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Old 08-31-2004, 10:00 PM
560slsteve 560slsteve is offline
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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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