my 1989 silverado 305 has 383,000 km's on it and it starts up fine but it idles high and low and it fluctuates when it is just sitting there, when you put it in to gear it goes into a low idle and stalls.
any help would be greatly appreciated
NEED HELP! 2005 Silverado Idle Problems
Re: 1989 silverado running problems
Well, with that many miles it could be number of things. From just an old worn out engine, to ignition problems, fuel delivery issues, throttle body problems, etc.
You might want to start by making sure the air filter is clean, there are no restrictions, make sure the fuel filter isn't clogged, etc. These are things that would make it idle low and/or fluctuate. You might want to also check fuel pressure, as the pump could be going bad and not producing enough pressure/volume.
Throttle body gaskets have been known to crack and cause a vacuum leak, which also can cause idle fluctuation. Check for any other causes of vacuum leaks as well such as cracked or dry rotted lines, hoses, and connections.
A check for any trouble codes as well would help tell you if there is a specific issue that needs addressed.
You might want to start by making sure the air filter is clean, there are no restrictions, make sure the fuel filter isn't clogged, etc. These are things that would make it idle low and/or fluctuate. You might want to also check fuel pressure, as the pump could be going bad and not producing enough pressure/volume.
Throttle body gaskets have been known to crack and cause a vacuum leak, which also can cause idle fluctuation. Check for any other causes of vacuum leaks as well such as cracked or dry rotted lines, hoses, and connections.
A check for any trouble codes as well would help tell you if there is a specific issue that needs addressed.
GM Dealer Technician For 18+ Years
In the automotive industry for 20+
In the automotive industry for 20+
Re: 1989 silverado running problems
Thanks, could it be the headgaskets? The engine overheats and there is no coolant flowing through the upper rad hose
Re: 1989 silverado running problems
Well that changes the story quite a bit!
Of course if you have internal engine issues that can cause a lot of different problems. If you do have something like a head gasket issue, you may as well be prepared to replace the engine or get rid of the truck. There is no chance of having a head gasket job turn out well on an engine with that many miles. You'll blow the bottom end out of it for sure.
Of course if you have internal engine issues that can cause a lot of different problems. If you do have something like a head gasket issue, you may as well be prepared to replace the engine or get rid of the truck. There is no chance of having a head gasket job turn out well on an engine with that many miles. You'll blow the bottom end out of it for sure.
GM Dealer Technician For 18+ Years
In the automotive industry for 20+
In the automotive industry for 20+
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NEED HELP! 2005 Silverado Idle Problems
This is nothing new to my 2005 4.8L Silverado. Usually the problem came and went but now it's staying. As soon as I crank my truck the electric fan cuts on and idles rough. As soon as I start to drive and apply throttle the temperature gauge goes from min to max (typically stays at 210) and the engine almost dies and cuts off, almost like it has bad gas. When I idle in drive the truck revs up and begins to speed up. Have big plans for the truck so I need help as to what to check or replace! Thank you!
Re: NEED HELP! 2005 Silverado Idle Problems
First thing I would do is hook up a scanner and see what your engine coolant sensor is doing. If there is a short to ground, it would read over 300 degrees F. That would throw off your fuel mixture because the computer reacts to the temperature. Unplug the coolant temp sensor and see if the temp goes to -40F. that's what the open circuit should read. Plug it back in and see what the reading is. If it shoot all the way back up you probably have a bad sensor. If it reads normal, check the wiring to see is you might have a spot that is rubbed through somewhere and shorted to ground.
If you hook up a scanner and the temperature shows a good actual engine temp then look at your fuel trims and O2 sensor to see what they are doing when the truck is acting up
If you hook up a scanner and the temperature shows a good actual engine temp then look at your fuel trims and O2 sensor to see what they are doing when the truck is acting up
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