LS1 - P0171 and P0174 both banks running lean
12-19-2014, 05:31 AM
#61
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In a perfect world you don't want ANY crank case pressure, but we don't live in a perfect world and you will always have some blow by creating crank case pressure. Correct me if I am wrong, but it sounds like you have a lot of pressure building up and when you reconnect your PCV hose its throwing the code.
HOWEVER: you say your getting 18inHg at idle, that converts to about 61kpa, which is NOT what the MAP sensor is reading. Maybe you have a bad MAP sensor
Last edited by Horsepwraddict; 12-19-2014 at 05:38 AM.
12-19-2014, 01:58 PM
#62
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You quoted me before I edited. I thought about it and I was wrong at first. I am beginning to confuse myself a bit with all the numbers in different posts. I apologize.
In a perfect world you don't want ANY crank case pressure, but we don't live in a perfect world and you will always have some blow by creating crank case pressure. Correct me if I am wrong, but it sounds like you have a lot of pressure building up and when you reconnect your PCV hose its throwing the code.
HOWEVER: you say your getting 18inHg at idle, that converts to about 61kpa, which is NOT what the MAP sensor is reading. Maybe you have a bad MAP sensor
In a perfect world you don't want ANY crank case pressure, but we don't live in a perfect world and you will always have some blow by creating crank case pressure. Correct me if I am wrong, but it sounds like you have a lot of pressure building up and when you reconnect your PCV hose its throwing the code.
HOWEVER: you say your getting 18inHg at idle, that converts to about 61kpa, which is NOT what the MAP sensor is reading. Maybe you have a bad MAP sensor
Last edited by RedHotMike; 12-19-2014 at 04:52 PM.
12-20-2014, 02:16 PM
#63
There are procedures out there similar to this:
http://troubleshootmyvehicle.com/gm/...-map-sensor-1#
But it occurs to me that if your physical gauge says one thing and your MAP(via computer) is telling you something different, that's a decent test right there.
http://troubleshootmyvehicle.com/gm/...-map-sensor-1#
But it occurs to me that if your physical gauge says one thing and your MAP(via computer) is telling you something different, that's a decent test right there.
12-20-2014, 10:31 PM
#64
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There are procedures out there similar to this:
http://troubleshootmyvehicle.com/gm/...-map-sensor-1#
But it occurs to me that if your physical gauge says one thing and your MAP(via computer) is telling you something different, that's a decent test right there.
http://troubleshootmyvehicle.com/gm/...-map-sensor-1#
But it occurs to me that if your physical gauge says one thing and your MAP(via computer) is telling you something different, that's a decent test right there.
12-22-2014, 04:02 PM
#67
code P0171, P0174 Just got back from a short road test. Went up the road for about 5 miles with the original MAP and it set a code P0174 about half way there. Kind of cool today and I think the outside temp was a factor in not setting both 171 and 174. Swapped out to the borrowed MAP and came back to the house without setting a code. Looks like we are on track to solving the problem. Before I commit to a definate bad MAP I'll put some more miles on the car. Stay tuned!
12-23-2014, 07:34 PM
#68
code P0171, P0174 Failure! The codes were set twice today. Each time I was either at idle or under 40MPH. If the codes are cleared and cruise at 65 MPH everything is fine with no codes. Even when the codes happen the engine doesn't stumble or give any indication of a problem. The hunt continues.
12-25-2014, 08:16 AM
#70
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So the map sensor kind of fixed it lol. Start checking the o rings/grommets around the purge solenoid and evap lines, brake booster vacuum hose, map sensor etc.
Have you checked the throttle body gasket?
Have you checked the throttle body gasket?
12-27-2014, 07:19 PM
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Ok - I'm nearly ready to call victory on this one. In exasperation I bought a intake gasket kit and swapped them over. When I pulled the manifold, as usual on this motor, everything was as clean as a whistle with no obvious signs of a leak. So, I swapped them over anyway and bolted it all back together. Started it up and it's ran cold better than it ever has since I broke the spring.
