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VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old September 9th, 2017, 14:43   #1
AZ98TDI
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Default Air Mass Value in VCDS

Hello all, I noticed my fuel mpg's had gone down recently between fill ups.

I hooked up my Vag-com and noticed in "measuring blocks group 000, box 10" the value for Air Mass was 133. The info box that popped up said it's suppose to be between 69-111.

Group 003, EGR System test at idle, air mass value was 195 with EGR on and 445 with EGR off. Suppose to be between 230-370.

So what's wrong here? Is my MAF on the fritz or my EGR?

Would these value readings throw off my MPG's? (got 36 mpg's on last tank and I drove it normal this time )

Is there anything else I should do in VCDS or change in adaptations?

I would like to be at the 40-45 mpg's range again.

Thanks for any replies that may help me.
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Old September 9th, 2017, 17:26   #2
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If you cannot run to redline (in neutral) and or VCDS doesn't show a MAF number of 950 (or higher- depends on EGR duty cycle) then your MAF is suspect.

When was the last time you were getting 40-45mpg and what have you done to the car since that time?
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Old September 9th, 2017, 17:56   #3
AZ98TDI
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If you cannot run to redline (in neutral) and or VCDS doesn't show a MAF number of 950 (or higher- depends on EGR duty cycle) then your MAF is suspect.

When was the last time you were getting 40-45mpg and what have you done to the car since that time?

I haven't tried redlining yet in neutral. Do I do this with VCDS connected and just punch the pedal to the floor?

I would say about 6 months ago I was getting the range of 40-45mpg.
Since then I have replaced all vacuum lines, replaced QA seals and set IQ in VCDS, replaced fuel filter and all fuel lines under hood, adjusted timing back to timing graph because it would hard start in cold mornings, removed snow screen from car.
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Old September 9th, 2017, 18:37   #4
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Generally, you cannot redline with a bad/subpar MAF. Just press down on the accelerator (no need to hammer on it, but no need to ease it either). I have not experienced an inability to achieve redline, though when the MAF on the wife's car was crapping out it was so bad that I felt little need to even try (MAF utterly failed to the point the engine was bucking).

What was your IQ at and what did you set it to? While you can bump via VCDS it's only really effective for smaller changes: big changes require hammer-modding. Also, have you done any adaptations to EGR? (folks do this trying thinking that it will reduce carbon build-up, but the ECU will adjust around any changes- proper way to deal with this is to get a tune).

Where is your timing at now? If you were "off" the graph I'd think that you shouldn't really be able to run w/o it exhibiting really poor performance. If it actually did run I'd have to stop and think if something else isn't off. When was the TB last done (and by whom)?
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Old September 10th, 2017, 05:23   #5
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Originally Posted by AZ98TDI View Post
Group 003, EGR System test at idle, air mass value was 195 with EGR on and 445 with EGR off. Suppose to be between 230-370.
So what's wrong here? Is my MAF on the fritz or my EGR?
That 230-370 spec...not sure if that's a VW spec, or Ross-Tech, but all of the ALH cars I have had ran around 270-275 at idle with EGR open, and 470-475 with the EGR closed. Under hard acceleration, MAF numbers were typically 800, with a couple spikes to 850 (Depends on how smooth/fast/slow the acceleration was). Of the MAFs I have had that failed, they typically reported decent numbers at idle, EGR open or closed, but would not climb above about 600 during acceleration.
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Old September 10th, 2017, 11:02   #6
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What was your IQ at and what did you set it to? While you can bump via VCDS it's only really effective for smaller changes: big changes require hammer-modding. Also, have you done any adaptations to EGR? (folks do this trying thinking that it will reduce carbon build-up, but the ECU will adjust around any changes- proper way to deal with this is to get a tune).

Where is your timing at now? If you were "off" the graph I'd think that you shouldn't really be able to run w/o it exhibiting really poor performance. If it actually did run I'd have to stop and think if something else isn't off. When was the TB last done (and by whom)?
I don't recall what the IQ was at before I replaced the QA seals. I did the hammer mod and set the IQ at 6.4 mg/str. This is what I've been running it at. Not sure if the value is too high? In VCDS 6.4 mg/str has the value of 32645. is the standard value suppose to be 32768? If I enter that value it will bring the IQ number down, is this what I should do?

I have not done any adaptations to the EGR. It is still set to the standard value of 32768. Should I change it? If so what other values need adjusted along with it?

