Air flow meter questions


jrm

New member
I am looking for another opinion, I have 3 from 3 different mech's. My 77 westy will only idile and run when the harness is disconnected from the air flow meter. And it runs rough. I thought the meter was bad but have recommendation that it is a fuelpump? one that says it is the control module? and one says it is a relay? Anyone have a guess from experience. I live in a remote mtn location with out much VW experience within 100 miles.

Thanks in advance
 

Capt. Mike

Moderator
Since checking out the FI system is so easy, do it yourself! The shop manual devotes an entire chapter, Section 10, to the late Type II FI system. On my pics site (link from home page), there is an FI troubleshooting chart in the technical diagrams folder.

All of these tests are with a simple volt-ohmmeter. The most difficult part is having 3 hands to hold the two test leads and the harness plug at the same time! A six-pack will usually recruit the necessary assistant.

You can check out the fuel pump as described in Section 10-4.1 but don't forget the possibility of the fuel pressure regulator 10-4.4.

The control module is tested via that troubleshooting chart, but is broken down into sections in detail in the shop manual. The intake air sensor is but one area that would give your symptom.

Relay testing is per 10-4.1.
 

ben

New member
Good day,
I have bought a few expensive Westy part like
Idle stab., Oxygen sensor, 2 Wiring Harness (Vanagon Syndrom), and 1 fuel pump. All are functional and i paid $170 CAD!!! for the lots. The garage as also a Air flow meter box for sell for ($100 CAD), should i buy it?, is the Air flow meter a known problem?
Regards, Ben
 

Capt. Mike

Moderator
Infopop error deleted problem description part of post.

My conclusion is that the internal connections in the Intake Air Sensor,PN 025 906 301, had opened up and no intake air temperature or air flow information was being set to the Control Unit. I checked the connections with an ohmeter per Bently 24.41 and schematic drawing 97.61.

I first thought tht the fuel or air flters had become clogged. I had already bought the filters from Bus Depot as I was planning to change them. The old filters had been in for about 25k miles. I changed the filter between the tank and fuel pump, PN 133 133 511, and the after pump filter, PN 71028. Blowing the fuel out of the old filters disturbed some black dirt. The filters were not plugged. I then changed the air filter element, PN 021 129 620. I finally figured out that I had to remove the 4pin air flow electrical connector, disconnect the hose crossing over the Intake Air Sensor and the hose connected to the top of the Air Filter Housing. Then by unscrewing the clamp around the plug at the output of the Air Sensor and releasing the five clamps holding the upper and lower Air Filter Housing together, I could seperate the upper and lower half's of the Housing to remove and replace the new Air Filter Element. See Bently 24.27. The old filter element was midly dirty. I was somewhat confused, rading the Betly; then I found that the water cooled 1985 was called a Digijet!

None of the above seemed to fix the problem so next I changed the Spark Plugs to BOSH W7CC0, recommended for California Models, with a gap of 0.028 in. The old plugs had eroded to a gap of 0.040 in. The plugs were last replaced aout 20k miles ago. The color of most of the electrodes were golden brown, indicating that they had been working at optimum temperatures; but on the electrode faces there were black patches, indicating that they had been recently operting at a lower temperatures.

Since none of this work fixed the problem I then checked;where I should have started in the first place; the Control Unit input cable with a volt/ohmmeter as shown in Bently 24.20 and 24.21. The Control Unit Box is shown on Bently 24.3. I located it on the aft left corner of the engine compartment,housed in an aluminum frame. To unplug the connector; with a broad bladed screwdriver, I pried up the snap spring on the top of the plug and at the same time pulled the top of the connector away from the Control Unit. The lower end of the connector was held fast by a pin across the plug opening behind a tang on the cable connector. When the cable connector was tilted past 45 degrees the tang on the lower end of the connector came free and I could remove it. I then swung the connector so the exposed pins were horizotal. This position was backwards from that shown in Bently 24.20 and 24.21, with the tang to the left, not the right. I made a sketch of the connector pins to avoid confusion while I was checking it against the table shown on the two pages. I then proceeded to check the voltages and resistances called out on 24.20 and 24.21. Everything checked out except that three of the injector connections was about 27 ohms. I may be able to fix this by cleaning the injector connections; the resistance between pins 6 and 19 and between 14 and 6 was an open circuit! This indicated that the Control Unit was not getting the Intake Air Temperature or Air Flow Informtion. I then checked the Intake Air Sensor resistance's as shown on page 24.28 and schemtic drawing 97.61, proving tht the flow and temperature resistors were open!

