Unusually high fuel consumption

[Lyrred]

Ive noticed that my car has terrible fuel economy. I recently replaced fuel filter and spark plugs and wires to try to combat this issue. Im sure it is running rich because I can sometimes smell a trace of fuel when I'm using ac.

Unsure if this is related, but when I use ac I feel about a 30-40% power loss in my engine. The engine sometimes lags when I press the throttle.
Your help would be greatly appreciated. Thanks.

[Herr Faust Schinken]

It sounds like your running way too rich

[future rs]

Ive noticed that my car has terrible fuel economy. I recently replaced fuel filter and spark plugs and wires to try to combat this issue. Im sure it is running rich because I can sometimes smell a trace of fuel when I'm using ac.

Unsure if this is related, but when I use ac I feel about a 30-40% power loss in my engine. The engine sometimes lags when I press the throttle.
Your help would be greatly appreciated. Thanks.

Have you pulled the plugs back out to check them? Just to make sure. you had the issue before replacing said parts right? (if not go back and check your install to make sure everything is installed correctly)

Checked o2 sensors? Any check lights on the cluster?

[rustybullet]

If you have an eta check the cold start valve, check for vacuum leaks and o2 operation.

[oldmann]

Ive noticed that my car has terrible fuel economy. I recently replaced fuel filter and spark plugs and wires to try to combat this issue. Im sure it is running rich because I can sometimes smell a trace of fuel when I'm using ac.

Unsure if this is related, but when I use ac I feel about a 30-40% power loss in my engine. The engine sometimes lags when I press the throttle.
Your help would be greatly appreciated. Thanks.

Is the car throwing any codes? Go after those 1st. Vaccum leaks would be next.

Bad 02 sensor can screw up your fuel mileage. TPS, Coolant temp sensor, Air intake temp sensor, can also screw up mileage.

CK this stuff out before throwing money at the wrong stuff.

CK fuel pressure regulator, is the vac line hooked up, leaking? CK fuel pressure, CK return line to tank, if plugged it raises fuel pressure when its not needed.

Fuel injectors need CK'd, leaking injectors can mess with the other sensors.

Only fix whats broke, wasted effort is just brain damage.

[dnguyen1963]

A common, but often overlooked, problem is cracked fuel line. Check your line for cracks because they are well over 20 yrs old.

[Nick_S]

02 sensor and spark plugs?

[nrubenstein]

Step one: make sure your odometer is working correctly. Terrible fuel economy often really means that you need to replace some gears. (I figured it out when I got down to 150 per tank in highway driving.)

After that, the car probably could use a tune up. But don't diagnose running issues based on economy when there is a good chance the odometer is fucked.

[dnguyen1963]

Step one: make sure your odometer is working correctly. Terrible fuel economy often really means that you need to replace some gears. (I figured it out when I got down to 150 per tank in highway driving.)

After that, the car probably could use a tune up. But don't diagnose running issues based on economy when there is a good chance the odometer is fucked.

Don't forget that he is smelling fuel...

[10Toes]

Step one: make sure your odometer is working correctly. Terrible fuel economy often really means that you need to replace some gears. (I figured it out when I got down to 150 per tank in highway driving.)

After that, the car probably could use a tune up. But don't diagnose running issues based on economy when there is a good chance the odometer is fucked.

I think most people have an idea of how far they are driving, not just using their Odometer. They would probably know the difference between 150 and 250.

[Lyrred]

Have you pulled the plugs back out to check them? Just to make sure. you had the issue before replacing said parts right? (if not go back and check your install to make sure everything is installed correctly)

Checked o2 sensors? Any check lights on the cluster?

Yea I pulled the plugs. They seem fine. I haven't changed 02 sensor since I got the car n 09 though. I'll check that.

[Lyrred]

Is the car throwing any codes? Go after those 1st. Vaccum leaks would be next.

Bad 02 sensor can screw up your fuel mileage. TPS, Coolant temp sensor, Air intake temp sensor, can also screw up mileage.

CK this stuff out before throwing money at the wrong stuff.

CK fuel pressure regulator, is the vac line hooked up, leaking? CK fuel pressure, CK return line to tank, if plugged it raises fuel pressure when its not needed.

Fuel injectors need CK'd, leaking injectors can mess with the other sensors.

Only fix whats broke, wasted effort is just brain damage.

I have an 87 325is so I can't get any codes. Where is the vacuum line located? Underneath name manifold? If so, then yep that's on. I'll try to buy a new 02 sensor.

[dnguyen1963]

Yea I pulled the plugs. They seem fine. I haven't changed 02 sensor since I got the car n 09 though. I'll check that.

You cannot tell anything by looking at an O2 sensor. If it is more than 100K then you need to replace it. Have a shop perform a smoke test to find the vacuum leak. You'll be amazed to see where the smoke is coming out of your engine.