High rpm while driving

Reasons the Temperature Gauge Reads High

If the temperature gauge reads high, it could mean your engine is overheating. Another reason your reading might be high is you could be losing coolant. A small leak or evaporation may cause your radiator to slowly lose coolant. A third reason your temperature gauge reads high could be because the thermostat is broken. If this is the case, you may need a coolant temperature switch replacement. The last reason the temperature gauge could read high is because of a water pump, or water pump gasket failure. If the water pump is malfunctioning, it may need to be replaced by a professional.

What to Do If Your Temperature Gauge is High

If your temperature gauge is reading high, it means your car is overheating. This is a very serious matter and you should never drive an overheating car. If your car starts to overheat, shut off the air conditioner and open the windows immediately. If this does not reduce the overheating, turn on the heater as high as it can go. If this still doesn't work, pull over on the side of the road, turn off the engine, open the hood carefully, and wait until the vehicle cools down. Never open the radiator cap while the engine is hot - coolant can spray and burn you. Once the vehicle has cooled, take the car to a mechanic right away so they can diagnose the problem. Cars are especially susceptible to overheating in hot climates, like what's common in cities like Los Angeles, Phoenix, Las Vegas, or Atlanta.
The temperature gauge is an important tool in your vehicle that shows the temperature of your engine's coolant. Contact YourMechanic and have your car inspected for overheating if it reads too high, as this can cause serious problems...

Reasons the Temperature Gauge Reads Cold

On most vehicles, the temperature gauge reads cold until the engine has run for a few minutes. If the temperature gauge still reads cold after the engine has warmed up, the gauge may simply be broken. Another reason the temperature gauge could read cold is if the thermostat in the vehicle stays open. With the thermostat stuck open, the engine can be overcooled, causing a low temperature reading. If this is the case, the thermostat may need to be replaced.

What you are describing sounds normal. RPM's stand for revolutions per minute. Each minute your engine is running, the pistons are going up and down. When you are not going anywhere, your engine is idling and so the RPM's should NOT be very high. However, when you race up a hill, your RPM's SHOULD be high because your engine has to work hard to climb the hill or to go fast.
Idle speed= 650 Revolutions Per Minute. That means your engine cylinders each work 650 times in One minute.
At freeway speeds, your engine will revolve somewhere between 1600 and 2100 times per minute. I hope that helps.

Is your over drive working ? If not that wuill make it use more gas.

Possibly but to find the fault have the fault codes read . It may be the accelerator position sensor . Don't waste money until you have the codes to point you in the right direction

Are you sure the gauge is reading correct? You also didn't mention how many miles the vehicle has. If it's less than 150k I would doubt the motor it worn out, (excessive bearing clearance would cause poor oil pressure even with high volume pump). Chevy's have a lot of issues in the dash with the motors that make the individual gauges work. I would check the oil pressure with a manual gauge. If you don't have the skills to do this yourself, a qualified shop wouldn't charge much to do it. If you find that the gauge is incorrect, there is a guy in MN that rebuilds the instrument cluster for $65 with all new stepper motors (the motors that work the gauges) and replacement of all the bulbs, plus gives it a lifetime guarantee. www.speedometerrepairguy.com.

While the engine runs hot there is a possibility that the RPM sensor goes off and shows the wrong reading. First of all check the cause for the overheatting before we can go further.
Some tips were given in your earlier request.

Normally 4 wheel drive HIGH is engaged on the fly or as you are moving more than 10 km per hour or 10 miles per hour but 4 wheel drive LOW is engaged at around 3 to 5 mph. no more or you could ruin the transfer case. Try going from 2 high to 4 high by switching back and forth and then try 2 high to 4 low when idling along. What usually happens is the mechanics under the car freeze up or rust up and you have to switch back and forth to free it up.

I have a 99 blazer and ever since I have owned it, it reads lower in pressure when idling, but will go up too 40 while driving. This is normal for the vehicle. If the pressure gets real low, and stays low, it means its time for an oil change.

As long as the pressure goes up when you give it gas, it is fine.

If grounding the dash does not work, try putting a mechanical gauge on it and reading actual oil pressure. Pressure does change while driving, but should not wander. With mechanical gauge, check that running hot at idle (in gear if automatic) pressure should not drop lower than 15psi (I'd rather see 20) High reading should be around 40 -50 but no higher.Low pressure indicates a loss of supply or bad bearing on the crankshaft, high pressure may be caused by sticking pressure relief or restriction in an oil passage.

At idle, at operating temp is there any ticking from top end of engine? Are there any knocking noises brom bottom end?
If no noises, change oil and add some Marvel oil to clean out galleys. If that dosent work, change oil pressure sendingf unit. Also, if you have a mechanical oil pressure gauge, hook it up and take a direct reading. Oil pressure (in any vehicle) at idle should NEVER be less than 15psi. Generally in 4.0 jeep engines it's never less than 30, with a high reading at driving rpm of about 40-60! (but, you did not mention what engine you have)