Top 5 Problems Toyota Avalon Sedan 1st Generation 1995-99

Hey, friends. It's Len here from 1A Auto. So today, in the studio, we have a first-generation Toyota Avalon. I wanted to go over some of the top problems that we've come to find, so let's get started.

Okay. For problem number one, we're going to talk about ignition coils. If you were to look under your hood right up across the top of your valve cover, you're going to find three ignition coils. Yes, this is a six-cylinder, but you really only have three ignition coils for this engine. Now, if we're going to talk about symptoms for a faulty ignition coil, essentially what you're probably going to find is a check engine light on the dash, you might find a misfire or even a stalling condition coming from your automobile. Now, we're going to, of course, talk about some fixes. For the fix for this, of course, you're going to want to diagnose what's going on. That's going to be easiest to do with a handheld scanner. You're going to need something that's going to be able to graph or at least be able to count the amount of misfires coming from each cylinder.

Once you've determined which cylinders are misfiring, that's when you're going to go ahead and you're going to remove the coil. You want to, of course, inspect that coil. There's going to be electrical connectors that go into it, and then, of course, there's going to be a wire and a connector that goes down to the spark plug on each one. Inspect each one of those connecting points. You want to make sure that you don't see any corrosion or anything the like. If you do, it needs to be dealt with. Otherwise, the coil can go bad internally. It has little electronic components inside, and, of course, over time, electronic components break down. If you wanted to, what you could potentially do is go ahead and take one of the ignition coils from over here and then swap it over to this one right there and then the like on the other side. The reason why I'd want to do that is so that that way there I can go ahead and clear the engine codes and then run the car.

As the car is running, I'm going to pay attention to see if the misfire stayed on the same cylinder that it was originally or if it moved to where I just switched that coil over to. If it stayed, well, then it's probably not an issue with the coil so much, but if it moved, well, then you know you've found a bad coil. And, of course, if you found that you have a bad coil, you're going to go ahead and replace that. Do you have to replace all three? Well, no, not really, but for me personally, I'm probably going to just do that. Now, for problem number two, we're going to talk about faulty O2 sensors. Here's an O2 sensor right down here, and they typically go bad.

Now, on this particular car, you're going to have two banks. And what I mean by that is you're going to have cylinders on each side of the engine. Well, really, on this one, I guess it's on the front and on the back. There's going to be three on each. Each one of those banks has to have a manifold, and each one of those manifolds is going to have an upstream O2 sensor in it. Other than that, you're also going to find that you have one downstream O2 sensor. That's going to be located underneath the car, down behind the catalytic converter. Now, these O2 sensors have a very important job. Essentially, what they're supposed to do is measure and decrease the amount of pollution that's going out into the atmosphere. What they really want to do is kind of measure the amount of oxygen and unburnt fuel mixture that's getting shot out through the exhaust and not necessarily getting burnt up in the combustion chamber.

So essentially what happens is you're going to have fuel and air mixing inside that combustion chamber as the piston comes up and down, big explosion or combustion inside the engine, and then it's going to come out through the manifold and get shot out that tailpipe. Along the way, you're going to have those O2 sensors, and, like I said, they're supposed to be monitoring what's going on. If for some reason there's an issue, the O2 sensor is going to pop up something saying, "Hey, I found that there's an issue, and we need to deal with this." Other times, there might not even be an issue with the engine that's causing the O2 sensors to send these codes. If that's the case, it's due to a faulty O2 sensor, and that's very common on these cars.

Now, symptoms for a faulty O2 sensor aren't going to be something that's very apparent to the naked eye, meaning you can't really just look at them and say, "I think something's wrong with that O2 sensor," but what you're probably going to notice is a check engine light that comes on in your dash. If you go ahead and pull the code, it's probably going to tell you that you're having an issue with O2 sensor, and at that point, you're going to want to diagnose to make sure it's an issue with the O2 sensor and not necessarily engine. If you find that it is the O2 sensor that's the issue, you're going to have to go ahead and replace it. It's very common when you go ahead and try to replace these O2 sensors, they're going to be stuck in the pipe, and that's typically because they've been inside there a long time, and, of course, the exhaust gets hot, cold, hot, cold and, of course, soaked with water over time.

