August 29

2006 Land Rover LR3, Throttle Pedal Replacement

Podcast2018, Land Rover/Range Rover


Mark: Hi, its Mark Bossert here with Mr. Bernie Pawlik. We're doing the Pawlik Automotive Podcast from Vancouver and we're talking cars. How are you doing this morning Bernie?

Bernie: Doing very well.

Mark: So, today we're talking about a Land Rover LR3 that had a throttle pedal problem. What was going on with this vehicle?

Bernie: The vehicle actually came to our shop with some suspension issues which we in diagnosing found there was actually nothing really wrong with that end of it, but there was also some intermittent faults with the vehicle would go into limp mode while driving it. Through the diagnosis process, we found that there was an issue with the actual electronic throttle body and with the throttle pedal assembly. We'll just talk about the throttle pedal assembly today on this vehicle.

Mark: Well, how does the throttle pedal be a part of a problem with the car going into limp mode?

Bernie: Well, basically the electronic throttle sends a signal to the vehicle computer to as to what the position of the gas, essentially the gas pedal where you put your foot. If it doesn't like the readings from that particular signal, it flags a warning and it'll cause the vehicle to just go into a limp mode. And because all the vehicle computers talk to each other, they want to know where the gas pedal is, how's the engine running, should the suspension be up, should it be down, there's a lot of the complexity of the communication in these vehicles, so one thing will cause another thing to happen and that's how it kind of goes into limp mode.

Mark: So, let's not assume this. What do we mean by limp mode?

Bernie: Okay, yeah, good question. Limp mode is basically there is a major fault or serious fault detected in the vehicle and it'll allow the vehicle to run at a reduced power rate so that you can basically limp it home or limp it to a shop to get fixed. So, you'll see that actually British cars are pretty good for that. They'll actually, a lot of Jaguars will actually say, "Limp Mode," but other vehicles if the transmission has a shift problem, all of a sudden it'll go into that mode. A lot of diesel vehicles, again a certain problem occurs, it'll go into that limp mode because either it'll be putting out excessive emissions or there's a safety concern with the way the vehicle's running. It allows you to get to a shop to repair it, but not much more than that.

Mark: All right. So, we have a throttle pedal assembly which is a pretty weird way of just saying a gas pedal. How come this is so complicated?

Bernie: Excellent question. So let's have a look at the item first.

2006 Land Rover LR3, Throttle Pedal Replacement

There's our throttle pedal assembly. I'll just move us out there. So there's where your foot goes. This part here bolts up to the firewall and, of course, this is the pedal that moves back and forth, and here is an electrical connector. Inside here there are springs, so it's got a, it gives you a feeling that you're pushing against something. Okay, the old fashioned way was a cable connected to the throttle and say on a carburetor there's a return spring, well there is on a throttle body system as well, a return spring so it gives you that feeling of you're pushing on something and it springs back. So there's all the spring feel is done in this pedal and then inside there's a couple of different sensors that sense the position of the pedal. That's basically how the unit works as you push it down, it sends the computer a signal.

It'll actually send at least two signals. One, and the sensors work in reverse. So one will go say from zero to five volts, the other one will go from five volts to zero depending on when you push it. The computer looks for a correlation between those two movements, those two numbers that are preset. And if there is any variation of any sort, it'll, the vehicle will immediately go into a fault, limp mode.

Mark: All right. So, again, why are we using electronic throttles? This seems like really complicated.

Bernie: Well, yeah, it is very complicated. The reason for using electronic throttles is, again, it's like through and a lot of engineering and vehicles, they, the engineers have found that there's ways to ... It used to be, I'll just say the old fashioned way, you open the throttle, it allows more air to flow and the engine increases in speed, and the throttle was the control for that. But they've also found that there with engine electronics they can because you have electronic control over the fuel delivery, you have control over sometimes the intake manifold runners, some vehicles even have a lot will have electronic variable valve timing. Once you can control all those things, the throttle doesn't need to be that primary controller of engine speed, and by doing so, you can actually have a huge effect on engine performance and a lot on exhaust emissions. When you close a throttle a certain amount it'll cause a spike in emissions, so if you can actually cut the amount of fuel to slow the engine down versus having a throttle close, then you can make a substantial reduction in exhaust emissions.

