SL/R129: '92 SL bogs when first started
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Newbie
Joined: Mar 2017
Posts: 1
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From: St. Louis, MO
1992 500SL
'92 SL bogs when first started
Hi folks! My '92 SL 500 has been given a lot of new parts to solve drivability issues. Fuel pumps, filter. pressure regulator, cold start valve, OVP, coolant temp sensor, crank and cam sensors, IAC. One problem still exists. When first started, it idles extremely well, but when first accelerating when temp is 40-55 degrees on the gauge, it bogs terribly, then builds power in a lag. Once up to operating temp, that goes away and it drives very well. Where should I look next?
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Joined: Jan 2006
Posts: 1,982
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From: Atlanta, unfortunately
'09 S600, (2) R129 300SLs, '03 SL500, '03 SL55
Possibly your engine hasn't quite reached the temperature where the mixture is being corrected via feedback from the oxygen sensor in addition to the base mixture setting being lean. To check that, locate the round diagnostic connector on the inner fender by the ABS control unit and remove its protective cap. Now with the engine warmed-up and idling, measure the DC voltage between sockets #2 and #3 of the connector. Divide the voltage by the DC voltage between #2 and #6. A result between .3 and .7 is within specification with numbers below .5 being lean and larger than .5 being rich.
