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hey guys and gals got a question for yall. i just got this car in today for just a fuel filter change. they said the car would stall every time you came to a stop. the fuel fitter looked like it never been changed so i told them to try that. well the car gets here today for me to do it and it was over heating when they pulled up. and it runs now while at a stop but it has a bad knocking sound. coming from thue back of the motor towards the middle it sounds. it almost sounds like a busted rod. not sure though. it almost sounds like a hammer hitting cast alum. n ow the knock is not constant only when your on the gas. please let me know what you guys think and as always thank you in advance..
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Try to isolate the noise to a certain area with a mechanics stethoscope or a long screwdriver(put your ear on the handle). You say it only happens on accel? Rod knock is usually more pronounced on decel. Can you post a video of the sound for us? How is the oil pressure? is the knock Rpm dependant?
it is important too note that a slight knock or tick is common in the 3100 SFI V6, or 3.1, the engine had issues with clearances between the pistons and the cylinder walls and over time excessive clearances would develop, when the engine is cold started at cold idle the pistons will slap agents the cylinder walls causing a ticking noise, this can get quite noisy at start up.
if the noise persists or worsens as the engine warms up then i would become concerned, but let the car warm up too operating temperature and drive it a little, and if it goes away and quiets down it is probably piston slap, in this case it should be fine, just take it easy on it when it is cold, it may burn a little oil so add some, other than that and the intake gaskets on these engines they are relatively tough engines.
hope this helps also follow up with Chevyman21s recommendations.
It doesn’t sound good. You might pull the plug wires one at a time to see if the noise changes or goes away. If it does on a particular cylinder, it’s likely something in the engine. More info here.
http://www.ericthecarguy.com/faq/diagnosing-noises-in-your-car
sorry i tried doing it from my phone did not work so well lol. im a pull the plugs today and see what happens. thank you for all your help
Good chance it is going to need internal engine repairs.
It has overheated and we know how much engines enjoy that.
You said you run a shop. Do you guys do engine rebuilds?
A little knocking is one thing but a hammer hitting aluminum? That is a horrible noise.It might be “something simple” but one should not bank on it.
Other things – did they change from conventional to synthetic oil? That is asking for problems on older cars.
Is oil pressure up to par?I’m not sure if it’s allowed if not I’m sorry. Here is a like to the motor running on YouTube let me know why you guys think. I pulled the wires no change
You might have to copy and paste it
definately sounds like internal engine noise, connecting rod, lifters, kinda hard to accurately pinpoint with video.
FYI if engine was not knocking,common stalling problems on those engines where caused by fuel injectors on the front bank with resistance below 11.6 ohms, also depending on which transmission the torque converter lockup solenoid would cause a stalling also.That is something internal. You can make sure all cylinders are at least firing and maybe compression test. But yeah, something inside is NOT happy.
With the injectors –
The resistance test is easy enough. Sometimes it is possible to test it at the plug itself but better to just do so at the injector.The TCC solenoid – ohhh yeah, VERY common failure for the 125C (FWD 3 speed automatic GM) The way to test for that is to disconnect it, drive it at least 45, and see if it no longer stalls at lights. Replacing it is not a horrible job usually, the trans doesn’t have to come out but the side pan does need to come off and THAT is where the fun begins.
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