I trying to get some dual instrument time in that I need before I can write my instrument rating written test next week. My engine is having other ideas, had to scrub several flights over the last 2 weeks because my engine is just not right.
Some baseline information, I have a IO-320 built to zero time with 2 Bendix mags, Precision Airmotive Silverhawk EX fuel injection. I have 178 hours on this setup. Last year I had a fuel starvation event on takeoff that resulted in replacing the bearing kit on the FI servo. The mixture wasn't setup correctly after that reinstallation (way too rich) and I had a couple of engine quits on rollout before that was fixed. Recently I noted a 400 rpm mag drop on the right magneto on runup and also had the timing on the left mag fixed (from 27 degrees to 25). Everything ran well after that, but I didn't get much time in. I changed the oil and filter a week ago.
Now my current issue. Last week I was taxiing for departure and found my engine was running roughly, almost like it was running on 3-1/2 cylinders. #1 CHT was higher than the others and #1 EGT was more than 100 degrees colder. Cancelled that flight and did some inspection. Injector and fuel line from the flow divider were clear. Spark plug (R mag) tested good (L had been checked 2 weeks earlier). My mechanic/engine builder pulled the R mag and replaced a weak coil, it tested good as new. Reinstalled the mag and did a couple of good runups. Mag drop was still a little high, right around 200, but much better and the engine seemed to run fine.
Today I went to try a test flight and after a fairly long ground run (with mixture leaned for ground running) I entered the runway and immediately did a 180 to come back off. Engine was stumbling badly. Did another runup and my right mag drop was pushing 260 with the last 60-80 coming with a lot of roughness. No real roughness on the left mag, 120 drop or so. #1 cylinder temps were 40F higher CHT (350) than the others and 100+F lower EGT (1000). Other cylinders were all similar temperatures. The roughness was getting worse, but was not constant - maybe 1/2 the time on a 30 second cycle or so. Taxied back to my hangar and shut down. My mechanic had me do a per cylinder fuel flow check. With a 2 second boost pump burst, front cylinders delivered less than the back ones, not by a lot, maybe 90%. #1 was the lowest flow but only by a slight amount.
In what may be nothing but coincidence, I had radio TX issues today too. RX was good but tower was having difficulty hearing me, saying there was a lot static. One radio was worse than the other and I'd never had this issue before. Maybe this is a hidden clue, maybe it's nothing.
Next troubleshooting session is tomorrow morning where we are going to check the flow divider, particularly at the #1 port and test the ignition harness. The thinking is that there is either something inhibiting fuel flow intermittently or the ignition wire from the right mag is faulty.
Anybody have any ideas what else might be causing these issues? My mechanic doesn't think that it should be a sticky valve, the engine isn't all that old (2-1/2 years) and has been well maintained. I just want to trust it again.
Some baseline information, I have a IO-320 built to zero time with 2 Bendix mags, Precision Airmotive Silverhawk EX fuel injection. I have 178 hours on this setup. Last year I had a fuel starvation event on takeoff that resulted in replacing the bearing kit on the FI servo. The mixture wasn't setup correctly after that reinstallation (way too rich) and I had a couple of engine quits on rollout before that was fixed. Recently I noted a 400 rpm mag drop on the right magneto on runup and also had the timing on the left mag fixed (from 27 degrees to 25). Everything ran well after that, but I didn't get much time in. I changed the oil and filter a week ago.
Now my current issue. Last week I was taxiing for departure and found my engine was running roughly, almost like it was running on 3-1/2 cylinders. #1 CHT was higher than the others and #1 EGT was more than 100 degrees colder. Cancelled that flight and did some inspection. Injector and fuel line from the flow divider were clear. Spark plug (R mag) tested good (L had been checked 2 weeks earlier). My mechanic/engine builder pulled the R mag and replaced a weak coil, it tested good as new. Reinstalled the mag and did a couple of good runups. Mag drop was still a little high, right around 200, but much better and the engine seemed to run fine.
Today I went to try a test flight and after a fairly long ground run (with mixture leaned for ground running) I entered the runway and immediately did a 180 to come back off. Engine was stumbling badly. Did another runup and my right mag drop was pushing 260 with the last 60-80 coming with a lot of roughness. No real roughness on the left mag, 120 drop or so. #1 cylinder temps were 40F higher CHT (350) than the others and 100+F lower EGT (1000). Other cylinders were all similar temperatures. The roughness was getting worse, but was not constant - maybe 1/2 the time on a 30 second cycle or so. Taxied back to my hangar and shut down. My mechanic had me do a per cylinder fuel flow check. With a 2 second boost pump burst, front cylinders delivered less than the back ones, not by a lot, maybe 90%. #1 was the lowest flow but only by a slight amount.
In what may be nothing but coincidence, I had radio TX issues today too. RX was good but tower was having difficulty hearing me, saying there was a lot static. One radio was worse than the other and I'd never had this issue before. Maybe this is a hidden clue, maybe it's nothing.
Next troubleshooting session is tomorrow morning where we are going to check the flow divider, particularly at the #1 port and test the ignition harness. The thinking is that there is either something inhibiting fuel flow intermittently or the ignition wire from the right mag is faulty.
Anybody have any ideas what else might be causing these issues? My mechanic doesn't think that it should be a sticky valve, the engine isn't all that old (2-1/2 years) and has been well maintained. I just want to trust it again.