Hey everyone,

I figured someone out here might be able to help solve this problem.

My buddys 560SEL acts wimpy, out of power, vacuum loss (measured by the econo gauge, stalls sometimes, when it hits 60C. Up until this point the car run fine. Once it passes this mark on the temp gauge all is right with the work again..

Anyone have any thoughts on this?

It has a recent tune up, new ovp, fuel pump relay....

__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k

Kris, light that car on fire already.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Replace the temp sensors that the ignition unit uses as well as the one for the engine ECU. Temperature related open circuit in the sensor makes the car think it is at a high or low temp. Mixture gets all screwed up. When the car warms up the sensor begin working properly and all is right with the world.

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I got too many cars!! Insurance eats me alive. Dave

78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k

The 4-pin CIS temp sensor has already been replaced. You do make a valid point though. I wonder if we were to wire in a resistor (= to 80C) if the car would exhibit the same behavior...

__________________
Cruise Control not working? Send me PM or email (jamesdean59@gmail.com). I might be able to help out.
Check here for compatibility, diagnostics, and availability!

(4/11/2020: Hi Everyone! I am still taking orders and replying to emails/PMs/etc, I appreciate your patience in these crazy times. Stay safe and healthy!)


82 300SD 145k
89 420SEL 210k
89 560SEL 118k
90 300SE 262k RIP 5/25/2010
90 560SEL 154k
91 300D 2.5 Turbo. 241k
93 190E 3.0 235k
93 300E 195k

That would be a good diagnostic test.

__________________
I got too many cars!! Insurance eats me alive. Dave

78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k

My 1986 500 sl had the exact problem. After testing all the systems, ignition, fuel, replacing lots of parts, I cut a hole in the exhaust before the cat converter and the problems all went away. Check for exhaust back pressure.

Wait, so it runs good cold until it hits 60, then runs crappy, then runs good again once it gets up to temp?


That totally sounds like a bad temp sensor. My 300SE is doing something similar right now, but I've been so busy with the heater core that I haven't looked at it yet. However, mine just runs like crap until it gets warmed up at this point. Temp sensors are testable.

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-tp


1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition