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rough idle 940 900 1991

uid 6185's pic
posted by  blue940 on  Thu Apr 26 14:05 CST 2007
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last visit: Sat Oct 18 21:11 CST 2014
[RELATED]

Car: 91 940GL B230F Bosch LH2.4 & EZ116K.
When starting from cold, the engine behaves as though it is running on 3 cylinders. It has also stalled a few times from a cold start. Seems to run OK when warm but sometimes idles slowly ~500 rpm. This morning though it started up and idled fine but after about 3 mintues driving (engine was almost fully warmed up) I went to accelerate up a hill and the engine stumbled for a second which it has never done before.
A couple of weeks ago I found that one the little threaded contacts on the end of a spark plug had come unscrewed (don't know how) and so the lead was just sitting on top of the plug. I fixed that up and the engine seemed much better but it's started acting up again. Warm starts are OK although sometimes it will idle slowly and the Lambda Sond light comes on but goes off as soon as I press the accelerator.
Spark plugs are good, I havent' checked the distributor cap & rotor yet (do that tonight). There are no fault codes logged. What are the possibilities? I'm thinking:
Injectors
bad contact somewhere
Air mass metre (do these play up then come good again or do they fail for good?)

Any help appreciated.
Brad
91 940 GL








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    rough idle 940 900 1991

    uid 6185's pic
    posted by  blue940 on  Fri Apr 27 16:26 CST 2007
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    last visit: Sat Oct 18 21:11 CST 2014
    [RELATED]

    Thanks for your reply Chris

    I made two discoveries regarding my 940's poor cold performance. First the insulation surrounding the inner electrode of the no. 1 spark plug has cracked and fallen off - somewhere inside the engine no doubt. So it was probably arcing out onto the head. I assume this means it got too hot right? Maybe it's related to the second, worse, problem.

    It look like the headgasket has blown. Coolant is leaking out between the head and block under the no 4 spark plug. It's definitely not coming from anywhere else like a heater hose spraying onto it and it's dry around the rest of the engine. I don't know how long it's been like this (I'll slap my own wrists for that). The car has 285 K kilometres on it so I'm hoping it's just age/heat that has taken it's toll. So it looks like I'm up for some work to the old girl. I have some idea of what should be done during this job. Can anyone add anything to this list:

    head gasket (obviously!)
    exhaust and inlet manifold gaskets
    valve seals, guides (maybe)
    new waterpump (existing one is leaking a little anyway)
    new front seals
    distributor seals (the dist. has to come off right?)
    check head for warping (God, I hope there isn't any - don't want to get a new head. parts like that are lots of $$$ in Oz.
    new head bolts.
    Anything else???

    Thanks for any wisdom

    Brad

    PS I tried to add pics of these problems but the site won't let me at the moment...I'll try later








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      rough idle 940 900 1991

      posted by  Paulii on  Sat Apr 28 03:34 CST 2007
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      last visit: Fri Jun 6 03:04 CST 2014
      [RELATED]

      Hello, clean up the head after removal and check for warpage with a good straight edge. If you can slide a .003 feeler guage under the flat edge anywhere you need to resurface the head. The next thing I would add to your list is a timing belt tensioner pulley, flame trap kit, NGK spark plugs, Thermostat, crank sensor, coolant flush, heater hoses and valve. While your at it clean throttle plate and idle air valve. Good luck, Pauli







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