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  #1  
Old 05-25-2006, 05:09 PM
brookspw's Avatar
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Join Date: Dec 2001
Location: Nashville, TN
Posts: 551
Question Bad Oxy sensor causes HARD shifting?

1994 c280.

Dealer replaced the crank sensor. When I drove in it shifted fine. When I drove out it shifted hard. The shifts are so harsh you think it is going to break something.

Research said a vacuum line is probably disconnected.

Diagnosis by said dealer: It is the Oxygen sensor -- no vac lines loose.

Now, maybe I'm missing the boat here -- but:

1. How does an O2 sensor cause this?
2. How did that mysteriously start at the time of that repair?
3. By the way, the duovalve also went out about 3 days after this repair.

Something fishy here. Thoughts?

__________________
1994 C280, dark green metallic
105k miles

1991 190E 2.6, Black
191,500 miles
(sold to another forum member)

2003 Chevy Tahoe LT, Redfire Metallic
105k miles

1989 Mustang GT Cobra Convertible
43k miles
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  #2  
Old 05-25-2006, 07:19 PM
Mike Murrell's Avatar
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Posts: 2,574
Someone knocked something loose while they were replacing the crank sensor.

The O2 sensor story is just more $$ for the shop.

My 2 cents.
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1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"
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  #3  
Old 05-26-2006, 12:39 PM
brookspw's Avatar
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Join Date: Dec 2001
Location: Nashville, TN
Posts: 551
Quote:
Originally Posted by Mike Murrell
Someone knocked something loose while they were replacing the crank sensor.

The O2 sensor story is just more $$ for the shop.

My 2 cents.
They insist it is the sensor. Can this possibly be true? I see no reason that would cause a hard shift problem.

They also insist that no vacuum lines are loose.

I have to go over there shortly. Any thoughts would be appreciated.
__________________
1994 C280, dark green metallic
105k miles

1991 190E 2.6, Black
191,500 miles
(sold to another forum member)

2003 Chevy Tahoe LT, Redfire Metallic
105k miles

1989 Mustang GT Cobra Convertible
43k miles
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  #4  
Old 05-26-2006, 02:12 PM
Ta ra ra boom de ay
 
Join Date: Jun 2004
Location: Pittsburgh
Posts: 1,915
A bad 02 sensor can play havock with your mix and cause intermitant poor running and stalling, bad fuel economy... but I fail to see how it could cause 'straight up' hard shifts with no other symptoms. The O2 sensor is a primary input into the computers fuel trimming, so if the system is running well, aside from shifting, I would say they are lying...
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-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html
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  #5  
Old 05-26-2006, 04:08 PM
brookspw's Avatar
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Join Date: Dec 2001
Location: Nashville, TN
Posts: 551
Quote:
Originally Posted by A264172
A bad 02 sensor can play havock with your mix and cause intermitant poor running and stalling, bad fuel economy... but I fail to see how it could cause 'straight up' hard shifts with no other symptoms. The O2 sensor is a primary input into the computers fuel trimming, so if the system is running well, aside from shifting, I would say they are lying...
So I pick the car up today. They replaced the duovalve and all is good with the A/C. She said they could find no vacuum issues and insisted it was the O2 sensor (no engine light, btw).

I explained how I didn't feel that could be it, that it has been fine forever and just happened to start hard shifting as I drove away from having a repair that disassembled the area containing the vacuum lines.

I'm eating lunch (15 minutes later) and she calls. Said she discussed it with her GM and they don't feel comfy with the issue. Can I bring it back in? They will keep it the next few days and give me a loaner (brand spaking new 230 Kompressor).

Gonna figure out what the harsh shift and starting problems are. Someone else was standing nearby as I explained the O2 to her. I think they must have told her that the tech may not be quite right.
__________________
1994 C280, dark green metallic
105k miles

1991 190E 2.6, Black
191,500 miles
(sold to another forum member)

2003 Chevy Tahoe LT, Redfire Metallic
105k miles

1989 Mustang GT Cobra Convertible
43k miles
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  #6  
Old 05-26-2006, 04:36 PM
Ta ra ra boom de ay
 
Join Date: Jun 2004
Location: Pittsburgh
Posts: 1,915
Good for you. Sounds like they will deal with the issue correctly this time.
And perhaps refund the O2 sensor work? Either way you can take out your frustrations on their kompressor for a few days

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html
Reply With Quote
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