My recently purchased silverado is throwing codes P0171 P0174 P0300, but it isn't idling rough, or seeming to be sluggish (other than from a start thanks to the torque management). It is whipple supercharged complete with all the awesome whipple electronics and extra injectors in the intake. I've tested with carb cleaner and it doesnt seem to be a leaky intake manifold gasket. The previous owner said he recently installed a K&N air filter, so could it just be the MAF being fouled by all the oil they put in their filters? I'm looking to get rid of the whipple electronics, and just upgrade my injectors and have it tuned, but I would like to get this issue taken care of first.

 

year, make and model?

 

sorry, 2002 silverado 1500 5.3L. Whipple supercharger, volant intake and header back exhaust. All this was installed when the vehicle had roughly 1300 miles on it, it now has 44,000 miles on it. The guy I bought it from said he has had no issues with it, he had a huge stack of papers with all the maintenance and rapairs done to the truck, and nothing threw up any red flags, thats the only reason I bought the truck having had this much work done to it, plus the guy the owned it was in his 60's.

 

Can anyone give me a place they would recommend to start looking? I'm thinking about pulling plugs tonight to see how they look. And I might be ordering the higher flow fuel injectors soon. Will I need an immediate tune when I change those injectors, or would it be capable of driving to a tuning facility? This is my daily driver, so I can't really afford for it to not be drivable. I might start looking into picking up a PCM that I can send off for tuning/flashing that can get me in a drivable state to make it to a tuner.

 

Thats what id do..

but it could be your 02s? 71 and 74 are lean codes.. and 300 is a misfire.

Throw some new plugs in it unless those are fresh.
see if you can clear the codes and see how long it takes to get them back.

 

First place I'd start is the catalytic converters and o2 sensors. You could pull the plugs and check them as well.

Can you get a scan tool to see what cylinder is misfiring?

 

I'll try and borrow a buddy's tomorrow to check and see.

 

Condition/Concern:


99 through 05 GEN III truck engines may experience any of the following:




1.

A cold rough idle that diminishes as the engine warms up.





2.

Possible DTCS P0171, P0174, or P0300.





3.

Random misfires at idle.


Recommendation/Instructions:


The intake gasket seals may be leaking around the intake ports, causing a lean condition. The intake gasket seals may leak around the bottom side of the port, making it a challenge to detect the vacuum leak. The technician may also notice lower than normal MAF readings if the intake seals are leaking.




1.

If leaking intake gasket seals are found, replace the intake gaskets. During the repair be sure to use the current GMSPO part number for replacement intake gaskets. The current GMSPO part number for intake gaskets will have a teal green intake gasket seal. The old version of the intake gaskets were orange in color. Use only the teal green colored gaskets for a repair.





2.

The intake plenum should also be checked for excessive warpage that may cause an uneven clamping pressure of the seal. If the plenum is found to be warped it will need to be replaced. Service Information states, "An intake manifold with warpage in excess of 3 mm (0.118 in) over a 200 mm (7.87 in) area should be replaced". Intake warpage is measured at the gasket sealing surfaces, and should be measured within a 200 mm (7.87 in) area. This measurement is across only two of the intake runner port openings. Measurements taken across the entire distance of all four intake runner ports will lead to unnecessary manifold replacements.

 

The following diagnosis might be helpful if the vehicle exhibits the described symptoms in the PI.

Condition/Concern:


Check Engine Light with a P0300 due to 2 - 4 cylinders misfiring on the same bank of the engine. DTCs P0171, P0172, P0174 or P0175 may also set for the misfiring bank.

Recommendation/Instructions:


If the published misfire diagnostic does not isolate the cause, perform the following suggestions as necessary:




1.

Perform a fuel injector balance test for all 8 cylinders. If a fuel injector concern exists, it is possible to misfuel an entire bank of the engine, causing multiple cylinders on the same bank to misfire even though the root cause is a single fuel injector.





2.

Inspect O2 sensor connections on the misfiring bank for corrosion or water intrusion. If water intrusion is found on the right bank, it may be due to the AC Evaporator Condensation dripping onto the O2 sensor harness. If this condition is found, reposition and shield the harness to prevent a repeat concern and repair the connections.





3.

Check for excessive exhaust backpressure using the restricted exhaust diagnosis from SI.





4.

Swap the Position 1 O2 sensors side to side to see if the misfires move to the other bank of the engine. If so, replace the O2 sensor.

 

Only 2 bulletins I could find that mentioned all three codes. Unless p0300 is unrelated to lean codes.