boosted nytro issues

[theflamanguy]

I recently replaced rod bearings because of the scavenge pump coming off mag cover. bearings were fine but replaced anyways. put sled back together and started right up. testing sled under load, i cant get over 7300rpm. seems like a lean mixture out or boost issue. also once sled is warm it wont idle unless i burp the throttle up to engagement rpm.
starting sled cold it idles fine, after light goes out it reduces to 1000-1200 rpm. sled runs fine from 1500 to 7300rpm. no issues in that rpm range.
im thinking fuel issue
what do you guys think?

 

[theflamanguy]

anybody want to wager a guess? how about a leak at the crank halves??? will this cause what i have explained. I would rather try simple solutions rather than cracking the halves again. Please help me out

 

[Nytro19]

Could be a couple of things so first I would check for an obvious vacuum leak. When the sled is idling spay some fuel or even WD40 into the intake but just a wee bit, if the idle comes up it's probably not vacuum, if it stays exactly where it is then for certain there is a vacuum issue.
The second thing I would check is for an obstuction in the charge pipe for the turbo and/or boost leak. Even a small boost leak will scavenge air to the path of least resistance under load.
Failing those 2 things I would look at the air idle valve. You can put the sled in diagnostic mode to check that the valve is functioning. My friend's Nytro was doing a similar thing and it was an ingested blue shop towel fried into each throttle body.

 

[bottlerocket]

Head gasket leaking from one cylinder to another. Have you done a leak down test?

 

[theflamanguy]

no leak down but didnt have the head off... replaced bearings with engine in machine. was thinking about doing a leakdown tho!