Hey guys, I think I have my answer but I want to make sure I'm not missing anything.

During the past week I noticed that sometimes when I start the car it will start and then die as soon as the rpm's come down (so within 2-3 seconds). No lights are up on the dash and I honestly can't remember whether the car was warm or cold each time. It's happened maybe 3 times so far.

Based on my search here I'm fairly sure I just need to re-clean my TBs (which I haven't done in nearly 2 years). Otherwise can you guys think of anything else? The weather will be decent here this weekend so I'm planning on some time under the hood. I do realize that at 108k miles I'm due for a plug change but my gas mileage is still good and the car runs normally otherwise with no other symptoms (e.g. - hesitation, knocking, strange odors) so I don't think that's my issue. I probably won't get to the plugs for another month when the weather lets up.

Thanks in advance.

- Bob

 

Clean the TBs. My car was doing the same thing a month or so ago. Good now. Just read up on how to reset the idle air volume learn, it is hit or miss whether you might have to or not.

 

Ah good call, thanks! I doubt i'll need to reset it though, since my normal idle is very smooth and the RPMs don't fluctuate.

 

IF you are indeed going to be cleaning your TB's, then what you've just said here suggests you definitely need to read up a bit more (just as surfjax recommended).

 

^ whs

 

Ah, but VQsmile, perhaps it is *you* who should be reading further! ha ha, just kidding dude.

I've cleaned them before but I don't remove or disconnect my TBs when I clean them. I've done it before in that manner specifically so I would not have to reset the computer. Perhaps over the summer I will, so I can clean further in, but for my purposes right now i will clean the intake side, the butterfly edges, and as far as i can reach in with the butterfly open.

Good looking out though!

- Bob

 

Not true...there are plenty of people who also do the same thing you did and still had to do the reset procedure.

The problem is that you may have gotten lucky with the previous clean, you may not be lucky in the next one, especially if you move the butterfly even if it is still connected. It's also impossible to clean the inner side of the TB if you don't remove it.

Plus, usually nobody has to clean the TB's...I just cleaned my TB's for the first time after 75k miles but my idle was never rough. My TB's weren't extremely dirty either. My car was never serviced for TB cleaning before.

Did you do some modding to your engine bay?

 

No worries Bob, if you've got a handle on the 'potential', then you're good and at least you can't be blindsided, which was what my (albeit cursory) reading of your post had suggested to me.

 

Well you're correct you can't really get far in there with the TB still bolted on but i just go in as far as I can with the butterfly open (which obviously isn't far but i was able to get in about an inch or so with a rag to clean it last time). I'll say though that I kinda saw dirty TBs as a bigger issue here, granted this place doesn't represent everybody so maybe i'm just fixated on too small a population.

Anyway, going back to the DIY it just states not to disconnect the harness but i'll take the lesson and say thank you for possibly saving me some heartache on a cold morning while i'm doing this. I'll be sure to be ready to reprogram the idle. I'm surprised it can still be an issue though. Is there a known problem with the sensor not rotating back to the closed position when you do this?

And no, no mods to my engine bay. My mods are all inside (gps carputer, parrot bluetooth, backup cam, etc).

- Bob

 

I suspect the issue is that, with this is being a DBW system, the car's "understanding" of where the butterfly is located is absolutely critical. If anything is done that causes an error in the ecu's estimation of the true throttle position, then you're likely to have undesireable symptoms and hence need to do a relearn procedure. What seems to be the variable here, is why some folks are able to move the butterfly during cleaning without any repercussion, while for others, merely altering it's position slightluy has had huge effects.

 

I didnt intend to come across as a douche. I'm humble enough to say I learned something today and I'll be prepared just in case!

- Bob

 

^^ I didn't think anything of it, so don't even waste a thought on it Bob. Besides, you were right inasmuch as I HAD missed in your original post that you had performed the procedure before ("re-clean").

 

Cleaned em out yesterday. I think there was a little bit of a high idle when I restarted the car but after two heat-ups and cool-downs it was gone. Luckily I didn't have to do the idle re-learn procedure. It may have been in my head though.

Coincidentally though my gas mileage has dropped sharply. Shouldn't be related but it's just odd....