kjiinpa

Hi all! Got a really weird issue going on with my '05 ML500. When the truck is first started, the idle surges. It will do this until the engine gets to it's normal operating range. However, off idle (1500RPM and above) she runs and drives just fine, even while engine is still cold. When we had our cold spells, (temps were in single digits) even when engine was at normal temp, it would still surge/miss at idle. Outside air temp would have to be 20 or above to eventually go away. One day, when our son was using it, it ran normally right from the get go, but threw a code for the egr valve. Other than that, no codes are thrown. So in summary:

Cold temps + cold engine = rough idle
Cold temps + hot (normal) engine = rough idle
Warm temps + cold engine = rough idle
Warm temps + hot engine = good idle
Above 1500 RPM, runs normally

Any ideas on where to start looking? Thanks in advance!

art_arev

Start with cleaning the EGR tube