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  #16  
Old 08-27-2004, 02:17 PM
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Join Date: Aug 2004
Posts: 20
Re. Need help with Idle control unit please

Yes, you can certainly use a jumper wire to go between the middle socket and socket furthest from the CSI to simulate a proper idle switch closure.

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  #17  
Old 08-31-2004, 02:27 PM
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Join Date: Aug 2004
Posts: 103
I am almost there

Facing high cost of replacing of replacing TVS, I did something creative. With wife in the car pumping the throttle, I manually push down teh air intake plate and just spary the whole can of Carb clean down on the throttle, focuing on the side with TVS. With that, I got my 0 ohms contact between Idle tips and got my normal idle. And I got 5V and 5 ohms on ICV.

Right now, each morning, I could start the car on the first try and get 800 on P and 600 on D. However, upon reaching work place 25 - 30 minutes later, I got 750 on D and 1200 on P. Something has happend when the car got hot.

I have gotten rid of those 1500 RPM high idle but still have to use extra brake in city traffic. The good news is that I know for sure every components are capable of working because I got good idle in the morning. The bad news is that I still have not clue where and what is lose upon the car got hot. The decent idle on D suggests the electronic system is not responing to extra load when engine is engaged.

My plan is to measure both ICV and TVS while car is hot to see if everything is still normal. Any suggestions and advises will be greatly appreciated.
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  #18  
Old 08-31-2004, 10:00 PM
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Join Date: Aug 2004
Posts: 38
same problem

hi. i have been reading your posts with interest because i have been chasing a high idle problem also on my '87 560SL. i did all the tests that you did on these posts, and originally thought that heat had something to do with it. many times the car would start in the morning, run good, and then went to high idle when hot. i figured a temp. sensor somewhere was messing up.

when the car went to high idle, the TVS was inoperative (pulled the 3 prong plug and nothing happened), the icv had 0 voltage, etc. When the car operated normally, all of these things worked within their specs. I looked in the CD manual, and concluded it had to be the icu (module behind the glove box) or the ovp relay.

the overvoltage protection relay powers a lot of this stuff thru the icu in this car. i checked it and the fuse was good. so it was between these 2 components, and i figured the computer was usually either brain dead or not, even though i have read about cold soldier joints, etc. i opened the module and nothing was burned and it looked new. so i decide to get a new ovp relay, thinking that maybe it was defective internally and supplying intermittent power or wrong voltages, etc. i spent about $80 on it, plugged it in and prayed, and it worked perfectly. The car idles better than it ever has, and its been 2 days of driving and its still good. so i'm guessing this relay has caused a lot of people a lot of trouble, and maybe you should consider this as the first replacement, especially if the problem is intermittent. hope this helps and good luck.
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  #19  
Old 08-31-2004, 10:55 PM
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Join Date: Aug 2004
Posts: 103
Did you have any other indications such as

ABS light on and hard start? Since I don't have any of those problems, I doubt it is the OVP.

This is what I found. When car is hot, I got an open circuit between idle tips of TVS and low voltage on ICV (3.5 V). I will measure again tomorrow moring when the engine is cold to see if I got a close loop on TVS idle point. May be, just may be, the TVS contact is loose and the expansion when car is hot makes it bad.

Where did you get your OVP? Does it come with one fuse or two? How did you pull the OVP out? Just by force? Thank you very much for your input.
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  #20  
Old 09-02-2004, 08:28 PM
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Join Date: Aug 2004
Posts: 38
benz;; i got my ovp relay from the benz dealer- around $80 total --could have ordered it but time was of the essence. it has 1- 10 amp fuse on the top of it, and has 5 prongs, whereas the original one had 4. the parts guy said it was the correct replacement part, and he was correct. the holder looks like it has 6 holes in it. the ABS light on this car never came on---and its not on now. the braking is good, but i have a feeling that the light is out in the dash. its one of those things you never notice until there is trouble, and i dont recall the light ever coming on when you first crank the car, as a check. it doesnt come on now when i just turn the ignition on---all the others do light up. I know the ovp problems is usually ID'ed by the ABS light, but in my case i think my "signalman" is dead. nevertheless, this seems to have fixed this problem--i have been driving the car as much as possible since i fixed it, looking for trouble, and it hasnt shown itself (YET!!!). To remove this thing, you just reach in the right side kick panel above the fusebox on this car, and pull it out. mine was kind of tight , and i wiggled it a little. I havent tried to figure out why the abs light is out, and i think i have to take the dash out. I hope this helps. good luck.
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  #21  
Old 09-02-2004, 08:46 PM
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Join Date: Aug 2004
Posts: 103
Thanks for your response

I still think my problem is throttle valve switch related because I could still get 5 V on my ICV, indicating power are going throuht ICU. I took out th eOVP last night and found the 87E (ABS) is connected with 87L (Idle). If there is a problem I will definitely see ABS light comes out.

I still could not get 0 ohms between TVS idle tips. Having done some research on the forum, I think I will still working on lubricating throttle linkage next. In one of the messages, he got his idle back by simpley spary Carb cleaner on the TVS.

Got some time this long weekend. If I can't get it done, the car is going to dealer shop early next week.
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  #22  
Old 09-14-2004, 09:22 AM
Neil ('92 300CE-24 cab)
 
Join Date: Sep 2004
Location: London, UK
Posts: 54
Have read this post and only saw one small mention by 'mctwin2kman' of the "Deceleration throttle micro-switch" which sits at the end of the throttle linkage. With the accelerator pedal up the top arm of the throttle linkage rests on the little button switch and needs to depress it sufficiently for it to 'click'. Have you checked/discounted this?

I only mention it as I had a similar high idle problem last week (1500 RPM in 'P' when engines at working temp) after getting the car back from the garage - was having the crankshaft position sensor replaced. As the mechanic duly went on holiday I did a bit of reading up to try to fix the problem myself. From some other posts I read about the significance of this little switch, and sure enough my linkage had somehow been altered so the switch no longer clicked. All I had to do was turn a little black plastic adjustment screw on the linkage a half turn, which slackened off the cable sufficiently for the spring to pull the arm more forcefully onto the switch. Immediately the switch clicked the idle revs dropped to 700'ish!

Might not be the solution for you but just thought I'd throw it in in case other readers are suffering due to something so trivial.
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  #23  
Old 09-14-2004, 01:42 PM
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Join Date: Aug 2004
Posts: 20
Need help with Idle control unit please

The reason I didn't mention the throttle linkage microswitch is that it doesn't apply in this case. The original poster has a 560 SEL and these cars don't use this type of switch. Instead they rely on the position of the TVS for "thrust cut-off".

T.C.

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