EGR del and CEL, new quick fix

[milehighassassin]

Can you just block off the exaust side at the manifold and make a plate with a filter on the egr side to pull in fresh air whenever the egr opens? This way the maf is still reading the difference in air quantity as it would with the egr intact (hence no cel), when really you are getting more air and no exhaust.
Maybe a hose from the egr to the air box or have a seperate filter on the end.

I thought about that, but the problem is that the intake is being pressurized by the turbo. The EGR opens up and dirty air is pushed in by the exhaust. Putting a filter on it would just create a boost leak.

 

[chinook]

forgive my ignorance but a scan tool would be neccessary for MAF rotation mod , don't have one , also
my motor is 1.9 liter ,you talk about 2.0 gas ?

 

[NarfBLAST]

forgive my ignorance but a scan tool would be neccessary for MAF rotation mod , don't have one , also
my motor is 1.9 liter ,you talk about 2.0 gas ?

Scan tool is recommended... you could just rotate a little and "take a shot in the dark". Still, you need something to clear the code at least.

The motor is a 1.9L ALH TDI... The references are to the 2.0GAS MAF specific VW part intended for the 2.0GAS motor of the same year 2001 which at one time was $80 at the VW dealer vs. $500 for the 1.9TDI MAF so that is why I have one .

I would swap in the working TDI MAF I have but this system is still working so perfectly and the fuel economy has never been better so I don't want to mess with it.

Shagin'wagen has his TDI MAF twisted, thanks shagin for trying this mod and posting the results!

Anyone else done the MAF twist? Please let us know!

 

[NarfBLAST]

Twist causes increased MAF reading at WOT!!!

Did some testing with my TDI MAF (the one on the right in the pictures) and will post some new graphs...

I had trimmed a bunch of plastic off the MAF element around the screw holes because I wanted to see what a small degree of rotation would do... this caused the grams/second numbers to go from 17g/s straight on at idle to 24g/s with a little twist and I had to twist further before it came down to 11g/s... I guess this has something to do with air speeding up as it flows over a wing? Also I was turning counter clockwise, I forgot to try the other way, but it was cold and dark.

The strangest thing I found was that the g/s reported by Scangauge sometimes went thru the roof of 125g/s up to 140g/s if you notice in the graph the MAF actual reads higher after being twisted!

Conclusion: this is non linear, but GOOD behaviour! MAF readings get reduced at idle and increased at 100% throttle... could not ask for anything better if you ask me.

 

[5DOTRZ]

NerfBlast,
I was wondering why go through the blocking of egr when just unplugging the vac line from egr and plugging the line? This would do the same thing. Also very interesting results you have posted here. I was also wondering why you get a code for excessive egr flow when there is no flow? It really should be a code for insuficient flow, shouldn't it? (just wondering out loud on that one)
I really have to get a VAG-COM.

 

[shagin'wagen]

NerfBlast,
I was wondering why go through the blocking of egr when just unplugging the vac line from egr and plugging the line? This would do the same thing. Also very interesting results you have posted here. I was also wondering why you get a code for excessive egr flow when there is no flow? It really should be a code for insuficient flow, shouldn't it? (just wondering out loud on that one)
I really have to get a VAG-COM.

I can answer that. Because if you did, you would get a CEL. Sure the EGR wouldn't work, but you get a CEL. The code is not a 'excessive flow' code, it is a 'EGR divergence' code.

Also, I had to 'over shoot' the twisting a bit on mine. When you are twisting the MAF and reading block 3, you need to have the 'actual' reading a bit lower than requested. When the weather got cold here, I got a CEL. and the only thing that I could think of that is causing it is that cold air is more dense and it causes the 'actual' reading to be too high. I adjusted mine so it is about 20 or so lower than requested. So far, no CEL.

 

[NarfBLAST]

NerfBlast,
I was wondering why go through the blocking of egr when just unplugging the vac line from egr and plugging the line? This would do the same thing. Also very interesting results you have posted here. I was also wondering why you get a code for excessive egr flow when there is no flow? It really should be a code for insuficient flow, shouldn't it? (just wondering out loud on that one)
I really have to get a VAG-COM.

Yes you can unplug the vac line or disable the EGR system any way you like, that is not what the MAF twist is about.

