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  #46  
Old 04-09-2009, 06:35 PM
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Quote:
Originally Posted by tinypanzer View Post
Also - Somebody posted a link to a PDF file with a complete theoretical description and diagrams of the Bosch CIS system. It's well worth the read. I think the post is maybe a month old? I highly recommend checking it out.
Is this the link?

http://clubgtinorfolk.com/downloads/Information/boschtech-12d.pdf

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  #47  
Old 04-09-2009, 07:13 PM
david s poole
 
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if i remember correctly there was a tsb by mercedes concerning a way to raise the idle speed by 50 rpm to handle your issue.you need to cut into the wiring at the ecu and find the purple wire.then scrape off the insulation at one point and attatch a wire which you take to ground[one of the brown wires in that same loom].
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  #48  
Old 04-10-2009, 01:14 AM
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Quote:
Originally Posted by tinypanzer View Post
Yes, you would need to check that with an analog meter for best results. Digital meters won't show dead spots, dips, or other non-linearities nearly as well as a needle meter.

Forgive me if you've already answered this question but, have you checked to make sure it's running in closed-loop?

Also - Somebody posted a link to a PDF file with a complete theoretical description and diagrams of the Bosch CIS system. It's well worth the read. I think the post is maybe a month old? I highly recommend checking it out.
Great link thanks.
I know the rough idea of what closed-loop means...but I am not sure how I exactly "tell" that I am in closed-loop.

Quote:
Originally Posted by david s poole View Post
if i remember correctly there was a tsb by mercedes concerning a way to raise the idle speed by 50 rpm to handle your issue.you need to cut into the wiring at the ecu and find the purple wire.then scrape off the insulation at one point and attatch a wire which you take to ground[one of the brown wires in that same loom].
This is not just a low rpm issue unfortunately.
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  #49  
Old 04-10-2009, 09:56 AM
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Originally Posted by ps2cho View Post
Great link thanks.
I know the rough idea of what closed-loop means...but I am not sure how I exactly "tell" that I am in closed-loop.
Monitor the output of the oxygen sensor with a high impedance voltmeter and when the output starts switching between approx. .2 volts and .8 volts you are in closed loop mode.

I know that you changed the o2 sensor but I can't remember exactly what replacement you used. I know that the Volvo 850 that I had was very picky about the sensor. I tried a Bosch universal with no luck and finally installed the Bosch with the OEM connector and all of my problems went away. Also, keep in mind that it is easy to contaminate the sensors with silicone. I have stopped using any RTV that is not sensor safe and no longer use silicone spray to clean up plastic and rubber in the engine bay. I also remember reading that you should not use any type of dielectric grease on the o2 sensor connection.
Good luck.
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  #50  
Old 04-10-2009, 08:28 PM
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slk230red - Yup, that's the link. Man, isn't that an awesome read? It really answered a LOT of questions I had about how this type of fuel system works.

Looks like I will have to fig into it this weekend - more than I had hoped.
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  #51  
Old 04-10-2009, 11:15 PM
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I chased a similar problem for approximately two years and it was solved last weekend. The round plate on the throttle body was bent and out of adjustment. (Most likely caused when the engine backfired a couple years ago.) Simply, the engine was getting too much air at low idle, causing it to run rich and idle poorly.

We replaced the round plate on the throttle body with one from old throttle body with the same part number that was lying around and the engine is now purring like a kitten. Just have a little anti-freeze mixing in with the oil after we put the engine back together. Front cover is coming off to look for a busted/leaking o-ring--but that is another story.

The plate has to be centered with a very fine clearance around the edge and, if I recall correctly the height of the plate should line up in the center of the 1mm ridge at the bottom of the opening on the throttle body. The adjustment for this in the SL (107) is a detente under where the fuel line comes into the right front of the fuel distributor as you face it. You can't get to the adjustment without removing the throttle body.

There was one other adjustment that was made after we pulled the throttle body and fuel distributor off. It was at the front of the engine where the rubber piece the throttle body sits on fastens to on the manifold. There was no spec for this that my mechanic could find, so he made a (very well) educated guess in his adjustment.

You may not have a bent plate, but it could just be enough out of tolerance to be allowing too much air into the intake at low idle.

Hope this helps.
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  #52  
Old 04-11-2009, 12:11 AM
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Originally Posted by sublettd View Post
I chased a similar problem for approximately two years and it was solved last weekend. The round plate on the throttle body was bent and out of adjustment. (Most likely caused when the engine backfired a couple years ago.) Simply, the engine was getting too much air at low idle, causing it to run rich and idle poorly.

We replaced the round plate on the throttle body with one from old throttle body with the same part number that was lying around and the engine is now purring like a kitten. Just have a little anti-freeze mixing in with the oil after we put the engine back together. Front cover is coming off to look for a busted/leaking o-ring--but that is another story.

