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I need your help guys, My 70 is misfiring when the trans is engaged and the brake pedal pressed (Ihave manual brakes). The whole car shakes like @#LL, but in park,neturel,or cruising purrs like a kitten, What could be the possible causes this problem?
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Sounds like you have a vacumn leak? The one thing that comes to mind is the vacumn modulator valve on the trans? Not sure it will cause your problem, but it's the only thing tied into the vacumn source, relating to the trans. JTS 71 Mach1
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I have a new Mod. Valve but I did not know if a faulty tq converter could cause this kinda issue. I'll put the mod. valve in and see what happens.
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02-29-2012, 04:01 PM
I would agree with the vacuum leak. Have you done anything to your engine recently. Perhaps moved any vac hoses, the intakes are famous for leaking, you can lightly spray a little wd40, (if your engine is not a show piece) around your intake and carb base and see if the engine idles up, if so you have a leak. Don't know if that may helps, just a few thoughts. If it is a direct misfire plug wires can lead you astray, they can act very intermittent if they are old.
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Vacuum leak would be most noticeable at idle. What you have is a bad plug wire or a fouled spark plug. I say that because it is missing under a load.
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I would agree with Don, leaning toward the plugs especially if it just gets started and shut off alot.(without driving enough to clean it out).
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I just replaced all the plugs yesteday and it still (misfires) under a load. It runs fine in park, netural, and driving. only acts up while stopped at a light. It's got me confused.
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compression test time im thinking.Vacuum test also.
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i would check timing chain, pull off dist. cap and turn crank by hand one way and until rotor turns, then turn other way til it moves should be next to immediate.if crank moves like a quarter inch or more your chain is hooped, if your chain is loose as you decelerate your timing will float around and cause the rough idle, yet unnoticeable at cruising and in acceleration the chain is tight keeping your timing consistent. i would bet on this being your problem.
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you think a .538 lift on this cam could be a issue?