Can Installing The Wrong Thermostat Cause A Car To Suddenly Run Rough

Posted in Cooling Perfomance | Asked on Jun 1, 2010

I have a 1986 Chrysler LeBaron and it normally runs just great, but today I installed a 180 degree thermostat in it, as the old thermostat stopped working and the car was running too hot.

However, when I removed the old thermostat, I noted that it was a 195 degree type, and I fgured that there could be no harm in having it open at 180 in the heat of Summer, so I installed the new 180 degree unit since I had already bought it.

When I tested the car shortly afterwards after the installation of the new thermostat and fresh coolant, the car seemed to run rough for no reason other than I think it might be that the thermostat is opening too quickly.

Am I right or not? Could it be the thermostat is wrong in this case and causing the car to run rough?

There are 12 Answers for "Can Installing The Wrong Thermostat Cause A Car To Suddenly Run Rough"

  1. cheyenne95129 says:

    thermostat shouldnt make it run rough. Did you check the spark plug wires? might have loosened one or got water / coolant into the dist cap.

  2. bryan k says:

    you probably pulled a plug wire loose while installing it. the thermostat shouldnt have any effect on that rough running

  3. Mr. KnowItAll says:

    Sure can make it run bad.

    On computer controlled cars, the water temperature sensor is set to activate at a certain temperature. Generally 190 Deg. F.

    If you have a 180 Deg. thermostat, the computer never goes into what’s termed “closed loop” and allows the computer to control the timing, air fuel mixture, and other engine stuff.

    Put the proper temperature thermostat back in.

  4. pbleek says:

    I doubt its the thermostat, you bumped or disconnected something, sometimes just moving spark plug wires can cause them to crossfire or short out against a metal part.

  5. ADDIX A says:

    check your sparkplugs

  6. pimpjon says:

    like mr know it all said, it affects the computer and also you won’t get as much performance. because the way a motor makes power is through heat pressure, well the more heat that is lost through the coolant system the less heat is available to make pressure. just put in the right thermostat.

  7. ucantcme says:




  8. John M says:

    I had the same problem. You need to replace the MAP sensor. You probably have gotten water in it some how. You can try to dry it out, but a new one will work much better.

  9. jakeu1701 says:

    Sure, if you install it wrong. There are two ways to install it, the right way and the wrong way. The wrong way will lead to engin over heating.

    It is possible you knocked something else loose, but the spark plugs screw in, the cables could be loose, but you should be able to push them back into place easily enough.

    Bottom line, check the cables if you want to, make sure the thermostat is in correctly and, if it still gives you problems, take it into a trusted shop.

  10. snowmobiler488 says:

    on a newer car it could run rough….. one person previously answered saying computer controlled cars may not function properly….not trying to dis your car or anything but a 86 LeBaron is not computer controlled. for this car, all it will do is run it at a slightly cooler temp. check other possible problem spots first like plug wires etc. if you still cant find it, then you may try replacing the thermostat with the correct temp one but i doubt it would have any effect on your car.

  11. Perry F says:

    First off your car IS a computer controlled car, a 2.2L would be fuel injected, a 2.6 would be carbutated with computer controlled fuel metering. A 180 degree thermostat should work just fine, as the computer controls the fan operation and will regulate the colling by cycling the fan on at 212 degrees, then turn off at 200, I have had many Chrysler FWD car and run 180 degree thermostats with no problems at all. Second, the fact that it runs rough may be a head gasket issue, very common, or a worn plug wire, distributor cap , rotor, etc. problem, if you spilled coolant on the cap- it could be affecting the spark distribution, causing a misfire.
    You stated that the car was running hot! In my experience the thermostat usually fails in one of two ways, open or fully closed, not to say that a thermostat never causes a car engine to run hot, just not very often. Look at the engine oil and coolant and pull the spark plugs an “read them” look for one that has little or no deposits on it, like it was steam cleaned (from coolant burning in the combustion chamber).
    Chances are that the hot running condition is a symptom of a deeper problem, like a cracked head or blown head gasket, If you have the tools try pressure checking the cooling system for leaks, internal and external leaks will show up as a slow loss of pressure, most likely you have other problems.

  12. opossum says:

    the thermostat is not at fault, something you may have removed in order to replace the thermostat is a more likely cause
    (ie sensor electrical connector not installed or damaged terminals while reinstalling—–or perhaps something inadvertently damaged during repair)

Speak Your Mind

Tell us what you're thinking...
and oh, if you want a pic to show with your comment, go get a gravatar!