What are some things to replace when a car hesitates at low rpms?
First off figure out and diagnose why its doing that, or else you wont have a clue what it is or else youre going to just be throwing parts at it and money down the drain by just simply guessing. From my experience its not one cut and dry answer It could be lots of things. Most likely if it has a carburetor the carburetor needs an adjustment, or spark plugs are old and worn out, air filter is possibly worn out and clogged with debris so its restricting the airflow. Oxygen sensor is a possibility. Or it could be a fuel filter/injector clogged/ fuel pump blocking proper fuel flow. The catalytic converter or exhaust could be clogged up with carbon deposits, but i doubt that. Lastly if its really high mileage like 200,000–400,000 miles and it could just simply be old and worn out and the piston rings arent sealing very well, so its low on compression which will make most engines low on power but thats pretty unlikely especially if youve taken good care of it, done oil changes on time and its maintained. All these items are consumables, they are regular car maintenance repairs. Its amazing how much better a car will run when you replace all those things and wear out over time. Take it to a reputable ase certified mechanic or if the car is under warranty go to the dealer. Or if you got a buddy thats good with cars take it to him. The good news is its usually something simple, and all those things arent hard to fix unless its the fuel filter/fuel pump. tell me how it goes. Good luck dude!
If your car blew a head gasket, would the check engine light always come on?
No. Watch for white ‘smoke’ from the tailpipe always and if the engine’s performance has changed in some way look for this. The ‘smoke’ is essentially steam from water getting into the cylinders.You will often see this on start up but that should only be natural moisture evaporating out of the exhaust system. If it doesn't stop soon after you are underway then something may be wrong.Keep after your coolant level and see if there is a constant reduction.If the engine begins to have trouble turning over at start up, this could be a gasket leak that is percolating coolant into a cylinder(s) while the engine is at rest.And note that airbags won't always work, good ‘idiot’ light or not, so folks please STOP depending on brakes (which can also fail) to save only YOUR life, and to not roll up on people at 50 mph at a stop sign or red light, who are walking across the street or driving and checking traffic or waiting for that light…or an emergency vehicle. :p