I got a (actually my uncle's) 91 Explorer with the v-6 motor. The main problem with it is that the transmission wont shift past 2nd. Its an auto tranny. Im not sure which one it is, but the pattern is P R N D OD 2 1.

The check engine comes on, so I'm wondering if I can pull codes myself? If so, where is the jumper? On my 93 f-150, all i have to do is ground a STI plug. I would assume the Explorer would have this too since its probably an EEC-IV computer. Right? Thanks.

 

Yes you can pull the codes. The engine is a 4.0L pushrod (the only engine in 91 - 94 Explorers). The computer is an OBD I system, and you can pull the codes with an OBD I reader, or you can use a test light or an analog DC voltage meter and a small jumper. The procedure for that is located here; http://www.troublecodes.net/Ford/

Also, run a search of this site on Auto Transmission shift. I recall seeing some posts about not shifting from 2nd to 3rd, but I can't remember the cause.

 

And, you are correct, a '91 Explorer is EEC-IV, just like your '93 F-150. Test procedures are exactly the same. The self-test connectors are under the hood, passenger side fender, somewhere between the air filter housing and the heater fan. A '91 Explorer will output 2 digit codes (not sure what a '93 F-150 outputs: 2 or 3 digit).

 

Sweet. Thanks for the input. I'll see what I get

 

Oh but get a scanner - so much easier. Guys from the old school like Mrshorty - how do you do it? I guess working at Intel has made me too high tech or something - yeah and still learning about EEC-IV's...

 

A short piece of wire is all I need.

Here's the retrieve codes:
KOEO = 11 (systempass)
CM = 41, 66

The 41 i can diagnose since I dealt with it on my f-150. The 66 is new. What is a TOT sensor?

Also, i tried running a KOER test but, I didnt get anything. I'll try again later.

 

Not related to the EECIV discussion but on the transmission.

I'm going from memory here but I think your issue may be with a vacuum line from the tranny up to the upper intake manifold. On the A4LD tranny there is a vacuum modulator on the passenger side up past the heat shield about half way up the housing. You can get at this from below (maybe) or above by removing a plate-cover on the "doghouse" under the carpeting in the front seat area of the cab.

Anyway. The vacuum switch has a 4-6" piece of rubber hose running to a hard vacuum line which snakes up to the top of the motor and then a 4-6" rubber vacuum line conects it to the vacuum tree on the upper intake manifold. Check to see that these are intact. Check for the proper level of fluid. I have also heard the modulators fail. They can be replaced for about $15.00 but check the vacuum lines and fluid level first.

P.S. if you replace the modulator watch out for the spindle that comes out when the modulator is removed. It's hard to replace. You'll also need little girlie hands for this job.

Remember I'm going from memory. For more information do a search on "vacuum modulators"

 

TOT is transmission oil temperature, but your Explorer doesn't have a TOT. On an Explorer, a 66 is an MAF low code. Considering that both the O2 sensor and MAF are the principle inputs to determining fuel mixture, I wouldn't be at all surprised if the two codes are related to the same fault. Let us know what the repeat attempt at the KOER test yields.

And as for This is a valid question. The answer lies in how much do you want to pay to get trouble codes. As near as I can tell, up to the '92 model year, EEC-IV computers don't have the ability to output real time data or anything else beyond trouble codes to a scanner. So you put all that money into a scanner, and all you get is trouble codes, which I can get with a paper clip. Some people prefer to buy one of the cheap EEC-IV code readers and feel they get some advantage to that, I don't know. As I see it, you can pay $25 and get a red LED that blinks (some even have a buzzer), or you can pay $0.25 and count the blinks of the check engine light. I'm cheap, so I go with this last option. As soon as someone tells me definitively, "I hooked up scanner Y to my '92 Explorer and got all the real time data." then I will be in the market for a good scanner.

 

I've gotten a MAF low code in the past, only once. It was stuck in memory from some event. I never adressed it and I never got the code again. Now that you have the memory codes, disconnect the battery to clear them and then see if they come back. If the truck is running OK and you don't have any more CEL and codes, nothing to worry about. If you keep getting codes, let us know like Mrshorty says and we go from there.

And I think this is a great point on scanners. My 93 is a little more advanced than they earlier models, apparently. If all you get is codes from the older PCM's then use a paper clip for sure. My 93 has the 3 digit codes. I can scan real time parameters which really helps in troubleshooting. Watch the O2's switch, watch for WOT AC cut off, watch for open/closed loop - it's great! For some dumb luck, planets all aligned or something, the timing of my new truck purchase in the 1993 model year worked out great. I have advanced OBD1 diagnostics, 4 w ABS, revised Intake and head gaskets, all the vibration control dampers, SFI (but that was standard in Cal) right and left O2's - all in a EFI control system that is not too restrictive. And now, chips are available that can be programmed with help from a dyno to exact my A/F and spark curve - which should be happening this week!

 

He said the motor is not the original one. The old motor overheated and seized. Its still the 4.0, tho.

While looking under the hood, I noticed some loose vacuum lines leading to nowhere. I'm gonna try to find a diagram and hook everything back up. I'll check the vacuum modulator as well.

I will clear codes and drive it to see if they come back. Also, i'll post the koer codes tomorrow.

 

As I see it, you can pay $25 and get a red LED that blinks (some even have a buzzer), or you can pay $0.25 and count the blinks of the check engine light. I'm cheap, so I go with this last option.

My Hayne's manual describes reading the codes with a volmeter and a jumper. How do you do it by watching the CEL? I have a '91.

 

The CEL blinks and you count. There's a pause in between the pulses.

 

While looking under the hood, I noticed some loose vacuum lines leading to nowhere. I'm gonna try to find a diagram and hook everything back up. I'll check the vacuum modulator as well.

My Explorers have the vacuum diagram under the hood right in front. Also, a symptom of a bad vacuum modulator can be loose vacuum fittings on the cluster that got contaminated by automatic transmission fluid.

 

Ahh thats right. There probly is a diagram under the hood.

 

I think the vac diagram under the hood only covers the pollution control devices. This is most of it but there is still vac to HVAC blend door and maybe other devices not on that diagram. Either a repair manual or Autozone.com have a more complete diagram.