16 MPG? Suggestions?

[MAXELHOFF]

valve lash, vacuum leaks?

http://ecomodder.com/forum/EM-hypermiling-driving-tips-ecodriving.php

[BROKINBIMMER]

http://ecomodder.com/forum/EM-hyperm...ecodriving.php

That's a pretty dumb website, but thanks

[TwoJ's]

I know you said you replaced the fuel filter, so did you also replace the soft fuel lines down there? I'd be sure that you're not losing fuel before it even makes it to the engine.

And I would recommend not messing with the AFM -- you're more likely to mess it up than successfully lean out the mixture. So it isn't throwing any codes? After replacing the items that you have, I'd look towards the O2 sensor and AFM. See if there is anyone local that has a spare AFM laying around. You could switch it for a week or so, go through a tank of fuel and check your mileage.

Also, 16MPG is too low for what you've got, but also keep in mind that you've got an auto trans and a 4.10:1 differential. So you shouldn't expect spectacular fuel economy. My old e30 got 22-23 mpg with 90% freeway driving. If you drive in town a significant amount of your time, I'd expect 20-22mpg.

[fronton]

Get new or rebuilt injectors. With over 200k, if they are original, regardless of better economy, you will have a much happier engine and enjoy the drive.

[BROKINBIMMER]

Get new or rebuilt injectors. With over 200k, if they are original, regardless of better economy, you will have a much happier engine and enjoy the drive.

Thanks for your feedback guys.


Would you recommend new stock injectors, or bigger ones?

[Danny]

General discussion is not a catch all for your issues. Please post in the correct subforum.

Thanks.

[meengreene30]

i use to average @14-16 mpg. changed to #17lb and went to 23-24. old injectors were real gunked up. and i am very heavy on the foot

[DrJosh]

Meaty snow tires, roof rack, and 4.10 LSD and I get around 17 mpg

[jlevie]

Which coolant temp sensor did you replace? The one for the gauge or the one for the DME? If the new sensor was for the gauge test the ECT sensor or replace it with a new part. Is the engine running at normal (80C) temperature? Check the head temperature with an IR or contact thermometer.

Unless you know they are pretty new, replace the ignition wires. I don't know what plugs you used, but the best will be NGK ZGR5A plugs. Also replace the O2 sensor and have a smoke test run to check for intake leaks and repair as indicated. Tee a gauge into rail supply line and make sure the fuel pressure is correct. At that mileage the injectors almost certainly need to be rebuilt. I like RC Engineering and the cost will be ~$25/injector.

[BROKINBIMMER]

Which coolant temp sensor did you replace? The one for the gauge or the one for the DME? If the new sensor was for the gauge test the ECT sensor or replace it with a new part. Is the engine running at normal (80C) temperature? Check the head temperature with an IR or contact thermometer.

Unless you know they are pretty new, replace the ignition wires. I don't know what plugs you used, but the best will be NGK ZGR5A plugs. Also replace the O2 sensor and have a smoke test run to check for intake leaks and repair as indicated. Tee a gauge into rail supply line and make sure the fuel pressure is correct. At that mileage the injectors almost certainly need to be rebuilt. I like RC Engineering and the cost will be ~$25/injector.

I replaced the lower blue CTS, not the dummy one for the gauge. So, new injectors will make the car more efficient? Shoul I stick with the stock size?

[dnguyen1963]

Stay with stock injectors and chip, unless you are planning to mod the engine.

[funcrew]

Lots of good information here. For sure, have a smoke test done. There are a ton of old hardened rubber connections in your intake tract that cause problems when they leak. Shop around - Prices near me range from $40 to $90 for a smoke test. Tip your tech in advance - you want a thorough write-up so you can fix all the issues found.

If you want to do injectors, I would suggest modern-design flow-tested rebuild units in the original 14lb flow rate.

If you didn't reset your DME when you put the new O2 sensor in, disconnect your battery for a couple hours. Someone correct me if that's off.

Test your compression. With 200K, there may be enough wear that your mileage and power suffer even though the car "runs fine."

[BROKINBIMMER]

Thanks guys, really appreciate your suggestions.

Next on my list is:
Valve adjustment
Plug wires
Fuel pump regulator
Rebuilt injectors
New vac hoses

[BROKINBIMMER]

Ok valve adjustment done (what an easy job)
Next is the spark plug wires.

I'll keep you guys posted

[BROKINBIMMER]

I'm also going to swap out the thermostat even tho I'm pretty sure it's good