As this is happening, it's going to build up a whole bunch of rust in between the threaded area between the O2 sensor and the pipe, and you're probably going to have an issue trying to get the O2 sensor out. If you end up having this issue, you could potentially damage your exhaust pipe, meaning the threads essentially. If that's the case, you're going to probably have a hard time putting in your new O2 sensor. Typically what you're going to have to do is just go ahead and replace that exhaust pipe and the O2 sensor at the same time if you end up stripping out the threads. Otherwise, maybe you could just try to do a little re-threading action, that might potentially help you out, but it could theoretically just be a temporary fix. Or you can go ahead and take a look at this one and see what this person happened to do, which I don't really recommend.

Now, for our third problem, we're going to talk about transmission shiftability issues. Now, the symptoms for this particular issue are more likely going to be found in higher mileage type of cars. Essentially, with this thing being a first-generation Avalon, it's got some pretty high mileage at this point. Some of the issues might include you try to take off from a stop, and for some reason, the transmission feels as though it's still in neutral, RPMs are going up, up, up, and then kicks into gear, and then down the road you go. Other symptoms, maybe it doesn't even have that issue, it takes right off like you want it to, but second or even third gear have that same little jolting action. They just don't feel as though it shifts when it's supposed to, it seems a little laggy, and you definitely don't seem like you have the power that you think you should have coming from this engine.

So let's talk about some fixes for this now. One of the first things that I would want to do is, of course, check the transmission fluid. You're going to want to do this while the car is running and on a flat-level surface. Assuming that it's running in on a flat-level surface, go ahead and pull out your dipstick and then go ahead and wipe it off. After you do that, inspect the rag clearly and see if you see any foreign debris in there. If you see any metal fragments or anything like that, that's very bad, and, of course, if the fluid looks like it's brown and not pink like this, well, that essentially means that the fluid's been burnt up and you probably wore out your clutches and your transmission. Now, something that I want you to think about when it comes time to checking that transmission fluid is if you did happen to pull out the transmission dipstick and the fluid looked very brown or even closer to black, or you found metal fragments in the fluid, that's not something that you're going to want to go ahead and try to change. More than likely you're just going to end up causing more damage to your transmission overall.

Other possible causes for this issue could potentially be your throttle position sensor is out of adjustment. Of course, if this is the case, your computer isn't necessarily going to know where the throttle position is at, so it doesn't really know when to shift that transmission, or, potentially, you could have an issue with your transmission shift solenoid. Now, fixes for this are going to have to be fairly vague overall because you're going to have to diagnose to see what exactly is going on with the transmission. Is it because your fluid's low? Is it because the fluid's bad in general, maybe contaminated in some way? Or maybe, like I said, you have an issue with the throttle position sensor or even that shift solenoid. Once you diagnose what's going on, you're going to have to continue going in that direction.

Now, for our fourth problem, we're going to talk about issues with the brake master cylinder. Now, your brake master cylinder is going to be located on your driver's side firewall closest to where your brake pedal is on the actual passenger compartment. The reason why it's located over here is because behind this area there's going to be a rod, and that's located right behind this right here, which is your brake booster. That rod is going to go right through your firewall and into where your brake pedal is. As you step on the brake pedal, it's going to push the rod in this direction, which is going to internally push on the piston in here, which will, in turn, go ahead and take some of the fluid from your reservoir and then force it through these lines. As it gets forced through the lines, it's going to go ahead and make its way all the way over to your ABS unit.

