How else does one narrow it down to primary injectors failing, tested ignition coils good. Tested plugs wires good. Brand new spark plugs. Fuel pressure is good. No fuel smell from under the hood but for some reason idle is slightly lower than usual and a slight rough idle. When im cruising it runs fine and still pulls plenty hard on boost....any input is appreciated. I have single surbo setup, fp, 550 primaries-factory, 1600 secondaries, aeromotive fp, hks twin power, pfc, 9's all the way around, when i say low idle i mean like 850-900 when light and elec loads are on....normally idles at 1100

 

Check all the mechanical stops,check your idle settings,vacuum leaks,check your iac valve.

 

Sounds like a vacuum leak.

 

correct me if im wrong but wouldnt vacuum leak cause high idle??

 

and i do have a brand new iac valve

 

Sometimes. What's the Afr at Idle? Really sounds like the idle stop screw backed out

 

12.5-13.0 at idle.....very weird...and i swear i am hearing a noise....slight noise almost sounds like exhaust leak or pulley or belt or something rubbing or going with the rpm...very faint tho.....

 

Check for vacuum and boost leaks

 

cant find any vacuum/boost leaks

 

Have you tried making a boost leak checker? Has the idle Afr changed with the recent idle change?

 

yes its gotten slightly more rich... it was 13.5-14.0 at idle.... and now 12.5-13.0 with the slight drop...something else...oil pressure is lower than usual....and when i rev it stick about the same instead of jumping up

 

When was the last time you changed your oil? Do you have a dataloggit? Has anything else changed with your current setup recently?

 

i do have datalogit....i have changed my oil within the last month...and spark plugs...and add half a quart of premix to my gas when i fill up...i have stainless OMP lines...original OMP im sure...is there something i can monitor with datalogit that i cannot see on the PFC?

 

And the idle settings haven't changed in the pfc? Check the idle stop screws on the throttle body and make sure they are not loose.

What does the sound you hear sound like?

 

like a slight belt squeal...or pulley squeal....goes up with rpm and then away when my rpm is high enough...and i have brand new belts and pulleys...all the idle settings are the same.... when i installed my new IAC solenoid about a month ago i had to re-adjust and secure all my idle screws

 

Have you checked the idle screws. Try re-adjusting them and then go through the whole idle re-learn procedure. Arghx has a thread dedicated to this.

 

si i definitely have no leaks in the intake....all settings in pfc r good. the best way to describe my idle issue is similar to that of a cylinder misfire on a piston engine....take a v8 and imagine 1 cylinder misfiring... thats my car.. not hunting idle...no lack of power... which is weird...and the car shakes slightly

 

Surprised no one has suggested this. Compression test?

thewird

 

yea compression test was 75-80 cold......95 ish after the car had been warmed up

 

keep in mind i stll have no lack of power

 

How does the car drive off idle? Pull off all the belts and see if the squeal is still there. Maybe you have a pulley locking up. Have you had the vehicle tuned? Did this all start outta the blue

 

Double check your vacuum line to the map sensor. Does the handheld read vacuum and boost right

 

the car rips and drives fine outta idle...and its been same tune for couple years... and the car shows vacuum and boost on both gauge and pfc....i did recently get sr motorsports full power pulleys with bando belts but its been a couple months....and i checked those first to see if they spun freely and made noise....its very weird...maybe im just freaking out over nothing.....

 

Try making a idle adj in the pfc and see how it responds. If not try going through The whole idle relearn procedure. The under drive pulley on the alt may have thrown it off.

 

very true about the pulley... didnt think of that at first but it could be making the difference at idle only