MAF, O2, Injector bandwith codes.

[Jeff H WV]

Hello,

I have been battling this problem for a long time as I only drive it sporadically. Is a 93 model with 4.0L. I get a CEL always in the same places, comes on when going up a long grade at around 2200' elevation. Got code 185 (MAF lower than expected) at first, checked harness best I could, so replaced MAF. No difference. It runs great, decent fuel milage, no noticable difference in running, only problem is that ocasionally (about 1 start in 20) have to give it a little throttle to start when warm after sitting a half hour or so like it's flooded. Idle also flutters a little at times. Now I am getting code 185 along with 172(O2 sensor not swithching-lean), 186(injector pulse width longer than expected or MAF lower than expected) and 187 (injector pulse width shorther than expected or MAF higher than expected. I am 99% sure not harness problem as always comes on and goes off in exact same spots, not related to bumps or turns. All wiring on it looks great also, no butchering or corrosion. Was wondering if anyone has had this combination of codes and figured out what was causing it? Sorry if this is a common problem. Takes me a long time to search with a 26.4K dialup connection. Forgot to mention these are only CM codes. Never been able to run KOER test when light is on. KOER and KOEO come up clean. Thanks, Jeff

 

[MrShorty]

Those codes as a group point to some problem with fuel control. These can be quite difficult to track down "by the book."

How old is the O2 sensor? The closest I've come to your situation was with a bad O2 sensor that would fail open when it got too hot. (Exhaust will be hotter when pulling a long grade like you describe). Some people consider O2 sensors to be a maintenance item, if it has been some time since it has been replaced, I would consider replacing it.

 

[Jeff H WV]

Thanks for the reply. It has 163K. I've had it since 120K, so hard to say. I've thought about that or the ECT sensor. Do you think the O2 sensor could be bad when at first I only had the MAF sensor code(s)? Would be nice to buy just one thing and fix it but we all know how that goes. Already stinging from wasting the money on the MAF. I did little reading after the original post and kinda though maybe my MAF is being contaminated. I did find a bunch of hickory nuts in the air cleaner once but that was long before the new MAF. How do you clean the MAF without damaging it. Thanks, Jeff

 

[Jeff H WV]

I also have a few other problems that might actually be related to this. I have noticed that the transmission will sometimes not shift into OD and the cruise control only works occasionally. Last two times I have driven it, seems like OD is more likely to work at lower engine temperatures. I was trying to read up on OD issue and saw that ECT effects OD also. Also see that VSS maybe causing the OD and cruise issue too. I am getting the O2 sensor as I am only getting 15mpg. Would really appreciate help since I am on dialup. Waiting minutes for pages to load is agony. Thanks.

 

[MrShorty]

I would expect if the ECT was contributing to any of the conditions, it would be easy enough to see with a voltmeter. The ECT is a basic thermistor. For it to affect the OD and such, it would have to be way off.

Because the 3-4 shift is electronically controlled, I usually suggest starting by determining if the computer can and is talking to the transmission, which is easy enough to do with a voltmeter. Set up your voltmeter so you are measuring the voltage drop across the solenoid, then enter the output state test (see my notes on pulling EEC-IV codes) to see if the computer can talk to the computer, then a road test to see if the computer is choosing to command the shift. If the computer commands the shift and the transmission doesn't respond, something is faulty inside the transmission. If the computer doesn't command the shift when it should, then something is wrong in engine management. VSS and BOO are the two things that would be in common with the cruise control.

 

[Jeff H WV]

At first, I replaced the ECT(because it's cheap) and air filter and cleaned the MAF with the cleaner. I drove it about 50 miles with no CEL. So probably that fixed it -- my guess is the nasty air filter was contaminating the MAF. Lesson here is to check the simple stuff first. I then replaced the O2 sensor which I believe was original. Had to heat the bung red hot and ended up pulling the threads off the old sensor. Luckily I had a 18mm tap to clean out the hole. I have since driven the van about 400 miles with no CEL coming on. Ready to declare victory in that battle after putting up with this for way too long.

Overdrive issue is still there, maybe getting worse. I can go days with no problem then it crops up. I was driving 70mph down the interstate stuck in 3rd, threw her in neutral and shut it off. Cranked it up, pulled it back down in OD and it goes right in. I have done this about 6 times, it worked 4 of them. I also tried pulling over and turning it off and "rebooting" it. Sometimes it works, sometimes not. I think it may actually be going into 4th when coasting and instantly going back to 3rd when giving any throttle but can't be sure because I can't hear the motor at low rpm at that speed and doesn't have a tach(it's an XL). Can you tell me which wire(s) are for the 3-4 solenoid? When I bought the van 10 years ago, someone had removed what I though was the torque converter lockup wire from the plug and taped it to the side of the harness. I re-installed it back into the plug. I may be loosing connection on that pin. I will rig up a test light through the emergency brake lever boot to see what has power if I can find out which pin(s) to hook to. I had a similar problem on my 95 F-250 only it was the pressure solenoid. After alot of hair pulling I figured out the solder joint between the solenoid and the internal transmission harness was losing connection in the new Jasper transmission the previous owner installed. That set the CEL which is not happening here. Maybe a similar issue, internally shorting solenoid or bad ECM ???? Nothing really seems to fit the symptoms to me. I'm open to suggestions.