Some of the symptoms that you might happen to find if you're having an issue with your master cylinder might be weak or even soft brakes. Essentially, you go ahead and you step on that brake pedal, it feels a little squishy, for some reason, your car just doesn't really want to stop the way that you're asking it to. Will it eventually stop? Well, probably, but is it going to stop on a dime? No, probably not. Other issues that you might happen to find is, underneath down where that brake master is, you're going to find some fluid residue. And, typically, it's going to go ahead and eat away the paint on that brake booster. So if you look down by the master cylinder along that brake booster where it's attached to, and you see that the paint all along the bottom aspect right there is all peeling and bubbly and nasty-looking, that's because brake fluid made its way on there, and it ate up the paint. If that's the case, you need to replace your master cylinder.

Of course, if you did happen to find that you had the issue where the master cylinder was leaking and causing an issue where fluid was coming down on that brake booster, you have to also look inside of your brake booster. Once you go ahead and remove that master cylinder, you're going to want to double-check to make sure that fluid didn't make its way into the booster. If it did, you need to try to get it all out of there. And if, of course, it comes time to replace that master cylinder because you did find that there was an issue, you're going to have to make sure that you manually bleed all of your brakes. Essentially what I mean by that is go ahead and open up all of your bleeder screws, take out all the fluid that's inside of them and make sure that it's replaced with brand new fluid.

Also, when you replace the master cylinder, the rod that I told you about that goes between the brake pedal and the master cylinder, that has an adjustment on it, you need to make sure that it's adjusted properly. If for some reason you don't adjust it, you might have an issue where your brakes are hanging up, and maybe even you try to go ahead and go, but the brakes are still kind of locked up, and the car just says no. Okay, friends, so stay with me here. We're on our fifth and last problem. For this one, we're going to talk about a faulty EGR valve. Now, your EGR valve is going to be located right on your intake system right here. Now, before we get into the symptoms about a faulty EGR valve, first, we should probably understand what an EGR valve is. EGR stands for exhaust gas recirculation, and the valve, of course, is the valve.

What that's supposed to do is it's supposed to draw the unburnt fuel-air mixture that's coming from your exhaust back up and into your intake so that it can get re-burnt back through and into that combustion chamber. The reason for that is essentially just to help out with pollution and emissions and all that other stuff. So overall your combustion engine should be running as efficiently as possible, but there are always cases where some unburnt gases are going to be making their way into your exhaust system. It's just going to happen. Typically what's supposed to happen is the EGR valve is supposed to open up when it feels as though it's needed to, and it's going to go ahead and draw in some of that unburnt gases and, like I said, back into that intake so they can be burnt up inside your combustion chamber. So if you're having an issue with the EGR valve, some of the symptoms that you might happen to find is more than likely going to be a check engine light on on your dash.

If you were to go ahead and pull that code, it's going to tell you that you're having an issue with the EGR, and more than likely it's due to the fact that it's clogged up with carbon. Other than that, you're probably not really going to notice any other symptoms, maybe a little bit of a runability issue, but it's not necessarily something that's going to cause a misfire or anything else, but your car is going to be having a whole lot of extra pollution going up and into the atmosphere. Now, reasons why your EGR valve might tend to go bad is because, like I said, it's actually attached to the exhaust through an EGR tube. Well, the exhaust is going to, of course, build up some carbon inside that tube and inside the valve. The valve needs to be able to function properly. If it's clogged up with carbon deposits, it's not going to be able to function properly, or even if it has a lot of carbon deposits inside of it, it could potentially just be blocked up and restricting flow.

In either case, more than likely what you're going to have to do is go ahead and remove that EGR valve and inspect it. Once you've inspected it, you're either going to have to determine whether you can clean it or even just have to replace it. Okay, friends, so that's what I've got for you for some of the top problems that we've come to find on a first-generation Toyota Avalon. Every car has its problems. Maybe you've got a car of your own with stories of your own. If you do, leave them in the comments section below because I always love to hear from you. If you like the video, smash on the like button. For me, it would mean the world. While you're at it, go ahead and subscribe and ring the bell. That way there you can be kept up with all of our latest content. Thanks.