EG–8 ENGINE – ENGINE MECHANICAL Troubleshooting If the CO/HC concentration does not comply with regulations, troubleshoot in the order given below. (a) Check (main heated) oxygen sensors operation. (See oxygen sensor(s) inspection in SFI System) (b) 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 • Open or crossed high–tension cords (2JZ–GE) • Cracked distributor cap (2JZ–GE) 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 systems: • Faulty fuel pressure regulator • Clogged fuel return line • Defective ECT switch • Defective turbo pressure sensor (2JZ–GTE) • Faulty ECM • Faulty injector • Faulty throttle position sensor • Faulty VAF meter (2JZ–GE) • Faulty MAF meter (2JZ–GTE)