stokes Posted January 23, 2013 Report Share Posted January 23, 2013 Was going to add this to my other thread,but it is unrelated.Car has been starting/running fine,but I started getting the "service engine soon" message.Run the codes and I get,I think it was P0171 and P0174 I think,but they transslated to "Fuel trim system lean" one was bank1,other,bank 2.When I cleared them the Service engine soon message would disappear,only to return after driving a while.Did this for a week or 10 days.On saturday I went to check under the hood and find the oil fill cap sitting where I left it when I added oil a week or 10 days ago,not where it belongs.Some oil across the engine cover,but not too bad.Cleaned it up,topped off the oil and replaced the oil cap.No more service engine message and no codes.I dont get it,no oil pressure message,but fuel trim system lean?I do hate these computers. Link to comment Share on other sites More sharing options...
rockfangd Posted January 23, 2013 Report Share Posted January 23, 2013 lol the fords dont tell you your oil pressure is low til the engine blows. I dont try to figure some things out. Thanks for sharing GM FAN FOREVER Nice, clean, luxury= fine automobile Link to comment Share on other sites More sharing options...
JimD Posted January 23, 2013 Report Share Posted January 23, 2013 ....but I started getting the "service engine soon" message.Run the codes and I get,I think it was P0171 and P0174 I think,but they transslated to "Fuel trim system lean" one was bank1,other,bank 2.....On saturday I went to check under the hood and find the oil fill cap sitting where I left it when I added oil a week or 10 days ago.... Leaving the oil fill cap out of place (or the oil dipstick not fully seated) provides an unmetered source of air to enter the engine and upset the desired fuel/air ratio. In your case the umetered air was entering the engine air intake plumbing via the Positive Crankcase Ventilation (PCV) system. Take a close look at the oil filler cap and the oil level dipstick. You will see O ring seals that should be inspected each time you add oil OR check the oil level. Jim Drive your car. Use your cell phone. CHOOSE ONE ! Link to comment Share on other sites More sharing options...
Cadillac Jim Posted January 23, 2013 Report Share Posted January 23, 2013 P0171 Fuel Trim System Lean Bank 1 P0174 Fuel Trim System Lean Bank 2 The PCM was doing its job, noting that the fuel injection could not provide a sufficiently rich mixture to meet the requirements of the engine. These codes, particularly when both of them are thrown, usually mean you have a vacuum leak, which you did. Continuing to run this way risks damaging the engine. Thus the "Check Engine" light when these codes are thrown, which is part of the OBD standard that everybody who sells cars in the US signs up to. I think it's great that cars are smart enough to tell you when something's wrong. That way you can minimize maintenance and repairs, find the cause of driveability problems like high, uncontrollable idle speed and engine stalling when cold, and keep your car running well as long as you want to drive it. The only surprise to me is why that much air passed through the PCV valve. I suspect that Ford allows for a high air flow rate through the oiling system to keep blow-by out of the oil when the engine is stressed, as when towing. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
snappytee Posted January 23, 2013 Report Share Posted January 23, 2013 your induction boot is sucking air......BIG TIME Link to comment Share on other sites More sharing options...
snappytee Posted January 23, 2013 Report Share Posted January 23, 2013 when this happens ALSO but in your case its good that your that you are no longer sucking dirt into your crankcase thanks to the much love computer LOL Link to comment Share on other sites More sharing options...
Texas Jim Posted January 23, 2013 Report Share Posted January 23, 2013 your induction boot is sucking air......BIG TIME Wrong.... his OIL FILLER CAP was not on. Link to comment Share on other sites More sharing options...
BodybyFisher Posted January 23, 2013 Report Share Posted January 23, 2013 The reason, I love the Northstar platform is BECAUSE of the diagnostic computer, in this case it operated perfectly. In this case, it would be as if the PCV valve was off and it was sucking in unmetered air. It best not to assume the "computer" is wrong and dump on it. I had never seen these codes related to the oil filler cap being left off in all my time here, usually its due to a bad intake plenum or over pressurization valve. Very interesting Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
stokes Posted January 26, 2013 Author Report Share Posted January 26, 2013 Yes,the cap was off,sitting on the cowling in front of the engine.Kind of surprised,but thankful, it was still there.When I first saw and looked up the codes,I thought about posting and asking about it here.Thought I'd poke around a while first.Although you guys say the diagnostics worked as it should,in this case I would think a "low oil pressure" code would be more helpful,no?I'm guessing that if I had posted here first,and I do have a world of respect for you guys and your knowledge of these contraptions,nobody would have pointed to anything to do with the oil system,afterall,the code was pointing to the fuel system.Getting the "Fuel Trim System Lean" code didnt alarm me too much,since the engine seemed to be working fine.Had it said "oil pressure low" I would have checked it immediately and found the dumbass mistake I had made.Guess I just havent gotten used to this modern electronics,I miss the good old days of simple engines that could be fixed without a degree in computer tech. Link to comment Share on other sites More sharing options...
JimD Posted January 26, 2013 Report Share Posted January 26, 2013 .....Although you guys say the diagnostics worked as it should,in this case I would think a "low oil pressure" code would be more helpful,no? No. Your air/fuel ratio codes had nothing to do with oil pressure. Your air/fuel ratio codes were caused by unmetered air entering the engine via the open oil filler hole. It's that simple. Remember the experience and motor on down the road. Jim Drive your car. Use your cell phone. CHOOSE ONE ! Link to comment Share on other sites More sharing options...
BodybyFisher Posted January 26, 2013 Report Share Posted January 26, 2013 HAHA, the oil filler CAP has NOTHING NADA to do with OIL PRESSURE at all. NOTHING, its where you PUT oil only. The PCV system SUCKS unburned emissions from the crankcase and redirects them into the intake to burn them. Leaving the oil filler cap off allows UNMETERED air into the intake system causing a LEAN condition. Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
Göran W Posted January 26, 2013 Report Share Posted January 26, 2013 I guess "stokes" ment that any amateur would go fill up oil and the problem solvd......... guess he´s right!? Link to comment Share on other sites More sharing options...
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