VCDS - Odd results

argiopeweb

Member
Joined
Nov 13, 2017
Location
USA
TDI
1997 Passat
Had my first chance to run some Vag-Com diagnostics on the car today and I'm a bit confused by the results.

I went on a ~20 mile drive followed by a 10 minute sit while I made coffee. I connected the VCDS module (HEX-V2 Enthusiast, purchased directly from Ross-Tech) and idled the car till the coolant temp in Block 001 showed above 80*C. At this point, according to a higher numbered block I don't quite recall the number of, intake air temps were 40*C (seemed high, but I suppose within reason for North Florida), fuel temp was ~65*C (again, seems high, but I suppose reasonable after a long drive on a nearly empty tank).

The resulting timing chart:



I'm confused by the fuel temperature here. I assume it's in Fahrenheit, but it's too high in both the "Fuel Temp" box and on the 'X' axis (which don't match) based on what I saw in VCDS measuring blocks.

Additionally, the IQ on the car seems super high (8.8mg/str) at proper 903RPM idle. myturbodiesel states that the default adaptation value for IQ is 32768 on all US TDIs from 1996 to 2003, but mine is set to 32710. If you asked me yesterday I'd say this is a stock, unmolested car, but this appears to suggest the contrary.

Can anyone offer advice here? I'm loath to go adjusting the timing given the weirdness with the fuel temp axis. I'm happy to provide any other info/measurements if needed.

edit: I'm also confused as to why the message is "Engine not warm enough" here. I checked before the timing graph and double checked after and coolant temps were above 80*C both times.
 
Last edited:

Steve Addy

Top Post Dawg
Joined
Aug 7, 2002
Location
Iowa
TDI
97 Mk3
Post up an pic the screen where it reads and reports the ECU information.

Do you know which ECU you have?

Steve
 

argiopeweb

Member
Joined
Nov 13, 2017
Location
USA
TDI
1997 Passat
I'm not even sure what the potential options are for ECUs on this car... Is ECU data on the 'main" screen for the "Engine" controller, or is there a measuring block?
 

Steve Addy

Top Post Dawg
Joined
Aug 7, 2002
Location
Iowa
TDI
97 Mk3
I'm not even sure what the potential options are for ECUs on this car... Is ECU data on the 'main" screen for the "Engine" controller, or is there a measuring block?
When VCDS first connects to the ECU it will report ECU information, that info will tell you (hopefully) what ECU you have. It might also report any changes to the ECU version because of installed perf chips etc.

Additionally, you ought to pull up the rain tray cover on the passenger side of the engine compartment and look to see what the part number on your ECU is and note whether you have a metal or black plastic case on your ECU.

I suspect since your car is 1997 that will have a metal cased ECU with the socketed chips but you never know. It's worth finding out.

As a side note I have seen extremely high fuel temps before but it was not a permanent situation. You might check again and see what you find now.

Steve
 

argiopeweb

Member
Joined
Nov 13, 2017
Location
USA
TDI
1997 Passat
Ah, got it. Thanks. I'll get a number and update the thread when I'm back out at the car.

Went out to check a few other things and came up with this image:



This was after ~5-10 minutes at idle (60%) and holding it at 1500rpm (40%). Fuel temp was slightly higher than coolant and intake air (~16*C vs. 12*C), but seems within reason. All values corresponded with the expected outside temp (a balmy 52*F). I feel like I can assume there's no issue here with the fuel temp sender.

I'm obviously very advanced.

I bumped the adaptation value for IQ up to its supposed factory setting (32768, from 32710). IQ dropped from 10.2 to 7.5, which probably isn't a bad given the temps. I'll drive it to town and report back. It's definitely got a bit of a rattle at idle with the lower IQ. I'm starting to wonder if the PO's PO did an injector swap (PO claimed not to have touched them).
 

argiopeweb

Member
Joined
Nov 13, 2017
Location
USA
TDI
1997 Passat
Here's what I have for output from VCDS.





I'll pull the rain tray cover and check the number in a bit. I do recall it's the metal cased unit.
 
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