Hi everyone! I have not posted in a while but have an issue that I hope you all can help--my mileage sucks! I bought this car from my Dad who had forewarned me of this drop in mileage (he claims to have always gotten 20+ mpg until this happened) and also told me about a racket that happened at start up. I've determined this is the smog/air pump in the throes of death and wonder if the two are related? I intend to follow the advice of some on these forums and remove the air pump and use the smaller v-belt...anyone up for the part number?

Here are some more specifics: rich smelling exhaust at all times; mechanically-inclined Uncle claims to have replaced the O2 sensor in the last year or so; wiring harness replaced; no CEL, although should the CEL light on key-on? If so, my bulbs missing :-( or burned out.

Just had it in for 150K service to the dealership and they replaced fuel and air filter, spark plugs (stated that incorrect plugs were in vehicle) and to check mileage. I doubt they did any significant research on this issue even though I told them of the poor mileage and rich smelling exhaust.

I've read about replacing the O2 sensor and unfortunately have been unable to follow the posts about how to test it...I can't seem to keep straight the ground this, jumper that and measure the millivolts across the source but not the heater wires :-) Also, not sure if the O2 sensor is in the exhaust or under the passenger carpet? Replacement appears to be easy..."15 minutes, tops. jack up the car, heat up the exhaust, screw out the old one and screw in the new one...", yeah right! While I claim no aptitude at being a mechanic, I do like to be able to research and solve problems on my car while saving money!

Anyway, at 18mpg (about 70/30% city/highway) and $2.47/gallon it's getting expensive to drive and I might as well take advantage of the employee discount and buy that new truck that gets 18mpg and will pull my travel trailer as well!

Last thing...the car seems to consistently run at the mark above 80 (is that 100?) and I've read that running hot is not good but don't know if that has any impact on the mileage issue.

Okay, I've rambled enough and thank anyone in advance of your help--I really appreciate it! Mike

The O2 sensor screws into the exhaust system and the wire goes through a floor pan grommet to the connector under the front passenger carpet insert. You need a special offset socket tool to remove the O2 sensor ... available at Pep Boys or other auto stores for around $12. I'd call the dealer and question why they didn't analyze the cause of the rich fuel mixture instead of merely replacing some parts and leaving you with a poorly tuned engine.

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Fred Hoelzle

is that 18mpg in the city, on the highway or mix? Just curious...

The 100 C running temp sounds normal - especially in the south west. The owner's manual says 120C in traffic is OK too. Bothers me when the engine gets to 120C though. My wagon is in the shop right now for running too hot - about 110C even when it is 75 - 80 F outside.

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dtf
1994 E320 Wagon (Died @ 308,669 miles)
1995 E300 Diesel (228,000)
1999 E300 Turbodiesel ( died @ 255,000)
2006 Toyota Tundra SR5 AC 4X4 (115,000 miles) rusted frame - sold to chop shop
2011 Audi A4 Avant (165,000 miles) Seized engine - donated to Salvation Army
BMW 330 xi 6 speed manual (175,034 miles)
2014 E350 4Matic Wagon 128,000 miles
2018 Dodge Ram 21,000 miles

If it were a new car to me , the first thing I would do is to go under the hood and see what codes are stored in the Diagnostic Modules .
Do a search on "Code Retrieve" .. tons of info..
.. then you will know where to start looking

Thanks for the info guys and by the way, anyone building one of Arthur's code readers should be aware that the LED part from Radio Shack is positive/negative sensitive. By that I mean that you must be sure to find out which lead of the LED goes to positive and which to negative. I found out the hard way after building it that I had the LED flip-flopped and so was not working--being a newbie to soldering, circuits, etc., I figured I blew something up in the car!

Anyway, after clearing codes and allowing for "reset", I am getting code 19 from the built-in LED and codes 13 & 20 on pin 8. I've researched what these are but have not found a clearcut answer that guides me in my troubleshooting...hoping someone out there can help!

Thanks as always for the great insight and fabulous resource this forum provides!! Mike

As far as LED's go, any LED I've ever seen has positive ( the longer leg/lead ) & negative.
NOT a good idea to reverse them.

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2007 C 230 Sport.

Every 300E I have (had) 3 all together ran at one needle width over 80 mark. Summer heat in traffic jam maybe 100. I would be worried about it running at 100. I would think about spending $25 bucks on a new Whaler 87 degree thermostat. 10 minutes to replace.

Steve

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The tool plan is clearly polarity notationed....

Code 19 Fuel injectors open/short circuit or emission control system adaptation in engine control module (N3/4) at limit


Impusle Counter scan tool HFM-SFI
Code 13 O2 system operating at rich limit, mixture too lean
Code 13 O2 system operating at lean limit, mixture too rich

Code 20 Self adaptation at idle speed too rich
Code 20 Self adaptation at idle speed too lean

To know if it is rich or lean, you will have to check codes with Hand Held Tester (HHT)

There are several things that can cause this

Intake air leak, fuel injectors, diaphragm pressure regulator etc. You will find informations on checking all these items in the archive.

I had the same codes, and I finaly fixed my "check engine light" problem by replacing the engine control module. The car was driving fine, I just did not like the red check engine light

I have seen many 94-95 W124 experience these codes on these forums.

If your check engine light was working, it would have come on.

Running at the rich limit is going to give you a little bit more power!

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Zafar
94 E320 58000 Miles