Throttle Body Problem

Hi all,

My virgin post here. Am from Singapore. Just want to check with you guys if you have similar problem as i do..

B4 servicing, fuel consumption went up.. Acceleration seems funny and jerky..
Went back to service, they told me that they have clean the throttle body says that its covered with carbon..
After collection of car, it really helps.. Fuel economy is better and throttle response and gear shift is much smoother..

About 2 months later, problem comes back again.. Now its worse.. My gear box is like jerking off.. in particular when car slows down n i accelerate... the gear and throttle just throw my car forward in an unusual manner.. Fuel consumption was from 9.5km/L drops to 9km/L.. I seldom ramp the car just cruise and drive normally..

Besides I am having the stupid front shock clocking sound problem again whenever i start the car in the morning or cold start..

My car currently is about 2.5yrs old and soon warranty period will expire.. Do you have any resolution to this problem that i have? My fellow forumers told me that he also have throttle body problem and after replacing it, it was solved!

p/s my ride is an IS200..

Russell, I'm no AS200 expert, but if the 6cyl is like the 4cyl in this, what about the air mass sensor??

I haven't heard much about a dirty throttle body affecting performance, but if the wire in the air mass sensor gets dirty it reads incorrectly.

Is there any oil in the air filter box? If you are getting oil coming out of the engine breather into the air filter box it may coat the wire of the air mass sensor and make it read incorrectly.

Certainly if I were you I would have it at the dealers every time it went wrong until they fixed it before the guarantee runs out!!

I agree greeneyes, I cleaned my MAF and it made a huge difference. Smoother accelleration and better fuel economy, not to mention the massive power gain, it was like a new car. This is especially bad with the TRD panel filter.

Takes about 2 mins to clean but you have to be very careful!

What did you clean it with Icarus?? Solvent? Soap & water? Wiped it??

Maybe THIS is the cheapest engine mod for more power!!

HI greeneyes, mine is a 6 cyclinder engine.. i do have a OEM drop in air filter in my ride and i have yet to check on that though..

geez.. bsides doing the normal things.. how am i able to know where the items that you have mentioned cleaned?

Infact my ride has been regularly serviced by dealer and they are the ones who told me that the throttle body is dirty.. being not to techie in it.. i believe..

Icarus, how do you clean it? What's MAF btw?

I did post in my altezza forum and few of them do agree that the Throttle body is quite prone to getting dirty or carbonize..

I will be sending in to dealer for service again and i will get them to perform a thorough check and making it sure that it will not come back again..

Will keep you guys posted.. Thanks alot.

Very careful use of a cotton bud and some electrical contact cleaner. Surprising how much crud can build up there...

Some more discussion here.

Some pics and instructions here for a different model of Lexus, but the design of the actual MAF is similar enough...

Mass Air Flow sensor. A sensor for measuring the mass of air going into the engine. Does this by holding a thermistor at a constant temperature. As air passes the sensor it cools it, dropping the resistance, so the system pumps more current through it to maintain the temperature. More air, more current and the amount of air passing can be calculated (in conjunction with knowing the ambient air temperature & humidity as these affect the ability of a given mass of air to cool the thermistor).

As you can apreciate a buildup on the themistor will interfere with its ability to measure the volume of air entering the engine, a possible cause of the hesitation you describe. As an aside, each time you turn the car off I believe the ECU heats the thermistor up to the max temperature it can handle for a few seconds to help burn off some of the scum that may have built up.

For more info search with Google for something like MAF sensor how works.

Yes, the throttle body does get dirty and can effect the way the car runs.

You can use brake clean on the Mass Air Flow sensor, it works better than electrical contact cleaner.

This post has been edited by greeneyes on Nov 24 2005, 07:10 AM

Regular throttle body cleaning is certainly a good idea with these cars, however i don't believe that the problem trd_rg describes is related to carbon build up in the throttle body or a dirty panel filter. MAF perhaps, however an RS200 here in Sydney had a similar problem, and all manner of cleaning and reseting did nothing. In the end, the entire throttle body was replaced and this eliminated the problem. In this case, the car would behave as you have described, with loss of power/throttle response, but only when it was revved hard above 6000rpm.

yeh if none of the cleaning options work. check the tps with a diagnostic tool.

hi all,

Thanks for the valuable information. I will probably pop my hood tml or so to check in particular on the air filter area. Else for the rest of the item, i will try not to meddle with it 1st cos i am afraid i am not able to put them back in their original location.

