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Oxygen sensor relay - discrepancies

Didn't want to bump a thread from 2003 so here goes;

Car started acting up so i checked my relay. As i suspected she was clicking on/off/on/off. The car ran like crap but when the relay clicked it ran okay.

I sourced a replacement from a local shop. It wasn't the VW factory relay, it was a bosch 0332019150. The diagram doesn't quite match the original relay.

Original;




The new bosch;


The problem is that with the new bosch, the car doesn't want to idle. Keeps surging at idle. If i pull the relay, idle smooths out but the car runs like crap if i press the throttle.

With the bosch, i checked and FV does buzz if i lift the plunger in the airbox (with key on)

Has anyone tried the bosch relays? Only difference i see in the diagram is the 85 to 86. Do i really need to source a oem relay? Or is there something else wrong?
Old 09-30-2017, 08:36 AM
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I think your place gave you the wrong relay. Pics below are of my glovebox spare Bosch I bought off pelican years ago which worked fine in my car for years. The diagram on mine looks like it matches your original but not your new one. Part numbers are different and the 85 and 86 are reversed it appears in the diagram.


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Last edited by schoward; 09-30-2017 at 12:05 PM..
Old 09-30-2017, 12:02 PM
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Please see the attached info. At the very bottom of the link the 2 different relays are mentioned with the summation that they both will work - bottom line - they both power 87 and 87b as needed - the rest of the diagrams should also be helpful.
Keep in mind you will always have a little roughness at idle as the Lamda control system is constantly adjusting the mixture - based on its input from the o2 sensor - as it attempts to maintain the optimum fuel/ air ratio of 14.7 when in "closed loop" after the o2 sensor has warmed up.

911 CIS Primer - Lambda Electrics
Old 09-30-2017, 12:27 PM
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Hmm that's weird the host sells this one? Which is still different from the original.



Tried to find a VW original relay but they're NLA
Old 09-30-2017, 12:34 PM
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Per Mr. Walker......

The relay on the right is the correct relay.
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Old 09-30-2017, 12:55 PM
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Were you able to view the link with the wiring diagram that I sent you? If so, you will see that 87 powers your O2 control unit and 87B powers the frequency valve. Since your idle changes when you remove the relay and you stated that the frequency valve is working, this confirms the fact that the relay is working correctly. If you are experiencing large fluctuations at idle you may have a way too rich mixture, air leaks, or other issues.
I have an 82 Sc and have had to chase down a number of CIS issues but once it is set up correctly it is a good, relatively trouble free system.
Good luck.
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Okay so with the "new relay" i get surging at idle. If i pull down on the plunger to lean things out, everything smoothens out.

I checked the new relay with multimeter;
87: 13.4v
87: 13.4v
86: 11.6v
85: 35.4 ? ( fluctuates with the surging)
30: 13.3v (thought this was supposed to be ground)

If i put the old relay in the car and force the "flapper" to connect (the one that keeps flicking on and off), the car will run great.

Old 10-01-2017, 07:04 AM
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911SC Frequency Valve problem
Old 10-01-2017, 11:23 AM
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Quote:
Originally Posted by flat6_911 View Post

I checked the new relay with multimeter;
87: 13.4v
87: 13.4v
86: 11.6v
85: 35.4 ? ( fluctuates with the surging)
30: 13.3v (thought this was supposed to be ground)

If i put the old relay in the car and force the "flapper" to connect (the one that keeps flicking on and off), the car will run great.
Actually, pin 85 should be ground or close to it. What were the units of measure for the 35.4 you read, milli-volts (mV)?
Pin 30 is tied to fused power and that reads good - this power will be switched to both pin 87s if the relay is working.
You can refer to the schematic link dhanl82 provided and you'll get a great idea of what's going on.

I can't account for the surging and other symptoms you are experiencing however.
If you get a chance, do continuity on your relays (out of circuit) from 85 to 86, from 86 to 85, 30 to each 87/87a (open), and the 87's to themselves(short).
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Old 10-01-2017, 12:19 PM
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Quote:
Originally Posted by flat6_911 View Post
30: 13.3v (thought this was supposed to be ground)
30 is not a ground. It is the power from the Lambda fuse.

