Jolt felt when driving - 03 Mitsubishi Diamante

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Jan 23, 2014
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Hi everyone, I have a 2003 Mitsubishi Diamante, about 120K miles on it. Recently I've noticed it jolts every now and then when driving at a steady speed. Sort of like the engine switches off momentarily. The jolt is more harsh than when the A/C compressor kicks in, but similar feel overall, however this has happened with the A/C off. Any ideas of what this may be?
 
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Dec 19, 2004
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beaver land EH?
I recalled you had performed valve stem seal replacement recently to deal with oil burning issue, so I'd assume that you may have disrupted the vacuum hoses, some vacuum-related solenoid or even wiring. Check those first. Q.
 
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Originally Posted By: StrangeBrew
Bad spark plug wires. Happened on my Fiat X1/9 back in the 80's.
There you have it. The definitive diagnosis of the unknown. Next!
 
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Bad magneto, happened on my model A in 1936. Or sediment in the float bowl that happened on my lawn boy.
 
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Seriously though, it sounds like an electrical connection between the crank sensor and coils. Check the harness. Shift the harness around while idling in the driveway.
 
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It sounds a lot like the symptoms I experienced when a throttle position sensor was going bad. Driving down the road at a steady speed there was an occasional quick drop in RPMs, just enough to feel the slight jolt and see the tach needle jump. When I asked the question here, I also compared it to the air conditioner compressor kicking on, just somewhat more noticeable.
 
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Originally Posted By: asand1
Bad magneto, happened on my model A in 1936. Or sediment in the float bowl that happened on my lawn boy.
Model A's didn't have magnetos.
 
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Any new OBD II codes or is the light on all the time? Perhaps no OBD II system to be plagued with in OZ?
 
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I suspect a loose/corroded, or breaking electrical connection that is breaking and reconnecting. Do a wiggle test. With the engine running at idle, in neutral or park with p. brake on, try to duplicate the issue by wiggling all electrical wires and harnesses under the hood. Then the wire harnesses under dash that you can reach. Of course it could be a failing component also, but an intermittent issue like you describe will be hard to pinpoint to a failing component. Do the wiggle test first.
 

hpb

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Originally Posted By: HerrStig
Any new OBD II codes or is the light on all the time? Perhaps no OBD II system to be plagued with in OZ?
Not on a Mitsubishi of that age.
 

Spetz

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As additional info to the problem: It has happened just a handful of times, so it's very rare. I drove 60 miles today with no symptoms. All filters, plugs, plug wires etc are new. If I understand the previous posts correctly, it is possible the distributor is starting to die?
 

hpb

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Distributor failing is possible, yes. Really, it could be anything, so before replacing components, get it along to a dealer and have them check for codes, at least that'll point you in the right direction.
 
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It can be an ignition distributor. One thing that really sucks about Mitsubishi distributors is that new ones are very expensive, and rebuilt ones only last one year.
 
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Originally Posted By: another Todd
Is it possible the the torque converter clutch is unlocking then locking again?
Good point. Mitsubishi uses SP-III in that automatic transmission, and if Dexron III is used, it will not function properly, and it will shorten the life of the part. Plus, Diamond-matic transmissions weren't very durable anyway. If you don't know how the previous owner serviced the transmission, you could have the wrong fluid in there.
 
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