My 99 civic (dx, automatic, sohc) starts up but then stalls, it will keep running if I give it gas but stalls when I take my foot off the gas pedal?
I took that civic to autozone and advanced auto parts and they ran a scan on my check engine light (CODE=P1509) and they both independently said that it is the "idle air control valve". this is the first time that i ever attempted to work on a car myself. so with help or directions, i took out the iac valve and cleaned it with carb. cleaner. After reinstalling it i started my car up a few times and it started up and stayed running. then i drove it around the block and it did not stall when i took my foot off the pedal at low speeds. so i thought the problem was fixed. but when i went to move the car out of the driveway 30 minutes later, the same exact problem came back. the car stalled after being started, and it will keep running if i give it gas. I have also put a can of fuel injector cleaner in my gas tank.
I have now replaced the iac valve but the problem persist, no changes. i have also replaced the spark plugs.
If the IAC valve was the problem, and you did not clear the trouble codes after replacement, trouble code P1509 will still be present in memory.
If trouble code P1509 did comeback after clearing the codes, and the new IAC is good, then there is a problem elsewhere in the IAC circuits. It could be a broken wire, poor connection, bad ECM, and so on. The path of each circuit between the IAC and the ECM needs to be tested.