Engine issue

[ArtVandelay]

With a clogged injector it is usually impossible to run anywhere near lean of peak. You typically see elevated EGT on the affected cylinder when running full rich and that cylinder peaks very quickly when leaning.
I have had two partially clogged injectors and both showed EGTs higher than normal. I don't recall exact numbers but I do remember it was obvious from the graph on the engine monitor. 

Another good reason to run LOP, because if you can’t get to LOP, that’s a red flag. If you’re running rich, then they can be way higher but still less than peak. Which is why engine monitor data needs to be carefully reviewed, too many unknowns.

[kortopates]

16 hours ago, teejayevans said:

But then it should be a small rise, ie stays below normal peak EGT, if already LOP it should drop, a spark plug problem will rise 75° or more, should be easily distinguishable.

 

15 hours ago, mooniac15u said:

With a clogged injector it is usually impossible to run anywhere near lean of peak. You typically see elevated EGT on the affected cylinder when running full rich and that cylinder peaks very quickly when leaning.

I have had two partially clogged injectors and both showed EGTs higher than normal. I don't recall exact numbers but I do remember it was obvious from the graph on the engine monitor. 

You both are essentially correct, but there is no rule about how much blockage we see. It can be minimal such that we would refer to it as dirty just causing a greater than normal gami spread. But from there it ranges to all degrees of partial blockage. The worst and most obvious ones are those that are just blocked enough to put the cylinder at peak at full power, since if ignored it can burn up a cylinder in short order. But there are all degrees and its not uncommon to be looking at a cyl that is actually running LOP from the blockage while all the all the others are ROP. Those that do run LOP are more likely to notice a partial blockage since even of they don't notice their leanest cyl has changed they'll surely notice new roughness if running moderately to deeply LOP. But then they might mistake misfire as an ignition issue when its really premature misfire from that one cylinder just running overly lean. With the more insidious ones its critical to look at downloaded data to verify what's going on and this is when real diagnostic data in the form of our Savvy Test profile enables eliminating the guess work and seeing what's really going on. For example, if it mixture, CHT will always follow EGT in either direction, but an induction leak can also appear to be a partial blocked injector with a MAP significantly lower than ambient pressure.  

(Thought I posted the above yesterday but it didn't go through - so this is bit late now....)

13 hours ago, teejayevans said:

Another good reason to run LOP, because if you can’t get to LOP, that’s a red flag. If you’re running rich, then they can be way higher but still less than peak. Which is why engine monitor data needs to be carefully reviewed, too many unknowns.

exactly right Teejay!!

[Bob_Belville]

Lee, with input from @kortopates and several experienced A&Ps, I can't add much but since you're unable to lean at all without the engine stumbling, I would be interested in a couple of big picture specs: are you seeing 17+ gph fuel flow on take off? How about fuel pressure, are you holding ~ 24"?   

[laytonl]

I believe we have it solved.  Apparently it was a clogged injector in #3.  When we cleaned the injectors the mechanic said he didn't install the #4 injector correctly.  Therefore, cleaning the injectors solved the problem and a maintenance induced failure created a new one. 

This is the problem flight.  You can see the #3 EGT high right after takeoff.  FF is shown on the CHT chart in blue.

This is today's flight after repairing the #4 injector installation.  You can see the EGT's within 30DF.  I left the cowl flaps open (because I was distracted watching for issues) so the CHT's are a little spread out.

I appreciate everyone's comments, suggestions, and concern. 

Lee

 

[takair]

Lee.  I’m curious, do you know how the injector was installed incorrectly?  Just as a point of learning...

[laytonl]

I’m not really sure.  He said it was leaking air which I took to mean it was either loose or that little silver sleeve was not seated properly.  It was a confusing time in his shop with about six people “hanging out” and one customer was trying to change his own oil and plugs for the first time and was interrupting the mechanic every 5 minutes with questions.  I finally told the mechanic I would go help the guy so the mechanic could focus on my problem.  Lee