Those are some of the reasons. A lot of it is driven by reduced exhaust emissions. It also effects fuel economy. I mean performance, you stomp on it, it opens. That's kind of affected differently. I think electronic throttle largely for emissions and sometimes fuel economy.

Mark: And you can really notice it with if you're around any older vehicles, and where I live there's a lot of hot rodder’s, we'll call them, with old vehicles and they drive by with lots of noise and there's a smell, a stink, that used to be what was normal and we don't notice anymore, I mean, in all the modern cars.

Bernie: No.

Mark: That's part of the throttle actually changing that?

Bernie: Well, that's to a certain degree. I think the biggest factor would be a catalytic converter, I mean, because that takes exhaust emissions even on a good clean running engine and reduces them enormously. But, yeah, the throttle’s all part of it. All the engineering that goes into a modern engine makes the difference, and a catalytic converter doesn't work instantaneously, so when you, you know some cars when you start them up and they're cold and they still have a bit of that smell, but it disappears pretty fast. But it is really a major difference and you kind of forget about how clean cars really are until you stand behind a, until you're following an old car somewhere and you go, what is that smell, and your eyes start burning and you go, wow. Everything used to be like that at one time. It wasn't that long ago, everything was like that. There's people out there defending oh, you got to have things simple and yeah, you do, but it's like you know, I mean we're ... I mean the poisons that are coming out of a car like that are just horrendous. They do look nice though.

Mark: So, how often do you find fault with electronic throttle systems?

Bernie: It's not really common, but we do see a few of them here and there. The more common problem is usually the throttle body itself will fail, and those are, throttle body it's on the engine, it lives in a much more hostile environment. It's a major moving part with motors and sensors, so there's a lot. A little more complexity to the actual throttle body, so they tend to fail a little more frequently than the pedals, but we do pedals on a variety of different vehicles.

Again, I was saying it's one of those components, the reason we replace this one it's had trouble codes and it's ... It's a lot of, what am I saying? It's a safety item like you don't ... When they engineer the vehicle, they don't want to have some kind of false signal or something where you're only idling and all of a sudden it thinks you're in full throttle. That's why they have so many, what's the word I'm looking for, redundancy built in. There's a lot of technology to this piece, and it's important. With a cable it's pretty straightforward, you either push it or you don't, but with the electronic, you don't want a false signal to the vehicle otherwise the vehicle might go flying through you driveway into a swimming pool like Audis used to. And they didn't have electronic, they did not have electronic throttles back in those days either, so.

Mark: No. Or even just the cases where cars had been hacked and people are, outside people are controlling your car, and changing the throttle electronically.

Bernie: Yeah, exactly. Those things all need to be considered and they do, at least hopefully. I'm not sure for hackers. I think there's always new frontiers that are they probably find out hey, we didn't quite bulletproof that thing as much as we should have.

Mark: And how difficult a repair was this? Did you have to take out the dash or any of that or are these generally pretty easy?

Bernie: Yeah, this is not that complicated. The assembly unbolts from under the dash and it's not really a super-complicated job. They're usually not too bad. They unbolt fairly, generally speaking, fairly easily. The nice thing about it you know the cables are simple, but it's actually ... Nice thing about modern cars with electronic parts is you basically unbolt a piece, you undo the electrical connector, bolt it back in, plug it in, do whatever reprogramming, and away it goes. It's a lot easier than having cables to hook up and in a lot of instances, so.

Mark: Fish through etc. So there you go. If you're looking for service for your vehicles that has a problem with it's throttle, the guys to see in Vancouver, or your Land Rover, service a lot of Land Rovers, the guys to see are Pawlik Automotive. You can reach them at 604-327-7112. Please note, that's a Vancouver number. If you're in the Vancouver area, we'd love to hear from you. We'll service your vehicle. If you're from somewhere else in the world because we get calls from all over, please, we can't diagnose your vehicle over the phone. That's not ... We don't feel like that's in integrity. We don't know there is too many variables there.

So we hope you're enjoying us on our podcast and we thank you for watching on our podcast. We have our video channel where there's hundreds of videos on there for all makes and models and types of vehicles. And of course, if you want service, give us a call. You have to book ahead, we're busy. as well if you're interested in our website. Thanks Bernie.

Bernie: Thanks Mark and thanks for watching.

About the author 

Bernie Pawlik

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