99 MERC P156, P455

Mercury Tracer



December, 20, 2006 AT 3:17 AM

Hey All. 1999 Mercury Tracer, 2.0 SOHC, Automatic, 124K. Purchased 3 mths ago after a lube shop replaced the head gasket. Check engine lights been on since the 2nd day. P1506 (IAC overspeed) P0455 (Gross leak) only codes left to fix. Idles btwn 1400-2000 warm or cold. When a/c compressor engaged, idle falls to 800-1000 but vehicle shakes very bad and (with brake applied) squealing from belt. Not enough vacuum at EGR valve to move the needle on hand gauge(at any time). Work completed= New plugs & wires-Almost all rubber vacuum lines replaced-ALL vacuum lines(rubber/plastic) checked and no leaks-Cleaned MAF sensor-Replaced Catalytic converter, PCV valve & both O2's-Removed & cleaned IAC-Throttle body-EGR valve & new gaskets-NO intake manifold leak found. IAC valve activates when unbolted & ignition turned to on but no change in rpm's when unplugged (installed). I hope you can help ! THANKS !


3 Answers



December, 20, 2006 AT 4:08 AM

Hey L2,
Believe it or not that p0455 could be the culprit of your high idle p1506. The evap system is all under a vacuum. I'd try to rule out the vacuum issues at the evap canister first. Or. Disconnect all vacuum to it underhood. Evap solenoids and see if your idle self corrects. I would also recommend to verify vacuum hose routing. Let us know!




December, 20, 2006 AT 7:27 AM

Definitly sounds like a vacuum leak. Inspect and test the canister and the control solenoid. For it to set that code it should be a fairly obvious leak



January, 11, 2007 AT 9:22 AM

I replaced the EGR vacuum solenoid- NO change ! When I can, I'll double check the canister. Thank You, 2carpro & carundell, MUCH appreciated !

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