Hi - I have a few issues with my 2007 MCS that I am trying to resolve. The car runs rough at idle, and then smooths out as it warms up, and it does take a while to reach operating temp. I have another 2007 MCS that warms up just fine, and blows heat very quickly

While the car is not fully warm, turbo boost will fluctuate on acceleration. No codes, and engine runs smooth, just has pretty inconsistent boost. Once warm, it has been much more steady. The issue is more pronounced in lower gears.

It also has no heat currently. Engine gets to typical operating temp according to logs (223 ish) and will blow warm-ish air then, but cools quickly. My hunch on the heat issue is a stuck open thermostat. Which would make sense with the long warm up times.

Could this also impact my boost issue? Or is this a turbo going out? I have read of turbos that were failing may have boost issues when cold and run well when warm.

Finally - my vacuum at idle is 1.5 to 2 psi lower on my problem car than on my other. Typical vacuum on idle is -8.5 psi, while my other car that runs well has -9.7 psi vacuum at idle.

And just for fun...problem car has timing that fluctuates at idle from -1.5 to 10.5 (ave 5.6), and the 'good' car has timing that fluctuates from 1.5 to 4.5 (ave 2.8). not sure if is significant. If anyone can tell me definitively, that would be much appreciated.

Worst case scenario is I'll need a new thermostat, new vacuum pump and likely new turbo. Best case scenario is it's a simple issue that you all can point me too.

Thank you!

AND - if anyone can tell me what typical catalyst temps should be, that would be great. A scan found my problem car had idle cat temp of 750 ish. The other car had idle cat temp of 410 ish. That big a difference surprised me.

 

Did you can the car for codes?

 

I have cleared all codes, and none have returned. I have a thermostat coming, and will change that out. I think that will address the issue with it running a bit cool and not having much heat. I have tested the vacuum pump and it is holding fine at 28 in hg (spec is at least 25, so that seems fine.)

I have heard that one sign of a failing pcv can be rough idle. The pcv may be original, so I could change that out for a pretty small investment.

The only other thing I can then try (re the turbo boost issue) is to swap out the turbo. Perhaps it's time to get the bigger turbo I've been thinking about. Or maybe I am manifesting problems to justify an upgrade...??? HA!