Running lean...

Is there a smart order to diagnose this problem? I've lost boost and my wideband sensors tells me I'm suddenly running very lean. I've unplugged the O2's and there was no change. Can anyone tell me what would be the best order to look for the problem. I guess fuel pressure would be a starting point?
Thanks for any help.
Marcus

 

boost leak test is more likely, fuel pressure test can be good too but unless you're using a known/trusted gauge (the individual unit, not just the brand) the results can be misleading. When you test fuel pressure at idle make sure you disconnect the FPR's vacuum line.

If the car idles fine but runs out of power once you start to get some revs up then a temporary FPCU bypass can also be a good check.

 

Where is it running lean? On or off boost? If it's lean under vacuum and rich on boost then Fists is right, it could very likely be a split hose. If it's lean across the range then it's something else.

How lean is lean?

 

I was thinking big pre-turbo leak, cracked accordion pipe maybe, should have said boost/vac test.

 

Fists, AndyMac - Thanks for the input. Sorry I forgot to mention that I've done a boost leak test and she is holding pressure well. Car seems to have a few issues maybe as it really isn't able to come onto boost, so running lean pretty well all the time....at idle and under load.

 

AndyMac - to answer your other question (how lean), idle is about 14 on the wideband gauge and under normal driving it's up around 17. Even under some load I'm seeing 15.

 

Yeah idle is ok, closed loop is a little high, although not by today's standards, but by the z32 maps standards it's well off.

You didn't fill it up on E85 did you by accident? :rolleyes2:

Anyway, some common ones.

- Dirty MAF or shot connector. Check the voltage reading on consult if you can the acceptable range is around this forum somewhere, I can't remember it, or swap out for a known good one for a test.

- VAC hose to the FPR, this could have come off, or is blocked, or connected incorrectly. It could be a culprit seeing your idle AFR's are ok and it's under fuelling as load increases.

- FPR in general is toasted, either check your fuel pressure however you need to do this throughout the load range, so perhaps just rustle up a known good one.

- 02 circuit is on the edge of acceptable tolerances. Unlikely as it goes into open loop past a certain load and rev level and runs off the map only. So it shouldn't impact your AFR's at full noise.

If it was me, I would get my hands on a working MAF and Fuel regulator and swap them out and do a test.

 

Thanks Andy, that gives me something to start with. I'll post up what I find.

 

Thanks Rob. I don't think it has anything to do with the O2s as I have them disconnected, but yes I have ECUTalk so will check out those AFM numbers....good place to start.

 

Disconnected O2 circuit will run richer rather than leaner.

I can't recall if O2 circuit codes will throw you into "safety boost" or not, and dependent on your boost controller routing if you still have the solonoids in play or not...this is stretching my Z32 memory...but it could be a reason for not boosting.

Also your 100% on your wide band readings? Are you taking it from both banks or just the one?

 

I've had the o2's disconnected before and it doesn't effect boost. As mentioned, it just runs a little richer. In this case I've only left them unplugged so that it is running richer. I was concerned that it would lean out dangerously. Another reason why I haven't been driving it hard or trying to push it hard to boost.

Wide band sensor is just on one bank.

 

Well to a degree if your O2 circuit is working then leaving them plugged in will richen it more if it's truly running lean. It will attempt to bring it back in line by increasing the fuel delivery.

 

New Information

Ok so a few things have come to light after a tinker this afternoon.

1. 
   Firstly the readings for the AFM are good (thanks Rob).

• 
  Interestingly my O2's (I reconnected them for a while) are not ok. These are new and have had little use in the last couple of years so not sure why they have died. Either way they are not the problem as they were not plugged in before.

• Car seemed to be running much better today and no where near as lean as last time I drove it??

• Not sure if this has anything to do with my problem but the dash lights come on and off when I turn the steering wheel, and when I rev the engine?? Anyone seen this before?? https://youtu.be/9hWmNO6WHMk
  Sorry never did work out how to embed the clips.
  

 

Random lights. Can't think of anything other than a wiring harness issue.

Also odd that you re-connected shot O2's, even temporarily and got better AFR's, do you have a standard map in play?

 

Unless the O2s have gone open circuit it will be hard to tell if they work while you potentially have other fuel metering problems.

The lights are going to be from a bad earth and/or bad alternator, beyond checking the major earths and the charging voltage the job is probably going to suck. If you have voltage problems then you may well have fuel pressure problems due to the pump running slowly.

 

+1

Seems to be related to a HICAS solenoid wire and your lighting wires shorting with each other .............


Only place I can think where they intersect or connect is behind the steering wheel........Perhaps this explains why it happens when you turn the wheel?


JC

 

Good thoughts thank you I'll check it out next.