quick tech question

[tom_rallye]

h, new owner of an s4 and too this forum. had an intermittant boost prob for the last couple of weeks, plugged it into the scanner at work and needs 2 egt sensors, also had both banks running lean, would this be caused by egt's or something else?
thanks for the help
cheers tom

[GrahamS4]

Someone with some first hand know how will surely answer soon, but I am sure I have read that a faulty MAF can cause the car to run lean and if prolonged can cause EGT sensor failure.

[s4yogi]

Yea I agree both banks running lean is usually Maf and will have killed the EGTs over a long period of time

[Harper--D]

So basically you need to replace maf and egt sensors!!

[KayGee]

Sounds like two or three problems to me. MAF/EGTs shouldn't cause intermittent boost. A better description of the symptoms would be usefull as would a vagcom log.

[yorkie]

A shot maf will cause the egt's to fail but the only two cars I have logged the fault of failed egt's on were both running about 50% boost permanently not intermittent.

You won't get a fault code for the maf itself if it is still talking to the ecu, just low airflow readings.

p.s. from your id can I gather that you own or owned a Rallye Golf?

Sold mine a year ago to move up the ladder of money pits!

[tom_rallye]

thanks for the help guys, ordered new egt's and airflow meter and got some new dv's and samco hoses whilst at it. Think i'll have the pre cats out next week and map it, how much boost are you guys running safely?
cheers tom

[GrahamS4]

My boost on a mapped S4 with stock K03 turbos is 1.2bar peak dropping to 0.8 at high revs probably tailing further at the redline (dyno plot didn't run to full rpm so not sure).

[HK-Steve]

Does Vag-Com tell you that the EGT's have died??

From memory I can see a reading or 0.3k ohm and 0.6k ohm or something like that.

I ask as I had a bad MAF for 2 months before replacement,
Had lean codes on both banks.

Car pulls like a train, but I have not been logging long enough to get any EGT temps over 750'c


Appreciate your comments
Cheers
Steve

[yorkie]

Yes, either "implausible signal" or "short to ground" are the usual faults listed.

I should know since I seem to be getting one of them weekly at the moment.