Excessive vibration

[mshac]

I do find it very odd that your bird has two new three-blade props, a fresh rear engine, but no engine analyzer? Priorities, my friend. You could determine your problem almost instantly if you had one installed.

IMHO this has nothing to do with the props.

Cold plug from #2 cylinder should be your main clue as to what is actually happening.

The following steps are recommended:

1. Compression test for #2 cylinder - If it checks out OK, go to step 2

2. Clean & inspect fuel injector. DO NOT STICK ANYTHING INTO IT! You may want to swap injectors from another cylinder just to see if the problem follows the injector.

3. So by now you've verified fuel and compression. The last variable is of course spark. From your report, the right mag may be weak. You don't say if they were OH'ed with the engine. Likely time to send them both out for OH.

Following these steps will resolve your issue.

As an aside, one of my V8 work trucks has a bad coil, so only 7 of 8 cylinders make power. Of course, there's roughness from the missing power stroke, but also from the fuel that was supposed to burn in the cylinder exploding in the exhaust pipe instead. Point being a cold cylinder will cause roughness in more ways than one.

[Rick Erwin]

I agree with mshac in that your best clue to the vibration is the cool #2 cylinder. Figure out why there's no fire in that cylinder.

Your 150-rpm mag drop is right at the limit for my TSIO-360CB. Yours might be different... Perhaps once you solve the cool cylinder issue your mag drop issue will be better also.

As for the increased force to move the rear prop lever ... If you have prop-sync, that's most likely due to the rear prop lever moves the prop-sync controller which is on the rear-engine. On the front engine it's a direct linkage to the prop-governor ... as I understand it. I had the same question when I got my plane and that's what I was told.

Rick

[mshac]

Another thought for you -

Use one of those cheap IR temp pistols to check the cylinders and exhaust pipes. You know the kind, they usually have a red laser pointer on them. Maybe $25, most likely less. We'll call it the Poor Man's Engine Analyzer!

You can take some live readings while the engine is running. More than any particular temp, you're looking for DIFFERENCES between the cylinders.

Measure cylinder #2 (the suspect) with both mags AND L/R ONLY! You want three sets of data. Knowing what happens on L/R mag only is very helpful in diagnosis.

Measure the exhaust temp about 1" below the cylinder head. Measure the spark plugs, measure the heads. You'll quickly notice any cylinder that's "out of whack", and you'll have a good basis for determining the cause.

EDIT: Here is one for under $25:
Etekcity Lasergrip 1080 Non-Contact Digital Laser Infrared Thermometer Temperature Gun -58℉~1022℉ (-50℃～550℃), Yellow and Black
by Amazon.com
Learn more: https://smile.amazon.com/dp/B00DMI63..._kmq7FbZP5ZR8C

[Learjetter]

Thanks guys! I’ll do as suggested.

Mshac— the airplane came to me this way, which is why my priority 1 is an EDM-960 or similar.

[wslade2]

Ditto. Mine came without engine monitor.

I’m in the process of installing engine monitor. Reason: had some cylinder work, mag work and Fuel system work done. On run up engine very shaky. We kept going over and over everything we did and couldn’t find a fault....until I leaned over and burned one hand while the other rested comfortably on neighboring cylinder. Problem was cold cylinder. Long story short. There was the smallest amount of grit plugging injector. Definitely work on your cold spark plug problem. I could have saved a couple weeks if I had installed engine monitor from getgo.

Also, 1 inch of movement seems like a lot. Look carefully to see if you engine is sagging. Motor mounts (rubber cushions) may be shot. I know cause just had that problem too.

Couple years back, had similar problem with my new to me 182 at take off. Wasn’t terrible but could feel it. It was everything together: bad mounts, 1 weak mag, high resistance plug, one cylinder had induction leak (caught those last three via engine monitor) and topped it off with dynamic balance. Wah-la! Problem solved.

[JAG]

Everyone has added great advice on digging further into #2 cylinder - so I won't dogpile on there.

Just a couple more thoughts on rough running/vibration. If your engine ignition, timing and mixture is all correct, you should not have any vibration. I can idle my rear engine at 675 RPM, and there is no vibration or beer spilling. Getting the engine set up right on the above items is important. A good A&P should be able to sort it quickly by starting with the simple things first; magneto timing, spark plug lead testing, spark plug testing (I would just replace with new ones...), cleaning and testing the injectors, checking for induction leaks, then performing the proper checks on the fuel system (SID97-3G).
Jeff