I need some help I’m not a mechanic totally but I have been going to school for it and my 03 Silverado 5.3 is misfiring and I don’t know what the problem could be I replaced the spark plugs coils and all the cylinders are getting spark and I had a compression test and the the cylinders have near perfect compression so I don’t think it’d be that. I even replaced the ecu/pcm in it and nothing changed it’s a hard idle and had no power can’t even make it a block really it also dies when I hit the brakes after going anywhere over 5 mph.
By Chuck B.
Anyone know what this noise is? It's very intermittent. Seems to do it most often between 40 and 50 MPH cruising with maybe a slight up hill. Never does it on coast or heavy acceleration. Very hard to tell where it's coming from.
2014 Sierra Denali 1500
Crewcab, 5'8" bed
3.42 axle ratio
about 118,000 miles
I have a 1993 GMC Sierra C1500 v6 4.3L with an automatic transmission and i have tried replacing the distributor cap, router button, spark-plugs and the module that sits under the distributor cap but nothing works it just rolls tries to kick and if it does start it dies instantly. also when trying to start it smoke rolls out of the throttle body I have no clue how to fix this
Our 2017 2WD Colorado Z71 with 33k miles started making a knocking sound at low speed, worst at around 20mph, sometimes more noticeable than others. First the dealer put it down to normal tire noise, then a few months later when the noise got worse said it was cupped tires and that we needed to replace them. They recommended less aggressive tires as the "stock" all terrain tires always cup and make noise apparently. So, we had a new set of tires put on and the rhythmic thumping was still there, more obvious now that it wasn't masked by tire noise. The noise seemed to come from the front of the car and was noticeable at low speed 10-20mph and would speed and slow with the car. Once you're tuned into it you can hear it/feel it around 40mph too but its more of a vibration.
Took it back to the dealer and test drove, they heard the knocking and decided to replace both front hubs under warranty. When we picked the car up they said the noise was gone other than normal truck noises, on the drive home it obviously wasn't. In fact it's worse under some conditions.
Now it seems that either the problem is getting worse or we're hearing/feeling things that aren't there. The knocking has become stronger but only sometimes, and at highway speeds it feels like the whole truck is buffeting and vibrating. It also seems to be slipping gears, or shuddering between changes at low revs.
Having taken it back tot he dealer they say there's nothing wrong, they can't hear or feel any problems, and to be fair to them the knocking was less noticeable when I drove it with them but the vibration and shudder was there. I did ask to drive a new one so I could feel the difference and perhaps it's just normal but they didn't want to do that.
I've now left it with them and asked them to test drive it more and if they're happy there's no problem then I'll pick it up and if it comes back I'll take it somewhere else for an independent test.
We're 100% sure on the rhythmic knocking/thumping, especially as it's the same issue before and after the tires and hubs were changed, perhaps this is normal. As for the vibration and buffeting we're less sure, it does seem like it's slipping gears and shuddering but after so much focus listening to the thumping perhaps we're just seeing problems where none exist.
Does anyone else have any similar experiences, or are we truly just going a bit nuts?
Currently in the process of trouble shooting a p0304 code. Ruled out a bad coil pack by hooking an ohm meter to it and also swapping cylinder 2 & 4 to see if the the Mis fire would follow. Replaced spark plugs, plug wires, and put a can of sea-foam in the intake. Not hearing any abnormal sounds coming from the engine while running. Just a steady misfire on 4. I’m thinking it is a bad injector. Anyone else experience something similar, and to also see if anyone yet has tackled changing the injectors on the new models. Thank you
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