Pickup coil went out . so i replaced coil and distributor . retimed truck and the vehicle runs perfect but governs out at 52mph hot or cold. Also replaced knock sensor egr valve and soleniod. I also swapped pcms with identical truck no change
My car has an automatic transmission.
There are a number of things I can think of that could cause this problem. Of course the obvious would be timing. Next I need to make sure you are aware of the ignition timing connector that is located on the passenger side of the dash next to the heater blower motor. If it isn't there, it will be under the hood, on the passenger side of the firewall, taped to the wiring harness that runs along the fire wall. Your year is a transitional year when it could be found either place.
Once you find this connector, you will need to warm the truck, disconnect the EST (electronic timing control) connector and then set the timing. Unplugging the EST connector stops the computer from making timing adjustments so a static initial adjustment can be made.
The other thing that comes to mind and is more common, is a plugged exhaust system. While the car is sitting still and idling, you should be able to feel a strong exhaust note coming from the tailpipe. To further test this theory, rev the motor up in neutral and see if it will reach the red line. If it won't, you most likely have a plugged exhaust. While reving it, have someone continue to feel the exhaust coming out the exhaust pipe. If it is plugged, there won't be much coming out.
The next possibility is, is the transmission shifting out of first or second gear. This is best watched with the tachometer.
Following this would be fuel pressure or volume. This needs to be tested with a fuel gauge that has a relief valve. Volume and pressure differences are nuanced and often difficult to explain. For this reason, this concept is best demonstrated.
There are a few other possibilities, but these are the most common. My instinct would be to check for a plugged exhaust first. If you should still need help, I recommend the following inspection to help you out; loss of power inspection which can be performed at your home or office. The description of this inspection may not be exactly what you are describing, but the skill set necessary for your diagnosis is the same.
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