[ashfleeburgooben]

Just wondering if there is a definitive test out there. I have a known good and a known bad that are passing all of the tests I've been able to find on the internet (voltage, 2 to 5g/s at idle in VCDS, etc)

I know it's good because I just bought a brand new one, and I know it's bad because the dealership told me it was. They mentioned they did a resistance test on it and it was supposed to be 2 ohms and it came out at 8 ohms. What test are they talking about?

Either way, car is still running like junk with either one in there.

 

[jfoj]

Unfortunately there is really no definitive MAF test that you can do with a Ohmmeter.

Some MAF's even read fine at idle and while under heavy load but under report the airflow at cruise.

There are MAF tests that you can run under WOT in 3rd gear and compensate for temp, altitude, barometric pressure, but even these do not flag all bad MAF's.

You need to look at a lot of different data points to really determine if the MAF is bad.

Also the false idea if you unplug the MAF and the engine runs better is not a test at all. This is normal, without the MAF input the ECU goes into a fail safe over rich mode to protect the engine, so unplugging the MAF enriches the air/fuel mixture.

Also MAF's get blamed all time for problems that they are rarely the culprit of.

So lets get to your problem at hand, describe what your problem is, your trouble codes and what you have done to resolve the issue(s) to date.

Do you have a scan tool that can read real time data?

 

[pencilneck]

Where did you source the new MAF from? If you didn't get it from the dealer, I would not trust it. If you got it from Auto-O-Pep box store... it is utter crap.

Provided the engine is mechanically good, do a test drive, full throttle in 2nd or 3rd gear. See what the peak grams per second reading is for the MAF. This numeric value should be about 80% of what the engine is rated in Horse Power.

The AEG engine is rated at 85kW @5200RPMs. This converts to 113.9 HP. 80% of 113.9 = 91.12. So provided the engine good, your peak Grams Per Second reading on a 2nd or 3rd gear pull should be around 91. Different things will effect this reading, but it should be in that ballpark.

This site might also be helpful in doing testing:

D-tips

Now having said all that... you state:

car is still running like junk

That doesn't give me any useful information. Can you elaborate? Does the car have poor throttle response? Does the engine sputter or back fire? Are there any fault codes? Is compression good? Does it have the correct spark plugs? Issues when hot, cold, up hill, down hill, wrong side of the tracks?

 

[jfoj]

Agree that you have to be careful where you purchase the MAF. There are a lot of counterfeit/China MAF's that look good but do not perform good. I ALWAYS suggest you keep your original MAF for troubleshooting purposes. I have seen drawn out problems where a MAF was replaced early on and then the problems do not clear up. I always suggest putting the original MAF back on and many times the problem was never the MAF, a crappy MAF was installed, other repairs were performed that resolved the issue, but until the original MAF was reinstalled the problem was not resolved.

I would say you can get good MAF's from other sources, but you do need to be careful.

Many of the cheap/counterfeit/China MAF's use thermistors rather than thin film platinum wire and they seem to read properly at idle and under hard throttle, however, for normal driving they tend to under report the airflow and cause the fuel trims to be way high and cause other problems with driveability and will likely trigger lean codes while cruising.

 

[ashfleeburgooben]

Thanks for your replies. I'll try to be detailed in my information.

All the problems began when I was idling the car for about 20 minutes while waiting for someone. The car was running fine when it very suddenly started shuddering, the tach started bouncing up and down, and after about 5 or 10 seconds the car died.

I left it for a moment and tried to restart it. It had no problems attempting to start but it would not turn over. After about an hour leaving it alone it finally started when I gave it another shot. I drove it directly to the dealership even though I have VCDS because I needed it done quick.

Dealership found:
1. P1128 Mixture too lean
2. P0301 Misfire Cylinder 1
3. P0302 Misfire Cylinder 2

This is what they did to the car.
1. Replace Ignition Coil
2. Replace Spark Plugs
3. Replace Spark Plug Wiring Set (They write carbon track and leaking spark)
4. Replace Fuel Filter
5. Clean Ground Wires (they write ground resistance too high)
6. Perform BG Induction Service

They wanted to do the MAF as well but didn't have it in stock and as I said I really needed the car quickly so I told them I had one I had purchased before that I would put on myself.

I got home and we had a storm that night so I didn't install the MAF that night. Drove the car around the next day with no issues for several hours when it started shuddering. I pulled off to the side of the road and the CEL came on. I turned it off and gave it a couple minutes. This time when I tried to start it I got nothing. The lights on the dashboard came on, but not a noise otherwise. After about an hour sitting there with occasional attempts to start it with the exact same results it finally just turned over. I drove it home and hooked up the VCDS and got these codes.

17663 - Engine Coolant Temp Sensor (G62): Short to Ground
P1255 - 35-10 - - - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 - -
16685 - Cylinder 1: Misfire Detected
P0301 - 35-00 - -
16946 - System Voltage: Too Low
P0562 - 35-00 - -
16686 - Cylinder 2: Misfire Detected
P0302 - 35-00 - -
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-10 - - - Intermittent
16685 - Cylinder 1: Misfire Detected
P0301 - 35-10 - - - Intermittent

Dealership tells me these could be from faulty MAF so I replace it yesterday with the new in box one. It was from NAPA but it is a Bosch and I didn't cheap out (it was still almost $200 for the part) so I hope it's a good one.

