Advice for Emissions Testing?
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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, Advice for Emissions Testing? in Past Cadillac Vehicle Discussion; Well, after working on my 1989 Brougham d'Elegance (carbureted 307) all summer in order to get it up to code, ...
  1. #1
    TurtleRanger's Avatar
    TurtleRanger is offline Cadillac Owners Member
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    Advice for Emissions Testing?

    Well, after working on my 1989 Brougham d'Elegance (carbureted 307) all summer in order to get it up to code, I've finally been sandbagged by something I've been dreading for months: Mandatory exhaust emissions testing for vehicles built after 1988.

    The car passed back when I originally bought it, so I valiantly faced down the treaturous emissions test armed only with a tank full of high-test and a hot engine. The result? Carbon monoxide emissions in six times excess of the allowable amount, followed by two times the allowable level of hydrocarbon emissions in parts-per million.

    When I asked the grease monkey who performed the test what the immediate cause might be, he said 'Everything' and recommended an expensive diagnostic. Not exactly great advice, in my opinion.

    Most of us here have pretty old cars, so does anyone have any advice from past experience? Have you lot had any noteworthy trouble getting through this sort of testing? I understand that emissions standards are different all over the world.

    I already replaced the catalytic converter a few years ago (expensive!) so that's not an immediate option, but I'm going to replace the ancient spark plugs in hopes of improving combustion and reducing the HC output. Timing adjustments/carburetor maintenance are supposed to help too...

    Any advice?

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    purepearl32 is offline Cadillac Owners Member
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    Re: Advice for Emissions Testing?

    My thoughts would be the correct plugs, wires, rotor, cap, ignition module, air filter, pcv valve, crankcase breather element, and definitely check/adjust timing. Possible bad O2 sensor, but that should be throwing a code. I assume your car passed the NOX reading?
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    TurtleRanger is offline Cadillac Owners Member
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    Re: Advice for Emissions Testing?

    Quote Originally Posted by purepearl32 View Post
    My thoughts would be the correct plugs, wires, rotor, cap, ignition module, air filter, pcv valve, crankcase breather element, and definitely check/adjust timing. Possible bad O2 sensor, but that should be throwing a code. I assume your car passed the NOX reading?
    Cheers, that's all very helpful. NOx readings are fine; just bloated CO and HC readings at the moment. The check engine light doesn't come on at all so, unless it's burned out, I don't think the ECM is throwing any error codes.

    I thoroughly cleaned the carburettor yesterday and the difference it's made is astounding! Huge improvements to starting, acceleration and engine performance as well as a smoother idle and over-all more even, less rattly sound. It will be very interesting to see the difference made by the other recommended maintenance too.

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    purepearl32 is offline Cadillac Owners Member
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    Re: Advice for Emissions Testing?

    Assuming the above items I mentioned haven't been done in quite a while and judging the positive effect you had with just cleaning the carb, you'll probably want to make sweet love to the car after it gets a complete and proper tune up
    talismandave and TurtleRanger like this.

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    jayoldschool's Avatar
    jayoldschool is offline GM RWD V8 addict
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    Re: Advice for Emissions Testing?

    First suspect would be a choke that is sticking closed. NOx okay means that the EGR is working fine. Were these readings at idle, or under load at what RPM?

    If you can post a pic of the actual test with the numbers, we can help more effectively.
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    Re: Advice for Emissions Testing?

    Quote Originally Posted by purepearl32 View Post
    Assuming the above items I mentioned haven't been done in quite a while and judging the positive effect you had with just cleaning the carb, you'll probably want to make sweet love to the car after it gets a complete and proper tune up
    Haha, really looking forward to that
    Quote Originally Posted by jayoldschool View Post
    First suspect would be a choke that is sticking closed. NOx okay means that the EGR is working fine. Were these readings at idle, or under load at what RPM? If you can post a pic of the actual test with the numbers, we can help more effectively.
    Sure thing, Jay; The exhaust emissions test has two phases. One at idle and one at 2500 RPM. Here are the numbers:

    2500 RPM
    Code:
    HC (ppm): 295/200 - Fail
    CO (%): 8.41/1 - Fail
    RPM: 2478/2250 to 2750 - Valid
    Dilution %: 18.01/6 - Valid
    IDLE
    Code:
    HC (ppm): 410/200 - Fail
    CO (%): 6.69/1 - Fail
    RPM: 860/< 1250 - Valid
    Dilution %: 17.29/6 - Valid

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    Re: Advice for Emissions Testing?

    Ok, the worst is the CO numbers. I think the HC numbers are a result of the high CO. You ever change your thermostat? I think it might be running cold.

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    TurtleRanger's Avatar
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    Re: Advice for Emissions Testing?

    Quote Originally Posted by jayoldschool View Post
    Ok, the worst is the CO numbers. I think the HC numbers are a result of the high CO. You ever change your thermostat? I think it might be running cold.
    Never changed it, but that's a possibility. Other vehicles I've had tested with high-octane petrol in the tank have heated up enough to bring on temp light after 2500 RPM on the dynamometer but this one did not. My heater-core and climate control module are toasted in this car so I can't use the heater as a telltale and I don't have any immediate method of monitoring the coolant temperature. Got any tips for testing the integrity of the thermostat?

    EDIT: Forgot to mention - the choke flap was not closing fully when the engine was cool but, aside from that, it behaves as it should. Cleaning the linkages and hinges seemed to help.

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    jayoldschool's Avatar
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    Re: Advice for Emissions Testing?

    You can test it in a pot of boiling water with a thermometer. An infrared temp gun on the engine should work, too. Or... just replace it for ten bucks.

    I would also suggest running 87 instead of 89/91 for your next test. Your car has low compression, and is designed for low octane. It can't take advantage of higher octane's slower burning properties.

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