Scratch

iTrader: (3)

Issue: once the xB (2005, 90k mi) is warmed up and has been driven a bit, when I sit at a light, in gear or in neutral, the idle drops. It sits at around 800/900 rpm then just drops down to 300-400 and then surges up to 1100+ and settles back to 800/900. When it drops like that, it just feels like the engine is shuddering something fierce. It hasn't stalled out yet, but I'm trying to look for the reasons why this may be happening.

The xB has had the full 90k service in the last few months from a Toyota Master Mechanic, the issue happened before that service. The only aftermarket part is the OEM AEM CAI that came stock from the factory.

Thus far I have pulled the MAF Sensor and gave it a cleaning with the MAF cleaner aerosol can (no carb or brake cleaners used), and I'm about to go fill up with a tank of 93 Shell just to see if that makes any difference.

I'm looking for any possible causes to check out. If you have an idea, let me know.

SentraSE-R

Check for a vacuum leak or a bad Idle Air Control Valve.

tkevin07

iTrader: (3)

You should get a voltmeter and check if it does that when there is an electrical load or A/C Load, maybe your battery is getting weak?

ajcadoo

The only time I had sporadic idle issues was when my MAF went out. I had to replace mine completely.

Scratch

iTrader: (3)

Vacuum Leak: Not Checked

Bad IACV: Not Checked (Hopefully not, $200 IACV is lame)

Current Load/Weak Battery: Checked (New Battery in December)

MAF: Cleaned but not replaced

I've also filled up the tank with 93 octane on Friday and have been driving over the weekend/work and the issue has been reduced slightly. The xB is peppier, but when sitting at the light the idle still fluctuates.

I'm thinking about looking for a stock airbox and swapping out the AEM CAI for a few weeks to see if that changes things.

Any other things to troubleshoot? I plan to look for a vacuum leak this weekend if the weather cooperates.

Would a weak alternator have anything to do with this? All belts were replaced at the 90k, I have been suspicious of the MAF/CAI since it was also cleaned/oiled at the 90k and cleaning it helped for about a day.

ajcadoo

I noticed bad idling a few days before my MAF went out. When my MAF went completely out, I got CEL, TRAC Off, and VSC lights, plus my car went into safe mode (Any RPMs over 3000 results in a bog down of engine.) I did try to clean my MAF but it did not help.

Reactor

Spray some WD-40 into IAC, let it sit for few minutes then start the car. May help if you repeat it a few times. You got to pull off the rubber duct off of a throttle body to spray into the IAC passage.

frogbox

Check all of your engine ground connections. On the coils , engine to frame ( actually on the transmission under air intake. A bad ground connection can cause all sorts of weird stuff.

Clean the area under it , getting the paint and or any oxidation off. Helped alot when mine started doing the same thing.

Scratch

iTrader: (3)

Month later, changed the intake to an Injen SRI (been planning to for awhile anyway) and bought a new MAF sensor. Helped for a day or two, but...

no change

Also went out and installed the Miko Homemade Ground Wire Kit from the tech section, and it seemed like it wanted to help. After 2 days of driving it...

no change

Got so mad at this stupid box, almost pulled over and put a .45 into the engine. Instead, got back in the car, kept driving home, and video'd the idle dropping so y'all would see what I'm talking about. This was a drop to a stoplight, going from about 55-60mph to sit at the left turn lane, in neutral, no A/C or Heat running. Had 2 windows cracked and the left turn signal blinking, so you can hear that in the video. If you watch the RPMs they just dip and dip and dip... makes me furious.

http://www.youtube.com/watch?v=dIczaqKljXs

Any other options, or things to try out?

SentraSE-R

Well, it doesn't appear you've checked the obvious likely causes, the vacuum leaks and IACV.

Scratch

iTrader: (3)

So the IACV, I've pulled them off Civics and checked, I haven't seen any obvious 'bad' indicator. Other than spraying some carb cleaner in it from the TB, it's just a replace it, $300 part. joy.

Vacuum leak... i've checked as much as I can. Spraying carb cleaner around hoses, of COURSE since the idle is just fluctuating normally I can't tell when/if the carb cleaner is getting sucked in and changing the idle...causing a surge or not.

SO... short of replacing every possible source of a vacuum leak.. I started with the old intake and MAF, so there are no leaks before the MAF and that would only leave some source of unmetered air coming in downstream from the MAF.

...just getting sick of this box.

frogbox

Check your VVTi oil control valve for sticking. Would act like a vacume leak if the valve were retarded .this would cause a "rolling" idle after higher rpms.

Scratch

iTrader: (3)

New development, might be the source of the issue... always the things staring you in the face (forest for the trees)...

Anyways, take a look at photo #1 on this older link for oil catch can install:

https://www.scionlife.com/forums/sho...crankcase+hose

The damn PCV hose, where it connects to the intake manifold has worn itself loose-ish. The stock pinch clamp has managed to compress enough to cut the foam over the hose in half, so now the stock pinch clamp won't even keep a solid seal there...

I wonder if THAT would be an issue. (facepalm)

Going to go swing by the store for some 'normal' hose clamps and see if that corrects the issue, then go buy a new PCV hose, and replace the valve as well.

SentraSE-R

I think you're onto something there ;).

frogbox

You may also want to make sure that the lines are going to there proper places.( example PCV valve line goes to the intake not the non-PCV valved cam cover line, just lke the pics in the former posts ) have seen some people when installing an intake swap the lines around causing BIG PROBLEMS.

Not installing the lines properly also cause MAF fouling that many have reported.

mrhat

iTrader: (4)

I have this same problem on my TC. I might have to start looking at my hoses and grounds. thanks for the leads.

Scratch

iTrader: (3)

@frogbox - Yeah that would be a genius move right there. I can see how people may do it when they are ripping out all those hoses, always better to replace one piece at a time, and for now I don't see any reason to add an oil catch can to the PCV hose.

Seems like the issue may be somewhat resolved. No recurrence of the idle surge at the level it was doing before. I can feel the revolutions of the engine try to drop, but it just won't do it.

I'm thinking the only additional thing I can do would be getting into diagnostics, hooking up an OBD2 connection that has a fast update and record the actual data coming from the ECU, try to track down any possible issues. This however is something I totally don't want to do.

Starting to think RedneckwithanxB had it right, that these cars just do this, and it's 'normal'.

Reactor

I believe you have a problem with the Idle Control Valve. It doesn't look like a vacuum leak at all from the video you posted.

Scratch

iTrader: (3)

That's the other possible bad spot. I also dumped some BG Throttle Body/IACV Cleaner into the TB while doing all this work. As per the instructions, did the work at normal operating temp and while running, hitting the throttle to keep the engine running. Of course it died once and threw codes like a christmas tree, but I took that time to angle the cleaner into the IACV and let it sit.

So that may have helped the issue as well, but not fully.

I think the next option is to pull the IACV off, clean it to death, and put it back. OR just buy a new one, which I'd rather not do with the cost being up there...

Reactor

Throwing codes while doing top engine cleaning is normal. I think if that helped the issue then you may want to repeat. IACV can have some rust, dried coolant, the bearing may be sticky, dirt buildup, etc. If you decide to remove the valve for cleaning, make sure you have a new gasket.