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sprinkles08
sprinkles08, ASE Certified Technician
Category: Australia Car
Satisfied Customers: 21599
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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I am just doing some research on idle problems and throttle

Customer Question

hi, i am just doing some research on idle problems and throttle problems with a 2000 Daihatsu Sirion
mainly looking for information on the Idle Air Control Valve and TPS, as i just replaced the fuel pump with what seems a little improvement
Submitted: 1 year ago.
Category: Australia Car
Expert:  sprinkles08 replied 1 year ago.

Hello and welcome to JustAnswer!

The idle air control motor opens to allow air into the engine when the throttle is closed to maintain idle. An IAC issue will usually cause a low idle or lack of idle without slightly opening the throttle.

The TPS is a common cause of an erratic idle. When a TPS gets worn it will start to create voltage spikes in it's signal which the engine controller will see and think you're opening and closing the throttle when you aren't, so the idle speed increases and decreases.

What symptoms are you having?

Customer: replied 1 year ago.
Currently at starting the vehicle is running at a rpm low enough to stall. it is a 5 speed manual model and i also have issues at low rpm in higher gears. Before the troubles started it was possible to travel at 60kph in 5th gear while only barely touching the accellerator. Now, if travelling at 60kph i get erratic response at any low rpm in any gear, so in order to travel smoothly at 60kph i am having to stay in 3rd gear.
Expert:  sprinkles08 replied 1 year ago.

Have you checked for fault codes?

Customer: replied 1 year ago.
I do not know how to check for fault codes. I don't even know what tool(s) i would need to check error codes. I usually work on my own cars, but most of my experience has been with older cars that use mechanical fuel pumps and distributors and points. Truthfully i am trying to diagnose and fix this at as low a cost as possible as i only need to have the car running for a few more months till i have enough money for a newer car.
Expert:  sprinkles08 replied 1 year ago.

A scan tool or code reader will need to be connected to the data link connector under the dash to read codes.

Are any warning lights on?

Customer: replied 1 year ago.
ok, i'll look into getting one. There are no warning lights on.
Expert:  sprinkles08 replied 1 year ago.

Does the engine light do a bulb check when the key is first turned on?

Customer: replied 1 year ago.
it does. If you like, this weekend I can take a short video of what it is doing including the dash bulb test and a short drive if you think that may help you some more.
Expert:  sprinkles08 replied 1 year ago.

A video would be great if it isn't too much trouble.