September 5

1993 Ford F250 Diesel, Transmission Rough Shifting

Podcast2018, Ford


Mark: Hi, it's Mark Bossert, producer of the Pawlik Automatic podcast. We're here in not very sunny Vancouver, actually. We're enjoying some rain for the first time this summer, and I'm here with Mr. Bernie Pawlik, the big bopper himself. We're talking cars. How are you doing this morning, Bernie?

Bernie: Doing very well.

Mark: So, today's victim is a '93 Ford F-250, the infamous 7.3 diesel that had a transmission problem. What was going on with this vehicle?

Bernie: So, this vehicle, well, in addition to a transmission problem, it also had an engine running problem where it would stall. But one of the main concerns with the client was the transmission would shift rough. As you drive, the first shift would be very delayed and would bang into the next gear, and it really ... an uncomfortable driving experience and not great for the vehicle. Also, there's an overdrive off, that it's a little lamp on the gear shifter stock, and it was blinking. As soon as it would make that missed shift, it'd start blinking, indicating a malfunction in the system.

Mark: So, a '93? This is getting on in age. Was it even worth, in your opinion, is it worth even fixing an old truck like this?

Bernie: Well, there's still a lot of value in an old diesel truck, one that runs well. But I guess my purpose around doing this podcast is really to illustrate just how complex diagnosing older vehicles can be as compared to newer generation technology. This is a '93. It's pre-OBD2. OBD2 had a much more sophisticated ... It was a government-mandated diagnostic system to track vehicle emissions. But along with it came very easy, I wouldn't say very easy, most of the time, you can plug a scan tool in, you can get a lot of information and diagnostic, trouble codes, data, all that sort of thing. As vehicles have got newer and newer, that data has got better and better and helps us diagnose things better. This much older than that. Also, the computer on this vehicle only does the transmission. The engine is actually all fully mechanical, so there's no engine electronics. They call it a powertrain computer, but it's really just a transmission computer. So, in answer, is it worth it? It really largely depends on the vehicle, what you're doing with it, your attachment to it. You know, the other areas, of course, around getting parts for older vehicles can be difficult, and we can talk about that a little later on. This truck was in pretty good shape other than the repairs needed, and I'm happy to say that once we completed all the repairs, which were pretty extensive, in addition to the transmission, there were some fuel injection issues, the truck runs really nicely. So, it should be good for quite some time.

Mark: So, why was the diagnosis difficult?

Bernie: Why the diagnosis was difficult, I was alluding to the diagnostic connector. This uses an old system that Ford had called EEC-IV. Now, some of the cars were pretty good, like, some of their cars and gasoline engines, you could get some data out of it, in addition to trouble codes. But in this truck, all there is available is trouble codes when there's fault, so that really leaves you very limited. It just gives you an area where things are going. I'm just going to share a couple of pictures, and then we'll talk a little more. Great, ok. 

1993 Ford F250 Diesel, Transmission Rough Shifting
1993 Ford F250 Diesel, Transmission Rough Shifting

Yeah, so there's our truck. A little dusty and dirty, but really in pretty good shape body-wise. There's no rust. It's old but pretty good. You'll actually happen to notice, there's a '94 Ford truck sitting the background here, which actually happened to come in simultaneously for the same problem, which is really bizarre. Very rare to have two vehicles of this vintage in our shop at all, let alone with the same issues. So, it was kind of a two-for-one diagnostic. They were both having the trouble codes. Anyways, pictures. There's our truck. This is the Ford EEC-IV diagnostic connector. Was very common on Ford for a long time. There's again, the test port and the connector.  So, you're asking why ... Again, we're talking about why it's difficult to diagnose, so basically what we're able to do is extract two trouble codes. There was code 23 and a code 29. One of those codes is for a throttle position sensor, otherwise known as a Fipple, on this engine. A vehicle speed sensor circuit out of ... I can't remember the exact code, but it's basically a vehicle speed sensor circuit problem. So, those are the two pieces of information we had to work with, and of course, there's no data on a computer to drive it and see, "Hey, is it getting the right signals?" Everything had to be tested manually, and this is where the diagnosis gets complicated. So, what we do to test the throttle position sensor is we hook a lab scope up, and we can take a reading of it. What we found is that basically, the sensor was dead. That piece was confirmed. The vehicle speed sensor was a much more complicated diagnosis because it gets a signal from the rear differential of the vehicle, sends that to the speedometer, the speedometer has a little computerized module which converts that signal into a square wave pattern. It sends a signal to the powertrain control computer, and inside there, that operates the transmission. So, you can see there's a few different things at play, and again, no data of any sort. Now, one thing we did have going for us is when we were driving it, the speedometer actually worked. It pretty much verified that the signal from the vehicle speed sensor was good, at least good enough to operate the speedometer. 

