P0171 P0174, Intake gasket?
05-03-2011, 07:52 PM
#1
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P0171 P0174, Intake gasket? I have an '02 z28 throwing P0171 and P0174. Running rough at idle and hesitates at low rpms. Just changed the fuel filter. Tried spraying throttle body cleaner and found that idle picks up when sprayed on the front of the intake. I'm guessing this means bad intake gasket. Wanted to confirm before I replace. Also, I've seen how-to's that show an upper and lower intake, do I need to replace both gaskets or just the upper. Thanks.
05-03-2011, 08:05 PM
#2
TECH Fanatic
Yep, intake gaskets. Practically all GM car/truck lines have intake gasket issues, very common problem. Pretty easy to do, rear intake bolts I believe need to come out with the manifold due to cowl clearance. Should just be a lower gasket set. I always get my lower intake gasket sets at the dealer. A little more expensive than the parts store, but your getting good stuff.
05-04-2011, 06:39 AM
#3
Just go to Autozone or Oriellys & grab the FelPro intake gasket set, its cheap & perfectly good gaskets. No need to pay the stupid dealership prices man. The Felpro valve cover gaskets are also good quality, hell I'd say better than stock on those actually.
Yes, rear bolts will have to be left in when you pull the intake. Watch out for the oil pressure sending unit behind the intake. Here is my suggestion for removal, I have done it many times without breaking the sensor.
1: Removel the PCV hoses
2: Remove the injector clips & unplug injectors
3: unbolt the rails & pop the injectors out of the intake (the stock fuel lines will give you some play, what I do is flip the rail upside down & turn them over toward the driver side fender. Let them rest there & you dont need a quick disconnect for the fuel line to rail connection)
4: reach behind the intake & feel around gently, you'll find a small vacuum hose, the oil pressure sending unit, MAP sensor & a larger vacuum hose that goes to the brake booster. Disconnect the small one & the larger one at the booster. Also unplug the oil pressure sending unit & MAP sensor.
5: unbolt the intake & remove all bolts except the last 2
6: Again check behind the intake with your hand & make sure nothing is gonna get caught on the oil pressure sending unit. Take a rubber band & put it on the last 2 bolts once you pull them up. Watch to leave clearance for the cowl.
7: grab the front of the intake & the rear, slightly lift enough to slide the intake forward from under the cowl & your all done.
Yes, rear bolts will have to be left in when you pull the intake. Watch out for the oil pressure sending unit behind the intake. Here is my suggestion for removal, I have done it many times without breaking the sensor.
1: Removel the PCV hoses
2: Remove the injector clips & unplug injectors
3: unbolt the rails & pop the injectors out of the intake (the stock fuel lines will give you some play, what I do is flip the rail upside down & turn them over toward the driver side fender. Let them rest there & you dont need a quick disconnect for the fuel line to rail connection)
4: reach behind the intake & feel around gently, you'll find a small vacuum hose, the oil pressure sending unit, MAP sensor & a larger vacuum hose that goes to the brake booster. Disconnect the small one & the larger one at the booster. Also unplug the oil pressure sending unit & MAP sensor.
5: unbolt the intake & remove all bolts except the last 2
6: Again check behind the intake with your hand & make sure nothing is gonna get caught on the oil pressure sending unit. Take a rubber band & put it on the last 2 bolts once you pull them up. Watch to leave clearance for the cowl.
7: grab the front of the intake & the rear, slightly lift enough to slide the intake forward from under the cowl & your all done.
