Quote:
Originally Posted by dkveuro
Check the MAF.
The spec' for the MAF at idle is 10grams per second ...if it is out of range, engine will add incorrect fuel amount at low rpm's where the 'cut fuel on overrun' programme turns fueling back on again at target speed...usually 1300 rpm.
Also....the engine bay harnesses insulation on these cars turn to powder, causing no end of problems.
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Ok, so I hate to reply to a thread from 2006, but here I go.. This is the only post I could find that describes exactly the problem I am having.
1997 S420 with a recently rebuilt trans. My local indy (former dealer tech) rebuilt it himself, and I have ZERO reason to doubt his abilities based on his track record. I bought the car from him last week.
I don't think the problem is necessarily transmission related in my case. Being a w126 owner, I have experience with what happens when the idle circuit microswitch on the throttle assembly acts up or gets out of adjustment, the motor fight with you a bit. This is sort of what it feels like with my 97 s420...
I can reproduce it fairly easily, but it doesn't do it every time. Also, I don't know if it's my imagination or something else I'm doing, but I feel as though if I let the accelerator pedal up abruptly, to 'snap shut' if you will, that the problem doesn't happen.
The trans basically has a couple hundred miles on it at this point - freshly rebuilt. I am VERY hesitant to go back to him with this issue if it's not transmission related. If it's the MAF, I can tackle it easily.
Is this a known issue, where you get a back-and-forth lugging or jerking when gradually decelerating? I can only find a few mentions of this on the web at all, but no real answers. The suggestion that it might be the MAF is intriguing. Are there any other throttle related parts I should check? The wiring harness should be fine, it looks great in the places I've inspected, and it's a 97 so shouldn't be an issue anyway.
The trans seems to work perfectly otherwise, smooth shifting and responsive. It's only as I near a stop sign or slow down gradually by trying to coast that it happens.