I am following this thread. I also get 12mpg average in my 300TE. I don't think plugs are your problem either.

Pawo: Since we are talking gear replacement get this -- I pulled the odo in my 260E and ran a drill on the back...the odo span fine. I plug it back into cluster and it would get to about 2/10 of a mile then stop. Any ideas?

There was a sticker on the back from a shop in LA who fixed it before...obviously didn't last long as it was noted at 80k miles...so it lasted 3k before failing again.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

Sounds like the cable is bad or kinked, or maybe it's buggered up where it meets the transmission. I recall seeing a Diesel that had the gear that drives the cable totally chewed up.

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-tp


1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition

Not sure, but yow, that is LOW mpg for that car. I get 20 mpg in town with my 300SEL. I think I have a failing o2 sensor, as I am getting an occasional check engine light after the car has been running for 2 minutes and goes off after 5 minutes. Quite strange.

Yep, I used to get around 20mpg as well, but something's gone amiss!

that is a drastic drop in fuel economy . could the cold start valve be leaking or not switching off ?
mak
300se/89

You don't need a garage to work on the instrument cluster....pull it out and bring it inside on the kitchen table on a towel or newspaper or something. That's what I do....

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'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Well, here's another update.

So far, I've driven around 255 miles and the fuel gauge is just below the quarter tank mark. At this point, it appears that I'm getting about 15mpg, as I'm burning a quarter tank every 75 miles. That would mean I'd get about 300 miles per tank. I'm going to try filling up at other stations to see if I get a better result after going through this tank, though I'm wondering if too much ethanol in fuel can have such a huge effect on fuel economy (20% drop!). The only place I can get gas without ethanol gas is at the marina, so I'll try to see if I can fill up a tank there to rule out the ethanol.

I dunno, Ethanol is supposed to be 10% less energy per unit than gasoline, and gas is supposed to have no more than 10% ethanol in the blend, therefore 10% of your fuel is 10% less powerful, meaning a total of 1% less energy in a gas-methanol blend of 90% gas 10% ethanol. In other words, in theory, you should only see a 1% drop in mileage with ethanol blended gas.

I'm beginning to think that perhaps something wasn't connected back correctly when the water pump swap was done. Perhaps a vacuum line? Maybe two were swapped accidentally and so everything looks ok? Kinda stabbing in the dark here.

Did you notice soot at your tailpipe? I would expect to see quite a bit of it if your MPG is really that low.

As for the odometer gear, if it's the same as a W126, it's not too hard to swap out by yourself, but I've never pulled a cluster out on a 124 personally.

__________________
-tp


1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition

255 miles a tank would be about 16.5mpg...

Put it this way, my 260E gets about 21mpg and it lasts 310miles a tank.

Something that may interest you as well....I just swapped the EHA on my 300TE and my MPG jumped from 12 to 15. No change in driving or distance. I've tested over 2 tankfuls now and its significantly better. My EHA checked out on the pressure test too, it came out 5.1 BAR dead on spec. Something you may want to keep in mind

__________________
2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

Hi tinypanzer,

Thanks for your suggestion! I'm going to recheck the vacuum lines against the diagram, as I only checked for vacuum leaks previously. I don't see any soot or smoke coming out of the tailpipe and am going to fill up without ethanol to see if that makes any difference on the mileage.

Regarding the odometer, my car's a W126 and I'm going to try and get the gears swapped this week. I think I just have to unclip the speedo cable under the floor mats and yank the cluster out with the homemade tool. Hope I don't accidentally break anything while I'm in there!

Hey ps2cho,

My car's a w126 which has a 20 gallon or so tank Thanks for the tip on the EHA, I'll try to see if I can find one at the junkyard. By the way, have you checked your EGR valve (if you have one) for leakage? It seems that they can get stuck open and cause a big vacuum leak. I'm going to test mine out this week when I get my mityvac back!

If your EGR valve diaphragm is shot, you can find out without a mityvac, although it does help. I just use my cheeks to suck the line down, which is usually plenty. If the diaphragm is torn, you'll find out very quickly. You'll suck it down and very shortly afterwards, the EGR pintle will move back into its original position.

You can also just plug the line to see if symptoms improve. Thing is, a vacuum leak will make you run lean, unless something is adjusted to compensate for it. This happens all the time when people can't figure out why their car won't idle so they richen up the fuel mixture thinking they're pretty clever. The car seems to run okay for a while but the rich running fouls out the plugs, etc., mileage sucks.....

I'm not suggesting you did any of that...... But, one thing I always keep in my glove box is a kit of vacuum line plugs. You can get them for a few bucks at autozone or advance. They're great when you're out on the road and you spring a vacuum leak. I haven't used EGR in a while. My diaphragm is torn, and I don't feel like spending $350 just for EGR. So, I just plugged the line going to it. Problem solved. No emissions tests in my state.

Anyhow, I don't know why I thought you had a 124. Must have misread something. So, you need the 12 tooth gear from odometergears.com and it's pretty easy to install if you are good working with small things. I recommend putting a dab of grease on it because the new one tends to click a bit.

__________________
-tp


1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition

Hey tinypanzer,

Thanks for your input! I haven't had a change to re-check the vacuum lines against the diagram but got my mityvac back today. I'm thinking that I have a vacuum leak somewhere, though the car idles and runs okay except for the poor fuel economy. I've replaced all the vacuum tubing and rubber connectors previously, and also changed the (4?) rubber hoses that connect to the idle control valve, air filter housing, air injection pump, and the other one that goes on the valve cover to I think the intake manifold. I'm not sure about this, but I think that the only other places that could leak vacuum are the EGR, throttle body boot (not sure what that part is called), and the injector seals?

Regarding my EGR valve, it appears to not have any vacuum lines running to it . I'm going to try and see if maybe it somehow got stuck in an open position.

Thanks for the tip on the odometer gear, I'm going to give it a shot this weekend!

Wow, it sounds like you are pretty on top of your rubber which is a good thing. It also sounds like you know all the suspect hoses and have replaced them....

A vacuum leak really should make your motor run rough. I'm beginning to think that you have taken good care of your rubber and that this isn't the issue. What is the issue then....... Looking at your previous posts, it appears that your lambda adjustment is correct. If you're not seeing soot build up inside the tailpipe, it's hard to imagine it running too rich at all.....

This is truly puzzling me. If lambda is correct, then in theory, you should be running at optimum mixture. Yet your mileage would indicate otherwise. I am wondering if perhaps idle mixture is perfect but your driving mixture is off. This is quickly departing my libretto of CIS knowledge.




Hmmmmm.........

__________________
-tp


1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition

Hi tinypanzer,

I swapped all of those rubber pieces out when I bought the car, as they were disintegrated The engine shakes around a bit under the hood, but I only feel a little murmur when idle. I'm planning on spraying some carb cleaner around the injector seals and will post back, assuming I don't spray too much .