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Thread: Lambda problem?

  1. #11
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    A glowing cat is much more serious than something being slightly out of adjustment.

    Backfiring it usually a sign of a lean misfire, but a glowing cat at idle is usually something way too rich. Are you sure the fuel distributor isn't stuck? How long has the car sat before you starting tuning it up? Do you get the normal resistance to a finger push on the throttle plate just after turning it off?
    Dave S
    DMC Midwest - retired but helping
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  2. #12
    Junior Member
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    I do have normal resistance at the throttle plate, it doesn't seem to be loose.
    The car sat for about 6 months while I did repairs to the brakes and body.
    The cat doesn't glow right away the car warms up first and then it starts to get red hot.

    Before I did the tune up, it ran well and smooth, and hunted on start up. Now it runs rough and no hunting. I never touched the timing, just replaced parts, and tried to adjust the co as per the article I was using. Still don't know why I cant get the dwell to show up.

  3. #13
    Senior Member Bitsyncmaster's Avatar
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    If your way off on the mixture, the dwell will read about 10 or 80 degrees after it warms up. But when you first start it (or press the WOT), you should read about 45 degrees. That would show your dwell meter is working.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  4. #14
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    Not getting 45 at start up or by pushing WOT.

    Bad o2 sensor?

  5. #15
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by delorean82 View Post
    Not getting 45 at start up or by pushing WOT.

    Bad o2 sensor?
    No. My guess is your meter is not working since your getting a buzzing FV.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  6. #16
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Agree. Here's an easy test. Yank the RPM relay and jumper the brown wire to the yellow/red wire. Key does not need to be on. The RPM relay will start buzzing at 50% (45 deg). You can now test your circuit and meter to your hearts content without running the engine and melting things. When you have the meter working and reading 45 (55 if/when you hit the full throttle microswitch) then you can go back to troubleshooting the engine.

    FYI - there is a series of simple tests given in the manual that are really handy to verify the electronics. (page D:04:05, paragraph 5). This seems mysterious to most but is works well.

    If you disconnect the O2 sensor and GROUND the connector on the car (not the sensor) the dwell meter should read 87 degrees. You will hear the FV change pitch as it moves. If you put a 1.5V flashlight battery + on the car connection and ground the neg of the battery to the frame, you'll see the dwell swing to 20 deg. With the O2 sensor disconnected (or connected with the engine off) it should read 45 all the time.
    Dave S
    DMC Midwest - retired but helping
    [email protected]

  7. #17
    Senior Member mluder's Avatar
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    I had a strong fuel smell and rough running engine. I tried adjusting the mixture with a duty cycle meter but could never get it dialed in just right so I bought a cheapy muilti meter with dwell from Harbor Freight.

    Once I hooked it up after letting the engine warm up I discovered that what I thought was a rich mixture (fuel smell inthe exhaust) was actually a lean mixture. I richened it up and now it's running smoother and the gas smell seems to be gone. I think I might dare taking it through the DEQ and see if it'll pass emmisions.

    I'm curious though... I have been using injector cleaner in the tank pretty regularly - my car had sat for 10 years before the previous owner got it running to sell. He re-did most of the fuel system but stopped short of replacing the injectors. DMCNW, who did the work) said to run injector cleaner through a few tanks. Can the injector cleaner in the fuel affect emmisions testing and cause it to read too many hydrocarbs? It would seem that injector cleaner should burn more efficiently. Any thoughts?
    Cheers
    Steven Maguire
    #4456


    IT'S A TRAP!!!!!

  8. #18
    Junior Member
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    Ok
    I have two digital meters and one analog meter. Not getting any results from them.
    Is it possible I'm connecting to the wrong connector? I'm using the white connector at the bulkhead with two wires coming from it with my multimeter. This the rear most plug with the group of other plugs.
    Today I richend the mixture and the car seemed to smooth out a little, still get the glowing cat and rough idle. All plugs are firing and the timing is approx 12 degrees, allthough I made a rookie mistake and forgot to plug the vacuum advance.

    Thoughts?

    I really want my car to run normally but more importantly I just want to know what the he'll is going on?

  9. #19
    Senior Member
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    Another quick thought. Make sure the cold start valve is NOT squirting. It could be stuck, defective (rare) Wiring or switch problem, or you did the plug swap and it is running full open. Pull the plug off of it.
    David Teitelbaum

  10. #20
    Senior Member Bitsyncmaster's Avatar
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    Look at the second photo in post #9 of this thread.

    http://dmctalk.org/showthread.php?17...you-hook-it-up

    That orange wire is probably a better dwell signal than looking at the FV signals for some meters. That is where I always check the dwell. That connector is on the back firewall harness in the engine bay.
    Dave M vin 03572
    http://dm-eng.weebly.com/

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