I'll share a couple of pictures here of some of the waveforms. What we use is a lap scope to test these items, and we have to test right at the computer for one of them, and right at the back of the speedometer for the other. So, again, we'll just go back in the screen share here.

1993 Ford F250 Diesel, Transmission Rough Shifting
1993 Ford F250 Diesel, Transmission Rough Shifting
1993 Ford F250 Diesel, Transmission Rough Shifting

Mark: Okay, wait a minute now. I've seen videos on YouTube that people hook scopes up and it tells them exactly what's wrong and what part there is that needs to be replaced, or else, that's what they claim. Isn't that how it works?

Bernie: No. It doesn't. And as I said, with the code, for instance, for the vehicle speed sensors, the code is sensor circuit out of range. Well, it doesn't tell you that piece, the vehicle's speed sensor's out of range, it just tells you the computers not getting the right signal. So, that could be coming from the speed sensor in the rear of the vehicle, it could be coming from the module, it could be coming from broken wire. It could actually be coming from inside the computer. The signal could be fine right to the computer and not getting it. So, the answer is, sometimes we can plug something in. We can get a trouble code. On certain vehicles, we know that 99% of the time that that particular sensor's a problem. So at that point, yeah, it's a good gamble to change it. But with this vehicle, it's nothing like that. It's all straight manual testing and very time-consuming. Did I answer the question?

Mark: Absolutely.

Bernie: Good. Awesome. And then really, for me doing this podcast is not defending ourselves and the time we take, but really just to show just what it does take to do a proper diagnosis on some vehicles. I say the older ones are often worse. We've got a couple of older Jaguars with fuel injection. Again, there's saying there's no trouble codes whatsoever, everything has to be tested manually, so you have to use your skills and intuition and start there and then start testing various sensors. It can take hours to get things figured out. Anyways, so what we're looking at here ... You can see this picture, correct?

Mark: Yep.

Bernie: So, this is a photograph ... This is the waveform coming from the vehicle's speed sensor while we're driving down the road. What happens with this wave, it's called an AC signal alternating current. It's generated by the sensor, and as you speed up, the height of the wave gets higher and it gets tighter. So the frequency of the wave changes, and this is the signal that comes from the rear differential of the vehicle. It goes to the speedometer, so we were actually able to verify that this signal was good. No problem with this one. Next, I have a couple of videos here, and hopefully, they'll ... So, we have one here ... You know what? I'm actually not even going to play the video because you can just see that it's the waveform. Now, this is the waveform that was coming right to the vehicle computer, and you can see it's now a square wave, not a AC sign wave, is what the other wave is called.

Mark: Yep.

Bernie: So, the other thing that's tricky is, we have this wave, and it actually varied when we were driving it. It would change height and it would actually change spacing. So we were verifying that it wasn't actually getting information, but the tricky thing about this is we actually didn't really know for sure if this was the right signal. There was no information whatsoever from Ford and any of our repair information. We have a lot of online data we can access. I couldn't find anywhere that said, "Is this a good signal or not." What was a little confusing is that even though it's a square wave, it starts at just over four volts and goes a bit under four volts, crossing zero. I'm thinking, "Is that right, or should it be zero volts up to eight or 10 volts?" We weren't really 100% sure. It looks like the right kind of wave, but I couldn't verify it. I even called the tech support line, and they couldn't even really give me 100% verification. But, based on what we saw, we figured that this is probably pretty close to accurate. It's getting a signal, and we decided the powertrain computer was at fault in this case 'cause the signal was going right to the powertrain computer. So, at that point, we ... I'll just a talk a little further since we're at the screen sharing mode, we don't want to change back. We actually pulled the powertrain computer out and found a lot of little nasty, a lot of nasty stuff inside here. It was not necessarily water, but a lot of powdery moisture. There's aluminum around the body of this. Clearly, some moisture had affected it and started flaking the aluminum off, which was a good enough sign that the inside of this computer was in bad shape.

Mark: Shorting?

Bernie: Yeah, exactly. So yeah. So, that's what we found, through again, some good rigorous testing and verification. But unfortunately, as I said, there wasn't really any data. We have a source of ... One of our bits of repair information that we can access actually has a waveform library where technicians have uploaded waveforms of various sensors, and I'm going to do that with this particular thing, so someone else can actually see what a good one looks like. Because it's good to verify this is what's good and this is what's not 'cause sometimes we're looking at something for the first time. Manufacturers never do this kind of stuff. They write crappy repair information most of the time and hope you can figure it out.

