Interpreting data. VS s3 Log

[MAGP]

I cut the wires for the extra o2 sensor as used for the VT. This seemed to make the first o2 sensor work properly.

Cut or remove from PCM connector?

I hope it's not an ECU issue

Starting to look like a possibility.

[Whyzee]

Nah I just cut them. I'll remove the wiring and pins too though.

Looks like I'll be swapping the pcm again lol

[MAGP]

Here's a scan from the VT engine manual with some things to check.

Make sure the engine earths are all correctly located (clean and tight).
Make sure there are no vacuum leaks (in the intake and exhaust system).
Make sure the PCM is correctly earthed (this includes the wiring loom earths in the engine bay).
Make sure the O2 sensors are fitted correctly.
Make sure the fuel system is clean.
Make sure coil, spark plugs, and leads, are in good working order.
Make sure wiring loom is fitted correctly and connections are clean and secure.

[Whyzee]

Thanks MAGP!

So even after changing sensors again, I lost all o2 activity after about 10 minutes of driving. Seemed to be once everything heated up - I assume there must've been high resistance somewhere. With the sensor connected it would read 4mv. When I disconnected the sensor it read ~500mv.

I cut the signal wire and connected it to my wideband at the ecu (to the narrowband output) and the ECU was able to read the data which indicated either a problem with the sensors or the wiring.

I had a spare 2 wire sensor here that I decided to try. Ran a separate earth wire to the inlet manifold, and a new signal wire all the way to the ECU. I did 70km in it today and all seems well so far. I also added an extra earth wire to pin A1 and A2 which may have helped. The CEL hasn't come back on... YET.

I still need to make an airbox lid that properly accommodates a straight tube for the MAF. The bend in the airbox lid DEFINITELY makes it run leaner and it isn't quite as smooth. I can't believe the difference the shape of the intake tract makes!

[VL400]

Can you post the log? Might have some further clues.

[MAGP]

Any update on this?

[Whyzee]

Update!

Since I rewired the o2 sensor it's been driving great! Doesn't randomly lose power anymore and has the power it should. Fuel economy for mixed driving is around 14.8l/100 which is around what it was before. I'm sure I could get it down to 12-13 if i was a little lighter on the throttle. I hadn't replied earlier as I wanted to test it thoroughly before posting back.

Another problem though (which has been present since I've changed to sequential injection) is that it's hard to start!

Sometimes In the morning it'll start first turn of the key (but quite rarely). Other times (hot or cold) upon initial cranking it'll try to fire but doesn't quite start. Once it does that it won't start unless I fully depress the accelerator and crank for a few seconds - slowly releasing the pedal allows it to start. Seems like it's flooding? Once it fires the revs fluctuate for a couple of seconds and then it settles at a normal idle....

thoughts?

[yoda69]

Sounds like it's flooding, I'd check for a leaking injector/s.
As you said earlier you think it has standard injectors the cranking bpw should be correct.

EDIT: also check that the diaphragm in the fuel pressure regulator isn't leaking, if there is fuel in the line between throttlebody and fuel pressure regulator the regulator will need replacing. Fairly common problem on V6 but not sure on the v8's.

[MAGP]

You have got the dizzy synced properly haven't you?

[Whyzee]

I haven't pulled the dizzy apart, so haven't checked if it's synced, that's still something I need to investigate. I'm going to buy another dizzy anyway as I wouldn't mind having a spare. Pulled the vac hose off the fpr and there'a fuel being sucked in. I'll change it AGAIN, fingers crossed it works this time. Hopefully that's the problem