My '94 Ford Explorer 4.0L has a rough idle (shakes) and occasionally the check engine light came and went off. Code 181 Adaptive Fuel Rich limit Reached Right Side, Code 189 Adaptive Fuel Rich Limit Reached left side, and Code 186 Injector Pulse width high
I've cleaned the MAF Sensor, Replaced the Plugs, replaced the PCV valve, tightened the lower intake manifold, and installed a new Fuel Pressure regulator. Still a rough idle. Could it be the O2 sensors?
[updated:LAST EDITED ON 09-Sep-02 AT 04:29 PM (EST)]One common cause for a rough idle or failure to maintain idle speed is the Idle Air Control valve. It can stick and not step open/closed properly under PCM control. You can remove it and clean with spray carb cleaner.
The codes you gave are continuous memory codes that indicate both sides of engine seem to be running lean and the PCM can no longer compensate for the lean condition by varing the injector pulse height/width. It is curious that no codes for O2 sensor lean condition was set also. Assuming you have O2 sensors on both left and right sides of engine, it is less likely that both O2 sensor failure is the source of the problem (but not impossible)
You may be on the right track, but I would make sure to rule out some things first as follows.
1. Clear PCM and run both key on engine off tests and engine running tests to rule out a sensor problem first. Repair any codes given in these tests first and foremost. Work on only the first code given, then re-run test again from scratch.
2. Remove and block all vacuum ports at the tree on intake manifold to check for unaccounted for air in intake system. (most especially the power brake booster). Also check the air duct between MAF and intake for opening which may be letting air in system after MAF.
3. Run a fuel pressure test with both the engine off and running. With key on engine off, pressure in the fuel rail should be 35-40 PSI, Engine running and regulator vacuum line on should yield 30-35PSI. Goose the throttle and make sure pressure is maintained at minimum pressure level. If it drops significantly, suspect a restriction in fuel system (Fuel filter) or fuel pump in tank.
If all above looks OK then try this to simulate an Open Loop running test. (Cold engine startup and run)
1. Clear the PCM again.
2. Disconnect lead from Temp Sensor to PCM to simulate cold engine.
Take a short test drive and see how engine performs. If OK then lean to O2 sensors in closed loop. (This may set a code but you can ignore it for now) If not OK the you definately have an air or fuel related problem. (Just because you cleaned the MAF sensor does not mean it is measuring airflow properly)
Don't forget to check the Throttle Pos sensor also, It can cause some really wierd results. Clear PCM EACH time you change any emissions related component.
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