2012 Ford Ranger

I have a 1987 Ford Ranger 2.3L 5 speed, with 139,000 on it, and about 12,000 on the engine.

The problem I have is that the engine surges from 3300-2700 RPM. It does not matter if I am on the highway, or parked. So far I have replaced both fuel filters, the low pressure pump, fuel pressure regulator, EGR valve. The fuel pump was dead, and the EGR diaphram was torn.

I have 32 PSI of fuel pressure at idle, 40 as soon as it speeds up. I have also connected and disconnected the EGR, and ther is no avail. The vehicle behaves the same wether its warm or cold. I also have a top speed of 62 MPH.

Any help? PLEASE?
October 18, 2007.

When was the last time you gave it a major tune-up?

Could be an oxygen sensor problem or a lean fuel condition is more likely a fuel delivery problem (weak fuel pump, restricted fuel filter, dirty fuel injectors or a leaky fuel pressure regulator) than a vacuum leak.

Check the exhaust for excessive backpressure to rule out the catalytic converter.

EEC system-such as the TPS/MAP/MAF sensors

Oct 18, 2007.
The cat was already checked. As far as a major tune up, I have no history of one. I swapped the coils for a known good one today, and if I feather the gas, I can get 4500-5000 RPM, but it acts as though the ignition is shut off as soon as I apply full throttle.

I am going to remove the ignition control module now, and have it tested to ensure it is good. I also put some fuel injector cleaner in it today when I fille dup the tank. I am suspicios of possible dirty injectors as well.

Once again, Thank you so very much for your help.

Oct 19, 2007.