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Showing results for tags 'lean'.
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Hello. I have a Silverado 1500 4.8L base model with 200K miles. I could use some guidance on how to troubleshoot two engine codes that my truck has. P0101 and P0171. I erased the codes, unfortunately. This is what I have done thus far: -Inspected the Air filter (it is clean) - Cleaned the MAF sensor with MAF cleaner. - The MAF values are responsive to changes in engine RPM. I don't have any special tools to check for vacuum leaks. I Took live readings with my Zurich ZR8 code reader The LTFT1 and LTFT2 hover around +14% when engine warm and idling around 600 RPM. Drove around a little and LTFT1 and 2 rose as high as 21%. MAP - 11 Hg MAF reads 0.52 lb/min TPS reads 9% Update 9/5/2021: I tested the fuel pressure and it is in the normal range, 58 while idling, a bit lower with the key in the "On" position. While running the engine, In short bursts, I sprayed brake cleaner around the air intake hoses and gasket and listened for changes in the idle pitch. Admittmedly, I may not have hit every crevice while doing this. No leaks detected. What are my next steps? -
If anyone knows of a previous thread that explains similar symptoms please let me know, I haven't been able to find any. I have been getting a CEL for p0171(lean bank one), p0405 (egr), p0449 (evap vent seloniod), and occasionally p0174 (lean bank two), and p0430 (cat system efficiency below threshold). It makes sense that all of these codes could come together so let me explain a little bit of what's going on. I bought the truck last fall with about 200k miles, and unfortunately had to have the trans rebuilt so I am trying to avoid throwing parts at it and hoping it fixes the issues. When I bought the truck there was a code for the evap vent seloniod, which as far as I know would more than likely just make it so that the gasses can't excape when fueling and casuse me to have to hold the handle so I haven't been in a huge rush to replace that. There were exhaust manifold bolts broken in the block so I decided to put shorties on while everything was apart since they were relatively inexpensive, but these didn't have the port for egr and I bought the egr block. When swapping the manifolds, I found out the collector on my y pipe was cracked and plan to drop that down and weld it up when it gets warmer out. So I expect those two codes. As far as the cat efficiency being off, that has only came up a couple of times and I haven't quite gotten a chance to figure out anything that happens consistently before that. When it was real cold my truck would somewhat surge when stopping at stoplights. Now the bank one too lean code is the one that concerns me the most. For some reason the bank two lean isn't as common, and is usually just a pending fault and not a current fault like the bank one is. I thought maybe the lean codes could be from the known exhaust leak but that seems inconsistent with the bank having most trouble. Monitoring my fuel trims using torque pro I found that my long terms were pegged at 25 and the short terms were even higher. The short terms dropped when I revved the engine up to around 2500 and I could hear a slight Rev when spraying the intake with brake cleaner. This was on the passenger side, near where the egr was. It was close to the throttle body, and a new gasket was super cheap so I decided to clean the throttle body and clean the gasket which didn't do much if anything for me. Everything I came across looking at fuel trims led to vacuum leak, so I thought maybe the maf was bad so I tried a new one which didn't change anything either. I put the old one back in and removed the egr block flipped the o-ring around and that seemed to help for a day or so. But it came right back to where it was prior, so thinking it could also be a fuel issues I checked the pressure with a loaner from oriley's. Originally the key off pressure was up near 55 psi, the I turned the engine over and the pressure was around 45. After revving it was around that range still. I let the pressure off the tester and turned the key back on and this time the pressure was getting up to about 30 and then coming to about 25 after starting The gauge could have bad calibration, or I could have a fuel delivery issue. Anyways I have not noticed any misfires, nor have I gotten any misfire codes. My fuel trims remain high at idle (ltft 25%, stft from - 3% to around +10%), and lower when under load, especially if I'm actually driving. I was assuming that if it was a fuel issue I would see the fuel trim higher under load and more normal when idling? Any suggestions as to what else I could do to try to narrow this down and avoid taking it into the shop? Sorry for the wall of text, but I wanted to explain the best I could as this doesn't quite seem to be making sense.
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So I drove my 96 Chevy k1500 with the 350 vortec over a train track like any normal day and all of a sudden my truck is shaking real bad. I managed to get it to a friends garage nearby but I couldn't accelerate. It would only coast. It was running really lean and would fall flat on its face when i gave it gas. It had low fuel pressure so changed the fuel pump and fuel filter. It drives a lot better now but it still starts to fall flat when I try to accelerate too much. I still can't figure out why it won't accelerate. So far I've replaced my... Fuel pump Fuel filter Idle air control valve Elbow tube on the pvc Breather tube grommet Spark plugs and wires I put a new mass air flow sensor on it and that only made it drive worse. What else could it be?
