erratic idle and running rich... massive vacuum leak?

Asked by Oct 14, 2014 at 09:10 PM about the 1990 Mercedes-Benz 300-Class 4 Dr 300TE 4MATIC AWD Wagon

Question type: Maintenance & Repair

We have a 300 that has a bipolar disorder.  It either runs great or it idles high, low and
dies and it is running rich - like 10 mpg rich...  I replaced the air idle valve and it was better
for a while but never perfect and now is up to its old tricks.  I also bought new hoses for
the connections to manifold and engine but have yet to put the engine side one because
the engine side is buried.  If you accelerated down a off ramp - 9 times out of 10 it runs so
rich you,d swear you were driving a hopped up diesel.  Also is there a large rubber gasket
in the intake that is prone to cracking.  Thanks.

1 Answer


sounds like a fuel pressure regulator

1 of 1 people found this helpful.

Your Answer

Mercedes-Benz 300-Class Experts

  • #1
    James Ramond
  • #2
    Tom Demyan
  • #3
View All

Related Models For Sale

Used BMW 3 Series
1,147 Great Deals out of 32,993 listings starting at $1,000
Used Mercedes-Benz G-Class
12 Great Deals out of 1,112 listings starting at $21,995
Used Mercedes-Benz SL-Class
57 Great Deals out of 2,934 listings starting at $4,500
Used BMW 5 Series
464 Great Deals out of 16,185 listings starting at $1,995

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.