Clogged Injector ?

Hello all -

A few minutes from landing on a flight a few weeks ago, I felt a very, very subtle change in engine vibration, so I had a quick look and noticed the CHT on #3 cylinder (IO540) had risen about 15 degrees and was suddenly the hottest cylinder (I was descending at medium power).

I fiddled with mixture and nothing improved (or got worse).

And i watched as the temperature continued to gradually rise by about 5 degrees until I was within range to reduce power and land, at which time it fell back in line with the rest of the cylinders.

At no time did the cylinder actually fail to fire, but it did seem 'unhealthy'.

I pulled the data from my monitor and I found that, just after beginning my descent, #3 started to rise and #4 started to fall, both abnormally (compared to data from other flights).

I inspected the injectors for #3 and #4 and saw nothing obviously wrong. I used cleaner on them anyway.

Test run was good. And I test flew it again today.

Everything seemed normal during test, until I saw that #4 had gotten unusually cool again.

Landed..ran it up....tested the leaning process...all normal.

Took off again...all normal, but I decided to postpone my 1.5 hour trip until I figure this out.

So, currently, I have a normal running engine that seems to have fluctuating temperature previously in 3 and 4, but now, just #4.

I also tightened the intake on all cylinders (to account for induction leaks).

Bottom line...I'm stumped.

The engine runs fine. Starts fine.

But, I want to understand this anomaly.

Ideas ?

Thanks,

Scott

When this happens was power pulled back, perhap at idle? If so, I would suspect a piece of crud in the spider blocking one of the spider?s small idle port.

Had a similar issue with another engine, one cylinder CHT went low (on the ground at idle). It was a real head scratcher until suddenly the problem moved from one cylinder to another.

Carl

It was just after power reduction....yes...while beginning my decent that is when I first noticed it.

I cleaned #3 injector...then during ground test it seemed that #4 was whacky but #3 was fine.

So, I cleaned #4....ran it up...and it seemed like #4 was fine but #5 was too lean.

So, I cleaned #5....

And all seemed fine.

Then, in the pattern, #4 gets cool on me again just before leaving for a flight.

I am throughly confused.

Is it hard to clean the spider ?

I?d call Don at Airflow Performance and ask about the spider.

Carl

The flow divider can be serviced by you and is covered in the manual Don sends with the equipment when you purchased it. He covered disassembly in the FI-101 class I attended; it's pretty simple.

I have knowledge of a IO360 that did similar. It had trash in the fuel spider. The trash was from dissimilar metals corrosion of steel fittings in the aluminum
spider. It was flushed out,fittings changed to stainless and problem was resolved...