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    1. 05-01-2008 06:19 PM #1
      I suspect that my MAF (Mass Airflow Sensor) is faulty. I've already cleaned it with alcohol, as discussed on these forums. Before I spend $280 on the part, I want to be sure that it is definitely the MAF. After reading up on this, it seems that the MAF and O2 sensor can have similar symptoms, so I thought I'd ask if anyone has any suggestions for testing the MAF.

      My symptoms are:
      - Occasionally the car has power loss/surge. It can happen while driving on the freeway, or after starting up. It typically lasts for a little while (1 minute). After that it usually goes away for a bit more.
      - If I let the car idle during a power-loss "moment", it idles very rough. It feels weak. If I give it a fair amount of gas, it'll get past the weak idle and rev normally.
      - It seems to happen more frequently on hot days, and when the engine is warmed-up. It's particularly common when the engine is already warm and I start the car.
      - When I first cleaned the MAF, I managed to stop the car right when the car had a power loss moment and unplug the MAF. To be honest, I can't tell for sure if it idled better not with the MAF unplugged.

      I have a Green (aftermarket) air filter. Not sure if aftermarket filters cause problems with the MAF. I just replaced the fuel pump. It was on its way out. Replacing the fuel pump seems to have reduced the frequency of the power loss problems.

      Any help appreciated!

      -Antun


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      05-01-2008 06:27 PM #2
      If your engine runs about the same with or without the MAF sensor plugged in, it doesn't sound like the MAF is the culprit. Usually, a bad MAF sensor will cause the engine to run rich at all times, not just occasionally or when the weather is hot.

      I'd vote that the problem is not your MAF sensor, especially since replacing your fuel pump seemed to improve matters. You might have a faulty coilpack - they are known to cause intermittent misfiring.

      Kenji

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      05-01-2008 06:51 PM #3
      if the maf is entirely dead you wouldnt notice a difference between having it plugged in and not plugged in. i dont think obd1 has the measuring blocks in vagcom to look at the maf flow, but i might be wrong. worth looking up to find out if thats an available option

    4. 05-01-2008 06:54 PM #4
      Hey Kenji,

      Actually, I've already replaced the coil pack less than a year ago. If it's broken already (unlikely) would that throw error codes I could look up?

      -Antun


    5. 05-01-2008 06:55 PM #5
      Hi crazysccrmd,

      What do you mean by this:

      > i dont think obd1 has the measuring blocks in vagcom to look at the maf flow

      -Antun


    6. Member ricardo's Avatar
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      05-01-2008 06:59 PM #6
      did you change the fuel filter?? hows your ISV muffler??? I removed mine (ISV muffler)and the idle became much more stable
      have you clean the throttle body?

      mine is still runnin rich....unplugging the MAF doenst make a difference in idle for me either... but I dont have the same simptoms...it just runs rich

      "Public transportation......because you're poor"
      done everything that's cheap....broke the most expensive parts....

      having cooling problems? check this out http://the-corrado.net/forum/viewtopic.php?f=1&t=68720

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      05-01-2008 06:59 PM #7
      Quote, originally posted by karlovac »
      Hi crazysccrmd,

      What do you mean by this:

      > i dont think obd1 has the measuring blocks in vagcom to look at the maf flow

      -Antun

      using vagcom (on a laptop) you can see what the ECU is doing and reading from the various sensors. OBD1 (95 and older) is limited on what can be viewed since the car's computer isnt as advanced as OBD2 (96 and up). i know that on OBD2 you can view the MAF sensor in terms of the GPH flow that it measures, but i dont remember if OBD1 can show that.

      measuring blocks are essentially the reference numbers used to view the various information available from the ECU when logging it


    8. 05-01-2008 07:11 PM #8
      Hey all,

      I just want to be clear on this: the rough idle/power loss/surge problem I have is intermittent. It's not like it *always* idles rough (although it always does seem to idle rich). The problem happens 1-2 times every time I drive my car (for around 20 mins).

      Is that something that's typical for MAF problems, or is that likely to be another problem?

      -Antun


    9. 05-02-2008 11:28 AM #9
      That's a good suggestion - I've never cleaned the throttle body on this car.

      -Antun

      Quote, originally posted by ricardo »

      have you clean the throttle body?

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      05-02-2008 11:32 AM #10
      Quote, originally posted by Dan J Reed »
      Step 1 - Throw antiquated worthless system tests in the Bentley boat anchor in the trash.

      You'll need:

      1 unfolded safety pin, 2 jumper wires, and a DVOM.

      Got them?

      Good.

      Lets begin.

      Looking from the FRONT of the car to the BACK of the car... there are 4 wires off the MAF.

      See them?

      Good, unhook the MAF the connector.

