: Crankshaft position sensor

12-21-07, 08:39 AM
99 SLS with 71k; engine dies or almost dies while coasting down at 20-25mph. It is intermittent but only happens at 850-900 rpm while slowing down. Rpm will drop suddenly from 850-900 to 400-450 rpm and usually recover back to 900 if A/C is not on or die if A/C is on. With A/C off, engine will cycle between 900 rpm and 400 rpm a half dozen times in 30 seconds. There is no stumbling or missing felt. If engine dies it will always restart. Only engine code is P1599(stall or near stall condition). This sounds like previous threads on crank sensors but problems were attributed to sensor design change in 2000 or later cars. CVRSS codes C1252 and C1783 are also set but seem unrelated. Any help would be appreciated.

12-21-07, 09:53 AM
Several conditions have to exist before P0335/6 or P0385/6 codes set. Your description sure sounds like the ol' CKP bugaboo.

From your post, you appear to have searched and read up on the subject: there's enough on CKP's in here to fill a NYC phonebook.

You might read up on throttlebody cleaning, IAC (Idle Air), and TPS (Throttle Position) to see if a good cleanup with throttlebody cleaner is in order before you go pulling the CKP's.

Do you ever do WOT runs or hard accelerations from "on ramps"?

Put your car, model, and year in your ^^^ profile.

12-21-07, 10:16 AM
I should have added that I tried a new IAC with no change and dealer did air intake system and fuel induction system cleaning 3k miles ago. I don't do WOT from on ramps, etc.

12-22-07, 01:02 PM
Thanks for tip on WOT; after reading tech tip, I will add this to my routine. Sounds like fun and it's good for the engine. What a country