Like what thunderbird mentioned, my local forumer had an RS200 and he also replace the entire throttle body and it was resolved!

The best is to go back to dealer and get them to rectify all these problems cos after my warranty period expires, i have to pay even more for the parts replacement

hey if anyone has a step by step guide on how to clean out the MAF please post and pm me...would like to do this very urgently

Hey Greeneyes, sorry I didn't get to check here yesterday.

In reply to what you have asked, I looked into this in great detail as I know they are expensive to replace and didn't want to bugger it.

I looked at many forums and consulted a number of auto electricians and came to the below conclusion:

Buy some electrical contact cleaner from Dick Smith Contact Cleaner + Price, This comes with a directional spray tube. Poke the tube into the part of the MAF sensor with the wires in it, being careful not to touch them, and give it a good blast with the cleaner.

They should be shiny and new after a couple of good soakings. Clean the rest of the sensor with the cleaner and let it evaporate before re-assembling.

It's that easy and with the spray cleaner you are pushing it to make any mistakes, you can drench it and it will just evaporate...

If anyone needs to know how to disassemble, I’ll put some directions together for that too.

Good Luck,

Joe

Hi xnickx,

I haven't got photos with me but here are the instructions for getting it out in the RS200 engine.

- Take the one bolt out that holds the front air intake in. This is just to the right of the bonnet catch from memory.

- Pull the intake from the main filter box (may require a little wiggle but should come out easily)

- Look for the MAF sensor, it is the thing screwed into the air box body with two gold screws in two corners. It has a wide plug in the bottom of it with brown ro grey heat shrink around it (again from memory, I am in my office right now).

- Remove the plug and screws and twist the sensor slightly to dislodge it. Don't worry, this shouldn't damage it as the important parts are protected.

- Complete the procedure in the above post and reassemble as is logical from what you have just done.

Hope this helps,

Joe

How to find:

This is good, but people have mentioned about cleaning out the throttle body, does anybody know how to clean it out?

If anyone is able to do some DIY Guide work on this, we can tidy it up into a downloadable PDF which we can put on the website with all the other DIY's.

You need a DIY guide to say, "take cloth, wipe out"?

back atcha!

If the "MAF Day" goes ahead over there, perhaps suitable photographs can be taken. Then, we just need some text along the lines of (Step 1, remove such and such, Step 2 find cloth etc) and we can then format and PDFify.

Fair enough, assuming a zero knowledge start point is a good idea for these sorts of DIY documents.

1. Take key, depress unlock button
2. Open driver's door (the side with the steering wheel)
3. Reach down and pull the bonnet release catch as shown in Fig. 1
4. ....



Seriously though, good idea.

Hi All,

Apology for the late reply with regards to this subject matter that i have raised earlier..

Went back to dealer to have my maintenance 1 month back and get them to check on the throttle body..

As per normal, they say they need to clean off the carbon and insist that the Throttle body is working perfectly fine.

Beside this problem i have, my soft standard suspension, is showing sign of degrading and i can hear very clear knocking sound whenever i go over road humps.. The dealer says that they will help to replace the whole set as this prb starts to surface just after 1yr anniversary on my ride.. Reaching 3 yrs end of June this year and they will replace as much things that is going to be replace those that are showing signs of failure including the suspension..

As for the Throttle body, i have checked thru the service manual, cant see where the hell that i can perform my own cleaning as my ride does not uses MAF as per RS200 model. Anyway am also quite tired after everyday work.. haha.. too lazy to check.. But i found a similar looks like MAF connector just after the air intake just as Jasestu showed in the picture posted.. Will try to take a snapshot and show you guys if it is the one or culprit..

sigh..