Has anyone experenced this type of failure?
What caused it?
Should I get a re-manufactured or new Air Flow sensor? Which is more reliable?
I probably will have to readjust the Idel Speed/CO adjustmets after replacing the Sensor?

lono
ben Member # 671 posted 08-13-2001 12:58 AM

Do you have the right fuel pressure?, most Vanagon "low power" related problem are mostly due to bad sensor/connector contact. Check every one of those fuel injection connector, simply unplug / plug every one of those (Fuel injector, air flow meter, temperature sensor, idle stab., fuel relay, Oxygen sensor&#8230
icon_wink.gif
also check continuity between the computer and the connector.
Regards, Ben

lono Member # 148 posted 08-23-2001 12:54 PM

Thank you, Ben for your input. I also found that the spark plug connectors had high resistance on my 1985 Vanagon.
 

Capt. Mike

Moderator
Transferred from other posts to consolidate similar topics.

Loss of power

Bjazz Junior Member # 76 posted 06-06-2000 09:26 PM

'84 Westy with new engine 25k miles ago. Had major tune-up which included a new O2 Sensor ($387). Departed Oregon via Spokane to Lookout Pass. Headed up the pass we lost power, jerky. Downshifted but it just got worse and blew carbon. Foolishly pushed her over the pass in 1st and 2nd. Shut her off and rested. Started up and she ran well for 4-5 minutes. I decided to turn her off and back on while moving and she ran well for the same 4-5 minutes. Kept this up till I found a dealer in Fargo. They said I needed a harness with a capacitor added to the O2 Sensor. Got one in St. Paul ($150) (they made the same recommendation) No change. I did the "re-boots" all the way back to NH. I probably need a new Cat Conv now. I called the garage that did the work in Portland and they said to clean all the FI grounds. If I can figure them out I will clean them.
Meanwhile, does anyone else have any ideas.

Thanks,

Bill

Capt. Mike Moderator Member # 11 posted 06-25-2000 08:09 AM

Your symptoms are almost identical to the Vanagon Syndrome, although that particular problem is not applicable to Digijet FI systems. However, the cause can be!
See the Vanagon Syndrome post under TIPS Forum to get an understanding of the problem. In the Digifant system case Poor signal caused the air-flow meter to flutter wildly and create baulky driving.

However the older systems have the same design. A signal from the FI brain moves the air-flow meter. If the signal is defective, it breaks down the regulated flow of air. Or if the air-flow meter is defective, it breaks down as well.

See your Bentley shop manual to test the FI brain signals and the air-flow meter.

Bjazz Junior Member # 76 posted 06-25-2000 10:22 PM

Thanks. I should be able to attack it during the next couple of weeks. I appreciate your help.

Regards, Bill

In preparation of following your suggestion I have been reading Bentley's repair manual. I know that I am new to the Westy but I can not find anything referred to as the Air Flow Meter as such. There is the intake air sensor box, the aux air regulator but no air flow meter. What am I missing?

Thanks,

Bill

Capt. Mike Moderator Member # 11 posted 06-27-2000 11:15 PM

Sorry, I'm guilty of using a generic or street name for the part the resides on top of your air cleaner. VW calls it the intake air sensor. Photo 24.27, checking page 24.28.
 

Capt. Mike

Moderator
Transferred to consolidate same topic.

scottjk Member posted April 01, 2003 08:55 PM

I unfortunately bought an 85 Westy that had the air flow meter box opened and tampered with. Since then I have put in a new motor, o2 sensor and catalytic converter. I have heard from various sources that it it nearly impossible to calibrate the flow meter.

