My 98 Chevy Blazer when I start it up, it idles at almost 3000rpms. I shut it off and restart it and same thing. It did this on Thursday while driving, but it stopped after awhile. Worked fine Friday and Saturday, but its doing it again today. Any ideas?
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is commonly caused by a dirty automatic idle speed control valve and
throttle valve. Buy a can of throttle valve cleaner from NAPA or
Carquest (made by CRC chemicals) and spray it into the air intake
while the engine is running, use up about 1/2 the can, engine will
try to stall hold the speed up, shut it down and let it soak for 30
minutes, restart and blow out the remaining fluid, shut it down and
disconnect the negative battery cable for 5 Min's to reset the base
Check for fuel pressure and check for spark during the no start condition. Also check the crank sensor, it is located behind the crank pulley mounted in the engine block on the 4.3 L engine I hope this helps.
Try giving it a shot of starting fluid. You don't say if it's actually firing. If it tries or runs for a few seconds off of the starting fluid then try changing the fuel pump relay. It's inside of the glove box on the left hand side behind the little door. If that doesn't work it's most likely the fuel pump.
I had a similar problem on my "93 Ford probe. The engine idled pretty rough with shakes, Turned out to be a head gasket leaking engine coolant into the cylinder during low rpm's. At fast rpm's it was fine becuase the internal cylinder pressure was greater than the hot coolant pressure & would prevent the coolant from leaking in.
A friend has the same problem with his "94 Blazer 4.3 L, throttle body injection, manual tranny. He hasn't fixed it yet, It started a few weeks ago & is getting worse. His gets a fast idle with hiccups which causes the engine shake. He already checked the EGR valve. He also has a severe exhaust problem, Not oilly but very gray & terrible smelly, but only when the fast idle problem happens. THis fast idle hiccup problem starts when the engine is warmed up.