I have this problem on idle running. After 1 minute from starting when the RPM becames lower (800 RPM) the motor gets shacking with regular cycles of 3-5 seconds and at intervals of 30 seconds the RPM becomes higher (2000 RPM) for 5 seconds and again from the beginning and so on. I replaced the Throttle Position Sensor, the IAC valve, the ECU, the spark plugs. The car doesn't have EGR valve.I checked the vacuum lines and seem OK, I measured the vacuum pressure and it is about 10, I checked the cylinders pressure and it is same for all five.
Have you checked your MAF/MAP sensor, or your fuel pressure or fuel pressure regulator. Are your throwing any codes at all? I would also look at your Cam & Crank sensors. Good Luck!
I checked all the codes and fixed everything with no luck. I will look into checking the MAF/MAP sensor and pick up a FPR tomorrow. We replaced the crank position censor last time we did a tune up as the error had come up for that so we know it should be good. Thanks for the wishes, I will update later.
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SOURCE: 2000 Subaru Legacy will not start
If you find that the engine is dying at intersections and runs a rough and fluctuating idle at start up, and you also sometimes lose power even though the engine is running then it is probably your Air Flow Meter or sometimes reffered to as a Mass Airflow Sensor. Eventually, as the AFM deteriates further you will no longer be able to start the engine as the ECU can no longer get accurate flow readings to work out air fuel ratios and shuts it all down to stop damage occuring. 2 ways to fix, replace AFM or upgrade your ECU to one that is capable of running MAPs for air fuel ratio, rather than using a sensor. Hope this helps.
SOURCE: Car won't start and floods
Locate your vehicle's computer connector (ALDL), most are on the lower driver's side. In some vehicles you might need to look around a little, on the passenger's side, and around the center console under a plastic cover. For more information, check your owner's manual. This device gathers information that was stored in your carsECM. This information ortrouble code can inform you the system or sensor that is malfunctioning. Look up the code in our diagnostic trouble code chart. After repairs have been made use the code scanner to clear trouble codes and recheck system.
B. Testing Fuel Pressure. Test for proper fuel pressure with a fuel pressure gauge. Connect the gauge to the test port on the fuel rail. Fuel pressure reading's very depending on the system your in our vehicle, but most throttle body injection cars (TBI) are between 13 psi and 17 psi. and most (DPI) direct port injection systems are between 40 psi and 55 psi. To find out your vehicle system fuel pressure consult arepair manual. If little fuel pressure is present the fuel pump needs to be replaced.
C. Test for Weak Ignition Spark. A weak ignition system can be a sign of a failing ignition component. Remove spark plug wire and insert an extra spark plug into end of wire, attach spark plug to engine ground then crank engine. You should observe blue spark between spark plug gap. If a yellow spark is observed, your ignition coil is weak and needs to be replaced. If your spark is not consistent you may need a ignition module.
D. Inspect the Main ECM Relay. If the ECM relay fails it will shut down the engine management system. This relay carries high amperage and is prone to failure. To test install new relay then test drive to recheck symptoms.
E. Testing the Ignition Switch. This test requires a electronic test light. When vehicle dies test the power side (+) of your ignition coil with the key on, the test light should illuminate. If your test light is not lighting suspect your ignition switch or ignition relay. To trouble shoot this condition you will needwiring schematic for your car.
SOURCE: 91 LEGACY STARTED RUNNING ROUGH
The cylinders are numbered as on the spark pack you changed. You might have done better putting the seafoam in the tank as an injector cleaner. Not sure why you changed so many parts, you seem to know how to get the codes from test connector lead hookup and the blink pattern. You might also want to check the fuel rail pressure and the crank and cam angle sensors. Before replacing the injector, swap the #4 injector with the adjacent one and see it the code moves with the injector or stays put. If the code stays on #4, then check the injector wiring, if it moves clean or replace the injector.
SOURCE: subaru legacy gt twin turruns like it only running on 3 cylinders
nee to test fuel injectors and watch engine electronics thru a scanner? another thing you might check is the airintake rubber bellows goes from air cleaner to engine for cracks or leaks? if all that checks out run a compression test ?
SOURCE: subaru impreza rs 2.5 insanely high idle
check you dont have a split in the corrugated pipe from the maf to the swirl chamber (the big black plastic tank attached to the inlet manifold) or a leak into the intake somewhere, doesnt have to be a small vac tube.
Also you may have a sticking TB butterfly as my learned friend suggested.
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