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Thread: Wont go to closed loop

  1. #11
    Senior Member hippieman9's Avatar
    Join Date:  Jan 2018

    Location:  Haw River, NC

    Posts:    285

    My VIN:    06668 81' Grey interior, 5 speed, Grooved hood. Previous owner of 16301, in 2001.

    Quote Originally Posted by David T View Post
    There are a lot of possible reasons the system won't go into "closed loop". First make sure the frequency valve is buzzing. If it isn't buzzing it can never get into closed loop. Make sure the motor is warmed up and the WOT micro is not "set" or closed. Check that there are no vacuum leaks. If the motor hasn't been tuned up for a while (or you don't know how long it's been) it needs a tune-up. If the mixture is way off, and it doesn't take much, a 1/2 turn one way or the other, it can keep you from getting into closed loop. Finally a bad connection anywhere between the Lambda ECU and it's sensors or the frequency valve can prevent closed loop. There are specific tests you can perform to try to force the system into different pulse ratios. Refer to D:04:15 in your Workshop Manual.
    David,
    When I jump the Rpm relay, the FV buzzes. WOT switch seems to work. (I dont have a smoke machine) to check for vacuum leaks, (any common places?)
    Ive installed new Bosch silver plugs, it has recent cap rotor and wires.

  2. #12
    Delorean Guru
    Join Date:  May 2011

    Location:  Northern NJ

    Posts:    7,151

    My VIN:    10757

    Club(s):   (DMA)

    Some very common areas of vacuum leaks;
    Injector seals
    Cold start valve plumbing
    Idle motor plumbing (especially that "O" ring seal underneath the mixture unit, the one that is hard to see!).
    All of the small vacuum hoses (also double-check routing)
    Vacuum advance solenoid
    Tamper-proof seal on the mixture unit (or whatever is stuck in there!).

    With a smoke machine I have seen a lot of unusual leaks too. The vapor canister, intake manifold, vac hose to the brake booster, Fuel tank evap system, etc. Do as good a visual inspection as you can.

    Make sure the air filter is clean. If the injectors aren't spraying equally and with good patterns and all opening at close to the same pressure it can be hard to get a good A/F reading.
    David Teitelbaum

  3. #13
    Senior Member hippieman9's Avatar
    Join Date:  Jan 2018

    Location:  Haw River, NC

    Posts:    285

    My VIN:    06668 81' Grey interior, 5 speed, Grooved hood. Previous owner of 16301, in 2001.

    Quote Originally Posted by David T View Post
    Some very common areas of vacuum leaks;
    Injector seals
    Cold start valve plumbing
    Idle motor plumbing (especially that "O" ring seal underneath the mixture unit, the one that is hard to see!).
    All of the small vacuum hoses (also double-check routing)
    Vacuum advance solenoid
    Tamper-proof seal on the mixture unit (or whatever is stuck in there!).

    With a smoke machine I have seen a lot of unusual leaks too. The vapor canister, intake manifold, vac hose to the brake booster, Fuel tank evap system, etc. Do as good a visual inspection as you can.

    Make sure the air filter is clean. If the injectors aren't spraying equally and with good patterns and all opening at close to the same pressure it can be hard to get a good A/F reading.

    Ok great thank you... I will double check all this tomorrow. I know it has new fuel lines, new style fuel pump. Replaced all hoses for evap system , new check valve , gas cap and seal..

  4. #14
    Delorean Guru
    Join Date:  May 2011

    Location:  Northern NJ

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    My VIN:    10757

    Club(s):   (DMA)

    Wholesale replacement is great but you have to watch out for two potential problems. You can get defective parts and you can install them improperly. Everything that was touched could be a problem till it is proven to be OK. Just because the parts are new does not mean they can't cause a problem. I like to do things in steps so if anything goes wrong I know what was most recently done so I don't have to go over everything to find the problem.
    David Teitelbaum

  5. #15
    Senior Member hippieman9's Avatar
    Join Date:  Jan 2018

    Location:  Haw River, NC

    Posts:    285

    My VIN:    06668 81' Grey interior, 5 speed, Grooved hood. Previous owner of 16301, in 2001.

    Quote Originally Posted by David T View Post
    Wholesale replacement is great but you have to watch out for two potential problems. You can get defective parts and you can install them improperly. Everything that was touched could be a problem till it is proven to be OK. Just because the parts are new does not mean they can't cause a problem. I like to do things in steps so if anything goes wrong I know what was most recently done so I don't have to go over everything to find the problem.
    LOL, Yes I agree, I have had brand new alternators fail 1/2 mile from the house. I always say anything man made, mechanical or electrical, can fail.

  6. #16
    Senior Member hippieman9's Avatar
    Join Date:  Jan 2018

    Location:  Haw River, NC

    Posts:    285

    My VIN:    06668 81' Grey interior, 5 speed, Grooved hood. Previous owner of 16301, in 2001.

    Ok following the tests in the manual, I get
    Test A 46
    Test B 46
    Test c 60
    Test D 20
    Test E 50

    All doubled for the 4cyl scale.

  7. #17
    Delorean Guru
    Join Date:  May 2011

    Location:  Northern NJ

    Posts:    7,151

    My VIN:    10757

    Club(s):   (DMA)

    Quote Originally Posted by hippieman9 View Post
    Ok following the tests in the manual, I get
    Test A 46
    Test B 46
    Test c 60
    Test D 20
    Test E 50

    All doubled for the 4cyl scale.
    Check the wiring from the O2 sensor to the ECU. Test C should be 87 minimum. Also check the grounds. Refer to the schematic on D:04:12
    David Teitelbaum

  8. #18
    Senior Member hippieman9's Avatar
    Join Date:  Jan 2018

    Location:  Haw River, NC

    Posts:    285

    My VIN:    06668 81' Grey interior, 5 speed, Grooved hood. Previous owner of 16301, in 2001.

    While the engine is running, i sprayed a little brake clean around the intake and injector seals, I notice that the engine starts to stumble, wondering if it has a bad injector seal.

  9. #19
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

    Posts:    7,408

    My VIN:    03572

    Since everything seems to be working but your still holding steady dwell with the value you get with a cold or disconnected O2 sensor I think you have to see it that O2 signal is getting to the lambda ECU. Hard to tap into that sensor wire since it is shielded. Maybe you can pull the ECU connector cover off and be able to measure the voltage with every still hooked up.

    Working lambda the sensor voltage should be 0.5 volts DC.

    Maybe your O2 sensor is faulty.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  10. #20
    Senior Member hippieman9's Avatar
    Join Date:  Jan 2018

    Location:  Haw River, NC

    Posts:    285

    My VIN:    06668 81' Grey interior, 5 speed, Grooved hood. Previous owner of 16301, in 2001.

    Quote Originally Posted by Bitsyncmaster View Post
    Since everything seems to be working but your still holding steady dwell with the value you get with a cold or disconnected O2 sensor I think you have to see it that O2 signal is getting to the lambda ECU. Hard to tap into that sensor wire since it is shielded. Maybe you can pull the ECU connector cover off and be able to measure the voltage with every still hooked up.

    Working lambda the sensor voltage should be 0.5 volts DC.

    Maybe your O2 sensor is faulty.
    I'll give it a try, It is a new Sensor, but could still be bad. if someone messed with the CO screw before how far would you have to turn it to get it back in? I have read the screw only turns a half turn and to adjust it 1/16" at a time.

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