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Chevrolet Repair/p0179 code and hard starts

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QUESTION: Hi I have a 04 tahoe with 5.3l engine.  I get po179 code which I know is high fuel comp. sensor,  Now my vehicle does have a fuel comp. sensor on it because I located it under vehicle on driver side, but there is a sticker on gas door not to use E85 which I haven't anyway and I also have a fuel pressure regulator on the fuel rail.  My fuel pump has been replaced because it went out.  But before the pump was replaced and now even after the pump was replaced, if the vehicle has been sitting like a week or more, sometimes I have to push gas to floor for it to start and it blows out black smoke, and stumbles and then it is fine.  I have checked the fpr and there isn't any gas in it. there are no other codes, I am wondering what else to check because the one time that I hooked up my actron scanner and let engine run the engine coolant temp senor appeared to be reading normal.    thanks

ANSWER: HI TERRY, OH YES,, THE FUEL COMPENSATION OR COMPOSITION SENSOR. THIS IS TO TELL THE PCM WHAT MIX OF FUEL IS IN THE TANK TO ADJ THE FUEL TRIMS. [FLEX CARS ONLY]..MORE THEN LIKELY IF YOU HAVE THIS CODE THIS SENSOR IS FAULTY.. WE HAVE REPLACED MANY OF THEM..ONCE REPLACED CODE IS GONE...IF YOU GO TO YOUR DEALER YOU WILL SPEND ABOUT 300.OO OR SO..WOULD SUGGEST GETTING IT ON LINE AT GMPARTSDIRECT.COM COST ABOUT$175.00. BUT AS TO YOUR PROBLEM I AM CONFUSED YOU SAY YOU CK FOR FUEL PRESSURE AND THERE IS NOT ANY THERE ???? HOW ARE YOU CHECKING FOR FUEL PRESS ,AT THE MAIN LINE AT THE FUEL RAIL [SHRADER VALVE WITH A FUEL PRESSURE GAUGE OR JUST PUSHING THE VALVE IN ??
IF THIS TRUCK SITS FOR ONE WEEK AND THERE IS A LONG CRANK BEFORE IT WILL START THIS SOUNDS LIKE A BAD FUEL PUMP REGULATOR WHICH IS BUILT INTO THE PUMP. IT IS BLEEDING DOWN AND NOT HOLDING PRESSURE. AFTER THIS SITS FOR A FEW DAYS OR SO YOU SHOULD BE ABLE TO PUSH THE SHRADER VALVE IN AND GAS SHOULD SPRAY OUT BEFORE YOU HIT THE KEY..IF NOT REGULATOR IS NO GOOD.IF IT SITS FOR 10 DAYS OR SO THIS MAYBE JUST NORMAL. FUEL WILL LEAK DOWN AT SOME POINT. AFTER MY CAR SITS FOR 10 DAYS OR SO THERE IS A LONG CRANK PERIOD AS WELL.  IS THIS A GM PUMP MODULE OR AFTERMARKET??? IF AFTERMARKET THIS MAYBE YOUR PROBLEM. I CAN NOT TELL YOU HOW MANY FAULTY AFTERMARKET PUMPS WE HAVE REPLACED...TONS.. I KNOW YOU SAID THIS WAS THERE BEFORE YOU REPLACED THE PUMP AS WELL. BUT I WOULD ADDRESS THIS CODE ISSUE FIRST AND THEN GO FROM THERE..LET ME KNOW HOW THIS WORKS OUT AND GOOD LUCK TO YOU,,,TOM...

