02 Silverado P0171/174 New MAF Installed -No start

I am at a loss for the green, yellow, red light.... lets start simple- 1) vehicle is STOCK no modifications, recient work or miracle aftermarket parts. 2) the only codes are P0171 Fuel Trim System Lean Bank 1 P0174 Fuel Trim System Lean Bank 2 both at same tine suggest a Vac leak- ck post MAF, PCV, etc Why did you condem MAF? for a no start - answer above questions, recheck codes do not erase, then using a fuel pressure gauge, post PSI and leak down rate, ck spark at several plugs.

1. 02 Silverado no modifications with a 5.3 gas 2. The only codes were P0171/P0174 I went the path of the MAF because after cleaning the original MAF seems to get better at higher idle but not on low idle, after reading website MAF was one of suggestive issue's. Then replace with new and truck would not start at that point. Code reader had following freeze frame info: (with red light on for fix issue) Fuel System 1:CL Fuel System 2: CL Fuel System 1 Calc Load: 3.9%, ECT 188, STFT B1 24.2 Fuel System 2 Calc Load: 3.9, ECT 188, STFT 24.2, LTFT 25.0 STFT B1 24.0 B2 17.9 LTFT B1 25.0 B2 25.6 MAO 11.5 Eng RPM 851 Vech Speed 4 MAF(lb/mn) 1.38 TPS(%) 6.2 Charged battery, Installed fuel gauge twice to verify connections, no gauge movement Prior to this truck appeared to start, then would not start after that. Engine cranks fine, No service engine or codes. Will be back to troubleshoot more on Friday Sept 28 (Biz Trip) Thank-you for any help to date!!!

Am I reading this correct- you attached a fuel gauge to fuel rail - key on and NO pressure? Check underhood fuse/relay box

Correct, No pressure with gauge Fuse ok, relay ok (swapped with horn relay to verify) Going to check/change fuel filter, then go to fuel pump, wiring, pump etc.

Replaced bad fuel pump in tank works find first week cleared codes Same codes showed again, cleared again but still show same codes and service engine light. Am I missing something still, truck seems to run fine!

keeping all on same page- I would check and post the codes- p0171 p0174 ONLY ? Check and post the fuel pressure- post fuel trims, you do have a scanner it seams- Map reading? As lean has us jumping to Vac leak- have you checked for vac leaks - easy spray trick? esp at the MAP area as you did work there.

I have cleared code again, to have them come back within a day. have looked for vac leaks and not seeing anything Fuel Pressure is at 50psi Kinda of leaning towards the intake gaskets as issue after review forum pages Using Innova 3130 scanner from parts store/does not do real time Scanner Reads: P0171/P0174 Fuel 1 CL Fuel 2 CL Call Loa% 2.3 ECT 15.9 STFT B1% 3.9 LTFT B!% 25.0 STFT B2@% 0.7 LTFT B@% 25.0 MAP 12.1 Eng RPM 572 Veh Speed 0 MAF 0.768 TIPS% 0

In my opinion your fuel pressure is still too low! it should be 55-60 with key on engine off and 55-60 at idle! Unless your new Maf is causing the issue but I've been bitten more by poor replacement fuel pumps then MAF's! Your code reader is showing that your long term fuel trim is maxed out! A vaccum leak should be showing a high short term fuel trim reading and a more normal long term reading! If the MAF is unplugged how do the fuel trims respond?

seconding what Jeff said FUEL PRESSURE is to low..!! Again Jeff spelled it out - Use an OEM pump -.... A hail mary - change fuel filter and repost fuel presssure.

#PIP3232B: Cold Engine Idle Misfire Or DTCs P0171 P0174 - keywords 4.8 5.3 6.0 air cold crack hesitate idle intermittent internal intake leak lean misfire miss P0171 P0174 P0300 power rough surge vacuum - (Feb 7, 2007) Subject: Cold Engine Idle Misfire or DTCs P0171 P0174 Models: 2002-2005 Cadillac Escalade 1999-2005 Chevrolet Avalanche, Express, Silverado, Suburban, Tahoe, Trailblazer 1999-2005 GMC Savana, Sierra, Yukon 2003-2005 Hummer H2 -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- This PI was superseded to update parts information. Please discard PIP3232A. -------------------------------------------------------------------------------- The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI. 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. Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

Well Guys... I am an expert at changing fuel pumps!! Now has OEM pump, pressure shows correct. So 2nd new pump(OEM), MAF, have checked for vacuum leaks not finding. (Also fixed water pump leak, drive serp belts) Still seeing same Codes 0171, 0174 Next step change Intake gaskets (Was suspect early on after first pump install, Well good learning curve!) Will update when changed, Thanks for the Expert Help Guys!

Now new intake gaskets installed (Teal color), original teal also). Had P0171/174 codes prior to install with high LTFT at 25 on Bank2. Check with scanner showed no codes, drove truck for day then went to return scanner and Sev Eng light showed up at parts stored. Showed same codes again as above. Double checked and cleared codes. What's my deal?? Am I playing catch up with the memory in the truck ecm?

trying to be Analyticl - so its step by step - we have P0171 and p0174? LTFT still pegged? fuel pressure is? PS - check messages

Have y'all figured this out? My 2000 is doing the same. Hand the intake manifold gaskets replaced and still here and driving horrible. I have P0171 174 420. I have replaced all O2 sensors, egr valve, cleaned the iac, had a complete fuel system cleaning performed and it still acts up. Any solution???

nmartin4149 - start a new topic.... which engine? Tell us anything added or modified, any replacement aftermarket parts......o2 sensors were AC Delco? Do you have a scanner - fuel pressure gauge?

Kev - posted Blake - has it been fixed?