rough running 912 ULS
in General Tech Discussion
9 years ago
For several weeks now I've been experiencing a rough running engine in my RV-12. Specifically, these
are some of the issues:
- engine starts easily but runs somewhat rough at idle warm-up
- after warm-up, as I increase throttle, the engine runs rough
in the 2800-3000 rpm range, then smooths out at 4000 rpm
- at mag check, on ignition B rpm drops around 80, on ignition
A, again the engine runs rough with a drop of 200-300
- after mag check, if I run at WOT for a few seconds, then
return to 4000 and do a mag check, both ignition A&B are ok,
but as I retard throttle back through 3000 rpm, the roughness
returns
- In flight, the engine runs smooth. I usually cruise around 5000 rpm.
- Initially, Lockwood was of the opinion that it was a carb problem,
and since I had exactly 200 hours on them, I sent them in for
overhaul.
- after reinstalling carbs and synching them with CarbMate, engine
still ran same as before overhaul of carbs
- Both carb bowls have been removed to check for debris & float wt.
Both set of floats were ok and no debris was present.
- As an experiment, a heat gun was used to warm up the ignition
modules, as some on this group has done. On warm-up the engine
seemed to run smoother. After warm-up the engine continued to
run smooth as the throttle was advanced. On mag check, both A&B
drop was only about 80 rpm. When throttle was reduced to idle,
again engine ran rough around 2800-3000 rpm range.
- Sparkplugs are new and gapped properly, although all plugs are
coated with dry black soot.
With all the above in mind, I'm leaning toward an ignition module failure on ign. A.
I would certainly appreciate any ideas on this problem before buying a new module,
since they are pretty pricy.
Thanks, Walt Shipley
are some of the issues:
- engine starts easily but runs somewhat rough at idle warm-up
- after warm-up, as I increase throttle, the engine runs rough
in the 2800-3000 rpm range, then smooths out at 4000 rpm
- at mag check, on ignition B rpm drops around 80, on ignition
A, again the engine runs rough with a drop of 200-300
- after mag check, if I run at WOT for a few seconds, then
return to 4000 and do a mag check, both ignition A&B are ok,
but as I retard throttle back through 3000 rpm, the roughness
returns
- In flight, the engine runs smooth. I usually cruise around 5000 rpm.
- Initially, Lockwood was of the opinion that it was a carb problem,
and since I had exactly 200 hours on them, I sent them in for
overhaul.
- after reinstalling carbs and synching them with CarbMate, engine
still ran same as before overhaul of carbs
- Both carb bowls have been removed to check for debris & float wt.
Both set of floats were ok and no debris was present.
- As an experiment, a heat gun was used to warm up the ignition
modules, as some on this group has done. On warm-up the engine
seemed to run smoother. After warm-up the engine continued to
run smooth as the throttle was advanced. On mag check, both A&B
drop was only about 80 rpm. When throttle was reduced to idle,
again engine ran rough around 2800-3000 rpm range.
- Sparkplugs are new and gapped properly, although all plugs are
coated with dry black soot.
With all the above in mind, I'm leaning toward an ignition module failure on ign. A.
I would certainly appreciate any ideas on this problem before buying a new module,
since they are pretty pricy.
Thanks, Walt Shipley
