2002 Avalanche 5.3 O! M! G!
Now I no longer get the P0300 but get P0174 and P0171(lean codes for both banks) now. Done smoke tests, nothing. Then I bought a used GM Tech 2 and saw my fuel trims were really out of range after watching your videos to learn how to use it. I thought it was a vacuum leak again being illiterate and tested again for a leak with the smoker, nothing again. I thought my MAF was bad. I had replaced it before but defective parts happen so I exchanged it for another new one.
The first day I drove it my LTFT was at 16 and 14 and my STFT were bouncing back and forth around 0 while driving. I thought it was running better and that maybe I just had a remaining vacuum leak.
Well in driving it the next day the fuel trims were back to their normal tricks: LTFT both sides pegged at 25 and the STFT jumping around between 10 to 16%. Driving it further fuel trims bank 1 was the same but bank 2 had a LTFT of 25 and a STFT of 54… Then I look again and both fuel trims on bank 2 went to 0 as well as O2S1 sensor was 0 and I did have a infrequent heater code for that O2 sensor. So I’m hoping that changing that O2 sensor will solve a lot of problems on bank 2. But I don’t think it will specifically will take care of the P0171 and P0174 (at idle 550 to 605 rpm) problems… or will it? Ordered the O2 sensor today.
Added info: I do have a frequent misfire on #6. Compression is 135 and changed the coil and plug again. I swapped the wire with the one next to it to see if it follows... it didn't. But, since changing the fuel injectors IF that engine is going to misfire, it does it mostly on #6. I also got a code P0151 at 1988 rpm, engine load 26%.
5.3’s are noted for intake leaks… I did the water test and the brake cleaner test but I think I looked at the scanner wrong after I did it. Only looked at the LT and not the ST. I didn’t have the scanner the first time I did the test. I was watching for the engine to run rough when I didn't have the scanner, but it really didn't run rough… and I’m still illiterate about all this. Lol, thanks again
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Another thing that also comes to mind is you may have to tune the ECM for the new injectors. What with both opening pressure and pintle number changing I'd wager that fuel map is all off in the rhubarb.
I'd tackle the cylinder 6 misfire first, though. That will definitely throw off your trims.
"Don't ever say 'easy' until the check clears."
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You threw a lot of parts at this truck so I would ask, why?
Three fuel pumps that did not work properly, are you buying junkyard parts? did you do any wiring testing?
All the codes you mention all have to do with a lean condition which is the lack of fuel, so the fuel pump, fuel lines, kinked fuel line and non OEM injectors are going to play greatly into your problem.
Old saying goes, "garbage in, garbage out". At this point trying to diagnose the problem with that much garbage in will only get a garbage out diagnosis.
Fuel pressure should be 55-62psi. I'd go back to the OEM fuel injectors and fix that kink. May have pressure but the kink can lower volume. That along with those "upgrades" are not helping.
Clear all codes and erase the memory to clear block fuel memory and get fresh data. STFT, LTFT and 02 voltage activity, ECT and MAF data at idle and any codes.
keep us posted on your results...
"an open mind let's knowledge flow in and wisdom flow out for a man who has neither never listens to those who have both".
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Before I changed the injectors I was getting a lot of misfires all the time on 80% of the cylinders. After I changed the injectors it pretty much dropped to 10% being that #6 cylinder. Like when I can get it to misfire now is to punch the gas from idle and back to idle again. On a misfire graph I have other cylinders that misfire also but #6 always is in the lead. I didn't check the compression on the other cylinders. At the time I was working was a mechanic via the internet and he asked what the compression was on that cylinder. BUT and I say but the place I got those injectors from said that nothing else needs to be done other than to put them in. It's some GM upgrade to the fuel pressure problems this circle of GM vehicles have with fuel pressure. Thanks for your input...
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On this stupid truck... I've never seen a vehicle with soooo many problems. The person who owned it before me absolutely didn't have a clue. I had to replace all of the steering components. The rear brakes didn't work at all. I couldn't even bleed the rear brakes. Had to replace the ABS solenoid body. Then found the brake hose for the rear cross threaded and leaking.
