Hey Ya'll- I've got a 1990 Ranger XLT with a four banger (2.3?), that is getting only 10mpg!! Runs like crap/ no power,etc. In the last month I have replaced the O2 sensor, air cleaner and cleaned the MAP sensor. The previous owner has installed sun gauges for eng. temp (190-195) and oil pressure. I've been reading the threads here about the engine not knowing it has warmed up and not ever going closed loop and thought perhaps the p/o had disconnected the ect sensor when installing the new gauges, so I went huntin' for it. My book shows it in the coolant hose near the water pump, left side. There is a piece of straight tubing inserted as a coupling in about the right place, but no ect and NO PIGTAIL to plug in. Is it possible it's located somewhere else on the '90 model?
I love my truck and want to keep it running 4ever, but not at 10mpg. It starts right up every morning and runs great til it warms up, then acts like a stuck choke would; no power, very rich smell, black sooty exhaust deposits,etc. I run fuel injector cleaner almost every tank. The trouble codes indicate that all the sensors could use replacing, but my budget says one at a time... HELP?!!

 

PS- also the truck runs MUCH better after the CEL comes on. Whats up wid dat?? Thanks

 

Get a manual and get familiar with it. That should help. The more you understand about how your electronic engine control works, the easier it is to start trouble shooting.

 

You have EEC-IV (aka, OBD-I). What you need to do is pull the KOEO codes and repair the faults causing these codes. You then clear codes, drive, then retest for codes. Hopefully all KOEO codes are gone (other than 11 or 111) then you move on and check for KOER codes. Once the reasons for these codes are fixed, repeat the clear codes and drive step. Next, test for KOEO, KOER, and CM codes. There should no longer be any KOEO and KOER codes and hopefully there are no CM codes. If there are, fix the faults causing the CM codes then clear codes, drive, and perform one final test for codes. All types of codes (ie, KOEO, KOER, and CM) need to be 11 or 111 in order for you to have completed repairs.

You MUST fix codes in the order I noted as a KOEO code can trip an invalid KOER or CM code. Likewise for a KOER code tripping an invalid CM code. You MUST also repair the codes within each tier starting with the LOWEST number; the reason is the same as for fixing KOEO codes before fixing KOER codes. If you do not follow what I just said, you will most likely spend extra time and waste money trying to get things fixed. A Ford factory service manual or one from Alldata are very helpful in that they have diagnostic flow charts and pinpoint test that guide you through the process of fixing the fault(s) that are causing the codes. One must remember that a code does NOT always mean a failed sensor; there can be other reasons. Some reasons include open wiring, electrical short, poor connection, maybe a missing sensor, etc etc. Finally, I highly doubt that each and every one of your sensors is bad all at once. The way to attack the problem is noted in this post. And whatever you do, do NOT buy any parts, including sensors, until you have proven that in fact the part has failed. Simply throwing new parts at a problem without proving that the one you have has failed the lamest approach to fixing problems on computer controlled systems as it usually proves to be expensive and the outcome is unknown. At this point in time, you need to do diagnostics to determine the cause of the codes.

*You note that you are on a budget; if you follow what I said above you will have more money in your wallet when you get done with fixing this as opposed to the alternative.

 

Thanks,and you're right. I've worked on motorcycles long enough to know that throwing parts ($$$) at a problem usually won't work. A diagnostic flow chart would obviously be very helpful. Does the Chiltons manual have the needed info? There's one on ebay right now, but no factory or Alldata books I see.
Thanks also for the right procedure to follow the faults. THAT wasn't in the Haynes!
Still like to find that #@&#! ECTsensor tho!

 

I kinda doubt you will find these charts in Chiltons; maybe go to a library and look to see if they have one before buying. Have you looked in the online repair manuals on autozone.com to see if they were kind enough to post a sketch/diagram?

 

I'm not sure, but the 90 models may still have the ECT in the intake manifold. It is in the center of the lower intake just out from the cylinder head. It is the only sensor there.
The sensors were later moved to the heater hose. Some were close to the firewall. Also, some models have the sensor in the thermostat housing, this may be the V6 models. I don't remember.

It runs better with the CEL probably due to the engine management system going open loop which means the engine is running on pre-set values as the problem will not let the engine go closed loop which is using sensor inputs for engine management. jd