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LS experts... P0171 and P0174

EmersonHart13

TCG Elite Member
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Jul 18, 2007
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I am getting a P1071 and P0174 code on occasion, it goes away after a few starts and then will pop back up again a month or two later. From reading I have gathered that this means that is on the intake side as I am getting both simultaneously. I have already re-tightened the stock intake twice. (I have a Svede to install but I was waiting to try to get this sorted out first) I believe the next place to look is the intake manifold. I tried spraying around the edges to see if I could get an idle change but nothing happened. Is my best bet to re-torque the manifold? I has to be a pretty minor leak I think but my logic could be completely wrong.

Your thoughts please!

Thanks in advance,

John
 

Stink Star

Don’t Drive Angry!
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Jan 20, 2008
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Big wood cock
well you aren't supposed to touch it, they expect you to replace it if its bad, but i sometimes take a 90* hook pick and GENTLY scrape back and forth on the sensor wires the entire 360* of their circumference. i only suspect MAF because i assume there is a k&n filter on this car. the intake being off raises an eyebrow for a twisted or pinched gasket of course. even though those gaskets are encased in a plastic frame they can still be crushed past the point of usability or cracked from over torque.
 

EmersonHart13

TCG Elite Member
TCG Premium
Jul 18, 2007
54,211
22,334
Right now it is a stock intake. I know it had an aftermarket on there before so it could be it. I had a leaky valve cover gasket that I had to replace because it was pinched so the intake is probably suffering from the same problem. I will check the torque first and then pull it if it shows again.

Thanks!
 
I know it's not LSx related, but I had the same two codes on my 97 Mustang. I tried all kinds of things to fix it including new (non oiled) air filter, new DPFE sensor, checked everywhere for vacuum leaks, replaced intake manifold and gaskets (upgraded to PI), among other things.

Turns out, when I pulled the engine apart to install new heads, I found a vacuum line going from the intake over to the purge solenoid, that was heated by a previous exhaust leak. The line looked fine, but when I bent it, I found it had thousands of tiny cracks from the heat.

Replaced the hose and no more codes!

Make sure you inspect your vacuum lines extremely well!
 
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