Is there any way to properly adjust the spring tension inside the box? One mechanic told me to just buy a new meter. Help.
 

powderhippie

New member
I drive (daily) an 87 Westfalia with 223,000 miles on original engine and have recently experienced signs & symptoms of "Vanagon Syndrome". I installed a brand new O2 sensor and the VW AFM harness and it runs much better, however not perfect. Upon inspecting the air flow meter I discovered the unit was obviously tampered with, and the sensor seemed very worn. I found a very clean factory sealed air flow meter Bosch part 280202106 on a 1991 VW Golf yesterday and installed it. The original part number ends in 079. Although the unit looks identical to the original AFM, and my van runs fine with it, did I screw up? I apologize for my mechanical ignorance as this is my first experience ever with an air flow meter, and appreciate any comments.
 

Capt. Mike

Moderator
The Bosch system is very similar, a variation of the same technology.

What you may find, if they are otherwise idential, is that the variable internal resistance is different for various throttle settings. The AFM feeds a resistance reading to the ECU based on throttle position. The ECU interpets that and adjusted the FI accordingly. It may run satisfactorily, but I would watch mileage, emmissions and performance at this stage, and ultimately consider that it may direct the ECU to lean the fuel/air ratio excessively at times, which can damage the engine. If your mileage drop and emmissions are up, the probably the former.
 

mr.rocksteady2

New member
Air Flow Meter, '85 Westy 1.9

As the title of my post suggests, I have an '85 Westfalia, 170K miles. My hiccup has grown into several hiccups per trip. I would describe this hiccup as moving along at a steady rate of speed and then the van momentarily looses power for just a split second. It is growing into more of a sputtering, almost backfire, powerless event at slow speeds around town. Once it rights itself, it does ok. But, with a little one in the car, it's time to get this taken care of. It has (knock on wood) never left me stranded and for that I am grateful, but my condition is getting worse.

Original Symptom occurred right at 50 mph. Hiccup. My van specifically has a hard time with roads that wind around where I stay around 50 mph. It has done this for 50,000 miles, but the new hiccups happen at lower speeds, usually after an extended run at 55 and then I slow down or stop, then try to get going again.

My mechanic warned me I would need to replace this part. Thank you for any suggestions.

Todd
 
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Capt. Mike

Moderator
First did he TEST the intake air sensor per Bentley §24.18, §24.20 & §24.39? I'd hate to see you replace a good item when it's really something else. Your symptoms could come from several sources so the entire FI system should be checked top to bottom per the troubleshooting charts in the Bentley and other topics in this forum.

Second, it basically operates as a variable resistor; as the flap moves, it changes the resistance by a contact moving along a coil, which in turn sends a signal to the ECU to adjust the fuel injection. This may be able to be cleaned with electronic supply house cleaner for contacts and rheostats. (Follow with electrically inert rheostat lubricant.) You might just have a dirty or burned spot from it sitting at the same point most of the time. Caution: Do not use "electrical cleaner" off the shelf at the auto parts store; it's not for electronics! ;)
 
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Ariplebib

Guest
I was driving down a ramp into an underground parking garage yesterday when the oil light came on, and a few seconds later, here was a loud noise about the same volume as a shotgun blast, there was a burning smell, and the car stopped running. I coasted into a parking spot and checked the oil it was full. Engine temperature was normal right up to that point. The car would start, but would not idle. I didnt try reving the engine, as I was afraid of hurting it. The car was running perfectly up to that point. It would occasionally surge slightly when cold, varying between 600 and 1000 rpm, and was slightly slow to return to idle, particularly when cold, but had never stalled before. I had it towed to a repair shop, where the problem was electronically diagnosed to be the mass air flow sensor. I have never heard of any sort of sensor exploding. Is there something more sinister going on here?

Terry McKitrick
1994 325ic
 

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