i have a turbo xs manual boost controller and today i did a boost leak test and the only spot air was leaking from was the boost controller,i know there supposed to bleed air, but i wasn't sure if that was normal or not. If i completly turn the controller to wastgate only it stops leaking. And the more i open it up the more it leaks, which under boost i know it's suppossed to leak-bleed but im not sure if it suppossed to juat by doing a leak test. But i gues i am pressurizing the system so? the reason i did a test is because my car has a misfire at idle and while cruising or keeping a steady speed the car will start to hesitate. The air/fuel gauge will go full lean and then start to go from full lean to full rich and that's when it will hesitate. It's not a all the time thing, i mean it's a daily accurence but it might drive fine for a hour and then it will start to act up. It is alright at full throttle, although yesterday in third gear throttle wide open it did studder at 5000 rpm's for a sec almost like it hit the rev limiter for a sec that is what it felt like. Also the idle will be rough and then it will smooth out and then get rough again, and if i hit the gas it will usualy smooth it out for awhile. Also if i turn the headlights on it will smooth out. It started last year after i hit some railroad tracks the car died. It didn't start until the next day ever since then i'v had the problems. So far i'v replaced plugs,wires,coils,maf,boost test,compression test 195 psi across the board, i hooked up a fuel psi gauge before the rail and at idle the psi was only 17psi which i think is a bit low,but if i had fuel issues i would think the car would run bad a full throttle full boost,the only code is a random/multiple cyl misfire. Any help would be great.

 

17psi is way too low for your fuel pressure at idle! Your fuel pressure should be 38psi at curb idle. It should be 47-50psi when you remove the vacuum hose from the fuel pressure regulator and cover the end with your finger. Check your fuel pressure!

 

i had a similar problem as well in the past wtih another car ive owned. Turned that the first set of symptoms and gitters at higer rpm's was due to a cheap MBC off ebay, then i replaced it with a Turbo XS MBC and fixed the problem.

The other issues you describe are the same as i incountered. It was all due to a small tiny little leak in the intake tube after my MAF and a lose connection/bad tip on the spark plug wire going to the coil pack. It kept coming lose and causing a no start or hestitaion/gitter and it all started after i ran over rail road tracks going very fast as well!

I replaced all the plugs wires with performance wires that were 8.00mm thick. It worked well for a day or two, then it came back...so i then replaced the wires again with stock replacement size NGK wires, and never had the issue again. It took forever to find out what was wrong with the car...i replaced and did every test you did too! The biggest pain was all due to that intake tube hole though because it wasnt consistant enough to diagnose and messed with my idle randomly and as well as driving the car under load.