      Ground one side of your meter to the intake manifold.
      (NOTE IT WILL STAY GROUNDED FOR ALL THE TESTS IN THIS SECTION!)

      Take your safety pin and stick it into the FRONT of the MAF harness. Insert it into PIN 3.

      Turn the Ignition ON in the car. DO NOT START THE CAR, JUST TURN THE IGNITION ON!

      You should get 12 volts or higher. (Battery voltage). If not, check the ECU and harness wires back at the ECU. This is the 12 volts sent to the MAF from the ECU to power the MAF.

      TURN THE CAR OFF.
      ---
      Set the meter to read OHMS. LEAVE THE CAR OFF!

      Next, move the safety pin to pins 1 and 2. (do one at a time, same test…)

      These are the internal grounds for the sensor, power and signal. You should get LESS then 3-4 ohms on BOTH pins. If you get MORE then 3-4 ohms check the harness for breaks or opens, or the connector at the ECU for damage.
      ---
      Last test, Pin 4.

      MAF signal return to ECU.

      Remove your safety pin from the MAF sensor harness.

      Set the DVOM to read Volts DC again.

      Plug the MAF sensor back in.

      BACKPROBE the RED wire, PIN 4 on the MAF sensor. Use the safety pin to SLIDE the probe down the wire into the connector base. The point is NOT to break the wires insulation.

      START the CAR. Yes, RUN the CAR. Yes, with the safety pin JAMBED into the wire harness.

      Voltage at IDLE should be around .9 volts DC.

      Use this handy, dandy chart as a guide:

      Idle .9 volts.

      2000/3000 RPM 1.5 volts.

      3000/Wide Open = up to 3.8 volts.

      Note the speed at which the MAF can respond to the changes and airflow.

      If your MAF is slow, or lazy, or does not match these values. Good chance its bad.


      From dan53:


      I was unable to get a power voltage reading on pin 3 while testing my MAF at first, but then I did a little research and found that on later model OBDII cars that the engine must be running versus the ignition being just switched to On to get a power reading. This could have saved me about an hour if I knew this! Dan J Reed, I implore you to make a modification to your MAF DIY test and mention this to save someone else the trouble in the future.
      "


      Modified by Dan J Reed at 2:09 AM 11-2-2007

      Follow my Audi 100, (I mean MK1), (I mean MK3) build on Instagram. User name: jkrew or http://ink361.com/#/users/322773/photos

    11. 05-03-2008 06:25 PM #11
      Thanks for the instructions! Here's what my readings were:

      Idle: Constantly jumped between 1.2V - 1.5V
      2000 RPM: About 1.9V
      3000 RPM: About 2.05V
      4000 RPM: About 2.35V

      Taking the revs up to 3000, the reading seemed to rise fairly quickly.

      My values seem higher than those given in the instructions, but mine is a VR6 and the instructions show a 2.0 engine.

      Do these readings seem OK?

      I let the engine run for a while, but it didn't do its power loss thing during the test. The idle was rough though.

      -Antun


    12. 05-05-2008 01:39 PM #12
      Over the weekend, I tested the MAF, and got the readings I posted in the last post. They seem higher than those listed in the how-to article. Is that because my engine is different? Also, at idle, the voltage was never completely constant. It constantly jumped between 1.2 and 1.5 volts. Is that normal?

      I also pulled the bellow off the throttle body and blasted it with carb spray. I didn't completely remove the throttle body; I heard that on some newer cars it needs to be reset.

      I also cleaned and re-oiled my air filter, and ran some Sea Foam through the engine.

      The car runs a little smoother, but the idle is still rougher than normal. I drove it for 10 mins, but it didn't do its power-loss thing in that time. Given the rough idle, I don't think it's completely fixed.

      One thing that I'm considering replacing is the fuel pump relay. It's cheap, and it's one thing that is known to cause intermittent power loss problems. No way to test it, as far as I know.

      -Antun


    13. Member ricardo's Avatar
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      05-05-2008 09:20 PM #13
      nice diy... I might check it tomorrow and see what I get
      "Public transportation......because you're poor"
      done everything that's cheap....broke the most expensive parts....

      having cooling problems? check this out http://the-corrado.net/forum/viewtopic.php?f=1&t=68720

    14. Member kevwithoutacorrado's Avatar
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      05-06-2008 01:00 AM #14
      Mine won't start at all (and dies immediately if unplugged) if the maf is not plugged in...

      What's the mean? TPS? Coilpack is new-ish.

      OBD1

      Sorry if this is a hijack...


    15. 05-06-2008 05:02 PM #15
      Hey Ricardo,

      If you do try it, please post the readings you get. In particular, I'm curious as to how stable the voltage that the MAF outputs is at idle.