Mark: So, was the computer fairly hard to find or get access to?

Bernie: Well, yeah. The computer was hard to find. I actually managed to find one good used one in Vancouver-

Mark: I meant on the truck itself.

Bernie: Oh, on the truck? No. Well, it's a bit of work to take out, but it's not that hard. Fortunately, being an old truck with a lot of space, there is room to test a lot of these things reasonably easily and remove them. This computer was kind of stuck, jammed in place. It took a lot of work to get it out. I think the moisture had stuck it in place, but yeah, it wasn't too difficult to get it out. And then getting onto the other question, where did we get one from? There are, of course, Ford doesn't sell them anymore. All our normal auto sources like NAPA, Lordco, our parts places we deal with, nobody like that sells it either. It's basically a special ... It's easier if you're in the U.S. to get these computers 'cause there are companies that remanufacture them. We get them from there too, it's just more of a process to get it to Canada. But I managed to find a good used one that worked really well.

Mark: And once that was repaired, you got a new computer in, changed the throttle position, the throttle, Fipple, whatever you call it.

Bernie: Yeah

Mark: Then the vehicle was running good?

Bernie: Yeah, it was great. The transmission immediately shifted right away perfectly. No more blinking overdrive light, and you know, hopefully, the used computer will last a long time. The thing with computers and electronics, you never know. Sometimes they'll last for a hundred years, and other times, they'll last for 10. You just never know.

Mark: Ten minutes.

Bernie: Or minutes. Yeah. Yeah, you never really know. The thing with automotive electronics is often, in the case of this one, often it gets damaged by moisture. That'll probably kill the next one too at some point down the road.

Mark: Yeah, it's a harsh environment. So, there are some definitely older vehicles still on the road. How old is too old to be practical to work on? I mean, assuming it's not a classic that's been restored or remodelled or hot-rodded?

Bernie: Yeah, like, you're talking everyday driver kind of vehicle?

Mark: Yeah.

Bernie: Regular usage. You know, it depends on the car, but I'd say once you get in the 15-year-old range, things start to get a little dodgy for getting parts. It really depends from car to car though. There's certain cars where you can ... If it's 30 years old, you can still buy parts for them. And other cars, and Ford is really bad for this, not even 10 years old, I've had Tauruses ... I mean, there's literally millions of them on the road, and you know, a rear ball joint, I remember trying order one, "Oh, that's obsolete." What? It's a Ford Taurus. There's like millions of them, but for some reason, the part was obsolete. So, you never know, but I think a lot of times with the European cars, parts tend to be available for a lot longer of a timeframe. American cars are often shorter. How long? I think it really depends from vehicle to vehicle, but sometimes too, it's what sort of generation of diagnostics. I mean, anything with OBD2 is much better to diagnose than this older generation. If I had a choice between, say a '96, is when it was mandated by ... Between buying a 1995 car or a 1996, I'd take the '96 any day of the week because it's got the OBD2 system and makes it a lot easier to diagnose. So, those are some things to consider. I mean, I guess it's on a one by one basis, but generally, once you get to 20 years old, it gets pretty hard to get parts for, for some cars.

Mark: Yeah, and how are these old diesels for reliability?

Bernie: These are really good. These are really solid. They're all mechanical. It's called an IDI. It's an indirect injection system as opposed to like ... Well, the newer Ford's the Power Stroke, which they're super reliable, but they do stink. I mean, they're awful. If we run this thing for one minute our shop, you can't breathe anymore, so you know, that's not a good thing. It's not good for the environment obviously, and that's why we haven't made these diesels for a very long time. But they are extremely reliable, and they're pretty simple. The key is keep your fuel clean, change your fuel filters, change your oil regularly, and these things do last a long time. I don't know the history of this engine. It's the first time we've worked on it, but it has 300,000 kilometres. We did put a new injection pump in it and a fuel lift pump and cleaned all the fuel tanks 'cause there was some contamination, but it runs really really well. These are the kind of engines that can last a million kilometres or miles. They're good.

Mark: So, there you go. If you're looking for service for your diesel in Vancouver, the guys to see are Pawlik Automotive. You can reach them at 604-327-7112 to book your appointment. You have to call and book ahead 'cause they're busy, real busy right now. Or, if you're looking for more information, check out their website, or our YouTube channel, Pawlik Auto Repair. Hundreds of videos on there. Thank you very much for listening on the podcast. Thanks, Bernie.

Bernie: Thanks, Mark. Thanks for watching.

About the author 

Bernie Pawlik

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