My First Post....Fuel Consumption Question
 

Hello Everyone,

This is my first post here. I almost gave up hope, but was thrilled when I learned about your site. I have a 1988 190e 2.3 8v and I've spent twice it's value in repairs (many , many, new parts) and don't have the heart to let it go, instead, I will continue to invest some more time and money and with your support, I believe this car will work like a top. I love this site!

My first concern is fuel consumption. There is about 130,000 miles on the car now and I'm getting about 200 miles per tank, mostly city driving and not abusive. I know I was getting better mileage before, but what is best I should be able to get?
Also, what is recommended to rectify this problem?

I've changed the fuel filter, air filter, and plugs about 10,000 miles ago and I've also cut out the catalytic converter, replaced the oxygen sensor (NTK), center resonator (OEM), and rear muffer (stainless steel performance). Also, I've run Liqui Moly Jectron through the system many times, which instantaneously restores the performance, but that is only short term.

Thank You in Advance

What is the engine coolant temperature? If it is consistently low (below 80 degree C, for example) your fuel consumption will be high.

I have a 85 190E 2.3 with 122K miles - gives me about 260-270 miles in suburban city driving before the red light comes on - 290-300 on the highway - I figured it gives me about 21-22 mpg city, and about 24-26 mpg highway. Zero oil consumption between oil changes (every 3K).

Hope that helps!

You didn't replace fuel pressure regulator, did you?

You should probably replace fuel pressure regulator every 150k km or also, it's cheap and easy to do.

My V8 400E gets better mpg than yours :D

Thanks blackmerecedes for the reply....

The temperature is around 10 degrees Celsius this time of year.
I have not been using A/C either. I'd like to achieve similar mileage as you are....450 km sounds very reasonable.

I had a compression test done approximately a year ago and the result was 174 psi on all four cylinders then. I suppose I should have one done now.

I've only ever used Liqui Moly MoS2 10w40 Synthetic oil ever since I bought it.

I haven't had any problems with oil loss for about a year and half, ever since I replaced the valve seals, but actually about 2 weeks ago I checked the oil and had to top it off...it was a little low. And this morning, I topped it off again, for the second time. There was a spot on the driveway from last night. I checked it over and it's not from the valve cover, but there is definitely a leak from somewhere, hopefully not head gasket...

To: loubapache
 

The temperature seems to hang around 85 and sometimes closer to 90. That is what I would say is the average. The temperature here has been around 10 degrees Celsius.

Does that seem like the right temperature for the engine?

To: agupta
 

Thanks for the figures. I guess you should have a good idea since you own 3 of them :D and a 16v.

I would like to be in that same ballpark for consumption. Sounds like that's the norm.

To: carman850
 

I haven't changed the fuel pressure regulator. Sounds like now may be a good time, considering the one in it looks like it's the original one, and I might as well but new injectors too.

Another thing I forgot to mention is that the car smokes now...white smoke all the time and black smoke on the highway. That is what I've been told from people driving behind me. I'm not sure what that means.

By the way, I love the 400e :D and especially the fact that it has better fuel consumption :confused:

philipminion:

Your coolant temp is normal so rule out a partially open thermostat.

That was an important clue, Black smoke usually caused by faulty Fuel pressure regulator and O2 Sensor.

Sometimes faulty fuel pressure regulator contaminates O2 sensor,
Even you just replaced O2 sensor, it might be already killed by faulty fuel pressure regulator.

Anyway, you can try fuel pressure regulator first.

Hi carman850
what kind of fuel consumption figures do you get on your 400E.
I get about 17-18mpg city (Lots of uphill and downhill driving) and around 26mpg highway on mine.

philipminion
changing the injectors along with the fuel pressure regulator sounds like a good idea to me. They are about $25 a piece and easy to replace. You might also want to have the fuel distributor checked. If compression was good 1 year ago there is most likely no reason tho have one done now unless you can the car low on oil or something like that.
Engine temperature seems about right.
Any problems with the idle? rough? intermittent shaking at a traffic light?If you had the cat cut out you might be looking at a backpressure problem.
Best of luck and keep it up!

2 months ago, I got the same mpg as yours, but now it's winter time, they switched to winter gas and I drive short distance per day(10 km oneway), I am getting 16 mpg on city drive, and haven't driven too much on highway since winter came.

It's not very cold yet, I will feel lucky if I get 15 mpg in January.