The MAF twist mod is what you do after you realize that your EGR delete causes the check engine light to come on. The most common way to stop the CEL is with a chip tune. This is an alternative.

You get a code for excessive flow because the computer sees more flow at the MAF than it expects. There is no sesnor to read EGR flow. The only way for the computer to calculate EGR flow is to check its affect on flow past the MAF. When the EGR valve opens exhaust gasses flow into the intake manifold, these gasses take the place of fresh air that would have come from the airbox. The result is a drop in MAF reading. When the EGR is blocked off (or the vac line is pulled) the computer still sends a signal to open the valve: when the valve does not open there is no coresponding drop in MAF reading and eventually the computer posts an error message:

P0402: EGR System Excessive flow (detected at the MAF sensor)

Its misleading.

 

[NarfBLAST]

Shagin'wagen, what exact code are you getting?

That is interesting that you had to readjust your MAF... With my scangauge on the dashboard I found that the readings at idle didn't change when it got cold... always within 1g/s of the target 11.1 g/s except when the engine is very cold. Haven't got the P0402 back yet.

 

[shagin'wagen]

Shagin'wagen, what exact code are you getting?

That is interesting that you had to readjust your MAF... With my scangauge on the dashboard I found that the readings at idle didn't change when it got cold... always within 1g/s of the target 11.1 g/s except when the engine is very cold. Haven't got the P0402 back yet.

Yeah, just had too tweek it a tad more counter clockwise. As for the exact code, I don't remember. But I do remember it saying 'EGR divergence' or something of the like. My numbers swing quite wildly when reading block 3. It varies around 30 or so, + or -.

 

[5DOTRZ]

Yes you can unplug the vac line or disable the EGR system any way you like, that is not what the MAF twist is about.

The MAF twist mod is what you do after you realize that your EGR delete causes the check engine light to come on. The most common way to stop the CEL is with a chip tune. This is an alternative.

You get a code for excessive flow because the computer sees more flow at the MAF than it expects. There is no sesnor to read EGR flow. The only way for the computer to calculate EGR flow is to check its affect on flow past the MAF. When the EGR valve opens exhaust gasses flow into the intake manifold, these gasses take the place of fresh air that would have come from the airbox. The result is a drop in MAF reading. When the EGR is blocked off (or the vac line is pulled) the computer still sends a signal to open the valve: when the valve does not open there is no coresponding drop in MAF reading and eventually the computer posts an error message:

P0402: EGR System Excessive flow (detected at the MAF sensor)

Its misleading.

Ahh, yes I see why the excessive flow code. I was thinking in terms of a system which actually looks at the flow of exhaust gas. Have you noticed any drop or perceptive change in fuel economy without EGR operating before the MAF twist? And if not, did you after the twist?

 

[NarfBLAST]

I am pretty sure the MAF twist makes do difference in fuel economy either way.

It would be really interesting to replace my broken EGR valve and untwist my MAF but I just don't feel like spending money to fix the system that clogged my intake once allready.

 

[shagin'wagen]

I noticed no decrease in mileage. Maybe even an improvement, as there is more oxygen in the cylinder, so the fuel burns quicker and cleaner. But that's just my guess.

 

[5DOTRZ]

I noticed no decrease in mileage. Maybe even an improvement, as there is more oxygen in the cylinder, so the fuel burns quicker and cleaner. But that's just my guess.

Thanks for the input shagin'wagen.

 

[5DOTRZ]

I am pretty sure the MAF twist makes do difference in fuel economy either way.

It would be really interesting to replace my broken EGR valve and untwist my MAF but I just don't feel like spending money to fix the system that clogged my intake once allready.

Unfortunately I have the new style MAF sensor so I guess I will put up with the check engine light and just check the code every once in a while in case something else should arise.

 

[Tom109]

I find it interesting that you get a P0402 code.

After cleaning the intake, I did a little testing with the EGR blocked-off, and got an intermitent P0401 code = EGR Flow Insufficient. I don't see how this would be any different from an EGR delete...


Tom

 

[NarfBLAST]

I find it interesting that you get a P0402 code.

