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i am working on my 2001 Tahoe with 5.3L Vortec engine, this is going to be case trial which i will be working on at home.. wanted to share with you all and maybe we can have interactiver discussions on where to start and best ways to tackle it.
The engine does feel like it is having a misfire which is confirmed by trouble code P0305 which is a misfire at cylinder 5 (The code was there but no SEL set). Flood starting the engine did feel like there is a compression problem which i need to confirm with a scope later (still didnt get my amp probe) or with my pressure gauge.
Other checks were with both O2 sensors, for Bank 1 did show on the computer as working properly as it did swing between 0.0350V and 0.9350V. bank 2 did swing between 0.0300V and 0.940V.
Fuel Trim checks on Bank one by adding both the Long Tirm and Short tirm was mostly in the range of +-10% but did go upto 20%
Fuel Trim checks on Bank two by adding both the Long Tirm and Short tirm was mostly in the range of 5% to 15% but did go upto 25%[url=http://alfaris.net/up/86/alfaris_net_1350292744.JPG]
the strange thing here is why is the FT on bank 1 more stable than bank 2 while the problem is on Cylinder 5 which is contributing to bank 1?
also, the car did pass the emissions test two weeks ago.
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Try swapping coil packs with another cylinder and see if the problem follows the coil pack. While you are doing that inspect the wires running to the fuel injector for any signs of damage and if the plugs have been in there for a while you might want to pull the plug on cylinder 5 to see if it is burning correctly. If you swap coils and the problem stays with cylinder 5 you will need to do some more testing but if it moves to the other location the coil may be getting weak. I am not sure why the fuel trim is more stable on bank 1 but I would start with the less complicated stuff and work my way up. Hope this helps.
what i did was just took a log of live data while i was on my way work… i will be using another scanner to see the live misfire info…
i will be doing a vacume leak and compression test, Spark test on each coil and test the fuel Injectors as well.. i dont really 100% trust the PCM for giving the right info thats why i want to confirm all of this first..
I’ve been here with the same engine. FYI I’m told there are known issues with the cylinder management system so it could be an issue involving that system if you have it on that engine. Personally since I’ve run into this and I hear it’s not uncommon I would start with that compression test or a leak down test.
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