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Thread: 86 Century T Type 3.8 Engine Roughness on Acceleration

  1. #16
    Senior Member 85_Ciera_Rebuild's Avatar
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    Quote Originally Posted by turbokinetic View Post
    check is the ignition coils...Measure the resistance of each and see what you measure
    Interesting, with 2.8-V6 coils, I recall it being an open circuit on new/old coils when measuring from across spark tops, when coils were removed from ICM. Primary circuit showed an ohm reading of some 5 k ohms or so.

    When I change out spark wires, I'll take a second look at ohm reading for spark tops.



  2. #17
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    I have a new problem, possibly related to the first problem? I'm still having the engine getting rough on moderate to hard acceleration but I've never had a stalling problem till now. Today at a long train crossing I shifted to park and let the engine idle. After a few minutes it began to stumble and slow down, the CEL came on and it stalled. It started right up again and would not stall while idling in drive only in park. I checked for codes and got #44 lean exhaust. I checked the oxygen sensor wire and connections and it looks OK visually. Could a bad O2 sensor cause engine roughness on acceleration? Is there a way to test the O2 sensor with a multi-meter? If it is the O2 sensor is it very difficult to get it out?

  3. #18
    Senior Member turbokinetic's Avatar
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    1984 Buick Century Olympia 3.8SFI Turbo V6
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    Quote Originally Posted by T Type View Post
    I have a new problem, possibly related to the first problem? I'm still having the engine getting rough on moderate to hard acceleration but I've never had a stalling problem till now. Today at a long train crossing I shifted to park and let the engine idle. After a few minutes it began to stumble and slow down, the CEL came on and it stalled. It started right up again and would not stall while idling in drive only in park. I checked for codes and got #44 lean exhaust. I checked the oxygen sensor wire and connections and it looks OK visually. Could a bad O2 sensor cause engine roughness on acceleration? Is there a way to test the O2 sensor with a multi-meter? If it is the O2 sensor is it very difficult to get it out?
    It seems these old LG3 cars all want to run lean at idle. It seems that a combination of small vacuum leaks, an aging MAF sensor, and aging injectors work together to cause this problem. The problem is going to be worse with less load on the engine. That's because the less load the lower the airflow and that is the region where the MAF is least accurate.

    The 02 sensor is easy to change. It is simply screwed into the collector at the rear manifold. There is no way to test it with a meter. It is a chemical sensor and would require calibrated test-gas and special equipment to test it.

    The "lean exhaust" code means that the ECM was trying to add fuel and correct the lean condition, however it reached the maximum allowable fuel trim without correcting the problem.

    A dirty air filter or dust on the MAF element will both exacerbate this problem.

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