My timing is just above the middle line now, almost "dead on". It was way advanced (probably belt stretch) before causing my long start in cold conditions.

My timimg belt has about 60k on it now. The shop I used only worked on VW's and used all the 100k parts for the belt change and timed it in VCDS.
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Old September 10th, 2017, 21:19   #7
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Originally Posted by AZ98TDI View Post
I don't recall what the IQ was at before I replaced the QA seals. I did the hammer mod and set the IQ at 6.4 mg/str. This is what I've been running it at. Not sure if the value is too high? In VCDS 6.4 mg/str has the value of 32645. is the standard value suppose to be 32768? If I enter that value it will bring the IQ number down, is this what I should do?

I have not done any adaptations to the EGR. It is still set to the standard value of 32768. Should I change it? If so what other values need adjusted along with it?

My timing is just above the middle line now, almost "dead on". It was way advanced (probably belt stretch) before causing my long start in cold conditions.

My timimg belt has about 60k on it now. The shop I used only worked on VW's and used all the 100k parts for the belt change and timed it in VCDS.
Why are you set at 6.4? Are you modded? If not, then a more "natural" number is around 3.0 to 5.0 (3-ish tends to be closer to what folks find work). Dropping from 6.4 to 3.0-ish is too great of a leap to do with VCDS. Yes, 32768 is the default value (IQ, not EGR)- I'd leave it set at that and hammer mod until you drop your IQ to around 3.0.

Timing set midway to upper line should be fine. No, belt stretch doesn't come into play to any real measurable degree: the TB tensioner will take it up; movement of your cam or IP gear, however, affect timing, and if those are properly tightened then the only real way for the belt to introduce timing differences is if it were to toss off a few teeth, which equals "BAD" (TB event).

Was the discovery of the timing being "way advanced" before or after the shop did the TB? I have found that advanced timing generally tends to help with cold starting.

I think you need to re-focus on the MAF. Low-hanging fruit. There are other things that can be checked if the MAF gets ruled out, but now's not the time to be leaping ahead of things.
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Old September 11th, 2017, 18:19   #8
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Why are you set at 6.4? Are you modded? If not, then a more "natural" number is around 3.0 to 5.0 (3-ish tends to be closer to what folks find work). Dropping from 6.4 to 3.0-ish is too great of a leap to do with VCDS. Yes, 32768 is the default value (IQ, not EGR)- I'd leave it set at that and hammer mod until you drop your IQ to around 3.0.

Timing set midway to upper line should be fine. No, belt stretch doesn't come into play to any real measurable degree: the TB tensioner will take it up; movement of your cam or IP gear, however, affect timing, and if those are properly tightened then the only real way for the belt to introduce timing differences is if it were to toss off a few teeth, which equals "BAD" (TB event).

Was the discovery of the timing being "way advanced" before or after the shop did the TB? I have found that advanced timing generally tends to help with cold starting.

I think you need to re-focus on the MAF. Low-hanging fruit. There are other things that can be checked if the MAF gets ruled out, but now's not the time to be leaping ahead of things.
I am not modded, for some reason it was not set at the default value of 32768 but 32645 which put me at 6.4

I went ahead and set the value back to default 32768 and the IQ dropped to 3.6 mg/str. This seems closer to the 3-ish you were suggesting.

My timing was never "way advanced" as I typed earlier. Must have had a brain fart and typed that. I had to go back and look at my previous post from January when it would hard start while cold and the timing was retarded.

So I looked at all the data again on VCDS when I got home while the car was still at operating temp.

In adaptation under channel 03 EGR, MAF (Specified) called for 280 mg/str and (Actual) was 435 mg/str
In measuring blocks group 10 Air System & Charge Pressure Control, the MAF (Actual) read the same 435 and then dropped to 270 which is within range. Not sure but it seems to be matching what is specified??

I did run it to redline and the highest number it went to was 490.

It did drive better today since I changed the IQ back to default.
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Old September 11th, 2017, 20:04   #9
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Good, making progress here! That IQ was clearly wrong. I'd leave it alone for now, but keep in mind that you can still drop it a little if desired (lowering usually gives you more fueling- lower it too much though and you'll get deceleration stumble).

