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#1
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87 300SDL intermittant high idle?
The car will normally idle around 700 rpm or so indicated on the tach, but sometimes when I come to up a stop it will stay at 900-1000, and at that speed its pushing against the torque converter pretty hard so it takes holding the brake pretty firmly to get it to stay in one place. If I keep my foot on the brake and rev it up slightly it will drop to normal, and the accelerator pedal is definitely all the way up when my foot isn't on it. It does it every time I drive it but usually only a couple of times, and the rest of the time it behaves normally. It doesn't seem to have anything to do with engine temperature or any other particular situation. Any idea what might cause this?
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#2
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Is the throttle linkage lubed?
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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles 06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU 91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion 19 Honda CR-V EX 61k mi Fourteen other MB's owned and sold 1961 Very Tolerant Wife |
#3
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This is a quirk of the EDS computer on the 86/87 cars. The redesigned (incompatible with 86/87) version in the 90/91 cars doesn't do this (it has it's own quirks). I had good success replacing the capacitors in my EDS computer on my '86 SDL and greatly reducing the irritating high idle issue. I have a thread on this forum somewhere where I documented it.
The other option is to unplug the EDS solenoid on the back of the injection pump and use the mechanical idle adjustment to set the idle speed to ~650 RPM.
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Current stable: 1995 E320 149K (Nancy) 1983 500SL 120K (SLoL) Black Sheep: 1985 524TD 167K (TotalDumpster™) Gone but not forgotten: 1986 300SDL (RIP) 1991 350SD 1991 560SEL 1990 560SEL 1986 500SEL Euro (Rusted to nothing at 47K!) |
#4
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Quote:
So other than grabbing an extra computer next time I have the chance and trying that it's probably not a big deal? On my old 300SD the governor failed and once it got over a certain RPM it would climb until you shut it off, so I wanted to make sure this wasn't something dangerous like that. |
#5
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No, the intermittent 900-1000 RPM idle is a well documented issue with the 86/87 cars. The cause is not clear, but it's definitely electronic. Even after a recap of my EDS computer, it still happened from time to time but more like once or twice a month instead of 3-4 times every time I drove the car. The base mechanical idle is set very low, 450-500 RPM and the EDS solenoid brings it up to ~650-700 RPM. At full extension, the max RPM of the EDS controller is ~1000 RPM.
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Current stable: 1995 E320 149K (Nancy) 1983 500SL 120K (SLoL) Black Sheep: 1985 524TD 167K (TotalDumpster™) Gone but not forgotten: 1986 300SDL (RIP) 1991 350SD 1991 560SEL 1990 560SEL 1986 500SEL Euro (Rusted to nothing at 47K!) |
#6
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I seem to remember some members found that the connector to the EDS from the pump was not making a good connection resulting in your issue. Maybe check that?
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2004 F150 4.6L -My Daily 2007 Volvo XC70 -Wife's Daily 1998 Ford F150 -Rear ended 1989 J-spec 420SEL -passed onto its new keeper 1982 BMW 733i -fixed and traded for the 420SEL 2003 Volvo V70 5 Speed -scrapped 1997 E290 Turbo Diesel Wagon -traded for above 1992 BMW 525i -traded in 1990 Silver 300TE -hated the M103 1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one 1979 Silver 300D "The Silver Slug" -Sold |
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