I have a 71 Challenger w/ original stock 340/Auto. The wiring and tack are stock and unaltered. The tack reads nearly 2 times higher than it should. At idle it is fairly accurate but above 1200-1500 RPM the numbers go up significantly.
Looking for ideas on where to start to troubleshoot this issue. The gearing in the car are stock.
Thanks

it does not use a sender but is directly wired? Kinda sounds like a tack issue itself (especialy if no sender) but I would take it out & jump it directly & see if it still acts up, red to power it, black to ground, green to coil neg primary (double check on the green if that is the correct sense wire on OE tacks)