Cleaned my throttle body

[Mark R]

My Lexus IS250 had developed quite a rough idle when cold, with lots of "hunting" for the idle revs.

So, I thought I'd take a look at the throttle body, to see if there was anything obvious in there. Boy, oh boy. It was covered in crud. I regret not taking a picture of it.

Anyway, I wiped it down with a few alcohol soaked rags, and took off loads of black tarry stuff. (What is this stuff and where does it come from?)

Started her up, and the car was really acting weird. Idling at about 2k and driving it in that condition was very disconcerting, as it really pulled in Drive. Anyway, after about 10 miles driving and about 10 minutes idling, it had sorted itself out, presumbaly, the DBW idle control had re-calibrated.

The idling is also a lot more stable, so it seems to have done some good.

Maybe next time, I'll disconnect the battery for 15 mins to reset the ECU. But it was literally a 5 min job to just disconnect the intake and wipe the throttle with a cloth.

Whether it'll do anything other than fix the idle, I doubt very much. But some other car forums have been suggesting all sorts of rather dubious stuff like "removing throttle sluggishness". Hmm. I think not.

 

[ThatsABigOne]

Your filter should have caught some of that crud... The reason why it is black is some dust accumulates on the oily surface of the throttle body. Do you use OEM filters?

 

[SparkyJJO]

Black crud can be because of bad PCV, either caused by a malfunctioning valve or just simply poorly designed PCV system. Doesn't mean there is dust.

When I clean my throttle body on my Trailblazer (dumb PCV system with NO valve) I disconnect the battery to avoid any weird idle issues. I usually clean it about once a year just to keep it from getting bad and actually causing any issues.

 

[kitatech]

Definitely check the PCV valve and replace with OEM if oily/gunky/sludgy...

 

[AMCRambler]

Some cars benefit from a catch can to remove oil from the crank case air and keep it out of your intake runners. A lot of ls powered car owners do this mod. The catch will collect the oil and periodically you gotta empty it out.

 

[phucheneh]

Black crud is definitely not normal. I'd expect it on an older car, but not on anything new enough to have electronic throttle. PCV itself shouldn't feed oil into it, as I can't recall anything that routes the PCV before the throttle body. But if there is an extra breather stuck into the intake tube, a plugged PCV may cause oil to come through there.

Normally you just see carbon in the throttle. It's hard and not wet (...yeah). And alcohol doesn't work terribly well. It will get it eventually, but you'll do lots of scrubbing.

Are you sure you don't need to do some kind of throttle recalibration? I think your car is pure TBW with the little compact throttle module. They often require a sort of 'relearn' be manually triggered. It's kinda like adjusting the TPS with a voltmeter on an older car, but the ECM does it itself.

 

[Vetterin]

Do have something against using throttle body cleaner? Just wiping what you could get at with a rag didn't do a lot.

 

[SpatiallyAware]

K&N?



I bought a can of the seafoam spray but I haven't had a chance to try it yet...

http://www.youtube.com/watch?v=Vqs8QWvssmg

It has a little doohickey that lets you spray it directly onto the throttle plate.

 

[evident]

i used valvoline carb and throttle body cleaner on my 96 camry when i had it. Worked wonders for getting rid of rough idles and trouble starting

 

[fstime]

That does not sound normal at all, the IS250 can be no more than what, 5-8 years old?

We have cars 3x that age that never required that sort of break down.

 

[Mark R]

Do have something against using throttle body cleaner? Just wiping what you could get at with a rag didn't do a lot.

I didn't have any TBC to hand, and just wanted to see what was going on, and thought I'd see how tough the residue was.

Anyway, the residues came off easily with alcohol and a cloth. The throttle butterfly and body were shining after a couple of minutes of gentle wiping.

It certainly did something quite dramatic, as the ECU had no idea what to make of the much increased idle airflow when I started it, although it has since adjusted to the new airflow.

After the improved idle performance, and the fact that the throttle body cleaned up so easily, I see no reason in going at it again with a stronger solvent.

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OEM air filter, changed as manufacturer recommendations.

Most of the crud was at the edge of the plate, and looking at the rags, it is seems to be mostly carbon - maybe mixed with a little oil