Then on to the codes... The truck ran like total shit on and off. Being that I already found the truck a mess with the brakes and steering I figured the motor is a mess too. So, I thought an oil change and a tune up was in order. Changed the plugs, wires, coil packs and all four O2 sensors. I found where one of the O2 sensor's wires had been worn through riding on the driveshaft. I really thought it was going to run right after all that and it didn't. I put my cheap scanner on it and I was getting only a P0300, random misfires, and no other codes.
I was like WTF? I had no clue at that point on what else to do. So I contacted the help of an online mechanic. He told me to check the fuel pressure... found it to be 48 psi. So he said to change it but warned me that these fuel pumps for these trucks either work or don't work. He also said that once he changed the fuel pump up to 5 times before he got one to maintain working pressure.
I first tried an ebay cheap Chinese fuel pump because I've had luck with them in the past. Not this time. Replaced it with a Carter fuel pump... another fail. Replace the Carter with a Delphi and got usable pressure 50psi at idle and 59psi at WOT. The online mechanic said that this is good since it's able to hit 59psi. In changing these fuel pumps I had to replace some fuel lines to boot and I changed the fuel filter while I was at it.
The truck still ran like shit. The machanic said he couldn't help me any further unless I got a good scanner and recommended a GM Tech 2. Found a used one. Dropped the mechanic support after I got my scanner cause the pretty much broke me buying that. Lol, I saw all the misfires with the scanner and changed all the fuel injectors. 80% of the cylinders were misfiring. That dropped to 10% after changing them.
Trying to pass inspection but codes p0174 and p0171, lean banks, keep me from doing so. Going to YouTube for help I stumbled onto reading fuel trims... and that's where I'm at today. That's my story and I'm sticking to it.
Was told by scannerdan and another scanner dude that it sounds like my MAF sensor. Changed it again. Oops forgot to mentioned I changed the MAF and MAP sensor. So I changed the MAF again and it did seem to run better the first day... I guess it was in learning mode because the second day it was back to running high trim numbers. Can't remember now but one of the scanner dudes mentioned a restricted fuel line and that damn kink line popped up out of my memory.
I don't have a blacktop driveway nor do I have a garage. So, I work on my vehicles when the weather is bearable or if I have to... which sucks.
Thanks for your help
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post the following info... short and long term fuel trims for bank 1 and 2 at idle, Idle RPM, idle condition (high, low and or rough) MAF g/s and engine coolant temp. 02 voltages for B1S1 and B2S1 and loop status.
increase RPM steadily to 2500 and note trims. Do the values increase or decrease. Note 02 voltage readings. Do they oscillate are they fixed high or low.
even though you cannot find a vacuum leak (external) you may have an internal one, but lets not get to far ahead at this point.
forgot to mention, check the 02 heater fuses... #31 and #32. If the 02 circuit shorted, it may have blown the fuse.
"an open mind let's knowledge flow in and wisdom flow out for a man who has neither never listens to those who have both".
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Keep in mind that B1S1 is stuck at like 472 and did throw a code P0134 for Insufficient Activity on B1S1.
At Idle: B1ST 50%, B2ST 2%, B1LT 25%, B2LT 25%
At 1500 rpm: B1ST 23%, B2ST -3%, B1LT 25%, B2LT 21%
At 2500 rpm: B1ST 52%, B2ST 1%, B1LT 11%, B2LT 21%
At 3500 rpm: B1ST 52%, B2ST 5%, B1LT 0%, B2LT 23%
Guess I'll get back to you when I get the other S1 sensor in... SMH
Thanks again
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do you have the tools to do voltage checks?
"an open mind let's knowledge flow in and wisdom flow out for a man who has neither never listens to those who have both".
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- Posts: 566
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"an open mind let's knowledge flow in and wisdom flow out for a man who has neither never listens to those who have both".
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- Posts: 566
- Thank you received: 140
"an open mind let's knowledge flow in and wisdom flow out for a man who has neither never listens to those who have both".
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