Check engine light turned on, codes P0420, p0430, P0174, and P0171?

Hi,

Two of the codes indicate faulty catalytic converters and two indicate a lean fuel mixture. So, at this point, I would not replace the sensors without performing some checks.

The most common cause of a lean fuel mixture is an engine vacuum leak. Let's first check if there are any.

Here is a link that explains how to check:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Next, low fuel pressure can cause a lean fuel mixture. You should also check fuel pressure to see if there are no vacuum leaks.

Here is a link that explains how that is done:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

You will need a fuel pressure gauge, but most parts stores will lend one to you. Also, I attached the manufacturer's fuel pressure specifications below.

Let me know if you are comfortable performing these tests. Also, let me know if the vehicle has a smooth idle.

Take care,

Joe

See pic below.

The car does have a smooth idle, but I have noticed it is idling about 200 to 300 rpms higher than its normal 800 RPMs. Also, the check engine is turning off for a couple of days and stays on for a couple of days.

Hi,

The high idle can be a result of a vacuum leak as well. Have you been able to check for one?

Let me know.

Joe

Not yet, I'll try tomorrow or next weekend. Thanks for the information so far.

I rented a vacuum pump, but I don't think the guys at the auto store gave me the right tool. I also have no idea where to connect the vacuum pump to, can you point me in the right direction? I'm going to attach some pictures.

Hi,

The tool they provided is useable for several different things, including vacuum testing. A vacuum tester can be used to check items such as a MAP sensor, EGR valve, vacuum canister, brake booster, or an HVAC blend door actuator. We haven't narrowed it down to a specific component.

The tester they provided is used to determine if a component holds a vacuum or if it is leaking. In most cases, a leak is the result of a hose issue or failed gasket. Have you done a visual inspection or used something like carburetor cleaner to check?

Let me know.

Joe

I did a visual inspection but did not find anything. Can you tell by the pictures where I'm supposed to connect the vacuum tester?

Hi,

As far as the pics, they are fine. However, a vacuum pump is used to check a specific component such as an EGR valve.

If you want to check the engine vacuum, any vacuum hose on the intake will work. I attached a pic of the PCV vacuum hose. When you connect to this point, remove the vacuum hose from the intake (circled in pic 2). That is where there will be vacuum.

Plug the opposite side.

Joe

See pics below.

I found the issue; I have air coming in through the intake manifold (see the picture). There is a small crack on the top. The gasket seems to have failed as well because there is air coming through where the 2 pieces meet.

Hi,

I can't zoom in tight enough to see the crack. However, if one is present and the engine speed changes when you spray carb cleaner on that spot, that is the problem.

If you plan to replace it, I attached the directions below. The directions include the torque specifications and sequence.

Let me know if this helps.

Joe

See pics below.