The plate has to be centered with a very fine clearance around the edge and, if I recall correctly the height of the plate should line up in the center of the 1mm ridge at the bottom of the opening on the throttle body. The adjustment for this in the SL (107) is a detente under where the fuel line comes into the right front of the fuel distributor as you face it. You can't get to the adjustment without removing the throttle body.

There was one other adjustment that was made after we pulled the throttle body and fuel distributor off. It was at the front of the engine where the rubber piece the throttle body sits on fastens to on the manifold. There was no spec for this that my mechanic could find, so he made a (very well) educated guess in his adjustment.

You may not have a bent plate, but it could just be enough out of tolerance to be allowing too much air into the intake at low idle.

Hope this helps.
I have adjusted the plate as per specs. The picture on the first page is from when I took it apart to adjust.

I am running in closed-loop then as the O2 sensor fluctuates. I will check it again tomorrow since I replaced the injectors and see how rich I am running according to the lambda.

I am going to read through the PDF tonight and learn as much as I can about the Bosch CIS-E.
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  #53  
Old 06-07-2009, 01:06 PM
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After driving the 260E for a month while the ignition tumbler was being replaced in the wagon...its easier to see what is going on.

It is very clear that the erratic vacuum begins when the car enters closed loop after being cold. I think my next course of action would be to replace the entire CIS fuel system with the spare I have and see what happens. With that, it will be the potentiometer, fuel distributor and eha. As was said above, maybe even though the potentiometer checks out, it could have a dead spot or something.

My second question -- If the timing is in fact within spec, can I rule off the crank pos sensor and hall sensor? Or could they still be potential problems?

Can anybody also explain to me how the hall sensor affects the CIS? Does it even affect the CIS? Whatever is causing this the rough idle is making massive overfueling and killing my power at the bottom end.
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  #54  
Old 11-29-2009, 02:05 PM
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ps2cho,

I have a 88 300TE, and went the same route. Concentrate on the potentiometer/air flow sensor. My sensor would do the same thing when it got warm, sometimes it would read off the correct reading, and sometimes not. (pins 1 & 2 .65v then intermittently to 1.01v - 1.04v)

This would be my second sensor that i've installed in the car in 2 years. First year the rpm gauge was sporadic(dead giveaway), second year(day before thanks giving 09') started to do what yours did in the video with the economy and rpm's,and later on my rpm's/idle got sporadic car started to die on occasion at stop lights or to turn.

Replaced mine, and set it to .65 and it runs great.
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  #55  
Old 11-29-2009, 03:27 PM
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Awesome thanks! I will grab 2-3 at the junkyard and give it a try...I have tested mine, but its about the only item I have not replaced so its worth a shot!
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  #56  
Old 11-29-2009, 04:40 PM
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I'm pretty sure the hall effect/crank position sensor only affects the ignition system...
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  #57  
Old 11-29-2009, 11:14 PM
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Originally Posted by ps2cho View Post
Awesome thanks! I will grab 2-3 at the junkyard and give it a try...I have tested mine, but its about the only item I have not replaced so its worth a shot!

I would check your sensors circuit board for scratches and test again to see if the voltage does the same as mine did before spending more money.

The picture is not the greatest nor is the camera but you'll get the idea. The shiny spots on the tracks are grooves made by the brush's that are attached to the sensor plate lever. Every bad sensor i've seen has this same scratch pattern, can't figure it out? And I couldn't tell yuh if a sensor that is working properly would leave a similar pattern or not, never wanted to look since the car was running fine,lol.
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Rough Idle Update on 300TE....I'm totally out of ideas-bad-sensor.jpg  

Last edited by Madd78; 11-30-2009 at 12:10 AM.
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  #58  
Old 11-30-2009, 01:02 AM
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I'm guessing that is worn out on my car too as it will do the idle up/down thing for a few seconds when you start the car warm or sometimes when you put it in park....it does always stabilize though. From what I have read, the potentiometer is virtually impossible to find as a new replacement. What happens when we can't find them anymore?

I have a spare that I found in the junk yard with very little wear on it, (looks like it was replaced before)........but finding a source of new ones would be nice.
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  #59  
Old 11-30-2009, 02:28 AM
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I read they do not sell the potentiometers separately -- only as part of the entire airflow unit which is several hundred $$$.

I will pull mine off in the next couple weeks after I get the 260E back on the road and check for the scratches!

You set the voltage to .65v based on its physical bolted on place...there is space for adjustment of the screws if I remember correctly?
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  #60  
Old 11-30-2009, 02:30 AM
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What is the method of testing the voltage to .65v while adjusting the unit?

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