August 18

1997 Mercury Grand Marquis, MAF Sensor Replacement

Ford Cars


Mark: Hi, it's Mark from Top Local. We're here with Bernie Pawlik, Pawlik Automotive in Vancouver, BC. Vancouver's best auto service experience. 22 time winners, 22 times as voted by their customer. The best auto repair place in Vancouver, BC, and we're talking cars. How are you doing Bernie? 

Bernie: Doing well. 

Mark: So today's victim a 97, a little bit of an oldster, Mercury Grand Marquis. Yahoo. It's a big one. You had a MAF sensor replacement on this vehicle. What was going on? 

Bernie: Yeah. So this vehicle came to our shop a couple of months ago. She had a large coolant leak coming from the engine. It was coming from the intake manifold, just anything manifold uses a lot of plastic and the plastic wears out. There's a big crossover passage that goes over the intake manifold. Plastic wears out. So we replaced the intake manifold, solved the coolant leak, but, a month or two went by and the check engine light came on and there was an issue with the engine. Made some rattling noises when we'd go up a hill. So that was her concern. So came back to see what was going on. 

Mark: So what was the diagnosis and how did that work out? 

Bernie: Yeah, so our next step, was to, first of all, just verify that all the repairs we'd done were fine and there was no problem with the manifold which we did.

The next step was to hook up scan tool. See what kind of readings, you know, see what codes were stored in the vehicle computer. The check engine light was on. So we came up with two lean fuel condition codes, one in bank, one and two for basically lean fuel condition, P0171 and 174. So that gave us a direction to go in as to what was going on with the vehicle.

Mark: So do we have some pictures? 

Bernie: We do have some pictures. And after retrieving codes, the next question is what do we do for diagnosis? You know what's the next step? So I'm going to share some of that here. That's really the purpose of doing this podcast, just to share what goes into our diagnostics.

1997 Mercury Grand Marquis, MAF Sensor Replacement
1997 Mercury Grand Marquis, MAF Sensor Replacement
1997 Mercury Grand Marquis, MAF Sensor Replacement
1997 Mercury Grand Marquis, MAF Sensor Replacement
1997 Mercury Grand Marquis, MAF Sensor Replacement
1997 Mercury Grand Marquis, MAF Sensor Replacement

So anyways, there's our nice, still a very nice condition for a 1997 car. I don't know how old that makes it. 23 years. It's still very good shape, this vehicle, very low kilometres too only about 65,000 K's. So you're in miles. It's only about 40,000 miles. So the next step, diagnostically with that code information, of course, there's information there, plus the intelligence of the technician working on it, and experience. 

So, our next step was to basically graph, go road test and just take some readings of things. Oxygen sensors, readings, there's a mass airflow sensor. This is a sensor and I'll show a picture of it.

The sensor located in the intake system. This is the main measuring sensor for how much air is flowing into the engine and what the density of the air is. It's a very sophisticated sensor, so it can actually pick up the speed of the air rushing into the engine. How much air is there and how dense the air is.

If you're down at sea level air as much denser than it is at say 12,000 feet altitude. So this sensor picks up all that information. It does it with this little, there's a little tiny, a couple of little wires in there and, basically they heat up, I believe a lot of them that they'll actually heat the wire up and depending on how it cools it'll take readings.

So it's pretty neat, pretty sophisticated device. There's a top view of the sensor. So I'm kind of jumping to conclusions of what we actually replaced here, but the next part of the course is the diagnostic. So this is some of the things that we looked at when we were driving the vehicle. So you see this graph here, longterm fuel trim to longterm fuel trim 1. These are each engine, the V eight engine. So each bank has a sensor on each side, it'll adjust the field trim on each side and the field trim is basically leaning or richening up the fuel mixture. 

Well, then there's engine load and grams per second of the mass airflow sensor. So this is actually reading how much the sensor is actually reading, and this is the engine load. Now this is a graph that I took driving up a very steep hill in Vancouver, full throttle. Every time you have these peaks, that's full throttle. And what this is telling the computer is at full throttle, the engine's only got about a 40% load, which is very low. It should be 80% or more, you know, because you're actually putting as much, you're demanding as much energy of the engine as possible. Also again, this is an experience type of thing, but the graph here when you're doing this full throttle, reading is 60 grams per second of an airflow, which based on experience is way too low. 

So the only thing is the fuel trim's in many of these cases, they go up to 25. This is as much as this thing will read. And 25 is enough if it's sustains that will set the check engine light on. So, anyways, that's pretty much indicated from there. This thing's got a bad mass airflow sensor. 

So cut into the, if you just remember these numbers here real quick, this is what the new mass air flow sensor, same hill the field trims are now showing up at the top here. But the engine load you can see goes up to 81% and the grams per second, 145. Huge difference. 

These trims still sometimes go up to 25, but over time I didn't reset the vehicle computer. Over time, these will actually change and they'll drop out. The vehicle is resetting, but you notice too, when you have full throttle, it's now gone down to zero. So it's making adjustments. That's the thing about modern vehicles, even though this is 23 years old, I still call it a modern vehicle. The fuel systems make adjustments on the fly. So there we go. That's what I'm trying to say. So, yeah that kind of paints a picture of, of what we look at.

