Skip the auto shop - Our mechanics make house calls

Q: My car rpm fluctuates slightly, during warm up and my temperature gauge also fluctuates intermittently.

asked by on

I bought this car used, has been running fine, but I just discovered recently after about 2 months of driving, that it doesn't maintain a steady rpm at times (not always). Rpm will go between 1200 and 800 during starting engine at different times. Also, when I engaged the transmission (especially in "R"), vibration is observed on the steering wheel. Though improves in the "D" shift position. However, after a few hours driving, these conditions are suppressed. The noticeable observation again, during this warmed up state is that I could see that the temp gauge needle fluctuates between coldest and normal working temperature of the engine (though never exceeds this level). This condition does not occur on every driving, say about 35% of all driving time.

My car has 239000 miles.
My car has an automatic transmission.

Hi, thanks for writing in. My first impression when you described the vibration is that you may have a bad motor mount. When you put the car in Drive or Reverse, the engine shifts slightly. If the rubber in the mounts is tired, it will transfer the engine vibration to the chassis of the car. As for the temperature gauge issue, it could be that your car is not warming up. If the thermostat was sometimes sticking open, it would prevent the engine from coming up to operating temperature. If the engine is not warming up, the injection system will remain in a cold running mode, producing a high idle. The best way to check if this is the case is to use a handheld non-contact thermometer on the radiator and the engine, you should be able to see weather the engine is up to temp, or if it may be an instrumentation issue. Replacing the thermostat is relatively inexpensive and is a good first step on temperature related issues. You can contact Your Mechanic and have the thermostat replaced at your convenience.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  • Home
  • Questions
  • My car rpm fluctuates slightly, during warm up and my temperature gauge also fluctuates intermittently.

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Vehicle vibrates while accelerating and stops when you take your leg off the pedal or accelerate more

I suspect you have a problem in a CV joint, or if you have the all wheel drive version; in a drive shaft. The joints that enable the shafts to move around can wear out and when they do, they...

Q: check engine light on, p0441, p0446, p0440.I was told i need a smoke test, to determine where leak is.Do you guys do that?

Yes, if a vapor leak from the EVAP system is suspected, if required during the diagnostic, the mechanic will apply a smoke machine. The codes you are referring to have many, many possible cause and so what you need is...

Q: ,my car has developed avery hard starting problem overtime and i am asking what could have gone wrong?

Hello, thank you for writing in. When it comes to a hard start there are several components which can add to the problem. If you had the starter bench tested, keep in mind these only measure it's ability to spin...

Related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...