1993 Ford Escort Overdirve downwshifts at speed and 1st sli

There is no light on. I have a scanner, but since the light hasn't come on, I didn't think I needed to check it. As of this past Monday, and since the fluid change, it no longer goes into overdrive at all. If you downshift from the Overdrive D to regular D on the highway at 55-60, there is no change in gears or downshift and it runs around 3100 rpm (1000rpm higher than it should with overdrive). Big gas burner now.

I think your torque converter theory is probably on the money. Could it be the shift linkage needs adjustment? But that wouldn't explain the slipping in 1st gear on a dead stop startup. I was told the single band is self-adjusting and cannot be the problem.

I'll run a scan ASAP and let you know if anything comes up. In the meantime, I'll find out what I'm looking at if it is the torque converter. I don't think it's going to get any better by itself. Thanks for all your help.

Ran a scan of engine off, continuous memory and engine on. No trouble codes came up and everything went normally. Took the car out for a drive after looking under the chassis and under the hood one more time for maybe something I've missed. It ran without a problem at first. After five miles at hwy speed it dropped out of overdrive. I took secondary roads home and used L to start from the red lights. It did not slip in 1st. But I think L is a direct drive gear from what I remember about an auto trans.(Spent most of my driving carer with manual sticks) So it doesn't count. Went back onto the highway and drove home without getting back into OD. Would the neutral safety switch be something to look at? I see it has an adjustment, but I thought it just controlled the backup lights and making sure you couldn't start the car unless it was in P or N. Any more ideas? I'm out of anything fresh. Thanks again.

That's interesting. I didn't think of those things. I'm not sure, but I believe that each time this has happened, I was decelerating for some reason, such as a car merging into the lane in front of me. My foot would release the pressure off the gas pedal and when the pressure is re-applied it would then do the downshifting. I'm not 100% sure that's what happened, but I'll have to test that theory out. That could be the throttle sensor.

The reason I changed the trans fluid 10,000 miles ago was that the car had already just blown the head gasket. My mechanic told me it would be $900 and up to repair and suggested I buy a kit and do it myself, knowing I had already done this on a couple of cars I owned in the past. My mechanic is the only guy I know who turns work away. I guess he's just that good :)! The time involved and the age of the car stopped me from doing it, but I found Barr's liquid head gasket repair at AutoZone for $10.00 and figured it couldn't make it any worse. After grilling their phone tech support line on how this could possibly work without destroying the cooling system, they convinced me that it was worth a try. I followed the directions exactly and in great detail and the blown gasket (between the cylinders) was fixed and has remained so. Tested cylinder pressure after the treatment was 1.178 2.165 3.165 4.165. All within 10% of each other per the specs. The engine (apart from a rough idle which I researched when I first bought it used and read is normal for these cars) runs fine. I also tuned up the car (new plugs and wires and replaced the O2 sensor) after the head gasket repair. They had all been fouled and ruined by the antifreeze leaking into the cylinders. It normally runs really well and I have found it very dependable as a getting to work everyday car until now.

I will look into the cost and procedure to replace the trans control module and the throttle sensor. Without a definite trouble code, it looks like this is now an educated guessing game and trying replacement parts at this point. It's still cheaper than a new vehicle.

Again, thanks for all your help.

I'll test the throttle sensor this weekend and whatever else I can think of to test. I'll let you know the outcome.

Sorry to hear about your dad. Mine passed in 1999 so I know how tough it is. He was a pretty fair mechanic and taught me a lot about the way things work on cars and other things.

Anyway, sorry it took so long to get back - life issues.

I was able to test the Throttle Position Sensor after gerry rigging some jumper clips and using a hammer to flatten one side of some 14 ga copper wire to fit in the slots where the connector fits. That allowed me to jumper to a digital multi-meter and read the voltage. Specs call for 0.00v at idle to 4.5v at speed. I got 4.95v-4.96v at all settings. No one had one in stock anywhere within 25 miles of me.I had to mail order it from Advance Auto and got the new sensor yesterday afternoon. I hooked it up and connected my testing equipment. The readings don't make any sense to me. They run from 0.00v to 5.01v. But they just wander all over at idle and as I accelerate. Nothing holds steady until I get to around 2000 rpm where it sits at 5.01v. Bad module? Or another issue with whatever feeds it the info? The idle did, however, drop about 100 rpm from about 750 to 650. According to my Chilton manual, the specs are 450-750. So I guess that's just normal. There was something wrong with sensor I had, so it wasn't wasted money.

I took it out for a test drive of about 6 miles on the parkway and it's still the same. It does not shift into OD. 3,000rpm at 55 and slipping at start up.

The next part in the electronic chain to look at seems to be the Powertrain Control Module. That is not a test, it's just a replacement. After that I see there is supposed to be something under the dash called the Transmission Control Module. AutoZone calls it the Engine Control Computer on their site.

I'm wondering if it's just the torque converter and I'm spinning my wheels?

If you have any more ideas, I'm listening. Thanks. I appreciate the help.

I had some trouble with discontinued parts, even at the dealer level, but located a "powertrain control module relay" which I replaced last week. It initially seemed to cure the shifting problem with the slipping in 1st from a stop and definitely did an upshift into 2nd and 3rd. But by the time I got to an open road it was the same problem. No OD and slipping in 1st.
I took out the ECM today but I don't where to take it or send it for testing. Checked on-line but didn't see anyone who tested modules and would like to do it locally, if possible. I would hate to buy a remanufactured unit and find out that it didn't need it.

Is there anything I may have skipped in the electronics chain? Any suggestions on where I might get this testing done?

Thanks.

I do not have much faith or trust in dealers since I bought a Focus new in 2001 with, at last count, 21 problems; 6 of them right after I drove it out of the lot. But, that's another story.
Funny thing happened to me with this Escort. I took out the computer so I could get it checked out somewhere (as you saw in my last post).
I decided to check all the fuses (under the hood and inside the car) one more time for continuity since I had been doing so much electronic poking around to be sure I hadn't blown any fuses in the process. The car was parked close to a fence in my driveway, so I had to reconnect the computer to start it. I did that and noticed that when it started and I moved it that the engine seemed to be running a little differently. Not smoother or faster or slower or better, just different. I checked all the fuses anyway (which were good) and decided to take it around the block. There was no first gear slippage noticeable and it went to 2nd and 3rd gear without the rpms going up and down wildly as they had been doing. I then had breakfast and decided to get really bold on a full belly and took it out on the highway. Lo and behold, it shifted into OD at 50mph and continued to upshift and downshift for the next ten miles until I parked it back in the driveway.
At this point, it appears that all it needed was a computer reboot. Or, one of the two bad components I replaced threw it off and after replacement required the computer reboot. Or, the weather change has affected it and it will do this again when the weather warms up. I don't know. But I will call the dealer and see what they say about getting someone to test the unit anyway.

Thanks for all your help and suggestions. I just can't believe we are so reliant on electronics today to run these cars. If you don't do this every day for a living, it can become a real crapshoot and very time consuming for the average DIY guy, like me.