78 super, Intake Air Sensor

BWOL · Posted: Mon Jul 25, 2011 12:24 pm Post subject: 78 super, Intake Air Sensor

I did some tests with my ohm meter and according to my Haynes manual I have a bad intake air sensor. Just wanted to clear it up. On terminals 7 and 8 the meter fluctuates as the book says, on 6 and 9 there is no fluctuation when i manually operate the flap. Does that mean its bad? If so where do I get a good replacement? The only one I've found is from Autozone. Its a Cardone and its $289... is that good?

Randy in Maine · Posted: Mon Jul 25, 2011 12:54 pm Post subject:

Does your double relay work? that has to work first I think.

Been here?

http://www.itinerant-air-cooled.com/viewtopic.php?f=42&t=5460

BWOL · Posted: Mon Jul 25, 2011 1:07 pm Post subject:

The double relay works. That was my first check. The relay is fairly new, new fuel pump too.

BWOL · Posted: Mon Jul 25, 2011 1:12 pm Post subject:

My manual explained how to test the intake air sensor. says to ohm terminals 6 and 9 while manually operating the flap inside. It should of fluctuated between 200 and 400 but it stays at 300 with no fluctuation.

I am assuming that it is bad, because the other terminals (7 and Cool

did fluctuate where it was supposed too. If I am wrong, please let me know so I dont have to spend $300 on a new intake air sensor

BWOL · Posted: Mon Jul 25, 2011 1:13 pm Post subject:

that happy face was supposed to be an 8 by the way

Randy in Maine · Posted: Mon Jul 25, 2011 1:41 pm Post subject:

Do you have these to do some testing with?

http://bama.ua.edu/~darren/boschindex.html

http://manuals.type4.org/ljet/

BWOL · Posted: Mon Jul 25, 2011 2:34 pm Post subject:

Nope. Thanks. Time to do some more reading

Randy in Maine · Posted: Mon Jul 25, 2011 4:33 pm Post subject:

Rare (although not unheard of) for a AFM unit to go bad.

Just confirm that what you have is really no good before you spend real money to replace it.

BWOL · Posted: Tue Jul 26, 2011 12:43 pm Post subject:

I totally agree. Thats what I was hoping to do here. I tested the AFM like I said and if Im reading correctly, terminals 6 and 9 are not operating like they're supposed to. I guess what I was looking for is a second opinion. would that keep my bug from starting?

rockerarm · Posted: Tue Jul 26, 2011 5:14 pm Post subject:

I know I'm gonna get jumped on but here goes. I am away from home and don't have access to my dealer stuff.
But it is my recollection that the AFM has 6 terminals. Two terminals are for the fuel pump contacts. Two more terminals are for the potentiometer which is attached to the flap. This is what tells the computer the VOLUME of air going thru the engine, and will show a variable resistance as the flap moves. The last two terminal are for the intake air sensor and will vary a small amount according to air temp.
How is your car running? We used to see bent flaps from backfires which would bind up the flap. And true potentiometers would be out of spec, but that was years ago.
Personally, if I needed an AFM, I would try and find a local rebuilder that is an expert with these parts.
Hope this helps, Bill.

MSmethers · Posted: Tue Jul 26, 2011 6:58 pm Post subject:

BWOL · Posted: Wed Jul 27, 2011 10:24 pm Post subject:

excuse my ignorance. Im still learning my bug. Im not sure what a TS II is?
I can explain what happened when it when out if it helps?

Car was running pretty rough so I adjusted my valves did the oil and spark plugs too. Got it running great again then while driving it started shutting down every time I let off the gas. It kept running (not 100%) as long as I held the gas and started every time it stalled out. Got it home a couple of miles later, re checked the valves and plugs, timing (with TDC and a test light because it wouldn't stay running). never got it going, then it stopped starting all together. Checked the double relay and fuel pump both ok. Dizzy looks fine wires are good, coil tested out fine... needless to say, Im stumped and don't know much else about it. Thanks for all the help everyone, hopefully I can get it going again.

rockerarm · Posted: Wed Jul 27, 2011 11:33 pm Post subject:

The TS 2 refers to the cylinder head temp senser. It is a thermister, which is a thermal resister that changes its resistance value as the temperature changes. It really hasn't changed much since the '68 T3 MPC (manifold pressure controlled) F I. On a properly running engine it has the greatest influence on the air to fuel ratio. Basically make sure its snug where it screws into the left cylinder head plus the two resistance values.
Your gonna have to invest in a decent DVOM (digital volt ohm meter). Sears has them for $20-30.
In the event you need to repair/rebuild either your AFM or ECU (computer) there is a cool web site based around SoCal and caters to some 914 Porsche cars. It is called PelicanParts.com. Possibly there is a readily available rebuilder to support those needs.
Hope this helps, Bill.

BWOL · Posted: Thu Jul 28, 2011 4:55 pm Post subject:

I will check it out now, actually in about an hour when there is some shade by the garage. I have a nice Fluke mulitmeter that ive had for a few years now. I appreciate all the info. Thanks a lot.

BWOL · Posted: Sat Jul 30, 2011 9:31 pm Post subject:

After tearing thru it and pulling off my air sensor, I found some bad wires and some vacuum hoses that were off. The power wire to my alternator was wedged behind my air sensor and almost fried in half. I also found a ground wire that was just about in two as well. After fixing these problems and checking timing again, it finally started again. Im glad I was wrong about my air sensor, that almost cost me $300 but if I wouldn't of pulled it off I never would of seen the bad power wire... Thanks for the help everyone.

BWOL · Posted: Sat Jul 30, 2011 9:34 pm Post subject:

By the way, its a little rough on the start and warm up. I think I read somewhere there is a cold start valve?? Where is that and how do I check it?

Randy in Maine · Posted: Sun Jul 31, 2011 5:29 am Post subject:

I am not a beetle guy, and I am just looking at photos from the gallery.

The cold start valve ("CSV") is kind of shoved in there and should have a blue electrical connector. This one uses the wrong fuel lines and crappy clamps, so keep that in mind. When the thermotime switch ("TTS") says "the engine is cold", it tells the CSV to give you 8 seconds of spray to richen the mixture. Beetle guys measure the fuel pressure by T'ing into the fuel line at the CSV with the fuel pressure gauge. It either works or it doesn't and should not drip fuel after the 8 seconds.

Image may have been reduced in size. Click image to view fullscreen.

I think the heart of your problem is more like is a dirty and not opening and closing like it should Auxillary Air Regulator. Remove it, clean it all out with Gum Out, and test it using a hair dryer and the freezer in the kitchen to see if the little door opens cold and closes warmed up. Some of them have a little nut that lets you adjust it. Test the connection to make sure it has about 30 ohms while you have it out. That 30 ohms is the electric heater that closes the door after a few (like 4-8 minutes). There should be a 2 big (13mm or so) vacuum hoses that go to it. One hooks up to intake vacuum and the other to metered vacuum headed to the S boot. No vacuum is able to go fromt he intake through the AAR to the S boot after the 4-8 minutes of warm up. Look for splits in the vacuum hose headed to the S boot.

In that photo, the AAR is just above the pulley.

Correct electrical connections are

CSV = blue (and it should have a fuel line going through it)
AAR = black (with the 2 big vacuum hoses)
TTS = brown

Just my 2 cents though....

rockerarm · Posted: Sun Jul 31, 2011 4:41 pm Post subject:

To help you thru your cold start and running (or transitioning to warm) remember the engine has to be in a good running condition warm.
The cylinder head temp senser is your "choke" or enrichment. We discussed it specs earlier. The auxiliary air regulator is your" stepped cam" for your elevated idle speed. It does not raise the idle very high. I do not recall a spec but make sure it is closed when warm. The cold start valve operates only while cranking. It gets its power from term #50 from starter. The ground is controlled by the thermal time switch. It has a heating element that turns off the ground after about 8 seconds. This prevents flooding the engine. Best way to check cold start valve is to remove the two screws and pull it up enough to clear housing. Disconnect coil wire. Have rags wrapped around area. Crank engine and view the spray pattern. It shoud produce a conical pattern for the 8 seconds.
Hope this helps, Bill.


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