D-jet woes

[Chilling in VT]

My brother has a 76 2.0 from CA. The car has been running great until this morning. The car starts fine and idles fine. It seems to load up and miss when given throttle. We have tried numerous things to no avail. As a last dich effort, I disconnected the plug from a small Bosch relay (#039 905 351) and the car runs like a champ.

So the big questions: What does this relay do? And will it harm the car to run with it disconnected? I have searched the parts finder here and it lists it as control unit lambda. Is this emission related? Thanks for any light that you can shed.
Joe

[Dave at Pelican Parts]

There should be no "lambda control" of any kind on a 914. They used "open-loop" FI systems, not "closed-loop" with lambda (O2) sensors.

Where is this relay located? What is attached to it? How many wires, and what colors? Can you post a picture??

--DD

[Chilling in VT]

Hi Dave,
I am not sure of what this is but came up with the name by typing in the Bosch number into your search engine and that is what they called it. It is a small metal box atatched to the right side of the engine next to the distributor. It is about 3/4" thick and 2 1/2" square. It has a 4 plug connector that plugs into one end and 8 white wires going to the 4 connectors. It has a VW/Audi (four rings) logo on it. Here is a picture. Thanks for any light you might shed.
Joe

[Tidybuoy]

I can't think of what the relay is for but I suspect that at one time the original relay went bad and it was replaced with the wrong part.

As dave said, no 914's every came with a Lambda system which is for the oxygen sensor.

Vern

[Chilling in VT]

Thanks Vern. Any idea of what relay is supposed to be here and what it might be for?
Joe

[Dave at Pelican Parts]

The interesting thing is that "039" is the part number prefix that means the 2.0 liter 914. But that part number doesn't show up as a 914 part number when I search my other documentation, as well as the Pelican site!

From the location and the appearance, I would say that it is probably the fuel-cutout rev limiter. Early 914s (70-74) either had no rev-limiter, or a distributor rotor that shorted the spark to ground when the engine was spinning too fast. However, this would be bad for a catalytic converter (used on CA-spec 75-76 914s). So they came up with an add-on box on the FI wiring harness that would cut the fuel injector signal when the engine spun too fast. This would act as a rev-limiter, but wouldn't dump raw fuel into the exhaust to burn out the cat.

That's what that part looks like to me.

--DD

[RustyWa]

Yep, rev limiter.

[Chilling in VT]

So no problem running without it? Dave, if you type in the part number and do a search, it does come up on the part site. That is where I came up with the lamda control name. Maybe it is not a regular 914 part? Thanks.
Joe

[Dave at Pelican Parts]

I have seen that it comes up on this website, but the name "lambda control" doesn't make any sense, at least not as far as 914s go. But the "039" prefix is almost always used for parts that are specific to the 2.0 engine... But the part number does not show up in my 914-specific documentation. Which is curious.

--DD

[Chilling in VT]

Thanks Dave. So if I understand things, this is not needed? The car has been backdated to a 73 exhaust and stainless exchangers so no cat to worry about. We should be able to use the 73 rotor to have a rev limiter? Thanks.
Joe

[Tobra]

Just use your right foot as a rev limiter

[Dave at Pelican Parts]

The box should not be needed. You can switch to the rev-limiting rotor if you like (it's about 5X more expensive than the plain one, though!) or as Tobra suggested, just use your right foot as the limiter.

--DD