Posted 08 July 2012 - 03:54 AM
Posted 08 July 2012 - 04:38 AM
1998 Trans Am - LS1/A4 - all stock - one owner - driven daily - Scan9495 author
Posted 08 July 2012 - 06:21 AM
Posted 08 July 2012 - 06:25 AM
Sounds more like the engine is experiencing misfires under heavy loads (low RPM in higher numerical gear). When is the last time it was tuned up? How old are the plugs and wires? Has the distributor ever been replaced? When were the O2 sensors changed? Have you scanned it for codes - easy to do on a 93 because all you need is a paperclip.
And as Gary points out, check the fuel pressure. Best way to check is at idle, with the vacuum compensation line off the fuel pressure regulator (FPR). Should be 43.5psi, with GM accepting anything from 41-47psi as OK. Reattach the vacuum line to the FPR, and fuel pressure should drop proportional to intake manifold vaccum - about an 8psi drop with a stock cam, less with a more aggressive cam. Than tape the pressure gauge to the outside of the windshield, take it out on the road and observe the fuel pressure under max engine load - over 5,000RPM/WOT. Should not drop below 40psi.
1994 FIREBIRD FORMULA
381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC M48 Pro engine management - 8 LS1 coils - 58mm TB - 74# injectors - 300-shot dry nitrous - TH400 - Gear Vendors 0.78:1 O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motor
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