GMC Repair: running rich, intake air temp, o2 sensors

Question
my car is running rich lt block lern is 108 integrator is 128 o2 is swiching 5-8 crosscounts @2000 rpm and is ok. check fuel pressure and pressure is 58 psi and holds after injector flush (motovac) disconect pcv and look for change hardly noticeable engine vaccume is 17"hg"simtoms are rough idle surging and misfire all secondary ignition has been replaced engine base timing it 0 deg btdc and is on the money idle air control is 51 counts after throttle plate and plennum bypass was cleaned temp sending unit is ok as well as intake air temp. egr valve was 14% @ 2000 rpm and spec was 3% replaced egr valve now within spec but still have symtom map voltage is 2.4v this is on a 1995 gmc safari van 4.3L cpi awd vin: w if you have any other suggestions other than a possible purge seloniod which im going to check next please let me know thank you.

Answer
What mechanical work has been performed on the vehicle recently besides what you have already done ?. As most problems that occur after a recent repair was made can be traced back to the area of where the repair was made.

Did this problem occur SUDDELY or has gotten worse over a period of time ?.


depending upon the type of scanner you have either atke a SNAPSHOT of the readings you are getting and or print them out or write them down.

Pull a major vacuum line OFF and note any changes in the sensor readings. A mis-routed vacuum line or a leak in any vacuum line will cause the engine to run rich. Also look for any exhaust leaks ahead of the o2 sensor(s). Intake manifold leaks can also cause a rich condition as would leaking injectors.

Also spray some carb cleaner into the intake and again watch for changes in your readings. Also make sure that the throttle plate area and the idle air control passages are clean and do NOT have a black residue on any of the channels.

The above 2 tests will test the ability of your o2 sensors ability to detect the air to fuel ratio.

Yes, Also check ALL of your emission sensors and ruber lines for being cracked, Loose or extremly soft to the touch. Soft to the touch that occurs on ANY vacuum line anywhere has the potential for being SUCKED FLAT due to heavy vacuum being drawn thru the line expecially when the engine is at normal operating temp.

You seem to know what your doing with the scanner, Just don't OVERLOOK the OBVIOUS. Go back to your BASIC engine design BEFORE electronics came out and focus on things that would cause this problem on a 15 year old vehicle.

Are you or have you EVER had the CHECK ENGINE light ON and or have ANY code(s) displayed recently ?.


Pull the spark plugs and look for obvious unusual discolorization of the electrode ends.


Let me know.


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