Does anyone have a clue as to what would cause my Trooper to lose power at exactly 47mph every time?

It happens while accelerating up through the gears normally, all is well until it hits 47 and the engine loses power slightly until it gets to 48 and then all is well again. It does not misfire or stall, its as if I let off the accelerator momentarily, I am clueless as to what the cause may be. It may not be related but I go through an ignition module about every 1 and a half years...

Any ideas?
Mark

Is it just tied to speed or rpm?

Can you duplicate the hesitation at the same rpm in a higher gear (lower gears may not help due to greater torque compensating for the hesitation)?

I have noticed it in fourth and fifth gear, its the strangest thing. Always in the exact same spot speed-wise, its a little more noticable if I am accelerating slower (I would guess because it takes longer to get through the 47mph sputter zone).

How's your speedometer needle at those speeds? Is it wiggling? If so it may be causing issues with the VSS (Vehicle Speed Sensor). Time to lube the cable perhaps.

Another thought is a dead spot in the TPS (Throttle Position Sensor). You could do a resistance check with a meter to rule this out.

Maybe it's time to check trouble codes to see if there's any lodged in the ECM's memory. It might lead you down the path to diagnosing your problem.

http://www.troublecodes.net/isuzu/ (to place the ECM in diagnostic mode, short the 2 pins in the corner of the ALDL plug under the main console lift-out tray, and turn the ign to "ON").