Mark: So that's how things looked at to the sensors replaced? How did the car run?

Bernie: Oh way better. Now, before I did notice and the car ran really smoothly before, but I noticed when I had accelerated it didn't quite have the oomph you'd expect out of a 4.6 litre V8 engine, overhead cam engine. Should have had more oomph. And it certainly had way more once we put this in. It just you know, especially at full throttle, it really went. So a big difference there. I would expect the check engine light will not come on anymore. 

That rattling in the engine too, by the way, was basically from a lean fuel condition, caused the engine to knock and ping. So again, when the mass airflow sensor, before it was just telling the engine there's not enough air flowing to the engine. So the engine's adjusting around that. And now the engine knows, Hey, this is how much air is flowing in, we need to deliver this much fuel. 

So the nice thing about doing these tests before and after, is first of all, we can see what's wrong with that. Second after we do the repair, we can verify we've actually found the issue and solved it. 

Mark: So, is this a time consuming part to replace? 

Bernie: No, it's actually a pretty simple part. I'll just go back to our picture again of where the part's located. This is looking at the top of the engine sitting over here. This is the air filter boxes here. There's the mass air flow sensor. It's really not a time consuming part to change. It's all located up top, a few screws and bolts and wires to disconnect and it's replaced. So it's a pretty simple replacement item. Really where a lot of the work goes into the diagnosis.

Mark: So basically it's a case of you guys just don't swap out any old thing you feel like that day and see if it worked. You're checking to see exactly what the issue is. And then repairing that specific part. So it's efficiency of time and materials and costs for the customer. 

Bernie: Absolutely. And I think people want to know their car's fixed right. And there's nothing more annoying than assuming it's one thing or another. I mean, there's a lot of things that could be assumed from those trouble codes. Like it could be that the oxygen sensors are bad or there could be a large vacuum leak and it's important to find out are those things in fact bad.

And once you verify how all those other sensors are reading, then it's a matter of testing things. And of course, a lot of it's experience. I mean, I've worked on a lot of these cars for years. So, I can kind of tell what can go wrong, but I don't just go, Oh, it's throw a mass airflow sensor, it'll fix it. It's like now we know we've done the right thing. And it costs a little more money to do that. But in the end it actually saves money because throwing parts in is just a complete waste of money. 

Mark: You might win or you can just go to the casino. 

Bernie: Yeah, that's right. Yeah. It's kind of like pulling on a slot machine. Sometimes it will pay out. But in this work again with experience, there are a lot of educated guesses. I don't mind saying sometimes we do get a code on a certain car for certain item, and it's, you know, 99% of the time that sensor.

But it's a matter of knowing that before you jump in and just making assumptions or looking on the internet and go, Oh, it's this. It's like, no, it's a lot of times you've got to test it because what's happening might be slightly different than what you read. 

Mark: So this is getting to be a little bit of an older vehicle, more experienced as we should say. Is it still worth fixing? 

Bernie: Well, I'd say so. I mean, the car's in beautiful condition, drives nice. You know, as I mentioned earlier at 65,000 kilometres, it's pretty low. I mean, that's still kind of a brand new car and, you know, it's been well taken care of. The body's in nice shape, the interior is in great shape. It drives nice. So yeah, right now, not the cheapest on gas, but for someone, you know, obviously he doesn't drive it a lot. You know gas is not such a huge expense as if you're driving, you know, doing a 50 kilometre commute every day. So yeah, it's a good car. Worth fixing.

 You know, always the issue that we find with older cars is parts availability. You know, they made zillions of these cars, I don't know how many, but an awful lot of Grand Marquees and Crown Victorias in these engines. So parts are still very easy to come across. 

Mark: So that needs to be figured into the calculation of whether your old vehicle is still worth keeping going or not.

Bernie: Absolutely. And we do run into old vehicles where parts are no longer available. Then to me, it's like, you may as well just get rid of the car and get something different. Unless it's something you really love and you you're willing to, you know, wait on the side for parts. I mean, I figure there's always some part and piece available on planet Earth, but you know, whether you want to wait around for it, you know, and pay the extra time and it's going to take to find it that's the other issue. But so far the I'd say this car is still worth fixing. 

Mark: So bottom line, if you're looking for proper diagnosis of your vehicle repairs and mechanics, that you can trust, service advisors and a whole team that's really dedicated to making sure that you're happy and your car's running right. And you're not spending too much money just wasted. He, he. These are the guys to talk to. Pawlik Automotive. You can reach them at (604) 327-7112 in Vancouver, BC, Canada, or check out the website, Hundreds of videos on there. All makes and models of vehicles, all makes types and all kinds of repairs.

Bernie:  Lots of repairs, lots of cars

Mark: And check out the YouTube channel Pawlik Auto Repair. Same thing, lots of videos on there, hundreds. And thank you for listening on the podcast if you're doing so we appreciate it. Leave us a review on wherever you're picking up your podcasts. And, thanks Bernie. 

Bernie: Thanks Mark. Thanks for watching. Thanks for listening. And, yeah, it's a pleasure.

About the author 

Bernie Pawlik

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