power relay, or the relays that provide power to the injectors, or coils.... Just depends on which one(s?) you have. Try swapping them around, ONE AT A TIME, with a known good relay. See if you can determine where the problem lies.

 

I know the code has been there before, when I have been at a workshop a few months back. So maybe there are 2 problems?
From the wiring diagram there is only one relais that provides power to both coils and injectors. So I will mark them up maybe and try to swap them?

I also found out know how that circuit works, haha (thanks YouTube ^^).
So the voltage gets send to the injectors and coils AND to the PCM which monitors the voltage.
So if the voltage at the PCM is not "good" enough it will throw the code, right?

 

Correct. So, just that one wire having a bad connection, or some other issue, will set the code.

 

Today I got the famous P0300 back again. Same behaviour as before. Running bad on gasoline, but perfect on LPG with seperate injectors.
So I assume it must have to do with the power supply of the injectors or maybe a bad injector maybe?
Is there any way to measure resistance or something on the injectors to know if they are electrically "good"?

 

I *think* injectors are supposed to be 12-16 ohms.

 

OK, thank you, will check them.
Today I also did some more testing again, P0307 was back as well.
I hooked up my Diablosport and was watching live data, I monitored injector timing on cylinder 1, 2 and 7.
When it started running sluggish again I noticed that 1 and 7 hat about 6500us and 2 had only 5500us. So about 20% longer opening times.
What might that say?
If it would be cylinder 7 only, I'd assume the problem is there. But 1 and 7 were identical, so both on the same side of the engine.
Maybe that's fuel pressure related?!
From the wiring diagramm the power supply is identical to all injectors though.

 

Was the PCM in closed loop at that point?

 

I can just assume that it was. Engine was hot, so should be. But I will have to check it again maybe if there is an info on the live data about that.

 

Yeah, there should be.

PCM adjusts pulse width on a per-cylinder basis, if 2 is just burning better than others, that would account for the difference....