Subaru Problems? Ask a Mechanic for Answers ASAP
Hi, I'm Chad. Welcome to JustAnswer. I'm reviewing your question and I will be posting your reply ASAP.
is there check engine light on at this time ?
have you scanned for fault codes & do you have them ?
have you checked for vacuum leaks ,especially air hose from air box to throttle body ?
what is the mileage on it ?
what has been done to it other than idle air valve cleaning & throttle?Please let me know
ASE Certified Technician
i will opt out your question and let another expert help you on this one .,not sure on it what would be the problem
Hi Im David, you have no fault codes? Somewhere along the lines when the ECM switches its fuel map after it warms up, you are losing the mix. It is either the fuel you use, a vacuum leak you haven't found, a bad ground or battery (or both), loose connection at a sensor or fuel pump.Vacuum leaks should have been taken care of when the engine was overhauled.Fuel is a tricky thing. If you buy cheap, you get cheap. If you buy a major brand gas, or a station that has a major brand label/sign, and the station doesn't see a lot of fuel traffic, water can be an issue, or the settlement of alcohol on the base of the tank is finding its way in to your tank.Bad grounding and/or conductivity. Electricity is the heart of everything electronic on the car. Sensors, actuators and the computers. If the systems do not have enough electrical flow for use, you get a dumbed down car. Think in relationship to a laptop or cell phone with a low battery, it slows down. Same with the ECM. And if the electrical flow is low,solenoids and switches will either work poorly or not at all. Start with the battery and check ampere output and work outward from it.Corrosion is resistance. loose pins at the plugs mean sporadic outputs or operation. Check them.Fuel pump could be running great and supplying sufficient fuel a for cold running engine and then as it heats up, with the engine, expansion of the metals in the pump or module reduces the pump output. Check the fuel pressure cold, then after the engine warms up and acts up.
you can also have a hairline crack in the igintion coil that will expand as it gets warm. i would check it very closely.
checking in to see how its going?
if you pull the fuel pump relay and there is no pressure left at the rail then it wont start, but, if the car was running , you shut it down then immediately pull the relay it should still start until the residual fuel is used up left in the fuel rail. if that isnt happening then yes, pressure is a problem. probably the fpr, which is supposed to hold pressure at the rail. tapping on the crank position sensor and getting that code is leaving me thinking the reluctor wheel that the crank positon sensor generators it signal from may be bent or full of oil or grime, causing intermittent issues.
absolutely, thats why a fuel pressure test needs to be done.