Thanks for the reply, carman850.
Looks like both our cars are were they should be in terms of fuel consumption figures. They do have about the same milage down.
What does yours look like?
Mine is desert taupe on cream interior and upgraded to '94-95 hood and euro headlights. I also have ASR.
Happy motoring and drive safely during the wintertime.
F.J.

loubapache:
 

Well, I've already changed my radiator, water pump, thermostat, coolant level sensor, drivebelt, auxiliary fan switch, I've run Liqui Moly Rad Clean and flushed the coolant many times, ....that's all I remember for parts that pertain to the cooling system.

carman850
 

Let's say I replace the fuel pressure regulator, how will I know if my 02 sensor is functioning properly?

F.J.Lahme
 

I am going to buy the fuel injectors and fuel pressure regulator today and I will check the fuel distributor.

I do have an idle problem , intermittent shaking at a traffic light also.

Exhaust seems to be working just fine as far as I can tell so far, but I will give it a closer inspection, as soon as I get this fuel issue resolved.

Replace the Fuel pressure regulator and see if you still get black smoke first.

I vaguely recall there is a way to measure O2 sensor with a multimeter, normal O2 sensor has 3 pins, one is common ground, one is the heater power: once you start the car, it heats the O2 sensor to let it reach functional temperature faster, the last one is the O2 volume indicator.

You can let the car run 10 minutes or so to let O2 sensor warm up, then probe the voltage from the O2 volume indicator between the common ground, can't recall what exactly the voltage should be, maybe something around 800 mV.

Actually for the fuel pressure regulator, you can also measure it first, I am pretty sure there is place in the fuel rail where you can attach a cheap fuel pressure gauge and measure the fuel pressure, but since fuel pressure regulator is cheap, you can just go ahead to replace it.

Keep us informed.

carman850
 

Thank you very much for that info.

I will get a compression test done, check the 02 sensor as you have described, do a fuel pressure test and post my results.

One other thing....The part number I was given for the fuel pressure regulator is 000 078 03 92 and it is very expensive.
Would you please verify that I have the right part number and possibly tell me the price you have found , since you said that it was cheap and to go ahead and replace it.

Thank you in advance.

philipminion

Sinceyou do have an idle problem,
I'm quite certain the culprit is the O2 sensor and the fuel pressure regulator.
Good advice from carman850, problem is on the KE Jetronic injection of the 190E you don't have a fuel rail to attach a measuring device to. You'll have to check if the regulator is producing a vacuum on the little black rubber hose that comes out in the front.
I had the same problem on the 88 300E, which has about the same injection setup. Turned out to be injectors, fuel pressure regulator and the O2 sensor. As long as you don't have a hard start issue, the regulator might not be involved though.
As far as I can remember the fuel pressure regulator is not too cheap, runs about $160 or 180 the last time I bought one. Expect the O2 sensor the cost about $130. These prices are for OEM quality german made products from either fastlane or megaparts.com. I wouldnt put anything less on my cars.
For now you can try to adjust the fuel/air mixture with a 3mm T-wrench. There's a hole in the center of the airfilter in which to insert it. Press the wrench down slightly until it catches and then turn slowly and release the pressure to see what the effect is. Right is richer, left is leaner.
You might have to take the air filter off and drill a little metal ball out of the neck that houses the adjustment screw to get to it. ONce the ball is out there's a little metal plate in there. You can just take that out. Its not attached to the surrounding metal.
Dont turn the screw too much though or the computer wont register the cange or screw up the setting even worse. Just a tiny bit at a time. A hair-turn can make a big difference.
You can also get a smell of your exhaust. Rotten eggs is too rich.
A car on the rich side runs a tad more powerfull, but will screw up emission control equipment like cat and O2 sensor. Expensive 5min of more fun.
To cheaply test the O2 sensor my ex-boss (now independent MBZ mechanic in HIlo, HI, MB tech since the 60's, trained in Germany, worked for MBZ of Hollywood) tells me to disconnect the O2 sensor cable and see if the idle changes. No changes, ergo O2 sensor bad. I'm not so sure about that, but you can try it.
Best of luck!
F.J.

P.S.
If you need more specific directions, I'll mail you a picture.

philipminion

in case you are interested I have the kind of fuel pressure regulator you are looking for. Its a Bosch, part number 0438 161 001, used, but I have only been using it for testing purposes on three cars and according to fastlane, it will fit your car. Its practically brand new, only that is show some wear, where the wrenches go. Im parting out all my parts and such as I will move back to the mainland early next year.
You can make me an offer on the part if you are interested.
F.J.

Sorry, didn't know Fuel pressure regulator for 190E costs that much.

The one on my 400E costs only 40 USD, and it took me 5 minutes to replace.

Hi carman850

what made you replace the fuel pressure regulator on the 400E?
I mean in regards to symptoms.

