Low idle and near stall when stopping
 

My TC is a 2007. 17,000 miles. This past week when driving back to MS for family business, I noticed the idle dropping to 500 and a tad lower when coming to a stop. The idle would go back to around 700 after sitting at a stop. Now I cannot recall but I could swear that idle was always around 1000. Anyway I took the car to the Toyota shop in Vicksburg, MS, which I refer to as Toyota of Hicksburg. They claimed no issue even though the car had a rough and low idle and I kept stating that it would almost stall out completely when coming to a stop. After they took the car down off the rack and I drove away I noticed a rattle which was not there before but I think that may be a different issue.

So what might the problem be? Its obvious something is wrong. I'm taking it to Scion of Long Beach, CA Wednesday and hopefully they know what to do. I was just hoping someone might have an idea. I had a friend state that it sounds like the alternator, which the amps Im running might have finally taken their toll.

Have you recently disconnected the battery?

idle should be at about 700 rpms, 1000 is high unless the car is using the enrichment cycle to warm the engine up faster.

as for the problem, it can be a few things, dirty air filter, MAF sensor, dirty throttle body.

if it is the alternator or the battery, there are easy ways to test their voltage levels.

Yes the battery was recently disconnected to install the navigation.

Now that you mention that it may have always been around 700 and I just really took notice of it because of the drop to 500 rpm when I come to a stop.

I have an AC/DC volt meter. What am I looking for when testing the alternator?

you would be needing to check that the alternator is indeed sending power back to the battery to keep the vehicle charged. a scangauge will read what the alternator is putting out if you have one. or find an NTB, they do complete charge system testing.

then, one last possible problem it could have is the primary a/f ratio sensor in the exhaust manifold, but if that wasn't working, you'd probably have a CEL.

I noticed a rattle starting about the same time but it may not be related. I located the rattle today and hopefully its covered under warranty. The rattle is at the joint that connects the muffler/exhaust pipe section, to the rest of the exhaust. It has two spring loaded bolts. I can move it back and forth lightly and you can tell its hitting metal to metal. Im assuming there is a donut type gasket that rides between those two flanges and its possibly failed.

Scion found no issue after hooking it up. They did find the rattle and I was wrong apparently. They say its the catalyst in the catalytic converter coming loose. They are putting a whole new exhaust and its covered under warranty so that's good.

I reset the ECU prior to taking it in for service and the near stall seems to have stopped but Im keeping an eye on it.

yeah dude everytime you disconnect your battery. You reset your ecu. It basically starts fresh and starts to learn your driving all over again after a few miles it should be ok just stop reseting it cause evertime you do your just starting over.

resetting ECU. just let he engine sit in park for 10 minutes.
 

Eventually I'll get to how I fixed rough idle at a stop, but the story is kind of important too...

I was having serious problems starting the engine with only 35k miles. It would take multiple consecutive cranks to initiate the engine. There was also a rough idle. I brought it to Firestone and they thought it ran fine but did a fuel injector cleaning anyway. It still had issues. I bought a new battery and installed it. Only then did I realize that the Progressive Snapshot device I had installed was setting off the fuel-cut off security system and messing up the fuel intake somehow. After I took it out, the car started fine, but the rough idle was still there...

A year later, I realized that when I changed the battery and had cleared out the ECU (I am not car-fluent), I did not properly RESET the ECU. I was suppose to LET THE ENGINE IDLE for 5-10 MINUTES! That's all I had to do! Everything runs normal now (except for the stupid noises coming from the hatch and minor AC rattle:flame:)

So, when you change or disconnect the battery, be sure that the first time you start the engine you let your car sit and idle for 5-10 minutes. The computer has to learn the new idle. Sorry if this is obvious to everyone else on this board, but I had no clue. I mean the manual says not to let your car idle when you warm up the engine...Before you look at your throttle body, spark plugs, engine mounts, or whatever, be sure you've done this, especially when you don't have 100k miles or more.

Good luck. Hopefully it's as simple as my solution was. I'm going to repost this around since it was such a idiotic revelation.

Scion TC 2006 stock.