Just failed air care

[greent3]

In B.C. we have a wonderfull thing called air care. The Gov't tests the emitions that come from your car. My 70 FI fastback failed, my hydrocarbons at idle are to high. I have never had this problem on my other air care tests. Can anybody offer any opinions on why the hydrocarbons may be to high and ways to fix the problem?
Thanks

[josh]

It's most likely running rich, or it might be caused by a miss or something.

What were the levels of the other chemicals in the exhaust?

Hydrocarbons are basically unburned fuel.

[greent3]

Driving - hydrocarbons 255.00 ppm
- carbon monoxide 1.24%
- oxides of nitrogen 1493.00 ppm
Idle - hydrocarbons the test only regesters 2000 ppm and thats what I got, so it's probably even higher
- cabon monoxide 2.4%

The others were not even close to a fail only the hydrocarbons at idle.

[KTPhil]

Wow, that's really high at idle! I would check for air leaks, especially leading to the pressure sensor. A leak would fool the EFI into thinking you are under load and it would enrichen the mixture.

If I remember, 70s do not have a mixture adjust screw on the ECU, so that isn't it.

My shop used to have a "test pressure sensor" that they epoxied a hex key to the bellows adjustment screw so they could "tune" it during test. Won't work with the latest test equipment. In California, cars this old are exempt so I don't worry anymore.

Check hoses, fuel pressure, and also check for a leaking cold start enrichment injector (if your year has one).

(edit) Another cause can be old leaky injectors or a stuck injector. This and the air leaks will show up at idle, but get hidden at higher RPMs as your readings suggest.

[Erik G]

if all else fails, fresh tune up, oil change, timing and valve adjust. good luck
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[Bobnotch]

Also check the voltage, as a lower volt reading (12.5 or less) will cause the car to run rich. The D-jet is a very voltage sensitve system, and they have a tendency to run rich as the voltage regulator starts to fail.
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[COFBack]

Getting the engine good and hot will also help
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[rloaircool]

[Russ Wolfe]

Check the resistance of the plug wires. You should be running the OE style with the replaceable ends. They should read under 1500 ohms. The resistance of the rotor should be under 5000 ohms. If you are running carbon core wires, get rid of them and go to the genuine Bosch wires.
And what Bob said. Check the charging system. Also, disconnect the fuel hose to the cold start valve, and plug it. You don't really need it.
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[greent3]

Thanks for the tips. I was able to get 3 months insurance when I failed, so I have some time to try and figure it out. I'll post the solution when I figure it out.
Thanks for your help
Eric