idle problem sl320

[anc4]

my 97 sl320 has needed a new mass air sensor for 6 months, i've been cleaning the old one, finally bought a new one from phil when the car developed a surging idle in the last month. it still lunges the car at stop signs even w/ the new mass air sensor! the car drives great once the rpm are above 1500. it also will sometimes hunts up to 2500 rpm. i've had codes, before changing the mass air sensor, of 110,100 and 170. now i sometimes get 170 and 507. any help would be appreciated.
ps 70,000 on the odometer

[bwheitman]

I am just going to pull one out here... but when my SL320 acted that way is when I knocked the vacuum line loose near the back of the manifold while changing the oil filter. There is a plastic vacuum line that runs right into the firewall from the manifold, if that is not the problem check all other vacuum lines, even the EGR under the coil cover, those plastic ones crack and fail due to excessive heat. If that doesn't fix pull the codes, that will tell you what is causing the problem.

[anc4]

it turned out to be the flap in the manifold, it was broken and was just hanging instead of opening and closing. phil hooked me up w/ the new part and the car is purring like it used to
thanx for you help