After cleaning the intake, I did a little testing with the EGR blocked-off, and got an intermitent P0401 code = EGR Flow Insufficient. I don't see how this would be any different from an EGR delete...


Tom

That is weird. Would be interesting to see the MAF requested vs Actual.

 

[FLMan]

Thanks Narf, I read this months ago, with NYS inspection coming up in March, I want to be ready. Well, this did the trick, so much for the Epsilon device days. Now I have an air bag sensor fault in the rear passenger side, Oh well, another forum for that problem.

This technique shoud definately become a sticky, TDI owners have been trying to solve the CEL with EGR delete for years.

PS, I should change my avitar now

 

[Dieselgeek]

I have just performed this adjustment to a stock 03 Jetta wagon with the EGR blocked off. The MAF on this car is a perfectly functional old style unit. Before I turned the MAF element counter clockwise I saw that specified and actual MAF readings were approximately the same at idle with the EGR duty cycle at about 5% (~260MG/stroke) but actual jumped up to ~460 MG/stroke when the throttle was blipped. I decided to "set" the MAF element when EGR duty cycle was high (EGR turned on). The screw holes for the MAF element are slightly obscured with this setting. I went on three test runs and checked for EGR codes each time and saw none. Power seemed the same as before the adjustment.

Will report back later with more miles driven.

 

[NarfBLAST]

The screw holes for the MAF element are slightly obscured with this setting. I went on three test runs and checked for EGR codes each time and saw none. Power seemed the same as before the adjustment.

Will report back later with more miles driven.

Awesome! Yes, some trimming may be necessary to get the screws back in... I used a file to remove just enough material to get the screws back in. What did you do in the mean time?

Glad to have you on the official test team with me, Shagin'wagen and FLMan! I wonder if anyone else has tried this but are not a member yet or have not posted? I really want to get as much feedback as possible.

 

[Dieselgeek]

The car I am tested this on has been out of commision for a while and isn't inspected or currently registered so I have not permanently modded the MAF for the twist. The element stays in just fine with the element o-ring's tight fit. Will try to get more cars to test the twist.

 

[shagin'wagen]

Well, it's been well over 15 000Km since I have done mine, and aside from turning it a tad more when the weather turned cold, and when my air box filled completely full of snow; I have not had a CEL yet.

 

[tdi4kev]

Another twisted TDI

Well, I just twisted my MAF, got specified/actual readings close to the same at idle. No driveability problems and it actually reads the same or slightly higher at WOT. Going on a 2k roadtrip starting tomorrow, will let you know how it runs.

BTW: I'm still running my original '03 MAF sensor, I seem to recall some discussion of early/late, Bosch, 2.slow, etc. Anyway, that's my setup.

 

[Turbospool]

Narf, I have deleted my EGR valve and blocked off /installed with DG racepipe, then blocked off the hoses...... and to my surprise never got a cell on my 2001 TDI Jetta. I have scanguage II , and plugged in the same settings on xguage as I believe you did. TXT 686af10110, RXF 044145100000, RXD 2810, MTH 000100010000. With the car at idle and warm I read .69 on the new guage, then in 3rd gear at 3000 rmps I read 7.04. Now I simply don't know what these numbers indicate, and if my MAF is really working or not? Can you help me?

 

[NarfBLAST]

MAF xGauge

plugged in the same settings on xguage as I believe you did.
TXT 686af10110,
RXF 044145100000,
RXD 2810,
MTH 000100010000.
With the car at idle and warm I read .69 on the new guage, then in 3rd gear at 3000 rmps I read 7.04. Now I simply don't know what these numbers indicate, and if my MAF is really working or not? Can you help me?

Thanks for posting... Looks like you have all the same values right, but its almost like your readings are one decimal place off as on a stock engine the readings should range from 6.9 grams per second to over 80 grams per second. Could you triple check the numbers you have entered? Especially math should be 0001 (multiply by 1) 0001 (divide by 1) 0000 (add zero).

Otherwise I guess your MAF could just be reading extremely low? How is the car runing anyway, you say you have no check engine light and no codes being reported... so the MAF reading extremely low actually does not make sense because that would have caused a CEL for sure. The easiest explanation is the coding of the xGuage. You haven't had the ECU programming modified?