---------- FOLLOW-UP ----------

QUESTION: Thanks, but what I was saying was that the fuel pressure regulator connected to the fuel rail, I would take the vacuum line off to make sure that there wasn't any gas in it, I understand that if the fpr is bad that there would be gas in the vacuum line or the fpr itself.  The pump was suspposely replaced back with an ac delco pump,  the vechicle kept cutting off when driving down the highway on vacation, it would restart but then started running funny and service guy said pump was bad so  I had it replaced but can a p0179 code cause my car to have a hard start , or it won't start unless i push gas down to floor and hold it, but this doesn't happen all the time it sits but it has happened about 5 times over the last  4 years.   thanks

Answer
HI TERRY, OH I SEE,WELL I WOULD LIKE YOU TO TAKE CARE OF THIS PO179 CODE. THIS SENSOR SOMETIMES WILL SEND THE WRONG SIGNAL TO THE PCM AND NOT ALLOW THE ENG TO START...WE HAVE HAD 2 TRUCKS TOWED IN TO OUR SHOP FOR NO STARTS AND BOTH HAD THIS PO179 CODE..IT IS SENDING THE WRONG FREQUENCY AND PULSE WIDTH TO THE PCM. WHICH WILL NOT SEND A SIGNAL TO THE FUEL PUMP RELAY TO START THE PUMP..  THERE HAS ALSO BEEN TRUCKS THAT IF YOU WIGGLE THE CONNECTION AT THE SENSOR YOU CAN MAKE IT FAIL....IF THE PCM IS SETTING UP THIS CODE AS A HARD CODE THIS SENSOR OR HARNESS TO IT IS MORE THEN LIKELY FAULTY..THESE PCM'S ARE VERY SMART.. CK ALL YOUR WIRING TO IT AND IF ALL LOOKS OK, IF IT WERE MINE I WOULD REPLACE IT...IF YOU DECIDE TO GO THAT WAY, GET IT FROM GMPARTSDIRECT.. GOOD PRICES..NO,MY FAMILY DOES NOT OWN THE PLACE...LOL..YOU ARE CORRECT, THE REGULATOR IS ON THE RAIL ON THIS ENG..[MOST] OF THE TIME A BAD REGULTAOR WILL HAVE FUEL IN IT IF IT IS BAD..[[BUT NOT ALWAYS]]IF YOU GO TO A REGULAR REPAIR SHOP OR DEALER CK WITH THEM AS WELL. I KNOW YOU DO NOT KNOW ME AND REPLACING THIS SENSOR IS NOT CHEAP...GOOD LUCK TO YOU AND I HOPE THIS WORKS OUT FOR YOU...TOM....

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TOM SHEETS

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PLEASE READ ALL OF THIS BEFORE ASKING ANY QUESTIONS. IF THIS CHEVY SECTION IS MAXED OUT.YOU CAN REACH ME IN THE OLDS/BUICK SECTION. Will answer questions from 6:00am to 10:00pm all days [EST][[[ NO DIESEL OR PAINT QUESTIONS]]] will answer all 1965 to present QUESTIONS ON ALL GM'S on mechanics of these cars. Keep in mind i am not there in person i am going on what you are telling me !! PLEASE IF ASKING A QUESTION GIVE ME AS MUCH INFO AS POSSIBLE. THE MORE THE BETTER. SUCH AS YEAR,MAKE,MODEL,ENGINE SIZE. THIS WILL HELP ME HELP YOU. I will not be able to answer all questions because of some situations that i would really need to be there and see things for myself,such as electrical issues. In many cases i would need wiring diagrams. I can also give you an estimate on what the cost would be at our repair shop as an idea to help you. Keep in mind that my answer is ONLY MY ADVICE,ck with your mechanic as well.. >> THANK YOU, TOM..

Experience

I have been a ASE certified master mechanic for over 30 years and certified IN ALL 8 CATEGORIES,[engine repair,engine performance,auto trans,manual trans,clutches,steering and suspension,brakes,electrical systems,heating and air/cond. I am also a state CERTIFIED inspector for over 30 years. I do computer work [pcm]fault codes,pcm flashing,state inspection monitor readiness,repairs on exhaust,fuel service,[injection and carburetor,] charging system problems, running issues,alignments,frame problems,tire balance,struts and of course standard and anti-lock brakes.

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nys state auto repair industry and ase group.

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high school,4 years of tech school,and many many hours of auto training with many gm classes and aftermarket training classes..

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ASE MASTER TECH CERTIFIED IN ALL 8 CATEGORIES.NYS INSP LICENSE AND A/C CERTIFIED

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MANY CUSTOMERS IN OUR BUSY SHOP.

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