      I've done the DIY, I just don't know whether my values were normal.

      -Antun

      Quote, originally posted by ricardo »
      nice diy... I might check it tomorrow and see what I get

    16. 05-06-2008 07:01 PM #16
      Have a 95 Obd 1. Had exactly the same symptoms. Ran the car with the maf diconnected. Car ran a little rich but did not show the symptoms any more. Ordered a new maf, bingo! The car never did it again. Runs perfect for a year now!!!

    17. 05-06-2008 07:09 PM #17
      Hey Jim,

      Thanks for your reply. Were the power loss symptoms you had constant or intermittent?

      -Antun

      Quote, originally posted by Jim_vr6 »
      Have a 95 Obd 1. Had exactly the same symptoms.

    18. Member ricardo's Avatar
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      05-06-2008 07:42 PM #18
      Quote, originally posted by karlovac »
      Thanks for the instructions! Here's what my readings were:

      Idle: Constantly jumped between 1.2V - 1.5V
      2000 RPM: About 1.9V
      3000 RPM: About 2.05V
      4000 RPM: About 2.35V

      Taking the revs up to 3000, the reading seemed to rise fairly quickly.

      My values seem higher than those given in the instructions, but mine is a VR6 and the instructions show a 2.0 engine.

      Do these readings seem OK?

      I let the engine run for a while, but it didn't do its power loss thing during the test. The idle was rough though.

      -Antun

      idle .908-.917
      2000/3000 rpm 1.33-1.6
      3000/4000 rpm 1.7-2.2

      but readings of contacts with the ignition on (oops ) forget it
      #1 10 ohms
      #2 43.5 ohms





      Modified by ricardo at 4:49 PM 5-6-2008

      "Public transportation......because you're poor"
      done everything that's cheap....broke the most expensive parts....

      having cooling problems? check this out http://the-corrado.net/forum/viewtopic.php?f=1&t=68720

    19. 05-06-2008 07:56 PM #19
      Hey Ricardo,

      Thanks - yours is a VR6, right? If so, then I guess my MAF is bad, because the voltage is so erratic, and higher.

      -Antun


    20. Member ricardo's Avatar
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      05-07-2008 12:45 AM #20
      Quote, originally posted by karlovac »
      Hey Ricardo,

      Thanks - yours is a VR6, right? If so, then I guess my MAF is bad, because the voltage is so erratic, and higher.

      -Antun

      no problem, mine is a VR6 but it also runs rich..... we need reading of a good running VR and OBD1

      "Public transportation......because you're poor"
      done everything that's cheap....broke the most expensive parts....

      having cooling problems? check this out http://the-corrado.net/forum/viewtopic.php?f=1&t=68720

    21. 05-07-2008 01:15 AM #21
      Check your blue 2 wire temp sensor. Mine was bad on my VR6 and I had a few of your symptoms. Rich sort of roughish idle. The engine felt rich and ran sluggish at certian temps. Its a cheap and easy sensor to change. I dont have the info available online but theres an ohm test for it based on what temp its at.

    22. 05-08-2008 10:44 AM #22
      The problem was there more often when the temps were high outside. And yes, it was intermitent. Cleaned the s'''t out of it but with no positive results. Checked everything else before concluding it was the maf. I got mine the cheapest from MJM. Chech everything else before assuming it is the maf. I tis pretty pricey on a OBD 1. Hope this helps...

    23. 05-14-2008 11:06 PM #23
      Hey all,

      I received my new MAF today and took some voltage readings as soon as I installed it.

      1995 VR6 Brand New MAF Readings
      Idle: 0.86-0.89v
      2000rpm: 1.27v
      3000rpm: 1.55v
      4000rpm: 1.85v

      In all cases, the voltage was pretty stable and constant. It would fluctuate by 0.03v at idle, but pretty slowly.

      It seems to have fixed the problem. I drove the car and the revs seemed to drop significantly faster when returning to idle, and there was no power-loss or misfires during my test drive.

      One big catch: After testing the new MAF, I put the old one back in to verify the old readings. Today, it wasn't reading high, but would occasionally fluctuate between as low as 0.5v and just over 0.9v when idling. The new MAF definitely didn't do that. I'm not sure why it was reading so low this time around. The temperature and humidity today were much higher than when I last tested it. Maybe that was a factor.

      The idle's still a bit rougher than I think it should be, but I think that's probably because I haven't replaced the spark plugs in 2 years. My VR6 has always seemed to want annual spark plug replacements.

      It seems that my problem's fixed, but I want to drive the car a little more before I breathe easier.

      Thanks for all the help, for now!

      -Antun


      Modified by karlovac at 8:08 PM 5-14-2008


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