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drive line hesitation 900

For some time I would have an occasional hesitation or shudder in the drive line, maybe one or twice a month. it has been happening more frequently and today it seemed like the car might not make the 20 mile drive to work. it did but I had to babby it. It drives smoothly until this event occurs.

It feels like the drive shaft or rear end. Transmission shifts smooth and has regular fliud changes. Any advice on where to inspect?
--
89 240 wagon, 94 940, 300K, 94 940, 141K





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    drive line hesitation 900

    Wanted to tie up loose ends on this. I thought the compressor needed to be replaced because the clutch or main body was seizing. I eventually noticed the harmonic balancer(likely 25 years old) was failing so I replaced it with one of the many used ones I have. Since then there has been no symptoms and the AC works great. What a car!!

    So it seems that a failing thou yet unnoticed balancer can lead to a progressively worse shuddering with the AC engaged.

    I do wonder if something with the compressor ruined the balancer.
    --
    89 240 wagon, 94 940, 300K, 94 940, 141K





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    drive line hesitation 900

    I have noticed some shutter occurring on my '92 940NA as the auxiliary fan kicks on during hot weather with the A/C on. It can be quite pronounced, why more so in hot weather? No idea.





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    drive line hesitation 900

    After trying a number of the suggestions here, the problem persists and is getting more frequent.

    As I said, it is heat related. So is the use of the AC. I have determined it only occurs when the AC compressor is on. It doesn't happen when revving in park; usually at higher speeds or accelerating.

    So any idea why I get a shudder/hesitation when the AC is on? I have marked up the harmonic balancer and there is no apparent shifting of the outer relative to the inner. The compressor is not making any noticeable bearing noise and the AC works well.

    Maybe something electrical?
    --
    89 240 wagon, 94 940, 300K, 94 940, 141K





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      drive line hesitation 900

      Dear j.pelchat,

      Hope you're well. I wonder if the AC compressor is misaligned, due to deterioration of the rubber mounting bushings. If so, the drive belt might bind against the pulley, causing the compressor to impose an extra-heavy load on the engine. For such a misalignment to matter, it would have to be easily visible and the belt should show wear.

      Another possibility is that the AC clutch no longer turns freely. This, too, can be ascertained by observation.

      Please post your findings.

      Hope this helps.

      Yours faithfully,

      Spook





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        drive line hesitation 900

        Spook, Thanks for diligently following up on my problems.

        Alignment is fine. I was unaware there were any rubber mountings for the AC compressor.

        Indulge my ignorance about the AC. The belt always runs when the engine is running. The front of the compressor spins when the system is on. I guess this to be the clutch. I hear no unusual noise.

        When revving the engine, the clutch will often momentarily stop spinning. This is obviously the cause of the hesitation. The freezing of the clutch must be impeding the smooth operation of the engine. There is no apparent change in the rotation of the main crank pulley and the belt continues to turn.

        The belt is tight and shows normal wear for 3.5 years. If anything the belt is too tight.
        --
        89 240 wagon, 94 940, 300K, 94 940, 141K





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          drive line hesitation 900

          Dear j.pelchat,

          Hope you're well. I concur with jd620. If the compressor is properly aligned and the belt is not over-worn, then the clutch is the culprit. Perhaps an adjustment is necessary, as the "momentary pause" seems to occur only when the engine is revved.

          Amarin - who hangs his hat in Malaysia - has encyclopedic knowlege of, and deep insights into, these systems. I hope he'll comment.

          Hope this helps.

          Yours faithfully,

          Spook





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            drive line hesitation 900

            Thanks Spook! I must have overlooked this thread being out of the country at that time. Anyway I have addressed the issue in the latest post:

            See: https://www.brickboard.com/RWD/volvo/1664762/940/960/980/V90/S90/seeking_advice_ac_compressor.html

            Regards,
            Amarin.





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          drive line hesitation 900

          I don't like mentioning it but I wonder if your compressor is about to lock up.

          I had a similar problem years ago on a 1980 240 that didn't have the low pressure cut-off switch for the compressor. I was driving along, the compressor locked up, and I thought the engine was going to kill. I reached over and turned the A/C switch off and the engine recovered.

          Try turning off the A/C the next time the engine stumbles.
          --
          Mine:3-940s running, 1-740, 2-940 parts, dtrs:3-940s running





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    drive line hesitation 900

    More info on this.

