I have 2005 M20M only 33.5 inches of Manifold pressure on Take off.

[jhealan]

I just got the airplane out of annual and it runs very rich at idle and rough. It will not get over 33.7 inches of manifold pressure on takeoff. All the other numbers are normal. Fuel flow 29.5 GPH. ITT 1420. The AI adjusted the fuel pressure up because it would get into the yellow in the teens. That was the only thing that changed. Anyone had a similar problem?

[AustinAir]

When I had a similar issue the MP gauge had failed and we replaced it with a JPI

[adverseyaw]

Could be a number of things. Low fuel pressure isn't great but I also don't know how it would contribute to the problem. I had a camshaft come apart (low lift on #1/#2 intake) and it resulted in low MP and inability to make full RPM. The pressure and differential controllers may need adjustment or replacement. The 540 is a complicated engine so is worth having someone familiar with it set it back up again. One note, depending on the temperature and pressure at your field, the engine may not make a full 38" at takeoff throttle even if it's running perfectly. It may only make 36 or 37". That said, 33.7" is low enough that it should be looked at.

[LANCECASPER]

1 hour ago, AustinAir said:

When I had a similar issue the MP gauge had failed and we replaced it with a JPI

Since his airplane is a 2005, it has a G1000 which includes all of the engine gauges, so it's not a matter of just replacing the gauge. It may have a faulty pressure transducer though. 

[PaulM]

According to the Lycoming manual that is below the lowest MP setting on the density controller.   Ask the annual shop what they "did" during the annual, they adjusted something. 

I would suggest that the procedures in the manual be followed for setting idle mixture and the density controller.  The Bravo should run perfectly smoothly at sea level once warmed up.   Mine has only glitched if there was a problem with either Mags, plugs, or  high airport altitude.  

When I first flew the plane after I bought it it wouldn't go above 34-35"  but this was Texas in December.   Since I thought this was low, I brought it by Dmax on the way home and they tweaked the density controller to spec, but I didn't realize until reading the manual that lower temps == lower max MP. 

[jhealan]

Thanks I think we try the density controller and readjust the idle mixture. I’ll let everyone know how it goes.

[Alan Fox]

17 minutes ago, jhealan said:

Thanks I think we try the density controller and readjust the idle mixture. I’ll let everyone know how it goes.

Check ALL the hoses , for loose clamps/leaks...

[carusoam]

Be extra cautious, be on the look out for exhaust leaks on the hot side of things…

Make sure your CO monitor is working properly…

Improperly torqued, or re-used Vband clamps can be hazardous…

 

This is most likely not the issue… but if it is, it is in the do not fly category… exhaust leaks prior to the turbo are really bad…

PP thoughts only, not a mechanic…

Best regards,

-a-

[affricate]

On 12/28/2021 at 8:59 AM, jhealan said:

I just got the airplane out of annual and it runs very rich at idle and rough. It will not get over 33.7 inches of manifold pressure on takeoff. All the other numbers are normal. Fuel flow 29.5 GPH. ITT 1420. The AI adjusted the fuel pressure up because it would get into the yellow in the teens. That was the only thing that changed. Anyone had a similar problem?

Just replaced mine this week, went out on takeoff over the weekend. Replaced with a digital MP Guage. Would have put a new JPI but just dropped $$ on a MOH!