2.9 rough idle and misfires at lower RPM, low power.

[JLArangerdriver]

I have a 1987 ranger 4x4 standard transmission with 59,XXX original miles. (although there's a chance it could be 150,xxx)It was well taken care of, but sat for years. It has random misfires at idle, no single cylinder is a dead miss. Same issue when driving, but down shifting, increasing the RPMs seams to fix it most all of the time. I just put in new injectors, new fuel filter, new tank and cleaned all the gunk out of the fuel rail and lines. The truck sat for about 4 years after I had replaced the injectors and filter, but not cleaned out the fuel rail, and only cleaned the rusty tank. I'm pretty sure the Truck wasn't doing this before the injectors in it when I bought it started to fail. I disabled the EGR, by disconnecting the electrical connector and capping off the plastic vacuum line, that was already broken. I assumed this would cause the EGR valve to remain closed, but is their a chance it's stuck open? The tiny plastic vacuum lines that go to the air cleaner box were broken when I got the truck. I remember it idled rough and high, but no misfires while driving. I reduced idle by turning the adjustment screw on the throttle body, I think I saw that you arn't really supposed to do it that way, but it worked. I've replaced the distributer cap, it was pretty warn, but I've seen worse still running okay. It didn't help. I can't find any vacuum leaks, the vacuum line for the MAP sensor holds vacuum... but tastes very bad, haha. I haven't done a compression test since it sat for a few years, I'll probably do that tomorrow. I have to borrow the tool. I'm between jobs right now and don't have extra cash to throw a lot of parts at it, unless I have to. I'm not the best at diagnosing 1980's EFI vehicles. The best I can figure is it's either bad MAP sensor, Idle air control unit, distributer, ignition module, O2 sensor, the EGR is stuck open, the cheaper injectors I put in it were bad ,or maybe the ECM/computer is messed up. I'm not sure how I'd even go about replacing that last one, does it need to be programed to the truck? I could probably spend a lot of money replacing all of these and with my luck lately, it still might not fix it. No oil in the coolant or coolant in the oil. I also had to solder new connectors onto the injector harness. What I'm asking is, what should I go after first, and are their ways to rule out any of these potential causes?

 

[ryan445]

I am currently chasing something similar. Currently I am at the last two possible things. Injectors or ECM. I'm gonna attempt to take out and clean the injectors. I am sure they are clogged with the 4 year old fuel I had.

If you have a code reader for the EEC-IV computer it may help you pin point something but the computer, really since it isn't that smart, it can come back all clear and still have issues.

Did you replace your fuel filter after it sat for four years? If not I would definitely start with that that. That gas was definitely lacquered after that long. Unless you had no gas in the tank and line at that time.

Do you remember what your plugs looked like when you pulled them? Did they look fouled or lean in any way? Plugs can help tell a story.

 

[PetroleumJunkie412]

I have a 1987 ranger 4x4 standard transmission with 59,XXX original miles. (although there's a chance it could be 150,xxx)It was well taken care of, but sat for years. It has random misfires at idle, no single cylinder is a dead miss. Same issue when driving, but down shifting, increasing the RPMs seams to fix it most all of the time. I just put in new injectors, new fuel filter, new tank and cleaned all the gunk out of the fuel rail and lines. The truck sat for about 4 years after I had replaced the injectors and filter, but not cleaned out the fuel rail, and only cleaned the rusty tank. I'm pretty sure the Truck wasn't doing this before the injectors in it when I bought it started to fail. I disabled the EGR, by disconnecting the electrical connector and capping off the plastic vacuum line, that was already broken. I assumed this would cause the EGR valve to remain closed, but is their a chance it's stuck open? The tiny plastic vacuum lines that go to the air cleaner box were broken when I got the truck. I remember it idled rough and high, but no misfires while driving. I reduced idle by turning the adjustment screw on the throttle body, I think I saw that you arn't really supposed to do it that way, but it worked. I've replaced the distributer cap, it was pretty warn, but I've seen worse still running okay. It didn't help. I can't find any vacuum leaks, the vacuum line for the MAP sensor holds vacuum... but tastes very bad, haha. I haven't done a compression test since it sat for a few years, I'll probably do that tomorrow. I have to borrow the tool. I'm between jobs right now and don't have extra cash to throw a lot of parts at it, unless I have to. I'm not the best at diagnosing 1980's EFI vehicles. The best I can figure is it's either bad MAP sensor, Idle air control unit, distributer, ignition module, O2 sensor, the EGR is stuck open, the cheaper injectors I put in it were bad ,or maybe the ECM/computer is messed up. I'm not sure how I'd even go about replacing that last one, does it need to be programed to the truck? I could probably spend a lot of money replacing all of these and with my luck lately, it still might not fix it. No oil in the coolant or coolant in the oil. I also had to solder new connectors onto the injector harness. What I'm asking is, what should I go after first, and are their ways to rule out any of these potential causes?

Man you have so many possible points of failure there...

Ok. One. Are you **sure** the injectors you bought are the same flow rate as the ones you took out.