I bought this 400E several months ago, I replaced a bunch of parts as preventive maintenance: (distributor caps &rotors, spark plugs, fuel pressure regulator, engine oil filter, air filters, transmission fluid and filter), I didn't replace O2 sensors and Cat, they looked like new, I guess previous own must have already replaced them.

It did shake and idle roughly, now it's smooth like silk.

I replaced fuel pressure regulator and O2 sensors (it has 3 of them!!) on my other car: Ford explorer, before I replaced them, it blew black smoke and I got 10 mpg, now I get 16 mpg.

This is what happened...The results...
 

uggghhhhh....I just finished typing my post and it said I wasn't logged on, but I know for sure that I was, and I lost all my text and have to do it all over again :( .

Just a reminder my car is a 1988 190e 2.3 8v

From the beginning....I took off the air filter assembly to expose the fuel system. I cleaned the entire area with a cleaner from Liqui Moly's Professional Line called " Intake System Purge" and noticed some oil around some of those shaped hoses and so I took the spacing element out from between the hoses and cleaned it well, since it was very dirty/blocked (oil). Afterwards, I took out and cleaned the fuel pressure regulator, cold start valve, and the throttle valve housing, inside and out. Next, I removed the injectors and cleaned all around there and installed new Bosch injectors and seals.

Now it was time to do a fuel sytem pressure test. I used the one made by MAC. First, I checked the fuel pump relay with this equipment and it is working just fine. Next, I did the pressure test and the gauge read 84 psi. I did the test 3 times to be sure.
Haynes manual says it should be 76.8 - 79.7 psi. Bottom line is that there was a lot of pressure. Whew, what a relief, saved me from buying that costly fuel pressure regulator.

Moving along, it was time for a compression test. Here are the results:

Test done without oil
Cyl. 1 150 psi
Cyl. 2 165 psi
Cyl. 3 165 psi
Cyl. 4 165 psi

Test done with oil
Cyl. 1 200 psi
Cyl. 2 200 psi ( maybe 198 psi )
Cyl. 3 200 psi
Cyl. 4 200 psi

Haynes says:
Compression pressure should be 145 - 174 psi
Minimum acceptable compression pressure 123 psi
Maximum compression difference between cylinders 21 psi

I did both tests because I was told that there is a way to diagnose an engine by doing this. My concern comes from the fact that I have noise coming from the engine that sounds like lifters or valves. I'm not sure and I'm hoping one of you guys may have an idea about this ;) .....I changed the spark plugs too. The electrodes were quite black, probably carbon deposits.

Last but not least for the day, after noticing that there was oil in the throttle valve housing which lead into the air filter body and the filter itself, I took out the filter and cleaned the entire air filter body and related parts and reinstalled without the air filter. Instead, I put a K&N air filter. Here is a pic...

I know I said that I check the 02 sensor, but I ran out of time...that's next.

Oh yeah, I adjusted the idle too. The car is much smoother now, idles better, more throttle response...overall a good day :D

2 Days Later
 

Well...it has been 2 days and I can say that my mileage has increased for sure. I will post figures once I go through a complete tank.

The engine is much smoother, and there is no hesitation.

I'm not sure about the air filter setup, it may not be breathing properly, but I'll give it a few more days to be sure. If it doesn't change then I'll go back to the normal style filter to see if that makes a difference.

I put a valve cleaner in this morning Luqui Moly's Ventil Sauber (valve clean) which made a difference right away.

My 230te can go as low as 18mpg doing the school run,1 mile there and 1 mile home but does 33mpg on a long run at 75mph so the tank range varies hugely and it shows how mpg varies bepending on the type of usage the car has!!
So don't worry so long as it stays consistently bad!
Hamish

MAJOR WORK AHEAD.
 

HELLO ALL.
I have the same fuel consumption problem as experienced by philipminion. I want to see if I can get some help from the experts.
Some mornings I have rough starts. The car shakes and vibrates like a massager:( well it feels good to have a massager but not if the whole car is one:mad: I also have the same vibration during stops i.e. at a red light. When I cold start the car in the morning, I can smell the rotten egg smell, but it goes away. I also feel as if I have lost power or the transmission is giving out (not shifting properly, very sluggish). I have to do some major work to this car to make it run like new again. Please Help me out here!!! :confused:
Thanks
By the way its a 85 190E 2.3 8V :)

Great Results !
 

Well the results are in. I got 260 miles the first tank. I'm up 60 miles. I'm really glad I cleaned the fuel system inside out and changed those injectors. I believe that made the difference. Something must have.

I'd like to thank all of you guys for your support and advice that you've given me to help achieve these positive results. This forum is really something great and makes owning a benz a delight.

Congratulation!!

I know the feeling of improving mpg by 30%, also the release from feeling guilty:D