IS200 expertise required please Over revving when driving

L3xu5 Mum · May 20

Calling IS200 experts!

2000 IS200 is dumbfounding mechanics with over revving issue.

timing belt changed

vanos unit changed

throttle chamber cleaned out

vvti solenoid has been checked

Current mechanic (Toyota trained apparently……) has had car for 2 weeks now and has had a number of differing opinions as to why the car is not running well - losing the will to live and worried about his bill………

Any words of wisdom would be most gratefully received!

Thanks

Jon Dee · May 21

It may help to diagnose the problem if you can provide a bit more information about how the "over-revving" problem presents itself. For example...

1. Does the engine start normally from cold and then gradually idle faster and faster until it sits at 2500 rpm (or some other figure you can name) when the car is fully warmed up ?

2. Does it idle steadily at the higher speed when warm, or does the engine speed cycle up and down like you were gently prodding the throttle ?

3. If you "blip" the throttle (give it a quick prod to make the engine speed jump) a few times when it is idling high, does it always settle back to the same revs or does it settle lower sometimes ?

4. Any other comments about curious throttle or idle behavior you can think of ?

There are a number of possible causes of high idle and the more information you can provide the better the chances are that someone will say... "Yeah, I had that happen to me and this is how we fixed it" 😄

Cheers...

L3xu5 Mum · May 21

So I asked my husband to give his take on your questions (very useful, thanks) as he has the job of dealing with the mechanic.

The issue started when I was driving car after about 5 miles on motorway the engine started over revving and continued after I pulled over.

1. The engine will idle when the car is stationary but when the car starts moving the engine revs high to about 2500rpm and stays there when the accelerator is not pressed.
2. The engine does not cycle up or down.
3. Blipping the throttle does not return the engine to idle.
4. Fault code P1349 has been showing but changing the vvt solenoid has not remedied the problem.

hope this helps to try clarify

Jon Dee · June 3

Sorry I'm late... I missed your reply. I can't find any definitive information on the type of idle-up system used on your engine. If you have a drive-by-wire throttle then the idle air is controlled by the ECU moving the throttle plate slightly. If you have a separate rotary solenoid valve bolted to the underside of the throttlebody that is also controlled by the ECU (engine computer).

Continuous high idle is almost certainly caused by excess air being allowed to enter the intake manifold, either by a vacuum leak of by a faulty idle air control valve (IACV). Rotary solenoids are prone to carbon buildup on the moving parts, and this can cause the valve to jam. This usually can be resolved by removing the ISCV, detaching the electrical part, and using carb cleaner or similar to remove carbon and restore full movement.

Cheers...

L3xu5 Mum · June 3

Hi Jon

thanks for this

I shall feed this back to my husband - I know the initial feedback from rac when I broke down was something to do with the solenoid. This has been remedied, the timing belt changed (not sure why as it was changed 5000 miles ago) - I’ll come back shortly but much appreciated that you’ve kept on this!

L3xu5 Mum · June 3

Thanks again. The mechanic removed throttle body and soaked it overnight and refitted it. Still same problem - he thinks new throttle body needed (but he also thought it was the timing belt and solenoid which he changed to no improvement). Thoughts? 😊

Jon Dee · June 4

If your car is an IS200 (GXE10) the most likely engine would be a 2-litre straight six (1G-FE) that has a drive-by-wire throttle. In which case the ECU adjusts the position of the throttle plate according to input from the throttle pedal position sensor and various other engine sensors. There are position sensors on the throttlebody itself to provide feedback to the ECU. If the car has a high mileage these sensors can wear to the point that they fail and no longer give the correct position signal to the ECU. Possibly this is what is happening on your car.

The factory repair manual will have some calibration and test information for checking the sensor outputs, and your mechanic should be able to verify if they are operating correctly or not.

Otherwise, it comes back to a vacuum leak. One test would be the manually apply some gentle pressure to the throttle operating linkage when the engine is idling high, and see if by pushing the linkage to close the throttle brings the idle down (temporarily). That would rule out a vacuum leak.

Cheers...