high afr's + code 34 + bad starting

[CruiseGTi-R]

I have a mix of problems (just great).

Started a while back with occasional bad starting. Would take a while to catch and only if you blipped the throttle loads.

Now getting worse, yesterday took ages, cranking for 20 secs, frantic throttle prods, eventually spluttering to life with a nice fat cloud of grey/white smoke out the back.

Once started it idles fine, runs well too.

Fault code check gives 34, so I know det circuit is out.

But, my afr’s are also high – around 12.6 on power. I thought code 34 makes ecu dump more fuel in?

If my timing is also being backed off (code 34) why would afr’s be high?

Code 34 wouldn't make starting difficult?

Where do I start?

 

[Shaun]

I would start with what you know mate i.e. the DET sensor as with it flashing a code you know it has a fault,i've just been talking to Ross about testing the DET sensor and across the pins on the sensor itself should be 560 ohms any less and you will need a new one.If that checks out ok then check the plug that connects to it and also the wiring.Once you have sorted it,then if you still have problems you can move on knowing its nothing to do with the DET sensor.

 

[youngsyp]

I'd agree with the above, eliminate the obvious first.
If you need a new det sensor, I believe there are a few on fleBay at quite reasonable money !

If it's running way rich, it would be quite difficult to start as, you're in a cylinder flooding scenario. I wonder if you may have a dodgy coolant temperature sensor too ?!

 

[CruiseGTi-R]

On idle/low loads it always sits around stoich, on power it only gets as low as 12.6 or so. So its not running rich (wish it was).

Its on oe ecu, which by all accounts should happily give 11.0 afr or so for 1bar.

I'm just surprised that det sensor mode isn't making it rich, thought it was meant to.

 

[youngsyp]

Sorry mate, mis read a bit !

Symptoms do seem strange though !

 

[campbellju]

I thought it retarded your timing and disabled the OE boost controller.

Running rich I'd put down to MAF or Lambda. Niether will necessarily give an error code when its on its way out.

I've been reading about the OE ECU learning mode that trys to modify the fuelling to adjust for age or blocked injectors etc. If I've read correctly, a dogdy Lambda could affect your ECU map through the entire rev range.

I'd go with the others first though of fixing the obvious before looking for the obscure.

Jim

 

[campbellju]

Of course if your Lambda is good, it could also be your MAF needs recalibrating.

There is a cover you can drill out to adjust the factory calibration across the range. The service manual goes into how to do this properly but you need your Wideband to recalibrate it.

Jim

 

[CruiseGTi-R]

I'm running lean, not rich

Recalibrtaing maf sounds interesting - must mean its a way of getting the ecu to add more fuel tuning wise?

 

[campbellju]

EF-EC400 & 401 of the first service manual for MAF checking and adjustment. For the lambda, I would have thought if it were also miscalibrated it could cause rich or lean conditions. I just misread/typed last time. The only bit I don't get is the manual makes out the Lambda and ECU should compensate automatically for changes with MAF or pressure regulator etc. so why would you need to adjust the MAF. I guess its just an imperfect world and the Engineers tried to give the mechanics as many options as possible to get the fueling right.

 

[campbellju]

Just read again, it says idle fuel adjustment. It might be possible to use it to just fuelling through the range too as the MAF doesn't know when its idling or not?

 

[CruiseGTi-R]

mmm, shame.

my car stoiches perfectly so I know lambda is fine. Its just reluctant to get anywhere less than around 12.5 afr.

I'll sort the det sensor (I reckon this is probably unrelated), then check fuel pressure/injectors/voltage at pump etc.

I'm also going to crack open the ecu, see if previous owner has bugared about with changing boards.

 

[hmmm]

Did you get this sorted mate?