87' 300E power loss - Page 2 - PeachParts Mercedes-Benz Forum

brewtoo · #16 03-06-2004, 08:22 PM

A meter with duty cycle will read the error codes, if any. You want the reading to VARY somewhere near 50%. If it's a fixed reading, it's a fault code.

It's only about $30 at Sears and looks a lot like the one you have.

psfred · #17 03-07-2004, 01:18 PM

Vin:

You are running either too rich or too lean (don't remember at the moment - dyslexia is like that...).

You can set the idle mixture with a standard digital VOM, but one with a duty cylce is MUCH easier to use, even the cheapest one there is.

What you want to do is set the idle mix to give a reading of about 50% duty cycle warm.

However, there are some things you must do first:

Find and fix any vac leaks. Just because a hose LOOKS OK doesn't mean it doesn't leak. My idle control valve hoses looked fine, but were very hard and floating around on the barb, and leaking. I replaced all the hoses in the vac systems except a couple connectors, and I will do those when I remember to order them.

You must also verify that the O2 sensor is working correctly -- if it is bad, the mixture will be off.

Peter

papadude21 · #18 03-08-2004, 09:05 PM

First I want to thank you guys for your help.
Key on engine off 68%
engine running cold constant 49%
As engine reaches 80c the car starts to idle rough for about a minute and the duty cycle raises. to 92% and idle smoothes out.
Now what do I do. Should I check it the same way with O2 sensor out and see what readings I get.
What do my numbers mean. I have read alot of posts related to this but am still confused. Whats my next step.
Thanks Again
Vinnie

brewtoo · #19 03-08-2004, 10:13 PM

The simple answer:

Looks like you're running rich. Turn the adjusting screw counterclockwise a bit and aim for 50-55%.

Has anyone been tampering with that adjustment? Seems pretty far off.

psfred · #20 03-08-2004, 11:49 PM

Vin:

Read the DIY post on electronic engine controls and test your O2 sensor -- if it is whacked, you are going to have trouble with the mixture! If it's OK, re-set the mixture and see what happens.

Don't turn very far, and wait at least 20 sec for the reading to stabilize, or you will just swing from way lean to way rich and back -- took me a while to get the hang of it.

Peter

papadude21 · #21 03-09-2004, 09:14 AM

I don't know if the adjustment has been tampered with I bought the car in Nov. and just got it on the road a month ago.
I will try to check the O2 sensor today if I get a chance.
Thanks again
Vinnie

papadude21 · #22 03-09-2004, 07:01 PM

Wasan't able to get under the car today so I looked for the connections for the o2 sensor under passenger carpet. Remember I'm new:-) There wasn't one plug but 2. One round one and 1 double rectangular one. Are these the connections for o2 sensor.
Thanks Again
Vinnie

brewtoo · #23 03-09-2004, 07:08 PM

Yes, there are 2 connectors. One is for the O2 heater. I believe the single one is the O2 output, if I remember right.

papadude21 · #24 03-09-2004, 07:12 PM

Now thats what I call a QUICK answer.
Thanks

papadude21 · #25 03-09-2004, 08:10 PM

I went out and dsconnected the o2 sensor and did a duty cycle test.
Key on Engine off 69%
engine cold 49%
Engine warm 80c 49%
Only difference with o2 sensor connected was warm engine duty cycle was 92% the other numbers were the same.
Again the only time I have power loss is when the engine temp. reaches 80c. is this the transition time when O2 sensor starts sending info to the fuel system. Do we think it is the o2 sensor. Notice I said we lol.
OH yea can anyone help with the file 07.3-0121 Testing electrical components of the KE injection system from the CD. Mine seems to be missing or is that not possible to do.

Thanks Vinnie

brewtoo · #26 03-09-2004, 10:40 PM

That 92% number; is it a fixed value or does it vary? If it's fixed, it's an error code but I don't remember what 90% error code means.

The 49% reading when the O2 sensor was disconnected was because the KE system was not operating.

Check and see what the O2 sensor is putting out. It should vary .5 to 1 volt.

The O2 sensor should be operating and sending info well before 80c.

brewtoo · #27 03-09-2004, 10:49 PM

OK, 90% says, "Current to electrohydraulic actuator implausible."

psfred · #28 03-09-2004, 11:58 PM

Sounds like something is wrong here -- mixture is OK until you hit operating temp.

Check the resistance of the engine controls coolant sensor (don't remember which one it is, will have to look it up). If that is flaky, you will get a goofy mixture correction or ECU error due to impossible temp. Obviously, this one fails the ECU to max rich.

Make sure the air inlet temp sensor is connected, too -- this often gets pulled loose when the air filter housing is removed and someone yanks on the hose to the grille vent -- the temp sensor is in that area.

Peter

papadude21 · #29 03-10-2004, 06:23 PM

Peter my 87' doesn't have an air inlet temp sensor on the intake horn like my 91. The resistance on the engine control coolant sensor was .48 ohms. I think it was the furthest sensor on the rear left of the engine near the valve cover right.

Brewtoo the voltage from the o2 sensor started at .36v I reved the engine for about 2 min and it dropped to .30v
Does the constant 92% duty cycle mean my EHA is bad or could it be that my o2 sensor at .36v is not sending a strong enough signal for it to work properly.

I wish the file 07.3-0121 Testing electrical components of the KE injection system from the CD worked for me. It seems to be missing on my CD.
Help with the numbers is appreciated.
Thanks Again Vinnie

brewtoo · #30 03-10-2004, 07:26 PM

Again, the 92% fixed reading would be an error code.

That is a low output for the O2 sensor. Should VARY, up to 1 volt.

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