1979-1993 & 94 Conv [Subscribe to Daily Digest] |
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Ok, heres the scenario I have been chasing for a month now.... running all the usual performance mods from SPG9 (stage 2 APC, 24lb injectors, RRFPR, big fat i/c pipes etc.) and any time under sustained boost of say 18-20psi I can watch my air/fuel ratio guage richen nicely to 0.85V and hold there... then all of a sudden the car has a slight ping (not audible) and the boost drops back to base boost (set at 7psi) for maybe 5 minutes. If i continue to drive the car it usually clears itself and I get max boost back. Its very strange and its got me beaten as its so damn annoying! :(
Now ive checked all the usual things (as per suggested by mike from SPG9) such as:
fuel octane?: I always run super premium 98RON (same as 95RON in the USA)
the ignition timing?: set at 16BTDC
vac advance unit?: brand new unit last service installed
engine temp?: guage indicates only a quarter to just under half with fans kicking in a bit over half
running lean?: definately not as RRFPR set at just under 2.5bar and am running the bigger injectors and have the a/f guage show me its rich under big boost
Fuel pump old?: replaced both the main and pre pump within the last year and have no buzzing or funny noises.
I dont know if this is relevent or not, but its taking a bit longer to start, almost as if the fuel pressure in line is not sustained. Im thinking that under boost maybe I have a leak in the rail that releases pressure somhow (checked it all for any leaks and nothing and no signs of any wetness on fuel rail or return hose etc.)
if anyone has any suggestions thatd be great!
cheers from down under
Steve and the silver sled
250,000km
my 900 aero site - check it out!
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