Do this and your car will always run better

    Do this and your car will always run better
    Photo by NeONBRAND on Unsplash

    Today, I’m gonna show you how to fix a car. In this case, Alexis, when a bunch of trouble lights come on in a dash.

    In this case, it’s got the check engine light. It’s got track off on me that’s required check vehicle speed control. And this giant one here that just tells you warning something wrong is happening.

    So we start with a simple thing. You plug the scan tool under the dash. In this case, it just goes under here and plugs right in here. Then have the key in the on position with the lights on, but the engine not running. Then we let the scan tool do its thing.

    It takes a minute or so, and Lo and behold, this baby’s got 14 different codes. Now, the first thing I want to do is look at the PO codes. Those are the codes that have to do with the running of the car. It’s PO 17174, so we know those are real serious codes.

    Then there’s these C codes. Twelve. One, two, three. Now, we’re going to start with the P codes, because the Pcodes are what make this vehicle not pass the state emissions test. The customer wants it to pass the emission test. He knows it’s an old car. It’s almost got 200,000 miles on it.

    He wants it so it’ll run decent and pass the emissions test. And I know for a fact on these Lexuses, they have strange software. All the Toyotas do that. If you get, uh, a Pcode, the check engine light comes on, but often that turns the traction control system off automatically by software.

    So you get the track off light. In this case, there probably isn’t a failure in the track system. Um, it’s just a check engine system is making that trip the code. Now, this is a V eight engine, so it’s got number one side and number two side, but both sides are running lean.

    They either have too much air or not enough fuel. Let’s hope it’s a vacuum leak, something that’s relatively simple to find. But I’m not all that hopeful. It’s going to be a vacuum leak. And here’s why. I looked at the freeze frame data, and it shows that the PO 171 code occurred at 63 miles an hour. And then I checked the PO 174 code. It also tripped at 63 miles an hour. The code tripped at a relatively higher speed. Vacuum leaks affect an engine the most. At low speeds, when the engine is barely going, you got a vacuum leak.

    That’s going to affect the air fuel ratio a lot more when you’re going slow than when you’re going fast. Normally with a vacuum leak, you’ll get the freeze frame data showing the car was going slow. But if there’s a problem in the fuel system itself not sending enough fuel, that will generally occur at a higher speed. But we’re going to check for broken parts anyways.

    You never know what could have come off or got loose. So we’ll take the stupid cover off. As I look around, there’s no obviously, um, broken hoses or connectors. So go to the air filter assembly and check that. Get the clips off, and we’ll take it out. Not much working room does have a leaf in it, but it’s pretty clean. That’s not a problem. But this mass airflow sensor, it could be dirty. So let’s take it off. They’re often hard to take off, so I got a long pair of pliers, squeeze it and try to pop it off. It can be a real pain in the butt. There it goes. Then we unscrew the thing. Two little screws.

    They often stick, so push down really hard. Uh, you don’t want to strip them out. It comes. Now, these sensors can often get dirty. I can see there’s a reasonable amount of dirt on the little part here, and then there’s an inside part. So we’re going to clean it. And when you do only use mass airflow sensor cleaner, you just spray it. That’s cleaning the part that you can see, turn it over, that. Then there’s stuff inside. You spray that one way and then the other. You want to get it nice and clean.

    Then you want the thing to air dry for about half an hour. You don’t want any residual stuff to be sucked in or any cleaner left on here. This stuff evaporates off, doesn’t leave any residue. That’s why you have to use the mass airflow sensor. Don’t use carburetor cleaner. Then after half an hour, you put it back in and put the screws in and hold it in place. Then plug the connector back in. Never clean it with a connector in. You don’t want any power going to it when you’re cleaning it. And snap the cover back on and put the stupid beauty cover back on. Then it’ll take you for a spin.

    We know the code came on at 63 miles an hour, so we’re going to go drive at 63 miles an hour. Well, here goes nothing. Well, let’s hope it’s something. And I’ve also reset all the lights so all those warnings that were on before are all gone. Now, you do want to go for a good 2030 minutes road test to really run it through to make sure it’s testing everything. Um, well, now the road test is over and all those nasty lights hadn’t come back on. Let’s get the scan tool to see what it says. It’s doing its thing. And look at that. Now, there’s no codes at all. Even though we didn’t work on the traction control system, the code didn’t come back because, as I said in these things, if you get a check engine light come on that’ll often, turn the ABS off, it’ll turn the traction control off, even though there’s nothing wrong with those systems.

    It’s a software thing that if the car isn’t running right it won’t let it operate those systems. So now thanks to the handy scan tool and the ability to have freeze frame data you always want a scan tool that can record the freeze frame data. So when there’s a trouble code it will show you exactly when it occurred and all the data that were around then when it did occur to fix it, right? Because as a warning to anyone, when you get an old car like that fixed and it’s ready for inspection, take it in and get it inspected because you never know what some other electronic thing is going to go wrong.


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