This is a only mildly experienced layman talking so it's worth what you are paying for it.

85 is the ground for the electromagnet. 86 gets power from the fuel pump. From how I read the diagram, the fuel pump is engaged (i.e., air sensor lifted) , power is sent to the magnet and then your relay is "clicked on"

This part of the circuit controls engagement of the relay and that is it as far as I know. Flapper pulled in or not pulled in.

87, 87b should provide the magic the Lambda box does with respect to the freq valve if 30 is providing power. (Mind you 85 and 86 work first or the lambda side can't talk between the box and the f valve)

If you have to close the magnet manually there could be a breakdown in the fuel pump feed circuit? Including a poor ground.

That's it on my basics. See diagram below.

Just a touch more wind.,.....

If your system smooths out but no power or revving capability (maybe some little backfires, too when blipping) your freq valve is not getting power. The freq valve must be powered for the car to run decently even in open loop (O2 sensor unplugged). The relay must be engaged thru the fuel pump circuit as well.

I might be talking trash but it seems to make some sense that the relay is powered by the fuel pump. For safety reasons?

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Old 10-01-2017, 12:57 PM
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Here is a better pin-out.

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Old 10-01-2017, 01:01 PM
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Quote:
Originally Posted by steely View Post
Actually, pin 85 should be ground or close to it.
Time overlap, Dan. Took me a while to post mine.

You have some nice practical checks.
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Old 10-01-2017, 01:13 PM
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If you disconnect the o2 sensor does it run better? Careful though that connector can be very brittle.
Old 10-01-2017, 04:08 PM
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Thanks for all the replies, will look into this shortly.

o2 sensor is actually already disconnected. PO set the mixture with o2 disconnected
Old 10-01-2017, 06:56 PM
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Quote:
Originally Posted by flat6_911 View Post
o2 sensor is actually already disconnected. PO set the mixture with o2 disconnected
Dude?!
So like, your O2 sensor is disconnected already?
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Old 10-01-2017, 09:53 PM
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Quote:
Originally Posted by Bob Kontak View Post
Time overlap, Dan. Took me a while to post mine.

You have some nice practical checks.
Hey Bob - np, besides, the better stuff takes a while and is worth waiting for.
I was wondering about those relays, but now I'm not so sure.
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Old 10-01-2017, 10:04 PM
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Hmmm i'd check the engine harness connectors in the back of the engine compartment and at the front of fuse panel in the rear. Maybe you are getting an intermittent electrical issue. The old relay was clicking on and off?
Old 10-02-2017, 03:37 PM
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If I misunderstood, disregard me, but in case I didn't, you should have the O2 connected if you are trying to troubleshoot the OXS relay.
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Old 10-02-2017, 05:47 PM
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Quote:
Originally Posted by gazzerr View Post
Hmmm i'd check the engine harness connectors in the back of the engine compartment and at the front of fuse panel in the rear. Maybe you are getting an intermittent electrical issue. The old relay was clicking on and off?
I checked the large connector for the engine harness near the strut tower in the back, seemed okay. I read that spreading the pins may help the contacts. might try this if nothing else works. Yes, the relay was clicking on and off consistently. If she clicked one way, everything ran smooth as it did before. the new relay is giving me rich conditions once engine is warmed up.

Steely I have my new o2 sensor disconnected. when I installed the new o2, the connector in the rear crumbled in pieces. I think PO set the mixture with no o2 sensor (or he thought it was connected but the connector was in pieces) I drove it for the past 3 years with no issues and o2 disconnected.
Old 10-03-2017, 02:29 PM
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Quote:
Originally Posted by flat6_911 View Post
I drove it for the past 3 years with no issues and o2 disconnected.
O2 input is not that critical. The freq valve MUST be working to give you the default duty cycle.

Another way to say it is if you are dialed in at idle w/o O2 input, your car can run fine at the expense of some fuel mileage.

That said, get the O2 sensor in the loop once you figure this problem out. You don't really piss away performance as the O2 is switched off at WOT, but when cruising, you ARE pissing away gasoline. These cars are pretty sweet when set up right per factory. 25+ mpg on the highway at a reasonable speed and when putting around, which is 90% of driving.
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