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Discussion Starter · #1 ·
Hi all, I have an issue that points to a dirty of bad MAF sensor. I took it off to clean it and remembered on other cars that you could test them using an ohm meter. The only problem I have is I can't find anything on what reading I should have and which of the pins on the MAF to use to check it. Any help would be appreciated.
 

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I a firm believer you CANNOT really test a MAF with a resistance test for many reasons.

You need to baseline the MAF in g/s at idle. If the value is low, you need to rule out vacuum leaks before you move forward.

Condemning a MAF is kind of black magic IMHO, you need a feel for it, but getting baseline data is a good start.
 

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I can always tell when my bug needs it's MAF cleaned. It takes an extra few cranks to start after driving and parking. MAF spray at Advance auto and let it air dry or light air blow dry
 

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Discussion Starter · #6 · (Edited)
A little back story to let you know why I want to test the MAF. With all the codes this car is throwing, the first thing I was told to check was for a vacuum leak. I went through all of them listed on the handy dandy vacuum chart under the hood and found nothing. I also found out that the oil cap and dipstick will be hard to remove if the vacuum is good. When I removed the dipstick, it came out hard and the car began to idle very rough. The MAF is the next thing on the list. I cleaned it yesterday. Of course, as often happens with older cars, another issue came up when the flex pipe on the exhaust busted off. Can't really test drive a car that loud in my town, so I'll deal with that next.
One more thing; when I clear the codes the car runs great for a while, usually a day or two. Then the codes come back and the car once again runs rough with no power.
 

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MAF's are rarely a problem and when they are it is usually pretty obvious for anyone that had any experience to flag a questionable MAF.

No disrespect, but here is the problem.

You claim you have a problem that points to a dirty/bad MAF, but you never bothered to provide supporting information or the history or the condition on the car.

I have never cleaned a MAF on any of my cars. They all still have original MAF's, some at 20 years old. Cleaning a MAF is HIGHLY over rated and rarely does anything or makes any change.

You looked over the vacuum lines, but this is NO WAY to find a vacuum leak. If you need to find a vacuum leak on most all vehicles the leaks are on the under side of the hoses or under the engine and hard to see. You cannot spray brake cleaner or carb cleaner to find most of these leaks, you need to smoke test the engine and crackcase.

You also need to provide ODBII codes, Freeze Frame and Fuel Trim info if you want any good advice. You are not going to do much with an Ohm meter and testing a MAF. We at a minimum need to see the MAF reading in g/s at warm idle, but this value alone is not a good way to condemn a MAF.

Also DO NOT buy a MAF from ebay or the local auto parts store. MAF's have Platinum in them and this is why they are very expensive, you will not likely get a sensor that works well for $50 or less. There are also a LOT of counterfeit Asian MAF's on the market and you have to be VERY careful where you buy your replacement MAF.
 

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Discussion Starter · #8 ·
Thanks jfoj. No offense taken. I will need to get more info. For what it's worth, this is probably a recurrence or continuation of issues I had last summer. Anyway, Once I deal with the flex pipe issue I can get back to it.
 

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The flex pipe problem can and will also cause air to leak into the exhaust and may impact the pre-cat O2 sensor the ability to properly register the air/fuel mixture and may trigger codes due to the air leaks.

Good luck, update once you get the flex pipe repaired. Often you can get a completer catalytic converter assembly with a new flex pipe for around the cost of the flex pipe replacement.

I recall there were some converters from a group out of Canada that were about $240 or so delivered as I recall.
 

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Discussion Starter · #11 ·
exhaust

Hi again. Finally had some time to get under the car to look closer at the exhaust. From the break in the flex pipe back to the union with the exhaust looks very good. From the union back through the first muffler is badly rusted. The second muffler (resonator?) looks good again. I'm considering replacing the whole system. RockAuto has Walker parts at decent prices. I have no experience with Walker. Any comments?
 

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See if you can find any decent pictures of the Walker parts.

