I have a fresh built motor with roughly 600 miles on it. I am having a lean tip in occur from idle rpm then immediate opening the throttle to at least 50%. There is a loud CLACK that comes from the engine.
Specs on the motor: N/A, LS rod/crank, b16 head, flat face valves, 81.5mm +4.5cc dome wiseco pistons (should net 10.8:1 compression discluding valves), OEM 3 layer gasket, stock d15 injectors :D, unmodded pr3 ecu, distributor king distributor.
It did have a vacuum leak that I traced down to the throttle body gasket, and replaced. It ran better with the leak. The engine runs fine in all other conditions though, but after fixing the vac leak i started getting a lean tip in. When I go into vtec it spits CEL 1 (o2 sensor), I've rewired it once, and checked resistance twice. Going to go through a flowchart on it next. Also the idle is high, and almost seems to be searching for idle on occassion. I've switched FPR's, I've switched IACV, fooled with the idle set screw, went through the process to set base idle. There is even an alan screw on the side of your IACV, I believe is 3 or 4 mm. I adjusted that, and could get no difference. (That screw adjusts the spring tension for the IACV btw). I mention the distributor because the timing teeth that insert into the camshaft has a little wobble to it.

 

you desperately absolutely NEED a tune. no ifs ands or buts about it. you NEED a full tune.

 

+1

 

Bah, I was trying to hold off until I got new cams and adjustable cam gears for a tune. Guess I have no choice, thank you guys for the help. What is the problem making me require a tune? My larger bore?
Thanks again. In the process of hunting down an S300.

 

The fact that the motor is not stock at all. all those parts will throw off the fuel trim. just tune it...

/thread

 

Gotcha, already talked to a tuner and set up an appointment.

 

Wonderful! Goodluck!

 

Just cuz I hate when a thread dies and the OP doesn't say what fixed it. It was my timing, I had replaced a cam seal and when I redid the timing the slack caused the intake cam to stay put while exh and crank rolled forward one tooth. After fixing that, my lean tip in was gone, and it idles perfect. I still get CEL 1 for o2 sensor when I go into vtec. And there is hesitation in the motor at lower rpm, and my top end power is significantly less than when the timing was off. But I have already ordered Neptune rtp and will get it tuned soon.

 

The "clacking" noise you are hearing is most likely pre-detonation or "pinging" STOP DRIVING THE CAR UNTIL YOU GET A TUNE.

 

My heart dropped as soon as I read that.