TIO-540-A2C (Navajo) Problem

[sniflevalve]

Hey guys and gals, need some help...

here is the problem:

Advance throttle from idle to full throttle. RPM and Manifold Px come up smooth.
At approx 1900 RPM the RPM hangs, decreases a smidge, verified by engine sound.
Still pushing throttle forward RPM stays at 1900 for a sec while manifold px climbs way up.
RPM then jumps to about 2300 or so and will start to surge and will try to overspeed if you push it.

If you pull the mixture back a bit, all this goes away and you can run the engine up to full throttle with full manifold boost no problem.

What I've done:

pulling the mixture back made me think fuel was too rich so I thought fuel injector servo was wonky, sent it to engine shop then tested in on their bench no fault found. So I put it back on.
Check the fuel injectors and upper deck, changed all the orings and black rubber tubes. No problems found.
No intake leaks to be found. Runs great at idle. Nice idle cut-off rise.
Started swapping parts over from the right engine..
Differential Px controller - no change
Waste Gate - no change
engine fuel pump - no change I thought maybe the diaphragm inside was leaking into the air reference line causing excessively rich mixture but it runs good at idle so that was all for nothing.
Gonna try the Density controller for giggles and lastly will be the turbo.

Interestingly enough a coworker had the exact problem on another navajo and they too chased the fuel around and went crazy trouble shooting. eventually they changed all the turbo components and the problem went away. They aren't sure what fixed it exactly and I don't supposed they care.

If anyone can tell me, if it is a Turbo issue, why the problem goes away when the mixture is leaned I'd be forever grateful.

Cheers

[040hurts]

This could be a serious issue,

Check the oil filter very carefully, examine with a microscope if reqd. Look for shiny metal.. a camshaft that is deteriorating will cause the same symptoms.

should it come up clean re check for induction leaks, this is the transition RPM for the turbo so even the smallest leaks will cause a lag in power. I have seen metal induction tubes warp at the flange and although they appered fine I had to double gasket all the pipe to cylinder mating surfaces to discover that this was the problem

More Importantly first eliminate the possibility of a deteriorating cam!!!!


Keep us posted

[Heliian]

That's a tough one, my first guess would be induction leaks as the fuel/air mix would have to be leaned for less air. Other than that, I can only speculate. Are both mags functioning properly? If one mag is failing, then you won't get the power. How's the oil pressure? if it's fluctuating, you could have a governor issue. Like I said, speculation. Navajo's are a mechanic's dream that's for sure. Good luck.

[Ballsssssss]

+1 on the Cam. Have seen that same problem caused by pooched Cam. Do check Mags too.

Ballsssssssssss

[sniflevalve]

Thanks for the replies, I'll definitely check it all out.

Can you explain though why, if it is a bad camshaft related issue, the problem goes away when the mixture lever is pulled back a smidgen?


Cheers

[ruddersup?]

Have you ever seen a Navajo take off with a bad cam? It's very obvious, with the trailing black smoke. Guess you'll have to watch while someone does a circuit, lol.

[pistonpounder]

turns out the mixture was off, set mixture and problem gone, runs like a top.