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Intermittent misfire and tach needle jumping
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Author:  grungypopeye [ June 10 2015, 5:45 PM ]
Post subject:  Intermittent misfire and tach needle jumping

I have a 5 speed 94 MX-3 with a 1.6. Lately about half the time I am driving it the tach needle will start bouncing up to higher RPMs erratically. There is a gain and loss of power with each bounce that feels like I am losing a cylinder to a misfire. This causes a lot of jerking during acceleration and it's really uncomfortable to drive this way, though the engine has never stalled out or had trouble starting. Sometimes it feels like a cylinder stops firing for long periods of time and then randomly comes back to life. It happens at all RPMs and seems to happen more often when the engine is hot, but I may be imagining that.

I changed the plugs, wires, cap and rotor to no effect. My intuition says this must be ignition related because of the jumping tachometer needle. Could it be the ignition coil? How could a bad coil only be affecting one or two cylinders? Is this the distributor? Sadly, this car is barely worth a new distributor.

Thanks for your help.

Nick
Austin TX

Author:  CaffeineTripp [ September 17 2015, 7:33 PM ]
Post subject:  Re: Intermittent misfire and tach needle jumping

Check your intake hose for any cracks that are straight through. The rubber intakes are getting even more and more brittle as time goes on and crack at the ribs. Can give the symptoms.

Do you have any codes?

Author:  4gotn [ February 12 2016, 4:32 PM ]
Post subject:  Re: Intermittent misfire and tach needle jumping

Late to the party again.... it sounds like either a vacuum leak, tps sensor, or if you have the DOHC b6 it could be the internal ignition module in the distributor....those things like to fry themselves and they act all screwy when they do.

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