If you run a log and capture your MAF readings when hitting redline in third gear you should see a minimum of 950. I mentioned running to redline in neutral to see if it could do it: it is something that I heard was one test- I have not verified this, but in theory it sounds correct as if the MAF isn't able to provide the sufficient readings then the ECU won't be able to command fueling sufficient to hit redline- that's my understanding. The TRUE test, however, because we don't sit around and run RPMs up in the driveway, is to see how actual on-road performance is. Best instructions for capturing performance info is available at Malone Tuning's web site (http://malonetuning.com/assets/files...ging_guide.pdf): they've got a neat new function (go to their home page) for generating graphs [though I like to see actual data, sometimes a picture can really make things pop out]
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Old September 11th, 2017, 21:15   #10
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Agree on seeing the actual data, a table is now listed below the graph as well
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Old September 12th, 2017, 18:17   #11
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Good, making progress here! That IQ was clearly wrong. I'd leave it alone for now, but keep in mind that you can still drop it a little if desired (lowering usually gives you more fueling- lower it too much though and you'll get deceleration stumble).
If you run a log and capture your MAF readings when hitting redline in third gear you should see a minimum of 950. I mentioned running to redline in neutral to see if it could do it: it is something that I heard was one test- I have not verified this, but in theory it sounds correct as if the MAF isn't able to provide the sufficient readings then the ECU won't be able to command fueling sufficient to hit redline- that's my understanding. The TRUE test, however, because we don't sit around and run RPMs up in the driveway, is to see how actual on-road performance is. Best instructions for capturing performance info is available at Malone Tuning's web site (http://malonetuning.com/assets/files...ging_guide.pdf): they've got a neat new function (go to their home page) for generating graphs [though I like to see actual data, sometimes a picture can really make things pop out]
https://log.malonetuning.com/chart/3...bCjQAAAA%3D%3D

I uploaded a log to malonetuning. Above is the link to view the results. I hope the link above works and can give some insight to what's going on with my car.
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Old September 12th, 2017, 20:33   #12
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The MAF seems fine, it's able to deliver what's being requested. Interesting, however, is that after 4k RPM, and it doesn't appear that you're dropping off the pedal quite yet, there's a rapid drop off in air. I don't know off the top of my head whether this is normal or not: don't have any old logs on-hand right now to look at. If this is in fact not proper then perhaps there's a restriction in your air intake pathway? How's the air filter? Snow screen, if you have one is it clogged?

At any rate, nothing here would seem to point toward a reason for your reduced FE (other than doing a lot of high RPM runs ).
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Old September 13th, 2017, 06:06   #13
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Quote:
Originally Posted by AZ98TDI View Post
https://log.malonetuning.com/chart/3...bCjQAAAA%3D%3D
I uploaded a log to malonetuning. Above is the link to view the results. I hope the link above works and can give some insight to what's going on with my car.
If it was me, I'd do the same tests you've already done, but include boost in the data. A good data log for the ALH is MAF, Inj Timing, and Boost, all together.

Is the check engine light on in this car?
Do you have any codes?

If I'm reading the graph correctly, your MAF specified looks normal at 850, but the actual numbers spike momentarily, and then drop off hard.

Before condemning the MAF, I'd want to see what the boost is doing at the same time.
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Old September 13th, 2017, 16:57   #14
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Rem, I looked at the data and things look good until just after 4k RPM and then the air just drops off a cliff even though the RPMs are still increasing (just before, what looks like, the OP let off the pedal). Under 4k RPMs I cannot see there being any issues, nothing that would suggest a big impact to FE.
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Old September 13th, 2017, 17:42   #15
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If it was me, I'd do the same tests you've already done, but include boost in the data. A good data log for the ALH is MAF, Inj Timing, and Boost, all together.
Is the check engine light on in this car?
Do you have any codes?
If I'm reading the graph correctly, your MAF specified looks normal at 850, but the actual numbers spike momentarily, and then drop off hard.
Before condemning the MAF, I'd want to see what the boost is doing at the same time.
Rembrant, I have no codes or CEL on the car.

I can run the log tomorrow but want to make sure I have the correct groups dialed in while in VCDS

MAF is Group 003 like before for EGR right?

Inj Timing, is it Group 004 "Start of injection" or Group 005 "Starting Conditions" ? or another group I'm not seeing?

Boost I'm guessing is Group 011 "Charge Pressure Control" ?

Also I removed my MAF insert today to inspect it and noticed that it had been replaced before by P.O. because it had a date code stamp of 04/06 and my car is a 2001 also I looked up the Bosch number on it (F00C 2G2 055) and came across a forum question about this part number being for a 130hp MAF and (F00 2G2 027) for a 110hp MAF. Do I have the right MAF installed in my car??

Thanks for your help and input.
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