    The symptoms were really bad on Thursday when it was hot, maybe 90 degrees. Friday and Saturday were much cooler, in the 70's and there were virtually no symptoms. Today, Sunday was hot again and the problem was back albeit not quite as bad as the other day. So this problem seems heat related.

    The center bearing and rubber mount were replaced less than 5 years ago. It looks ok. I couldn't find excessive play or binding in any of the u-joints, though I didn't unbolt any of them. I did notice a lot of oil on the differential. It has obviously been leaking from the seal. I haven't been able check fluid inside the differential yet.

    Given the obvious heat related nature of this, any further thoughts?
    --
    89 240 wagon, 94 940, 300K, 94 940, 141K





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      drive line hesitation 900

      Dear j.pelchat,

      Hope you're well. Yes!! An engine temperture sensor (Volvo#: 1346030; Bosch#: 0 280 130 032) - mounted in the block, sends a signal to the Engine Control Module. If this sensor's signal fails, the fuel/air mixture is other than optimal. This sensor's failure usually degrades fuel mileage. An over-rich mixture can cause carbon deposits on the spark plugs. That could produce rught running all the time, i.e., not intermittently.

      Another possibility is that the ignition control module - mounted on the inner fender wall (driver's side, North American models) to the rear of the headlight - has failed. This sensor is heat-sensitive. When its signal is lost or becomes erratic, the engine will not run smoothly. I think this is the most likely culprit.

      A third possibility is that the fuel injection relay (radio interference suppression relay) - mounted on the inner fender wall (passenger's side North American models) to the rear of the headlight - has failed. The engine should run rough as injectors sometimes don't get the power they need. This relay's intermittency could vary according to ambient temperature.

      Hope this helps.

      Yours faithfully,

      Spook





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        drive line hesitation 900

        Spook,

        As always, a thoughtful reply. I don't think it is engine related as the symptom has been presenting in a very limited way for a long time. Also, it feels like something is slipping in the driveline. Not a big expert here but have been working on this car for 11 years.

        The ignition control module was re-pasted 5 years ago, but I do understand the heat related failure of this component. It's any easy swap and I have a couple so I'll do it. I'll put in another radio relay, too.
        --
        89 240 wagon, 94 940, 300K, 94 940, 141K





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          drive line hesitation 900

          You can also check OBD-1 fault codes:

          https://www.brickboard.com/FAQ/700-900/

          Though the fault may be faulty connection to ground or power. Like the fuse and relay board (usually) hidden by the ashtray. Corrosion can form at the connectors. See any heat warped plastic. Or can be a corroded connection in a wire harness connector.

          How do your fuel pump(s) sound to you?

          Hope that helps.
          --
          Give your brickboard.com a big thumbs up! Way up! - Roger Ebert.





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    drive line hesitation 900

    Dear Mr Pelchat,

    My first thought would be broken/loose prop shaft centre bearing rubber support (not the bearing itself). This could present itself from giving off occasional jerking (often went unnoticed) to sudden full blown situation. Happened to me once while driving on highway. At worst it sounded like loose marbles in a tin can from under the car. And the car was still drivable albeit slowly (around 30 to 40 km/h). I was able to drive home and waited next morning to drive the car to my Volvo mechanic. Recommended to also replace the centre bearing at same time.

    Second thought could be the rear wheel bearings. Haven't happened to me. Usually the wear would give some rumbling noise before anything happens.

    The centre bearing itself would give some early low rumbling noise so this couldn't be it. And the U-joints are very sturdy. I had asked my mechanic to replace the joints during the repair episode above but he refused as he tested the 20+ years joints were still good.

    Lastly could it be loose wheel lug nuts?

    Still need to go underneath the car to see whats really the issue.

    Regards,
    Amarin.





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      drive line hesitation 900

      Good thoughts, Amarin.

      If it is a case of a beat-up center support cushion you would expect it to shake around all the time, not intermittently. Same thing with the trans output bushing.

      I'm wondering if a U-joint is seizing up once it gets hot.

      Joe,
      You may already know this, but before you pull the drive shaft apart, mark all of the pieces such that you can reassembly them in exactly the same relationship to each other as they were originally. The two halves of the drive shaft are "phased" in a certain way to maintain balance. The center splines on our 1990 740 were keyed in a way that you could only mate them one way, but I'm not so sure that is always the case.

      --
      Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)





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