Car Starts But Engine Won’t Rev

Symptoms

* The car starts and idles normally.
* When you try to accelerate, the engine doesn’t rev up.

Causes

There are several possible causes for this problem:

* **Fuel system problems.** A clogged fuel filter or a faulty fuel pump can restrict fuel flow to the engine, causing it to stall or run poorly.
* **Air intake system problems.** A clogged air filter or a faulty mass air flow sensor can prevent the engine from getting the air it needs to run properly.
* **Ignition system problems.** A faulty spark plug or ignition coil can prevent the engine from getting the spark it needs to run.
* **Exhaust system problems.** A clogged catalytic converter or a faulty oxygen sensor can prevent the engine from expelling exhaust gases properly, causing it to stall or run poorly.

Diagnosis

The first step in diagnosing this problem is to check the fuel system. Disconnect the fuel line from the fuel filter and see if fuel flows out. If it doesn’t, the fuel filter is likely clogged and needs to be replaced.

Next, check the air intake system. Remove the air filter and see if it is clogged. If it is, replace it with a new one.

Next, check the ignition system. Remove a spark plug and connect it to the ignition coil wire. Hold the spark plug against the engine block and have someone crank the engine. If you don’t see a spark, the spark plug or ignition coil is likely faulty and needs to be replaced.

Finally, check the exhaust system. Remove the oxygen sensor and see if it is clogged. If it is, clean it or replace it with a new one.

Repair

Once you have diagnosed the problem, you can begin to repair it.

* If the fuel filter is clogged, replace it with a new one.
* If the air filter is clogged, replace it with a new one.
* If the spark plug or ignition coil is faulty, replace it with a new one.
* If the oxygen sensor is clogged, clean it or replace it with a new one.

Prevention

You can help prevent this problem by following these tips:

* Change your fuel filter regularly.
* Change your air filter regularly.
* Get your spark plugs and ignition coils checked and replaced as needed.
* Get your oxygen sensor checked and replaced as needed.