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DISCUSSION => Engine management => Topic started by: Threehz on November 21, 2011, 08:41:58 PM

Title: "Intermittent" Check Engine Light
Post by: Threehz on November 21, 2011, 08:41:58 PM

So there appears to be nothing wrong with the car (91' 318is) but after driving it a while, if I come to a stop and have it just idling for a while the check engine light comes on. The second I start moving again or possible give it gas it goes away...

Anyhow have a clue as to what this is?

You can't really check it unless the light is on can you?

Title: "Intermittent" Check Engine Light
Post by: vpilarry on November 22, 2011, 11:52:27 AM

Yes, the ECM will store the codes. Do the "stomp" test. With the key in the On position (but don't start the engine) stomp the gas peddle to the floor 5 times then wait. The Check Engine light will start flashing the fault codes. Long pause then flash 1st digit of 1st code (ex, 3 flashes = the number 3), short pause then flash 2nd digit of 1st code, etc, etc. There'll be a long pause between codes. Each code has 4 digits and you may have multiple codes. Once all codes have been flashed it will repeat them until you turn the key off. Get the code meanings here: http://ee1394.com/bmw/docs/bmwDTCodes.pdf (http://ee1394.com/bmw/docs/bmwDTCodes.pdf)

I'm guessing its the O2 sensor.

Title: "Intermittent" Check Engine Light
Post by: Geoff on November 22, 2011, 01:29:29 PM

my guess is the code will be o2 sensor,  but the reason will be vacuum leaks;)
                                                                   Geoff

Title: "Intermittent" Check Engine Light
Post by: DesktopDave on November 22, 2011, 05:52:22 PM

+1.  I'm betting a code 1221, O2/lambda sensor.  I'd suspect a cracked hose in the rat's nest under the intake.  Remove the main intake hose, flex it carefully and see if you find any cracking.  They're pretty cheap if you need a new one.  Don't seal it with RTV, some types will kill the O2 sensor.

Alternatively, the O2 heater relay might be flaky.  If it's not heating up the sensor you might see that.

Could also be the fuel pump (relay, wiring connector, filter, etc.), though that's less likely.

Title: "Intermittent" Check Engine Light
Post by: Threehz on November 23, 2011, 02:21:28 PM

Yeah turned out to be a 1222, Lambda #1.

Mess under intake has been removed by PO, I'm going to remove and clean the throttle body today and I was thinking I might just replace every hose on the entire car soon just for peace of mind and to blot out some doubts! Thanks guys I'll investigate!