Cruise never works now, at least not normal. I have turned it on and it won't hold speed or accelerate. Sometimes after I do this the motor won't go back to idle when I coast to a stop. I think it may be trying to work, but can't pull the throttle. I have tried 3 different amplifiers. I don't have another vehicle with this type cruise that runs that I can test them on to be sure they work. I also snagged a cruise servo from a 90 F-series but the plug is different. I had an intermittently working cruise on my 98 Explorer also and never did fix it. The cruise light in the dash would work when the button was pressed but wouldn't stay on. It worked 75% of the time, right up until I sold it. It never got this bad. This must be a common problem, but doesn't look like it is related to my other problems though.

Thanks for your time and responses, I appreciate it. Jeff

 

[MrShorty]

Can you tell me which wire(s) are for the 3-4 solenoid?

Not off the top of my head, but the wire colors/pin assignments have pretty much matched what the wiring diagram in Chiltons says they should be for my '92.

 

[Jeff H WV]

I drove the van to town tonight, about 20 miles each way. On the way, it shifted perfectly. I made a few stops in town, got gas and started for home. After filling up, I ran 5 miles of interstate, I had no OD. I stopped on exit ramp, put it into park, shut it off, restarted it and took off. I had OD the rest of the way home. Most of the time, but not always, simply restarting the van makes the OD work. Shifting from OD-D-OD repeatedly never fixes it, which would seem to eliminate shift position sensor. No CEL, so I would think this would eliminate TPS. My best guess as to what can cause this kind of problem is a set of mechanical contacts that are not getting good continuity when they are closed. How does the constant 12V get to the transmission plug? Is it controled by a relay? I think this is the most probable area to look since once I lose OD it doesn't seem to matter what I do short of restarting the van, I never get it back. If it were on the negative side the trans apparently switches, everytime the PCM turns on and off the command to shift, it might fix itself. I don't notice TC lockup without OD, either. I haven't had time to actually check the current at the plug. Where is the actual switching done for the solenoids? With the current draw I would expect the solenoids to have, you would think the PCM would use relays to do the switching. Do you know where the actual switching takes place? Is it inside the PCM itself? After reading a little more, I see it is only a 3 wire plug and the one wire is hot all the time. I guess I will figure out which is one is hot and wire two lights on the others to see what is going on while I am driving. Thanks, Jeff

 

[MrShorty]

which would seem to eliminate shift position sensor.

Not shift position sensor (other than the park/neutral switch) on the A4LD.

My best guess as to what can cause this kind of problem is a set of mechanical contacts that are not getting good continuity when they are closed. How does the constant 12V get to the transmission plug? Is it controled by a relay?

I would agree that something intermittent like that seems like an electrical fault. As mentioned before, a wiring diagram (even from Chilton's) would be helpful in seeing how this is wired. Power for the transmission solenoids, along with the rest of the engine management system, gets power through the EEC relay. However, since the rest of engine management seems to be working, a problem with the EEC relay doesn't seem indicated. You would need to look at the wiring/connectors between the EEC relay/PCM and the transmission.

Where is the actual switching done for the solenoids? With the current draw I would expect the solenoids to have, you would think the PCM would use relays to do the switching. Do you know where the actual switching takes place? Is it inside the PCM itself?

It's inside the PCM. I've never looked inside, so I don't know exactly what is involved inside the PCM, but the switching does occur inside the PCM.

After reading a little more, I see it is only a 3 wire plug and the one wire is hot all the time. I guess I will figure out which is one is hot and wire two lights on the others to see what is going on while I am driving.

Sounds like a plan. FWIW, I usually use a voltmeter across the solenoids rather than lights.

 

[Jeff H WV]

I finally got a chance to look at it. When I unplugged the connector, it was obvious what was wrong. When the TC lockup wire was taken out of the plug before I owned it, the guy slit the silicone plug in the back of the connector to pull the wire out. When I hooked it back up, I tried to seal it back up with Permatex, but apparently the silicone plug worked its way out of the back of the connector because it couldn't hold its shape. The wires were corroded pretty bad, especially the red which I believe is the hot wire to both solenoids. So I guess it was a mechanical contact, just not one in a relay. I took the contacts out of the connector and the one for the 3-4 solenoid, orange I think was mangled and not repairable. These are oddball terminals, they are female spade terminals, but not like normal ones but look like small alligator clips with a c-shaped spring on the inside. I also cracked the shell getting them out because of the corrosion. I went to the Ford garage today and had no luck getting the pigtail or terminals from them. I am going to see if NAPA has the terminals but I doubt it. Looks like a trip to the junkyard although with the high price of scrap, it is getting tough to find stuff this old anymore around here. I may put some of the small regular individual female spade terminals temporarily until I get a chance to get the connector. It's hard to see the plug on the transmission, even with a mirror. Thanks, Jeff