hello, i have a problem that has been affecting the performance of my truck (85 ranger 2.3 5-speed) for a while now.

my truck misses at highway speeds when i try to go at a constant velocity. the miss seems to come in a repetitive pattern--about 5 seconds of running smoothly, and then the miss returns. the only thing that breaks the truck out of its missing is me punching the accelerator. if i want to truck to run smooth, i have to always accelerate, which causes high speeds and speeding tickets. it seems that if i drive it for a while, and let it get warm, then shut it off for only a few minutes, say enough time to get gas, it is more likely to run poorly.

the truck also idles poorly, its idle will go way down, and the truck will sputter, and then it will correct itself for a while until the idle sinks again...only to repeat this pattern. i have noticed a decrease in gas mileage, black smoke coming from the tailpipe, and carbon fouled plugs.

i have recently given the truck a full tune up, and replaced the egr valve. when i run the codes, i get a code 31, which indicates that the egr valve is not closing completely. this seems consistent with the problems i have described above. what would cause this, and how can i fix it?

 

An EGR valve that is not closing completely will definitely affect part throttle & idle much more that wider throttle openings. I'm not INTIMATELY familiar with the EGR in Rangers. But, I have several easy tips. There is a vacuum line going to the EGR vacuum diaghragm. This is what opens & closes it. If you disconnect that vacuum line, and plug it up, and the truck CONTINUES to run bad, there's a good chance the valve needs replaced. If the problem disappears while the vacuum line is off, then the circuitry that controls the vacuum signals is at fault. It could be the solenoid valve that controls the vacuum (they do fail eventually). Or, it could be a sensor that "tells" the solenoid when to operate. Do the vacuum thing first, and let us know what happens.

 

Not sure if this will help:

http://www.smpcorp.com/download/view/Tt2Q00.PDF

 

hey thanks for the great advice! i plugged up the vacuum line you wrote about, and the truck has been running remarkably well. i suppose this means that the problem lies in the solenoids or the wiring? i will check them out, and let you know the outcome. will it do more harm than good to just leave that vacuum line plugged, or simply block the egr valve off altogether? i dont live in a state with emission testing, so that is not a problem. thanks again.

 

The only 2 possible results from running with NO EGR are [1] possibly increased NOx emmissions (no big deal), and [2] possibly increased level of pinging (increased octane requirement). If you hear no pinging, you don't have to to ANYTHING ELSE. Just drive it.

 

just make sure you hook it back up for your yearly emissions test.

Also, I would guess the problem is in the PFE. Older Rangers used a PFE instead of a DPFE that newer models have. They do go bad.