background information. I have a 93 R1 with a streetport running with the stock twins at 10 psi. I have the usual bolt ons (catback, midpipe, DP, M2 intake, pettit SMIC, Power FC, 1300cc bored out secondaries, 3mm seals, pulleys, etc). I was driving carefully because the engine was just rebuilt a couple thousand miles ago. When I gave the car half throttle the car stumbled/hesitated strongly. I immediately let off the throttle and the car drove fine. I checked the commanders settings and everything seemed to be in order. I drove the car again and when I gave it half throttle the car stumbled/hesitated again only this time the car lost all power and slowly came to a stop and died.

I know, I know, classic signs of a blown motor , but when I gave it a compression test I got around 80 psi across all faces(test done on cold motor). Low numbers but I should atleast be able to start with these on a streetport. When doing the compression test I heard a loud buzzing noise under the extension manifold about where the injectors are. The noise continued after I had stopped turning the motor over for two minutes slowly decreasing in noise. I am currently using the FSM to take me through removing the extension manifold and testing the injectors. I would really appreciate your opinions on what this might be though. I found spark on all the plugs.

Thank you for taking the time to read my post.

 

One more thing, the buzzing only occurs when the key is in the acc position after the car has turned over.

 

I can't get the sound to occur again now that the extension manifold is off. I am thinking possibly a stuck injector but I am not sure.

Any and all opions are welcome, thanks!

 

try unplugging the Idle Control Valve (white plug on the back of the UIM) then attempt to start the car.

 

Thanks for replying. I currently have the extension manifold off but as soon as I get it back on I will try unplugging it. I will let you know how it goes!

 

^^ no problem, i had a similar issue, not as bad as not starting, but i had the buzzing too. It is the idle control valve trying to open or close (i'm not sure which one) once you have cranked the car over and not started it.