I steered clear of the Walker down pipe and converter assembly because all of the pictures I found looks like the Walker has some sort of corrugated flex coupler rather than a mesh covered flex joint like the OEM part.

Look at ebay, I think I got my down pipe and converter assembly from a Canadian supplier for around $240 on my door step. The pipe I believe was stainless and I liked the converter and flex pipe.

See this thread - http://newbeetle.org/forums/1-8-liter-turbo/58904-marbles-can-resolved.html
 

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Discussion Starter · #13 ·
After further review

The Walker items I was looking at were the two muffler pieces. Their down pipe with converter didn't look the same as the OE. So I was not really thinking of that piece.
I was recently laid off so I have to reconsider my plan of total replacement. I spent an hour this morning testing every part of the bad section of muffler and found no holes, just a lot of rust flake.
Also, the more I think about it, the existing converter is OE and in good shape with no rattles or noises when you shake it. I think I'll go back to my flex pipe repair. At least then I can go back to fixing the original problem.
 

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Discussion Starter · #14 ·
O2 sensor question

While fixing the flex pipe, I looked at the O2 sensors on the cat. The upstream one was replaced about a year ago, but the back one has some frayed wiring and should be replaced. Does the engine code matter on this sensor? Any particular brand recommendations? Pricing on these seems to be all over the board.
 

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Search by correct engine code; get oem Bosch, exactly the same from VW factory. Get the "oe" version; not the "universal" version, oe will be the same as the original one. Look up your correct parts/02 sensor here: (best prices; typically amazon)

https://www.boschautoparts.com/en/auto
 

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Discussion Starter · #16 ·
Thanks for the link. I found my part number 16978 on Amazon with the description "OE Type Fitment". Their picture looks different than the same item at Autozone. Bosch wouldn't have the same part number on two different parts, would they? It's $30 cheaper on Amazon.
 

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If you want to know for sure; you could call Bosch tech support.

Bosch Technical support:

Contact Us
888 715 3616
8AM - 5PM CST MON-FRI

My theory; is this: lately, I am seeing Bosch parts attempting to simplify their product line and make their part cover MORE cars by designing parts to cover a wider range of applications (thus, the included extra connector/plug). This would reduce their manufacturing costs and eliminate making so many different parts; for different applications.

The example I have experienced lately; is their fuel pumps and elimination of separate fuel sending unit, now they are integrated. Their instructions; also related about a "extra" screen and that was integrated as well; thus, why I called their tech support. They explained everything to me and were very helpful!

In the case of the 02 sensor; they are including the extra connector/plug, so it can fit more cars. As for different pictures; it is possible, that Amazon may have a more up to date picture, than Autozone. There also; maybe, still some of the new old stock; still in the supply chain and make take some time to be sold, flushed out of the system.

The "universal" version of the 02 sensor; requires, that you splice in your old connector and do it that way. I would rather have a Bosch/oem factory assembled wiring harness with the full integrity of the wire. I believe this to be a superior solution; even, if it would require me, to remove the connector and add the correct factory style connector/plug (included in the kit). A little extra work but a better solution, than cutting and putting butt connectors on the harness.

To know what is the current production part and a full explanation; contact Bosch tech support. Please, if you call them; tell us what they say and their explanation of what is current, etc.
 

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The Bosch catalog should be correct assuming you looked up the part correctly.

Very often Amazon and even Auto Zone/Advance have the wrong pictures.

I would go by part number LONG before I would worry about pictures.

ECSTuning has a very good and accurate set of pictures for almost all of their applications.
 

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Discussion Starter · #19 ·
I bought the Bosch sensor and repaired the flex pipe. My wife has driven it for a bit and now instead of multiple codes, I'm down to a P0420 code. That kind of surprised me since the only things I did were to the exhaust and a new O2. Anyway, the little bit I've read on it shows it to be either the cat or an O2 sensor. One of the O2 sensors is new, the other one is about 20,000 miles old. Is there anything I should look for to figure out what is throwing the code?
 

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