Banged on the vac gauge and it's idling at 20 inHg which is about 2inHg better than before. I left it sit there idling for 25 min or so whilst I packed up tools etc and it was rock solid for all that time and didn't throw a code. I'm still not completely sold on the codes because it's gone for an hour or more in the past before returning again but I'm encouraged. A huge thanks to everybody who chipped in with suggestions etc
Of course it's not possible to fix 1 thing without something else going wrong - now there is a metallic rattle which sounds like the exhaust. Cbf'ed looking at that right now - could be a loose baffle (I hope).
Banged on the vac gauge and it's idling at 20 inHg which is about 2inHg better than before. I left it sit there idling for 25 min or so whilst I packed up tools etc and it was rock solid for all that time and didn't throw a code. I'm still not completely sold on the codes because it's gone for an hour or more in the past before returning again but I'm encouraged. A huge thanks to everybody who chipped in with suggestions etc
Of course it's not possible to fix 1 thing without something else going wrong - now there is a metallic rattle which sounds like the exhaust. Cbf'ed looking at that right now - could be a loose baffle (I hope).
12-29-2014, 03:37 AM
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So you did Intake gaskets A second time and this time it worked? That's interesting, either way I'm happy for you, things like this can wear you down. It's rewarding when you finally get it nailed down
12-29-2014, 04:41 AM
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Nah - only once. Hadn't touched them before that. All I can think of is crazy pressures with the broken valve spring punched a small hole that I couldn't see. Either way it fixed (for good I hope)
12-29-2014, 09:47 AM
#75
code P0171, P0174 Our codes are the same but I'm starting to think the cause is different. I also replaced the intake gaskets but still have the codes. The other day I took the temps of the headers and discovered that the two back ones (#7 & #8) were cooler and #8 was very cool at about 180 degrees. Thinking back, the engine was setting for several years before I got it. My bad that I did not clean the injectors but it did fire up and run good. As a side note sometimes it only sets code P0174 which supports the cool temp on #8. Always wanted to make a test stand to clean/test injectors so I ordered new Orings and an ultrasonic cleaner. Maybe I should test vacuum too like Mike did.
01-10-2015, 01:45 PM
#76
Codes P0171, P0174 Built a primitive injector cleaner and got an ultrasonic cleaner. To test I cleaned a buddy's old spare injectors. Four would not even click. Ran them thru the ultrasonic cleaner with water and Shout, then on to the cleaning station. Used carb cleaner in a large syringe, 9 volt battery and a momentary switch to pulse the injector. As the cleaner was forced (2lbs?) thru the injectors I could see the spray pattern change and the liquid coming out a light brown with a smell of varnish (mason jar catcher). Cleaned my injectors and took it for a test drive today. No codes is a 3 mile test. Will test more when the weather warms a bit but before I cleaned the injectors it would have set the codes.
01-11-2015, 04:30 AM
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Our codes are the same but I'm starting to think the cause is different. I also replaced the intake gaskets but still have the codes. The other day I took the temps of the headers and discovered that the two back ones (#7 & #8) were cooler and #8 was very cool at about 180 degrees. Thinking back, the engine was setting for several years before I got it. My bad that I did not clean the injectors but it did fire up and run good. As a side note sometimes it only sets code P0174 which supports the cool temp on #8. Always wanted to make a test stand to clean/test injectors so I ordered new Orings and an ultrasonic cleaner. Maybe I should test vacuum too like Mike did.
01-11-2015, 04:43 AM
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01-18-2015, 10:07 AM
#79
Codes P0171, P0174 My success was short lived. Set he codes twice today. I've replaced the intake gaskets, cleaned the injectors, replaced the fuel pump, replaced the fuel pressure regulator. Noticed the fuel pressure still hovers around 50 PSI. Usually the codes set while at about 45 MPH or coasting down. While at highway speeds everything is fine. Any ideas?
01-18-2015, 12:02 PM
#80
You need to see why your only getting 50psi.. you need to be at 58psi for it to run correctly. What pump are you using now ?...
What brand is the regulator ? for my Vette FPR.. I stick with name brands Delco GF822 or WIX33737
Any kinks in the lines ?
BC
What brand is the regulator ? for my Vette FPR.. I stick with name brands Delco GF822 or WIX33737
Any kinks in the lines ?
BC