I am having a problem starting my car when it have sit for a long period of time like overnight.
I would have to step slightly on the gas while turning the ignition key to get the engine to catch. When...
This sounds a lot like a knackered air valve. This valve regulates the idle speed. When it fails open, too much air gets in, forcing the system to richen the mixture ratio. When it fails closed, not enough air gets in causing you to make up the difference by stepping on the gas pedal. Depending on fuel system type (Bosch or Regina) it could also be a failing air mass meter (Bosch only) or a faulty MAP sensor (regina).
I see you changed the air valve, but did you check the connector for cleanliness? A low voltage on the connector makes it do weird things.
If the replacement air valve is known good, then that leaves the air mass meter (Bosch) or the MAP sensor (Regina). The 0xygen sensor is a PTC on the Regina system - so if you changed it make sure you got the correct type. Most Oxygen sensors are like galvanic batteries, not resistors, but on Regina fuel systems the latter type applies. It is just a resistor.
If you have a Regina fuel system (square ignitor on the driver's side) the MAP sensor will fail like this. Ensure the vacuum line is connected to it and the connectors are clean. If the system can't find the MAP sensor values, it guesses and you get a rich mixture by default.
If you made it this far, check out your ignition system - the crank angle sensor sometimes gets flaky and the ignition system starts to guess as to where Cylinder 1 is - and retards the timing, sometimes shutting off power to the ignition coil completely if it gives up.
Taking this one step further, the fuel pressure regulator could be bad - resulting in too high fuel pressure causing a rich mixture ratio.
Read the codes from the fuel and ignition system. This involves opening the Lego like cover to the diagnostic jack, driver's side. Position 2 is for the fuel system and position 6 is for the ignition system. You plug the test plug into each port respectively and press the button for at least one but not more than three seconds. Any blinking code other than 1-1-1 is a fault code. The system flashes the codes by blinking the LED, pausing, blinking it again, pausing, blinking one more time. For example, I have code 232 (Incorrect mixture ratio - 02 sensor at backstop) it would blink twice, pause, three times, pause, twice, pause and stop.
Always read the codes with the engine off and key in the ON position.
Good luck - take your time and don't waste money on mechanics' work you can do yourself. Not to knock any mechanics out there (I have been doing this work for 17 years!!) but some will take your money - best method to empowerment - DIY.
Nov 01, 2010 |
1990 Volvo 740