SOURCE: Check engine light on
There are three kinds of gasoline engine misfire scenarios, first there is the "under load" misfire and there is the "at engine idle" misfire, and finally there is misfire continuously. All engine misfires exist because one of three things has occurred. First, a cylinder has lost compression, a cylinder needs a certain amount of compression to operate correctly. Second, the ignition system has failed or is failing intermittently, spark is needed at the time of compression to ignite the fuel air mixture. Third, the fuel air mixture is incorrect, proper mixture is needed for the ignition system to ignite fuel properly. If any of these conditions occur in the engine, the engine will misfire.
1. Low or no compression can be caused by
a. burned or leaking intake or exhaust valves
b. worn or broken piston or piston rings
c. worn out camshaft
d. wrong weight motor oil was installed holding the cam followers from adjusting
e. broken valve spring
f. failed head gasket.
2. Ignition system has failed or is failing
a. spark plug has fouled or is worn out
b. ignition coil
has failed
c. spark plug wires have shorted
e. engine control module coil driver has failed
3. Fuel/Air Mixture is incorrect
a. vacuum leak at the intake manifold
b. fuel injector has failed
c. EGR valve is stuck open
d. mass air flow sensor has failed
e. oxygen sensor has failed
f. air intake boot is cracked
common problems:
1. fuel injector has failed or is failing
2. spark plug wire has shorted
3. spark plug is worn out or is cracked
4. ignition coil has failed is failing
Testing a coil on the car is pretty easy. No special tools are required. Just remember to be careful, the amount of electricity generated by your ignition system can be dangerous.
If your coil is already off the car, or if you would like a more specific data-driven test, you can bench test your coil. To set up the test, remove one spark plug wire from its plug, then remove the spark plug using a spark plug socket. Next put the spark plug back into the spark plug wire. Be careful not to let anything drop into the empty spark plug hole -- very bad.
SOURCE: 97 Camry Rough cold idle, weak accelleration and noisy exhaust
Lots of times the idle air control valve gets stuck on these engines. You can try cleaning it. Remove the air intake hose from the throttle body. Start the engine and spray throttle plate cleaner through the hole in the bottom on the throttle body. This will run the cleaner through the idle air control valve. make sure to keep the RPM's at about 2000 to 2500 throughout this procedure. You may need to install a new idle air control valve if it continues to happen.
SOURCE: Very Rough Idle and sometimes cuts off while idling
sounds like bad Idle Air control valve Not Cheap
SOURCE: rough running, erratic spark
Run a compression test on the cylinders.If reading is low on any drop a little engine oil into the pot. If compression rises you have compession ring problems. Remove all plugs before you try this and place leads away from engine.
SOURCE: Check engine light comes on temporarily - engine chuggs at idle
Before changing you pcm try cleaning your egr valve. remove the valve and see if its stuck in the open position if so use a small pick to clean around the spring.
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