First timer !  I have a 2002 2.5 FI on my gyroplane.  It has purred for 200 hrs over 12 years,  It sat unused over the winter ( same for the [past 12 years ).  On my first long taxi, 10 days ago, the engine coughed and sputtered.  It ran smoothly from a cold start until about 150 degrees water temp.  The it had trouble between 1,500 and 2,000 RPM.  A friend had a code reader and we thought the problem was the Throttle Position Sensor.   we installed the new TPS yesterday;  no help, no fix.  We pulled off the Idle Air Control ( it looked fine but not sure what to look for.  I am running with 2 fuel pumps; one is full-time, the other is a switchable aux.   It seemed to run a bit better with both pumps ; certainly not  smooth though.  Anyone had a similar situation ?  Hope this is  a proper area of the Forum.  I tried in Engines, but it said I could not start a new topic.   Thanks in advance for any help.   Tom T. in MN.

Check maf and coil/plugs/wires. Vacuum hoses as well. 

Simple first. Drain and flush that old fuel all the way to the fuel rail. Look for water and dirt. 

By the way how are you controlling the injectors? I'm interested in aftermarket fuel controllers. I have a Jag V12 and their control system give me fits.

Tell us a bit more about your setup. Fuel control system. Any feedback system? (O2 / A/F sensors)

Ignition system?

Roo & Fairtax,   Thanks for your suggestions !  I have not modified much after buying it , in 2002, from a Forester roll - over wreck.  Same fuel injectors; dual fuel pumps ( for a 1980's vintage Ford F150 pick - up ).  One O2 sensor, not sure which.  I am getting a lot of good input, both here and the Rotary Wing forum.   I will investigate all; but the fact that it runs well from a cold start to about 140 degrees is still curious.  Will report !         Tom in MN

Are you using the engine control computer from the forester?

MAF or MAP sensor?

 

 

Are you determining engine temp based on computer reading or from a separate guage? If from a guage, what does the engine computer say coolant temp is?

If the computer temp sensor is bad the fuel mixture will still be too rich and can cause issues.

Fairtax,  I am using the engine control computer;  not sure what the MAP or MAF are ?   The temp. is from a gauge.   When we had the code reader hooked up and had the smart phone app going, the gauge agreed with the code reader values.  ??    Thanks Tom

This sounds very much like the motor is ready for new spark plugs and wires. NGK brand hold up best. It's good maintenance in general since these motors are hard on them. I'd start there before worrying about fuel etc.

Here's a thought. Since it runs better with the aux pump on, could be low fuel pressure. Check the fuel pressure regulator.

Adventure and Roo,   All good thoughts, thanks.   I think I will do the plugs and plug wires; not sure how to check the fuel pressure regulator.  It seems to be a simple ( maybe cheap ? ) devise.  I will also empty the fuel and try to purge the fuel rails as well.  The inexpensive things first.     Tom in MN

not sure what vehicle the pump came from, but some owners of gen2 legacy-based cars have had a broken 'cap'/ bad o-ring problem causing fuel pressure loss.

Borrow, buy, or rent a fuel pressure gauge. The fuel rail should have a fitting to screw it onto. All that I have run into look like a tire valve (schrader fitting). Just screw it on and run the fuel pump. I don't know the exact spec. but should probably pump up to around 35psi. It should also hold that pressure when the pump is turned off.