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Engine Miss at 4500 rpm

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Ray Smith

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An acquaintance of mine has a Bj7 that has a misfire problem. He has replaced the dist cap, plug wires, rotor, points, and coil. The car runs fine until it reaches approx 4500 rpm. At that point is starts to miss.

He mentioned one thing that I found rather strange. He indicated that when the timing was retarded, the engine did not miss at the 4500 rpm point, but that it obviouisly had a loss of power.

Any hints on how to correct this problem?

Ray
 
Is it an advance problem? Either the balance weights not moving out or a leak in the vacuum advance? This is a guess!

Alternatively is it the corrcet distributer - is the advance curve wrong for that engine???
 
I had the same problem with my engine. I would not rev above 3400 rpm, and the engine started to misfire, and massive loss of power. I checked everything, fuelpump, carburettors, needles, and the distributor(check springs and weights).
When I took the engine out this winter to change the cam, I found out that the timing chain was offset by two teeths.
Hope that this is not your friends problem.
 
My problem was fuel when I could not get above 3500, only running on one carb.
Bob /ubbthreads/images/graemlins/england.gif /ubbthreads/images/graemlins/cheers.gif
 
Ray,
A vacuum check should help to diagnose late ignition timing, value timing, carburetion and a whole host of other engine related maladies. A “normal” engine should pull at a steady vacuum reading in the 16 to 22 Hg range at idle. This just might be worth giving a try in order to eliminate some of the mechanical affects.

Also look into electrical things such a failing ignition coil. Good Luck, GONZO
 
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