Sit in the car idling for about an hour and sure enough. Takes it a long time but the shaking starts, it dies. These are the codes it throws this time.

17663 - Engine Coolant Temp Sensor (G62): Short to Ground
P1255 - 35-10 - - - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-10 - - - Intermittent
16685 - Cylinder 1: Misfire Detected
P0301 - 35-10 - - - Intermittent
16946 - System Voltage: Too Low
P0562 - 35-10 - - - Intermittent
16686 - Cylinder 2: Misfire Detected
P0302 - 35-10 - - - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-10 - - - Intermittent
16685 - Cylinder 1: Misfire Detected
P0301 - 35-10 - - - Intermittent
16486 - Mass Air Flow Sensor (G70): Signal too Low
P0102 - 35-10 - - - Intermittent
16496 - Intake Air Temp. Sensor (G42): Signal too Low
P0112 - 35-10 - - - Intermittent

On a side note, the battery was dead yesterday when I went out to do the work and this morning even though he was running for several hours yesterday. Battery and charging system were tested by dealer as good, might have to recheck that myself.

I have VCDS-Lite, a Bentley Service Manual, and a Haynes Repair Manual. My own personal knowledge is just as a tinkerer though. Still have lots to learn.

Anyway, there are all the details. Sorry for the book. Just wanted to be thorough.

 

[red99]

The car was running fine when it very suddenly started shuddering, the tach started bouncing up and down, and after about 5 or 10 seconds the car died.

Engine speed sensor! These are known to fail by becoming intermittent. This provides the input to the tach as well as the ECU, so the tach bouncing is a dead giveaway. See the end of chapter 24 in the Bentley.

 

[red99]

16486 - Mass Air Flow Sensor (G70): Signal too Low
P0102 - 35-10 - - - Intermittent
16496 - Intake Air Temp. Sensor (G42): Signal too Low
P0112 - 35-10 - - - Intermittent

These are both part of the MAF sensor assembly and share the same 5-pin connector. Check to make sure that all the contacts in the connector are making good electrical connection. Look for any bent pins or contacts in the connectors.

 

[ashfleeburgooben]

I'm pretty sure these codes were triggered while I was testing the MAF according to these instructions.

Part 1 -MAF Sensor Test: Jetta, New Beetle (5 wire type).

I cleared the codes and they didn't return once I finished the testing. The connector should be tight and connected on the MAF.

These are both part of the MAF sensor assembly and share the same 5-pin connector. Check to make sure that all the contacts in the connector are making good electrical connection. Look for any bent pins or contacts in the connectors.

 

[red99]

What about all the misfire (P030x) codes? Do those continue to come back after clearing? Seems odd after the dealer replaced the plugs, coil and wires.

 

[ashfleeburgooben]

The misfire codes came back before I replaced the MAF (two days ago when it died while out driving), and after I replaced the MAF and cleared them but it died while sitting idling outside where I was working on the car.

So yes, they are coming back.

I should also clarify that the tach bouncing did correspond with the actions the car was taking when it was struggling to stay running. I'm going to check the engine speed sensor as well though anyway.

What about all the misfire (P030x) codes? Do those continue to come back after clearing? Seems odd after the dealer replaced the plugs, coil and wires.

 

[red99]

The speed sensor may test OK even if it is causing the problems. The failure can be intermittent where the sensor switches back and forth from totally normal to totally failed while the engine is running.

 

[jfoj]

What is the story on the fuel filter? How long has it been on the car?

Possible fuel pump going soft?

 

[ashfleeburgooben]

Well, it made it back to the dealer today and I just got a call that they say a cell died in the battery and it overtaxed the alternator and killed it too. They say they can do nothing until those are replaced to determine whether the codes being thrown aren't just errors due to the battery.

So my question. The car went in with a perfect battery and alternator last week where they performed this service.

--------------------

Complaint: Clean Ground Wires
Cause: Ground Resistance too high
Correction: Clean battery ground and ecm ground. Reinstall all component back and recheck operation ok.

--------------------

I should clarify I didn't actually ask for this service, it was something they recommended. I'm not saying it caused the issue, as of course they deny that possibility, I'm just wondering if it's possible this could have been the cause. In addition the car was in for an oil change and check up on Feb 21 where they tested the battery as good.

Really trying to avoid spending thousands of dollars on this poor old car but it sure looks like it's not going that way.

 

[billymade]

Any update or resolution to the ongoing issues with the car? I hope you got it fixed; would be interested, to hear what the problem ended up being!

 

[ashfleeburgooben]

Update! Sorry for taking so long on this. The bad news is that I never did get it figured out. It was to the point that there was really nothing left to replace other than the Catalytic Converter. I have no idea if that would have even helped but the car just kept throwing those same codes.

The really bad news is that the beetle just got too small for my work equipment and I ended up having to sell it anyway and bought a new larger SUV. I still miss it!

I'm already planning on buying another here next summer and having a new toy to play with.

Appreciate all the help on this one! It's somebody elses issue now though.