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Old 08-03-2003, 11:43 PM
lylemiller lylemiller is offline
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Join Date: Aug 2001
Posts: 32
rough running when running A/C on hot day

91 300SEL 150K. New copper plugs (.035); plug wires & cap are recent; fuel filter replaced a little while back; OVP just replaced too! Air filter is clean, radiator was flushed this spring (by myself) and new thermostate. Car always starts fine and idles smooth at start up.

OK, when I drive the car without A/C and its hot outside the car temp will get between 85 and 95C. The car seems to do fine, a very slight rough idle (not much) at a stop light after some stop and go, but nothing to cause me concern.

Here is my problem. When I drive with the A/C on, like a 30 min. highway drive to work with a little traffic (if any) along the way the car temp runs 85, maybe 90. When I get close to work I hit a traffic light or two and here comes Mr. Rough Idle, sometimes really rough to the point of not being to accellerate through the last light. The car temp hits 110 plus....the ABS light comes on...even after I relaced the OVP last week!

Do I simply need a professional radiator flush? It seems as if the car just can't handle the A/C being on when its hot. Does a car that gets too hot trigger the ABS? Is 110C too hot (I read a post that suggest not)?

PS, After I recently had my upper timing chain replaced my mechanic told me I should replace the valve seals too. I did not do the valves. I still loose a little oil over time, but the plugs don't seem to be fouled too bad. So could poor valve seals cause overheating and rough idle at high engine temps...and cause the ABS light to come on with a new OVP?
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