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-   -   ’’88 way to rich maf code (https://www.buickforum.com/forum/century-22/88-way-rich-maf-code-1847/)

happygeorge 11-15-2008 09:50 AM




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Hello all you smart Buick folks,


I have a ''88 century3.8 sfi vin 3 that runs way to rich all the time. MAF code..replaced twice checked last one on O''scope and is within spec.


Symptoms: Runs way to rich in open and closed loop. Black, hot, exhaust and melted bumper. Sooty plugs (all 6). Bucks like a stallion (like bad MAF). Idles too high. Runs same w/ maf unplugged (limp mode bad too?)


What I''ve done: Replaced MAF twice, last one tested ok on bench. reset computer numerous times. MAF code keeps comming up shortly after startup (I believe it''s because the high idle compared to sensor reading being bogus). Checked wiring and connectors ok, checked temp sensor and all read correct at different temps, checked cam and crank sensor connectors, wires and outputs on scope ok, adjusted crank sensor, made it a little better idle.Cracked open exhaust, in case cat plugged, no difference but i''m deaf and suffered rich exhaust inhalationnow. Replaced O2 sensor, haven''t checked signal but problem occures in both open and closed loop. Checked wiring harness and connector to ECM and sparc control mod ok. Replaced sparc control mod no difference.Good wires, plugs, cap etc.Checked forvac leaks, no obviouse ones. PVC ok.Manually opened EGR valve and made run a little better (as it should on richrunning engine). TPS tested OK, no dead spots. Check fuel pressure regulator and operates correctly. Checked for leaky injectors, rail holds pressure as expected. Noticed when I introduce big vaccuum leak, obviously runs better (leans out) but not a good fix. I''ve run out of ideas other than expensive ECM or Mechanical issue.


Possible?: Would ECM (computer) cause it to run rich all the time even if sensor signals are getting through? It seems full width pulse on injectors all the time.


If I replace ECM and does not solve problem, what next.


Problem was there before I rebuilt engine, (son spun a bearing), figured It might go away after a fresh take (yeah right).


I just thought of something, I''m real particular when installing timing components, but..if the mechanical timing was off, would this possibly cause the computer to make a rich condition (I''m not sure how it would?)





Anyone else had similar problems and found culprit?


I''m frustrated, Older cars w/o computers and injection were a piece of cake.


Thank you for your time. Power in numbers!


Sincerely,


George




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