i have 1991 ford ranger 2.3 with the 8 spark plug ignition 5 spd . the engine starts up fine every time with no problem. when i start driving if i just hit the gas anything more then 1/2 it will bog and eventually stall and or backfire bad..(all i have to do is turn the key off and than start it again and imediatlly it will run again).....if i just gentlly bring the Rpm's up i can drive it normally untill im on the highway. Once i throw it in 4th or 5th on the highway and get above 55 it just boggs and eventually stalls and or backfires like b4.. it seems if there is any strain in the engine it will bogg and by strain i mean bringing the rpms up at a normal pace...i can drive it as long as i baby it really bad and it will be fine till 45+..i have put a fuel pressure tester on it and when it boggs it loses fuel presure, i dont knwo if thats normal or not. I have replaced the injectors,changed all the gaskets, cleaned the head ,intake, and pistons. nothing helped its just doing the same thing as when the last owner had it. i just dont think its the fuel pump because why would it be able to rev up as long as i dont hit the gas hard, if the fuel pump was bad i would imagine that it wouldnt matter what gear or what mph or what throttle it was at it wouldnt get gas...... please help !!! -Tom

 

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A few things occur to me right off. One is the fuel pressure regulator itself, and another is a clogged filter restricting flow. With all you've tried so far I would assume you replaced it already and just forgot to mention it. It's alsompossible for the fuel pump to be going bad in such a way that it's putting out adequte pressure from time to time, such as when the engine is under no load or light load but not be able handle the higher load situations. Also, there is a small filter screen at the base of the pump that could be partially clogged. (Sorry, it's in the tank just like the pump so tank or bed removal is required to get to it.)

You didn't say what your actual FP reading was. It should be in the range of 35-40 psi and no, it, shouldn't drop like that when it bogs.

Also, you should put a code scanner on it and pull the codes. Just because the CEL might not be coming on doesn't mean there aren't codes being generated and stored. Here's some more info on that:

http://fordfuelinjection.com/?p=13