TXD 686AF10110 ;reads OBDII MAF
RXF 044145100000 ;the number 4 in the 5th position gives you two decimal
RXD 2810 ;specifies scangauge to read 2bytes (0 to 655.35)
MTH 000100010000 ; math is simple, multiply by 1, divide by 1, no adder

idling with egr operating (no vag-com egr adaptation) ~230mg/R @ 900rpm = ~6.9g/s
idling with egr operating (with vag-com egr adaptation) ~370mg/R @ 900rpm = ~11.1g/s
3rd gear accelerating wot >800mg/R @ 3000rpm = >80.0g/s

 

[Turbospool]

Thanks Narf, I'll have to do a triple check on the numbers because I had double checked???? I'tll be a few days however, since the car is down for a nozzel upgrade (Sprints 520's). Once I get the car back I'll check and post again. Yeah , the car seems to run great since I removed the EGR valve, good power, great milage (mid 50's) I had bought the car used with 120k on it, so I don't know if any reprograming was done, i was told the car was stock by the dealer , but who knows .

 

[NarfBLAST]

Sorry for having to request a triple check, the math is the most logical explanation... actually I was thinking about the math and it is actually in hexadecimal (base 16) so if you move the decimal place one place over it may divide the reading by 16... So if you take .69 to 7.04 multiplied by 16 it would be 11 to 112 g/s which is very close to what mine reads! I highly suspect this what is going on.

Also, an update: after doing some reading I turned my EGR adaptation back to stock for better fuel economy about a week ago and I still haven't gotten a CEL without re-adjusting the MAF Twist from the "reduced EGR adaptation" setting.

 

[shagin'wagen]

Also, an update: after doing some reading I turned my EGR adaptation back to stock for better fuel economy about a week ago and I still haven't gotten a CEL without re-adjusting the MAF Twist from the "reduced EGR adaptation" setting.

how does the stock EGR setting improve mileage? I might just put the setting back to stock to see if mileage improves, but I don't know the stock setting, as I changed it to the lowest possible one. What is the stock setting?

I also have been CEL free since I did the mod, except my MAF sensor has died in the meantime, but I think that it was already on its last legs because when I bought the car it had a K&N air filter on it, and a while ago my air box filled full of snow. I have a new MAF on order.

 

[NarfBLAST]

Re EGR adaptation affects timing/mpg: Anyone reactivate EGR for better mpg?

Sorry about your luck, Shagin, when your MAF died what was the indication? Shouldn't your car have stock snow screen in the snorkel? Were you using the air filter with the snow screen built in?

edit: re-read your post there and I picked up on the K&N reference... also, these MAFs all seem to go some time, at least the prices are better than ever, right?

 

[shagin'wagen]

Re EGR adaptation affects timing/mpg: Anyone reactivate EGR for better mpg?

Sorry about your luck, Shagin, when your MAF died what was the indication? Shouldn't your car have stock snow screen in the snorkel? Were you using the air filter with the snow screen built in?

edit: re-read your post there and I picked up on the K&N reference... also, these MAFs all seem to go some time, at least the prices are better than ever, right?

Thanks. First it was something along the line of "Implausible MAF signal" then in a brilliant brain fart, I tried to clean it with methanol. Well that made it worse. Now I get "MAF open or short to ground" *Sigh*
I know that the oiled filters kill MAFs, that is why I ditched it immediately after I bought my car. When I bought it, it had a cool air intake on it. I now have a stock airbox that has the piece of snorkel that ends right behind the headlight. I know that it is not all of the snorkel, that is why it filled with snow. I need to find the rest, but I had no luck. It now has a paper filter in it with the snow screen built in, but that don't help when the whole box fills full. I think the snow filled box is what finally killed the MAF, because a few weeks later, it finally gave up.
Just to make sure that the wiring is not bad, what do I have to measure with a multimeter on the plug? I know I read something somewhere on it before, I just can't remember where it was.

 

[NarfBLAST]

Cleaning will sometimes kill a MAF... I would not worry about the wiring harness, haven't heard of these failing, not sure what you should measure but here is some info on what pins do what, and other MAF tidbits including another way to get rid of the EGR CEL (under Temporary EGR fix): http://www.geocities.com/tech4tdi/