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I'm currently down with the flu so I am going to try my best to type coherently lol.
I've had this 03 Silverado 1500 4.8L from 211k to 260k miles and I cant lie these things will never stop running. Everything is stock except a half rusted out flow master, thought I would add this as it could play a role in my problem. Im wanting to sell it now but i have a problem i have to fix that im clueless on. Sorry for the long description, I just think more details will help you guys.
In my time of owning the truck, intake gaskets about 35k ago, coil packs, wires, plugs, 02 sensors about 25k ago, fuel filter a month ago, and thats about it for mechanical maintenence. One problem ive had with this truck for the longest time is that it likes to misfire when heated up quickly i guess i could say. It doesn't throw a solid engine light however as i think its because i know how to make the truck stop misfiring. Here is my best description for when the problem occurs. While at my moms house, living in a neighborhood, I can always start the truck in the morning give it a couple mins and be on my way with no problems, truck runs strong. However at my dads house, living off a state highway, for some reason, when the truck warms up faster than neighborhood driving it loves to misfire and it will run like a pos and drive me nuts. This will happen any time of the year and only when I get on a road that is 60mph+ where the engine is revving more/heating up to operating temps quicker. If the misfires go on long enough though, the engine light will stay on with codes for random multiple misfires. When it does misfire, if I coast the truck in neutral and give it some nice 5500rpm jabs on the throttle, 1,2 maybe 5 or 6 times, the misfires will stop and it will run like a champ. I have no idea if a vacuum leak could be causing this as I have never been able to fix it/only deal with it. Maybe I screwed up the manifold gaskets but I'm not sure, this is my only thought on what could be going wrong. Spraying carb cleaner around the gasket causes no change in rpm but this is my only method to test for vacuum leaks because nobody rents/sells smoke testers or vacuum testers at all for some reason. I would like to know there is no vacuum leaks first for peace of mind I have just never been able to correctly do it. How can I go about this without solely relying on the carb cleaner test. Its just so weird to me how the truck will run perfect sometimes then like a pos other times, from what I notice, heating up quickly.
Any help/suggestions will be greatly appreciated as this annoys the crap out of me and I would like to send this down the road.
Any help/suggestions will be greatly appreciated as this annoys the crap out of me and I want to send it down the road.
Last edited by Jacob11531; February 10th, 2020 at 11:32 AM.
Like I said, when the truck is taken on the highway and heats up quickly, for some odd reason it loves to misfire, unless I coast it in neutral and give the throttle some high revs to make the misfiring stop like I have been, it will hold a solid engine light. The codes I will get are a random multiple misfire and bank 1 bank 2 lean. The more I think about it, I have a hard time believing its a vacuum leak because it will only happen on that initial drive on the highway and not the neighborhood. Just maybe a sensor or something? Definitely cant be simple to say the least.
Are you able to monitor the misfires in real time with either a code reader or an OBDII dongle and a smartphone app like Torque Pro? If you have normal power brakes, have you inspected the vacuum hose that goes between the vacuum booster and the intake manifold to make sure it is not cracked and leaking?
Unfortunately no. I don't have access to a reader unless I can rent one which I doubt is possible or end up having to buy one which I'm sure is expensive. The line off the brake booster is tight and has a hose clamp as well.
). I have two of them and they are worth their weight in gold!!!! Then, providing you have an android smartphone, purchase, download and install Torque Pro. This will allow you to monitor many, many engine parameters such as misfire counts by cylinder, engine coolant temperature, MAP pressure, etc. It will be of major assistance in helping track down the problems you are experiencing. This way you can logically track down the source of a problem rather than just replacing parts in a shotgun manner.
If I were you, I would order a BAFX OBD II scanner (https://www.amazon.com/BAFX-Products...s%2C218&sr=8-5). I have two of them and they are worth their weight in gold!!!! Then, providing you have an android smartphone, purchase, download and install Torque Pro. This will allow you to monitor many, many engine parameters such as misfire counts by cylinder, engine coolant temperature, MAP pressure, etc. It will be of major assistance in helping track down the problems you are experiencing. This way you can logically track down the source of a problem rather than just replacing parts in a shotgun manner.
February 10th, 2020, 11:26 AM
03 Silverado Misfire Help
