Throttle Body

The Air Con is a load so the engine will decrease in revs! Do the engine revs drop when the engine has warmed up after say 10 minutes?

Dear Mr Truman,

Let says if the engine rev not drop after 10 minutes.

Appreciate you advice.

It's most likely a simple vacuum leak(first thing to check). Get a can of starting fluid, and spray it on/around your throttle body and vacuum hoses. If you hear a change in idle speed when you spray a particular location, you have found a leak.

Good luck.

Can i used the WD-40 a lubricant for corrosion to test the leakage?

Appreciate your advice.

WD-40 would work, it will decrease the idle, while starting fluid would increase it. listen for a change in idle.

Well here in the USA there are a variety of emission control aspects that effect the operation of the throttle body. One of these is the idle adjustment servo that does multiple functions depending on the temperature of the vehicle and which mechanical loads have been applied to the engine. Because of this when the AC gets turned ON the idle speed does not drop because of the closed loop control keeping the idle speed at the correct rate.

The problem is constant.

But the SC says, it will effect a bit fuel consumption.

So, i will check first for the leakage right??

i agree a vaccum leak but most of the cars I have had lately idle arounf 950 instead of 850 rpm but on start up they run about 1100 for couple of min

Follow this man's comment. Check the cleanliness in and out.

yes it is normal for a high idle when you start cars up with computers while the computers go thru all the check list . then the idle should drop if the battery is strong and does not require a lot of charging .

Used throttle bodies are a lot cheaper if you can find one

What fuel, petrol or diesel?

I made asimilar check with my car with petrol fuel. Found 900 rpm idling, when stared AC, in marginally reduced, approx. 850 rpm. I don't see anything wrong with it, rpm is reducing slightly due to increased load.

I observed during climbing steep roads, if we switch off AC, acceleration improves.

When the A/C compressor clutch engages there in a new load on the engine. This will result in a drop-off in RPM.

Hello. On high mileage vehicles many throttle bodies are condemned due to wear around the shaft.This prevents the throttle valve from seating properly and lets in air around the shaft.Both of these will cause an increase in idle RPM.They can be repaired with accurate drilling oversize and bushings.Not often but i have seen throttle bodies condemned and all that was needed was a base gasket.Hope this helps.

In older non drive by wire cars, the accelerator was conventional like a normal carb,

There was a idle speed motor that was used to regulate the idle speed.

I had an idle speed problem in a carburated Toyota that drove me nuts. As it turned out Toyota mounted a solenoid valve on top of the valve cover where it got hot. That solenoid valve controlled the EGR valve in a bizarre way. When off, there was full vacuum to the EGR. So, the EGR valve was used as an anti-dieseling device.

It stuck under a weird combination of driving. The car needed to be fully warmed up. Then turned off for x to y minutes and it would stick. Outside of that range it would be fine.

Dear All,

Problem solved.

The faulty rubber parts attached at the throttle body is the main cause.

The rubber cannot be replace and need to change whole set throttle body.

Buy a used TB and cost me around 100 USD with installation less than SC charge. Yeahhh

Good deal, thanks for the feedback and glad your able to get it fixed for less.

What method did you use to determine which parts were failing?

I sent to mechanic, dismantle the throttle body, and check the physical found the rubber is stretch.

No WD-40 involved....haha

Anyway thank you to all.