I have a 96' ranger that has been missing quite regularly. The vehicle has over 200,000 miles on it, but has been taken care of regularly by me since 75,000.

Problem: When I start the vehicle, the engine takes a little bit to find the idle. It spits and fumbles around some until it finds a somewhat rough idle. Often, when I first start driving in the morning, the vehicle really jumps around due to misfiring. Even after running smoothly for awhile, the vehicle with sporadically misfire with no rhyme or reason. This is particularly true when climbing a grade. When sitting at a red light and idleing in gear, you can definitely feel the truck shaking from side to side. Also, when idleing in gear, the battery gauge on the dash fluctuates, but when the vehicle is in park the battery gauge doesn't fluctuate...it just idles a little rough.

I had the Ranger to a garage and had them check the battery and alternator connections and ground to try and figure out what is making the battery gauge fluctuate...alternator and battery checked out...no diagnosis for fluctuation.

I replaced all plugs and wires and also checked the coil pack. One of the coils (#6) had some build-up in the top. I cleaned it out and replaced all the plug wires and everything snapped in place and fit fine.

The garage did tell me that an error code came up with the EGR valve and or sensor. They didn't seem to concerned about it. Does anyone think the EGR valve could be the cause of all the stuttering and misfiring going on with the ranger? I really don't know where else to look. Maybe replace the coil pack? Any suggestions would be appreciated. I can provide additional info on request.

Thanks

 

I think the EGR is worth a look. If it's stuck open, then it can contribute to poor running. It doesn't take much EGR flow at idle to stall the engine. In fact, in the early days of smog checks, the gas stations would disconnect the EGR vacuum line and pull a vacuum on the EGR valve to see if it would stall the engine. If it did, they knew the EGR valve at least was able to provide exhaust flow into the intake (assuming it was commanded to do so).

It could be stuck open because of crud buildup (it lives a pretty hard life) or because it's getting vacuum when it shouldn't (leaky/stuck EGR control valve). Or, the computer is commanding EGR flow when it shouldn't be.

 

It could also be a dirty Idle Control Valve. I have a 94 and had the same problem. The batt guage fluctuates as the idle goes low. I cleaned the Idle control and the map, and everything settled down.

 

Welcome to FTE.

You may have more than one problem.

Which engine does your Ranger have???

Might be helpful to know the EGR trouble code the garage found, so post All trouble code Numbers found, as they can offer up good trouble shooting clues. The DPFE sensor is a common problem part in EGR system woes & that trouble code the garage found sorta sounds like it could be for it. We aren't to have ERG feedback at idle.

Driving with the engine misfiring can damage the cat converter & cause it to overheat & melt down internally & that can cause excessive back pressure & all kinds of other woes, so did the shop, or you perform an exhaust back pressure test???? If not, hook up your vacuum gauge & perform scenario test #14 here. How to Use and Interpret a Vacuum Gauge While you have the vacuum gauge hooked up, you might look at some other tests, like for leaking valves, timing, vacuum leaks, ect.

The coilpack is known to crack underneath & arc to ground, so you might unbolt & prop it up with an insulator, then idle the engine at night & look for an arcs & sparks light show as you spritz it top & bottom with a spray bottle of water. Might not be a bad idea while your at it to spritz the new plugs & wires too, just in case one is bad.
As has been said, low idle rpm can cause the alternator to act out. Good idea to have had the electrical system checked out. Most autoparts stores can & will do it at no charge if you need to have it done in the future.
More thoughts for consideration, let us know how it goes.