E30 325 - Ultra bad gas milage -13 mpg Need assistance!

[mgromero]

Hi guys!
I own a 1986 E30 325 (eta engine) with 180k miles on it.
Im in love with this beauty but the fuel consumption is killing me!
Getting 14mpg in the city and 25 in highway

So far changed:
- Spark plugs
- Spark plug wires
- Oil and filter
- Fuel filter
-O2 Bosch generic Sensor (3 wires)
Cleaned:
- AFM, checked that a "clean" track is being used.

Questions:
- Wich sensors in the thermostat housing should I measure? and wich values should they have?
- values in ohms for TPS on idle and WOT?
- values in ohms for temperature sensor in the AFM?

Any information would be appretiated, free beer for everyone if my MPG goes from 13 to 27 in the city.

:rofl:
Thanks!
_Mariano from Argentina.

[89 e30]

Might be the fuel pressure regulator

[HR2L]

Might want to think about checking the resistance on your Coolant Temp Sensor. Not sure how many miles you have on it, or when it may have been replaced last but you may be running in Open Loop (basicly the DME thinks the engine is always cold because the CTS is faulty) and is making the car run pig rich, hence your poor fuel economy.

It could also be the FPR as well, but I'd start with your CTS as its easy to check the resistance and eliminate it as a possibility.

Good Luck, and keep us in the loop on what you find. :)

[Madhatter]

have a look at your tailpipe, is it black with lots of soot? if not, check your oil level and see what the oil smells like. If you suddenly have more oil in the engine than you should have (it will usually smell a bit like fuel), then you have a leaking injector.

[mgromero]

Might want to think about checking the resistance on your Coolant Temp Sensor. Not sure how many miles you have on it, or when it may have been replaced last but you may be running in Open Loop (basicly the DME thinks the engine is always cold because the CTS is faulty) and is making the car run pig rich, hence your poor fuel economy.

It could also be the FPR as well, but I'd start with your CTS as its easy to check the resistance and eliminate it as a possibility.

Good Luck, and keep us in the loop on what you find. :)

Thanks HR2L
the CTS is the part 12 here right?

http://www.realoem.com/bmw/showparts.do?model=1254&mospid=47308&btnr=11_0759&hg=11&fg=35

(BTW thats the realoem for my car)
As per Bentley page 42 on the Fuel system, the CTS should display:
on 20°C 2100-2900ohms.
And the CTS is the most "hidden" sensor in the thermostat housing? There is one right underneath the intake manifold near the 1st cylinder.
Am I right?

Might be the fuel pressure regulator

I am looking for price quotes, we dont have too many E30 down here. :)

Thanks everyone. keep the info coming!!

[jlevie]

The first checks should be for intake leaks, correct rail fuel pressure, and engine temperature. The O2 sensor is a scheduled maintenance item with a replacement interval of 100k. An aged sensor will result in the engine running richer than normal. Small intake leaks, that are otherwise unnoticeable will also result in increased fuel consumption. Too little or too much fuel pressure will affect fuel consumption. If the engine is running cold (bad thermostat) or the DME thinks the engine is running cold (bad ECT sensor) fuel consumption will increase.

[bowtie2bimmer]

I'd yamk the rail, make sure every thing is working well. Also smell your exhaust to see if it smells rich when warmed up. If so agree with above and check CTS

[dchun]

How does the engine run?
Is it smooth or rough?

[mgromero]

have a look at your tailpipe, is it black with lots of soot? if not, check your oil level and see what the oil smells like. If you suddenly have more oil in the engine than you should have (it will usually smell a bit like fuel), then you have a leaking injector.

Yeap black tailpipe, oil leves are normal and it doesnt have fuel smell.

The first checks should be for intake leaks, correct rail fuel pressure, and engine temperature. The O2 sensor is a scheduled maintenance item with a replacement interval of 100k. An aged sensor will result in the engine running richer than normal. Small intake leaks, that are otherwise unnoticeable will also result in increased fuel consumption. Too little or too much fuel pressure will affect fuel consumption. If the engine is running cold (bad thermostat) or the DME thinks the engine is running cold (bad ECT sensor) fuel consumption will increase.

-Ive checked for intake leaks with the carb cleaner method and I didnt find a single one.
-The o2 sensor is a Bosch generic one, brand new.
-A new thermostat 80°C is on the way, possibly next week.
- Wich one is the ECT sensor?

Thanks everybody for the tips.

The engine runs super smooth, acceleration is good but not good enough for my dyno butt. The idle is super smooth, but I can feel some slight rumbling when sitting in a red light after giving a hard run.
The tailpipe is a little bit black and smells rich.

A full tank last 180 miles!!! this is killing my wallet.

[jlevie]

-Ive checked for intake leaks with the carb cleaner method and I didnt find a single one.

Which only means that a) there aren't any leaks in the few places that carb cleaner will work, or b) the leaks in the places you checked are smaller than can be detected with carb cleaner. There are a number of places where carb cleaner just won't work and since several small leaks can add up to a big leak you really need a test that will find any leak regardless of where it is or how big it is. That means a smoke. There is just no substitute.

-The o2 sensor is a Bosch generic one, brand new.
-A new thermostat 80°C is on the way, possibly next week.
- Wich one is the ECT sensor?

The ECT sensor should be the one closest to the cylinder head on the thermostat housing. A quick check of the engine's temperature is to point an IR temperature meter at the thermostat housing.

[mgromero]

I just measured the ECT sensor while cold (multimeter set to 20.000 ohms) and gave a value of 2,15, I guess a 2150 ohms while the manual indicate a normal reading between 2100 and 2900

That would be a normal reading? I dont know why the other settings in the multimeter were not giving me any reading. (2000, 200, 20 ohms)

[mgromero]

Update.
I measured the ECT part# 13 here 13621357414, white one

http://www.realoem.com/bmw/showparts.do?model=1254&mospid=47308&btnr=11_0759&hg=11&fg=35

with the engine cold after night:
Air temp aprox 25°C = 1810 ohms
with engine hot after a quick trip to work:
needle on half mark = 2870 omhs

That means that the sensor is gone right?

[jlevie]

Part 13 typically would be the gauge sensor and part 12 should be the ECT. But the readings that you got don't make sensor for either sensor.

At 25C the gauge sensor should be about 530 ohms and the ECT about 2030 ohms. At normal engine temperature (80C) the gauge sensor should be about 71 ohms and the ECT about 330 ohms.

[mgromero]

but the gauge sensor isnt the one with only 1 prong? and brown color
Like this one:
13621357414


the one I measured is white, first from the cylinder, white color 2 prongs.
part # 13621357414


I think that RealOem doesnt have the sensors in order as they appear in my thermostat housing.

[jlevie]

The single prong sensor should be the gauge sensor. Now that I think about it, I used the equation for a blue ECT, which may not be correct for the white sensor. I'll have to look and see if I still have that data.