EM-2 ENGINE MECHANICAL (2JZ-GTE) - CO/HC If the CO/HC concentration does not comply with regulations, troubleshoot in the order given below. (1) Check heated oxygen sensors operation. (See page SF-82 ) (2) See the table below for possible causes, and then inspect and correct the applicable causes if necessary. CO | HC | Phenomenon | Causes Normal | High | Rough idle | 1. Faulty ignitions: • Incorrect timing • Fouled, shorted or improperly gapped plugs 2. Incorrect valve clearance 3. Leaky EGR valve 4. Leaky intake and exhaust valves 5. Leaky cylinder Low | High | Rough idle (Fluctuating HC reading) | 1. Vacuum leaks: • PCV hose • EGR valve • Intake manifold • Air intake chamber • Throttle body • IAC valve • Brake booster line 2. Lean mixture causing misfire High | High | Rough idle (Black smoke from exhaust) | 1. Restricted air filter: 2. Faulty SFI system: • Faulty fuel pressure regulator • Clogged fuel return line • Defective ECT sensor • Defective turbo pressure sensor • Faulty ECM • Faulty injector • Faulty throttle position sensor • Faulty MAF meter 1997 SUPRA (RM502U) Author : Date : 1107