I have a 2010 DBS that has been doing some bizarre idling every now and then and wanted to see if anyone else has had this problem....
Upon starting the car, it idles just fine. About a minute into the car idling, the car's idle will change and it will "hunt" for idle for about 30 seconds. The rpms fluctuate up and down about 100 rpms during those 30 seconds (after the car has been started for approximately 1 minute). Once those 30 seconds or so are up, the car idles perfectly fine again until the car is shut off. Then once the car is started back up, the car does the same thing. No error codes are thrown. If I let the car idle after driving it (but without turning the car off) the idle is fine. Again it's just on the start up. The car drives perfectly otherwise, just this strange 30 second time frame after start up.

It doesn't matter if it's a warm or cold start, this issue arises regardless.

Coil packs and spark plugs were replaced recently so I doubt it's them and also the fact that it is short lived and no other issues leads me to believe it's not a coil or plug. Hard to think it could be an idle control valve or sensor as well since the problem doesn't continue.

Car does have VAP tune/headers/secondary cats/air box deletes (with mrp air straighteners)

My only guess is this is related to the secondary air pump? I believe these vehicles have one. My next thought is to ask VAP if their headers delete the connection for the secondary air pump (if there is one I'm not sure of the layout on the DBS but know my prior M3's had them) and that the car isn't tuned for this pump being removed. The vehicle then expects the air pump to go on and it doesn't (or it's still plugged in electrically and therefore the car expects the air in the system to change, but if it's not hooked up to the headers etc then the air flow won't change). Not sure if that makes sense, but I can't think of anything else.

 

i would suspect the aftermarket changes. mostly the airbox deletes. air intake is precisely designed, for volume and resistance. i would put them back on and test it. you may find the engine runs better, in general, and with more power too.

 

That’s why I added the air straighteners, everything seems fine on that front, if it was an issue with the air box I’d imagine that would be constant and also throw a check engine light. Again this is a very brief issue that occurs….

 

Not equipped with secondary air injection, and no IAC valve. Not much you could do unless you call Velocity AP and see if they can change something. ON Start up your in open loop for a minute or two. Pluses and minuses of the modified system.

 

It's lazy/degraded Lambda sensors.

I have it on my car.

They are slow in responding so the engine is compensating rich/lean causing the engine to hunt.

They need a refresh.

 

an OBDBii reader (i have the foxwell 520) with aston software on board will monitor the 02 (lambda) sensors in real time. with one, one should be able to determine whether or not they are functioning properly. if one or more need to be replaced (there are four of them), aston wants about 10 times the price they are worth. most are, not surprisingly, all the same, except for the length of the wire that is attached. they shouldn't cost more than 20-30 dollars each and are a DIY job if one cares to indulge...

i had cause to think mine were faulty due to the inability for the emissions test "drive cycle test" to succeed. apparently i wasn't driving the car in exactly the way it needed to be driven to trigger the proper tests.

 

Thanks! Wouldn’t a faulty o2 sensor cause an emissions light though?

 

from what i've read, it may or may not depending on the severity of the malfunction. apparently there is such a thing as a "slow" O2 sensor that will cause problems but not enough to throw an CEL. i have no idea whether or not this is apocryphal. it's interesting how they work to detect O2 in the exhaust though...

in my vantage there are two on each catalytic converter, about 6-10 inches apart. they are identical except for the length of the electrical cord that attaches them to the ECU. they are, at the business end, screwed into the cats similarly to how a sparkplug is screwed into the head.

they all send a signal to the ECU at all times using the voltage of the signal signifying how much O2 is present.

because the O2 sensor in front receives the exhaust flow first and before the cat has a chance to remove O2 it will always show the most O2 present. then because the second sensor on the cat receives the flow AFTER the cat has had a chance to remove O2 it should always show a lessor amount of O2. the ECU knows to subtract the former voltage from the latter and interpret the difference into the effectiveness of the cats. the O2 sensors are assumed to be working properly. it would be difficult, but not impossible to determine whether or not a malfunction is in a sensor or in a cat.

by watching the voltages being sent to the ECU from each O2 sensor (as mentioned in a previous post) a human can make an educated guess as to the condition of the O2 sensors.

in my case, after watching the sensors in real time with the motor running, i wasn't completely convinced i had a sensor problem, so in a last ditch effort to get my car registered for 2022, i resorted to taking it to a (may the good lord forgive me) honest-to-god aston dealership to fix it.

and ya, i'm retired and have plenty of free time to write half-truths about things i know little about on car forums that are of little consequence to just about everybody.