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Discussion Starter · #1 ·
My daughter has a 2001 New Beetle 2.0 and we have been having a serious issue with the check engine light.

The DTC originally thrown was a bad MAF sensor, or vacuum leak, yada yada.

The car sometimes starts losing power, shuddering and shaking where she has to pull over and wait a few minutes before she can start up and drive normally again.

The car has only 89k original miles and is in pristine mechanical and cosmetic condition.

I have replaced the MAF, replaced the MAF plug, all vacuum lines.... Everything except the air temp sensor, which I cannot seem to find anywhere since it is molded into the filter box to throttle body hose.
The entire throttle body and gasket has been replaced, wires and coil pack has been replaced as well as new filter, etc.

The car is due for registration and cannot pass smog here in California with the check engine light on.....

Has anyone had a problem like this? And if so, what did you did to fix it?
Anyone have any suggestions I missed? Besides move out of California?
 

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Start with a fresh scan for trouble codes; note, the codes and report back here, what they are (please post the codes and not just the descriptions of the codes). You, might also; clear the codes and try running the engine or do a quick around the block test drive, see what codes come back.

Also, what scan tool are you using and can it read live data?

As to the replaced parts; what brand maf, did you buy? Only oem Bosch MAFs; tend to work correctly, if you installed a cheap aftermarket version, reinstall the original VW/Bosch MAF and see, if this helps your problem.

NOTE: It is crucial, for ALL replacement parts; to be high quality oem parts and not typical aftermarket parts, that are sold at most local auto parts stores. A good portion of our troubleshooting discussions; are exacerbated by installation of poor quality aftermarket parts and correct diagnosis, installation of oem parts, for defective ones, will normally restore the car to proper functionality.

It sounds like you have a major issue; that is probably, causing the misfires, dying, no start problem and horrible drivability issues. Things, tend to narrow down to ignition or fuel delivery faults. Scan for codes and post them here; we can go from there. Thanks.
 

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Discussion Starter · #3 ·
Start with a fresh scan for trouble codes; note, the codes and report back here, what they are (please post the codes and not just the descriptions of the codes). You, might also; clear the codes and try running the engine or do a quick around the block test drive, see what codes come back.

Also, what scan tool are you using and can it read live data?

As to the replaced parts; what brand maf, did you buy? Only oem Bosch MAFs; tend to work correctly, if you installed a cheap aftermarket version, reinstall the original VW/Bosch MAF and see, if this helps your problem.

NOTE: It is crucial, for ALL replacement parts; to be high quality oem parts and not typical aftermarket parts, that are sold at most local auto parts stores. A good portion of our troubleshooting discussions; are exacerbated by installation of poor quality aftermarket parts and correct diagnosis, installation of oem parts, for defective ones, will normally restore the car to proper functionality.

It sounds like you have a major issue; that is probably, causing the misfires, dying, no start problem and horrible drivability issues. Things, tend to narrow down to ignition or fuel delivery faults. Scan for codes and post them here; we can go from there. Thanks.
I will do that today. I have a solid scan tooI that can read live data and even explain DTC'S and offer repair advice. I reset the codes every time I replace or fix something, but, It will pop back up within 50 miles. I believe this MAF is a cheap one. The third one we've bought. I will pickup a Bosch again today and see if it helps.
I've been reading in this forum and remember reading about a similar problem of loss of Power, etc., and it was suggested to try replacing the cam or crank Position sensor. Since I am out getting another MAF, should I pick one up as well? I mean, I've replaced damn near everything else, right?
 

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I would not replace a crank/engine speed sensor; unless, there is a associated trouble code with it, when they fail, a code is thrown.


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Here is a overview of maf testing; basically, you want to see the readings at idle and max at WOT, wide open throttle in second gear. If the readings are out of spec; then, the maf typically, needs replaced. Stick with oem Bosch mafs; as cheaper aftermarket versions, do not read correctly and cause drivability problems.

Look at the Ross Tech link about maf testing and review some videos on yiutube as well.


See, if your scan tool; can monitor the maf readings and then, you can try testing it, see if the readings are in spec. Report back your readings and we can discuss things further, go from there.
 

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Here is a thread; where we discussed maf testing and a value range that would be “normal”.


Quoting Ross Tech:

"Assuming, this test is done at or near sea-level, the peak output of the sensor in g/s should be roughly 80% of the rated horsepower of the engine."

So, the normal 2.0L is rated @ 117 HP and 80% would need to be calculated to get a idea of what the peak output of the MAF sensor, should be.

117 X .80 = 93.6

horsepower X 80% = 93.6 grams per second maf max reading: for a 117 HP 2.0L 8V engine.

