EGR vs. MAF

highmileage

Veteran Member
Joined
Sep 17, 2013
Location
new jersey
TDI
2005 passat bhw tdi (presently), 2001 jetta alh tdi (previously), 1998 jetta ahu tdi (previously)
While doing my regular scan with VCDS the other day I observed that the specified maf reading was 240 and actual was 460 or so. Having learned that the egr shuts off at idle and a tap on the accelerator turns it back on and balances these numbers, I did that. To my surprise on accelerator increase the actual maf reading did not decrease, but increased toward 600 range. I then shut the engine down, restarted and rechecked and it responded as expected (actual decreased). Then a third time and again no decrease in actual. Is this an indication that egr valve is failing, dirty or something else? Thanks in advance. BTW no codes and engine runs well. If I had not run vcds, I would be unaware of any issue.
 
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highmileage

Veteran Member
Joined
Sep 17, 2013
Location
new jersey
TDI
2005 passat bhw tdi (presently), 2001 jetta alh tdi (previously), 1998 jetta ahu tdi (previously)
after numerous retries - all back to normal, i.e. the actual balances to specified each time
 
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oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
I was gonna say, if it was not seeing something it was not expecting, you'd have some DTC set before too long.

On the BHW, I have found that an occasional EGR valve cleanout (just the valve, nothing else) can help keep those numbers happy. I like to time it with the air filter change every 40k miles, because I lift the whole air cleaner assembly out of the car (I clean them out, blow the snowscreen clean, wipe out the bottom, etc.) and that is the perfect time to get at the EGR and slide it out of its slot and clean it.
 

highmileage

Veteran Member
Joined
Sep 17, 2013
Location
new jersey
TDI
2005 passat bhw tdi (presently), 2001 jetta alh tdi (previously), 1998 jetta ahu tdi (previously)
That sounds like a plan. I will get to egr valve now as I just recently changed all my filters, so that valve will be on schedule. Thanks for the tip!
 
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