Getting only 15MPG on my 92 325is (manual)

[R_F_L]

Hey guys, I know this issue has been discussed before but coudn't find the threads. Since I purchased my E36 (5 months ago), my gas to milage ratio has been gradually decreasing. I'm only getting 18MPG highway and 14-15 City. Some people suggested tuning-up the car and changing my filters. I replaced the plugs, both air and oil filters and oil (top quality stuff). The tune-up did not a make a difference.

Someone else suggested replacing the fuel filter and O2 sensors. I have not done that yet but want your suggestions before doing so. I also want to install a perf. chip but heard that they work differently with different models. Any suggestions?


Thanks in advance,

AT

[SSJShadow]

This isn't an answer actually.. I have the same problem :P so any answers would be much appreciated!

[bimmerguy82]

I would definately change the fuel filter and O2 sensors if your not sure the last time they were done, or it's been more than 30,000 miles. Maybe even try getting your injectors cleaned. I have done all of this to my 92 325 and i'm getting 29mpg hwy, and 20-22 mpg city.

[kmf60]

I realize that this is going to sound strange...... but I have a '92 325i with a manual trans & usually get between 25 - 30 mpg. During the cold, it dropped to less than 25. As it warmed, I expected the milage to improve, but it did not! Then the fuel pump failed.

Replaced the fuel pump & milage right back up there.

Coincidence?

[nukeduster]

Yea, even when Im not racing along my 92 is getting 20mpg combined highway/city at best.. i was gunna do o2 sensor and probably swap in some fresh fuel injectors since these ones have 205,000 miles on them, figured they might just be leaking fuel.

[nukeduster]

I just ordered my o2 sensor, just gotta wait for my car to get out of the shop before I can swap it in, but anyone have any updates on their cars about what they may have found out about what was wrong with theirs?

Thanks.

[R_F_L]

My Bosch O2 sensor just arrived but still waiting for the fuel filter. Once I have both, I will install'em and let you know.

[R_F_L]

Oh man. I went to advance auto today and asked if they had the wrench to remove the O2 sensor. They didn't so I bought a regular adjustable wrench and stayed under my car for over an hour trying remove it. I got really pissed and went to my friend's shop and got it out.

I replaced the sensor and took the car for a serious test drive. Though the old sensor was old and worn out, I didn't notice any difference in performance with the new one. I will replace the fuel filter tomorrow and see what happens.

[seven]

I had almost the same problem a couple months ago. fuel milage kept getting worse and performance dropped. turned out it was the cat converter. seems the honeycomb stuff inside broke free and clogged the exhaust flow. "cleaned out" the cat and performance was better than ever and fuel milage went right back up about 23 city and 29 to 30 highway hope that idea helps

[Starmavin]

Originally Posted by R_F_L

Oh man. I went to advance auto today and asked if they had the wrench to remove the O2 sensor. They didn't so I bought a regular adjustable wrench and stayed under my car for over an hour trying remove it. I got really pissed and went to my friend's shop and got it out.

I replaced the sensor and took the car for a serious test drive. Though the old sensor was old and worn out, I didn't notice any difference in performance with the new one. I will replace the fuel filter tomorrow and see what happens.

A 7/8 inch wrench works great. They do sell the O2 sensor sockets. However with out a swivel and an extension, and even then they are not very helpful if it's really stuck.

A dirty maf can cause poor fuel economy symptoms.

P.S. After making any changes you should reset the computer so it'll re-adapt to any changes. Do this by unplugging the computer or disconnect the battery for 30 sec.

[R_F_L]

Originally Posted by seven

I had almost the same problem a couple months ago. fuel milage kept getting worse and performance dropped. turned out it was the cat converter. seems the honeycomb stuff inside broke free and clogged the exhaust flow. "cleaned out" the cat and performance was better than ever and fuel milage went right back up about 23 city and 29 to 30 highway hope that idea helps

Interesting...do you clean it on your own or take it to the shop? If the former, then how do you do it?

Originally Posted by starmavin

A 7/8 inch wrench works great. They do sell the O2 sensor sockets. However with out a swivel and an extension, and even then they are not very helpful if it's really stuck.

A dirty maf can cause poor fuel economy symptoms.

P.S. After making any changes you should reset the computer so it'll re-adapt to any changes. Do this by unplugging the computer or disconnect the battery for 30 sec.

I'll definitely do that after installing the fuel filter.

p.s. When testing the car yesterday, I noticed this burnt electrical/rubber smell after reving the engine pretty high. Is this normal or do I have to worry about it?

[seven]

I did it myself. not the best way but I removed the cat from the car cut the top took the internals out and welded the piece back so it is now "cleaned out"

[Starmavin]

Gutting your cat is not only illegal, but your car will fail emissions testing (if in your area, if not, it will be).

[seven]

no emmision testing here I know it was only a temp fix will be putting a new exhaust on soon. just waiting on my bonus. but it did work great and cheap

[R_F_L]

I just finished replacing the fuel filter. Interestengly enough, I drove the car for about 6 miles and only getting 12MPG! I know it's not long enough but I'll wait and see.

Thanks for all the replies guys!