So, you would be looking for roughly 93.6 g/s. with some slight variation, taking into consideration your current elevation, of where you live and the car is tested at.
 

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VW scan tools and service manuals; typically use the metic system, based specs and so, you would need to covert your standard readings, to compare to metric. (pounds to grams)

Example:

Pounds Per Minute (lbm/min) to

Grams Per Second (g/s)



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Discussion Starter · #11 ·
Ok. After I read your post, I freaked out because at those calculations, I was WAAAAY off.
So. Replaced the MAF and it now reads 0.76 lbs/min (5.745 gms/sec) at idle. It also is idling very smoothly and maintaining 785 rpm. As far as throttling wide open in second gear? I didn't do that. I wasn't sure if I understood you right. But WOT in park pulled 5.5 lbs/min (41.573 gms/sec). This isn't near the 91 You mentioned above, but, I may not be doing it right.

But, at any rate, it is running smoother, so, we are on the right track.
 

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The Wide Open Throttle “WOT” in 2nd gear; is when you are driving, this makes the maximum airflow the engine is capable of. Then, as you do this, look at the maf live data reading, in your app; you can have a helper view the data or if by yourself, try to position your phone so you can do both at once safely. I tend to do this while on some safe deserted back roads, a big empty parking lot or à highway on-ramp, etc.

A safer way, would be to do a graphing recording and view it; after you do the wot tests and see what the readings are.

After multiple pulls; you should get a general idea of the average max maf reading. The readings at idle is good to know but a out of spec or erratic max airflow reading seems, be the typical indicator, of a dying maf sensor.

Another thing that i have found; the 2.0L responds well to, is a throttle body clean and alignment procedure.


By the way; what brand maf did you buy? Hopefully, a high quality oem Bosch part!
 

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Discussion Starter · #13 ·
I paid for the Bosch. $148.00 . :sick::sick::ROFLMAO:

I will take it out and do the WOT test tomorrow. It is already past midnight here.

And I think I am actually below sea level here... I'm about 80 miles east of San Francisco in a freaking bowl. So it shouldn't be a problem with the readings. So far, no Check Engine light. All day. Hopefully this fixed the issue.

The throttle body is brand new. Did that and the alignment about 2 months ago and the car has been sitting..

Fuel pump was replaced at the same time....as well as the coil pack, wires and plugs. NGK triple point plugs? I think that is what they are called. And the plug to the MAF is brand new.

I don't have a Vag reader or a system on my laptop. I do have an OBD reader that will graph live data though. I actually have a VagCom cable for a laptop I've never used, though!
 

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Discussion Starter · #15 · (Edited)
I bought it through the Ross Tech link about a year ago. I'm a Nissan guy, so, I bought the Nissan tuning program from...... Jeez..... I can't remember, but, I'm sure you know the one I'm thinking of. Never used it because the wife wrecked my Maxima. I've built another, and am still working on the finer details. Not going on the street until I'm satisfied this time....and SHE ain't driving it!

I'm from Modesto, btw...

On to the good stuff..

Took it out a little while ago. Warmed it up then did the WOT test.

.76 lbs/min (5.7455 gms/sec) is the idle
14.2 lbs/min (107.3502 gms/sec) in second gear and 6600 rpm.

Don't know if having my 6'-3" son in the passenger seat matters to load, but, with my 240 lbs and his 200 lbs, this car got a little pep to it!:ROFLMAO::LOL::ROFLMAO:

Trying to upload a pic of the graph, but, evidently my phone hasn't enough memory. 8 GB of ram in my phone is more than I have on my laptop...lmao.
I will try with my tablet..

Are we getting close to what I'm supposed to have here?

And thanks, Billy. You are really good at being quick to respond and have been very helpful....

EDIT: Nistune is the program.....had to look it up...lol
 

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Yes, based upon your readings; you are in range and a bit better, possibly because of your altitude.

If one wants to get nerdy and a more accurate spec, of a estimate of your engines maf reading , you can use a

VOLUMETRIC EFFICIENCY CALCULATOR:


Based upon the rough ross tech calculation; i would say your readings are excellent and very good! :)
 

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Discussion Starter · #18 ·
According to the calculator for volumetric efficiency, I'm at 86%.

It says 75%-90% is great, I guess I'm alright then...😆

But I have seen this car work great, everything be running fine and smooth...then ...BAM!... Engine light on, problems.

Keep your fingers crossed. If it pops up again, I shall return!
 

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Good work, you have good maf reading then and now you have a more accurate spec to compare to. :)

Report back and give us situation report; whether good or if a issue pops back up. Thanks.


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