'93 300E(2.8) fault codes revisited!

[dacia]

My 300E(2.8) developed an ugly surging at idle a couple of days ago, which got progressively worse. Air/fuel mixture is very rich, car is visibly smoking (smoke is black however, sign of overly rich mixture). I have retrieved the fault codes yesterday from the 16-pin connector:
Pin 6-- 3 blinks, followed by 8 blinks and then 9 blinks.
Pin 7-- 1 blink
Pin 8, 10, 14 no response.
Pin 1 is ground, Pin 16 is power.
Erased all the codes, drove the car at least 3 drive cycles and checked the codes again this afternoon after I changed the oil.
This time:
Pin 6-- 1 blink
Pin 7-- 13 blinks
Pin 8, 10, 14 no blinks.
Removed the connector from the coolant temp. sensor checked resistance OK. Removed the connector from the fan switch resistance is OK. Removed and replaced air intake temp. sensor, not sure about checking though.
Drove the car around the block seemed OK. No surging.
Checked the codes again.
Pin 6-- 1 blink
Pin 7-- 1 blink!!
Code on Pin 7 disappeared on its own!
Pin 8, 10, 14 no response.
However after checking Pin 7 the little red led on the air recirculating switch on the dashboard started to blink. What?!
The car does not have factory alarm installed and in any case the ignition was on. And if I start the engine without turning the key to the left first, the heating /air-conditioning does not work. After restarting the car it works again. Strange.
Now the surging is back, the air/fuel mixture is very rich, car is running very poorly. During code checking on grounding Pin 10 an audible click can be heard from around the throttle control area.
I am not sure what it is.
This is where I am standing right now. Any help or idea would be appreciated. The car just went through a major tune-up; every maintenance item was changed.
Sorry for the winded post, tried to be as clear as possible.
Thanks for your help,

Alex

[dacia]

I just drove home from a friend's place. The car idled badly, surging between 400 and 1000 rpm. About 1/2 mile from home it smoothened out. Seems to run fine although it may be in limp-mode. I am not sure how to tell, the car is new to me, do not have enough experience regarding expected performance.
On Friday I called MB Canada regarding the wiring harness issue. The warranty department assured me that in Canada the 124 model did not have those problems, it may be strictly a US experience. His explanation was that because of the different pollution control equipment the harness may be different between the US and Canadian models.

Alex

[dacia]

Well I found the solution to my problem with the help of my trusted mechanic and for future reference: it was the MAF (Mass Airflow sensor).
I always had fate in the abilities of my mechanic, he suggested on Friday that the solution would be to change the sensor, but I wanted to poke around the engine over the weekend and maybe learn something in the process.
This morning he lent me a used one, drove it over the day and the car is a dream. Will install a rebuilt one tomorrow.


Alex

[jsmith]

at least it's something you can install yourself. what's a rebuilt one cost? glad you have it figured out!

BTW - that line from MB in Canada about the harness sounds like such a crock, typical of MB speak. How does one get any relief from them? No answer to that one...

[dacia]

Well I have a good relationship with my mechanic (I have sent a couple of customers to his shop, I know him for a few years), so the rebuilt will cost me $300.00 canadian with one year warranty.
I think it is reasonable.
I still haven't figured out why the little red light on the dash switch started
blinking during checking the fault codes. It went away after i turned the ignition off. Strange.

Alex