Idle Problem After Alarm Installation

[YarisGLS]

Dear all,

I fitted an alarm to my Yaris yesterday. During the process, I disconnected the battery's positive terminal for safety.

After installation, and everything put together the car seems fine, starts, drives...etc But I notice that the idling rpm is lower than before, as the engine vibrates (more than usual) at the red lights. A slight push on the accelerator smoothens the engine again.

Could it be the ECU resetting itself causing the problem? Or could it be me who accidentally knocked something in the engine bay during installation that caused this problem?

Any help would be greatly appriciated!

Cheers!

[armoredfist2002]

it's probably due to disconnecting the Battery, this resets the ecu.

Don't think there is anything under the engine bay to knock to cause problems.

Idle should be about 500-750rpm, may even be lower once the engine is warm, and could be higher from a cold start.

give it a while and see if it corrects itself, if not ask your dealer, see what they say.

[clarky]

The idle rate can be adjusted by the nut and cable arrangement at the throttle cable as it goes to the engine - aslong as the nuts cant be moved by hand and isnt loose Id say its unlikely to be the culprit.

Id say most likely the above - just that the cars still 'learning' after the Battery reset.

If it is the throttle cable - its a two minute job to adjust - I had to do mine after I fitted the apexi, header and a few other bits and peices last summer...

[Ray99]

Sorry to say that Clarky's advice about adjusting the idle speed is completely wrong. Do not adjust this cable in an effort to gain a higher idle speed. The idle speed is controlled by the ECU using the idle control valve. If you adjust your cable, yes you will increase the idle spped, but the ECU never gets the "throttle closed" signal and therefore never switches on the idle system. You will get all sorts of idle problems from varying loads, from racing to stalling. If you have altered your engine from standard there is a fair chance you will fail the emissions test at your next MOT. Also to dispel another myth- the ECU does not "learn" anything from the engine. It's not that intelligent. It simply responds to the input from its sensors. If you have a lower than usual idle speed, then something is causing it. Look for loose pipes, especially small diameter vacuum pipes that are easy to dislodge. Make sure that you have used the correct wires to link to when installing your alarm, and double check that you have refitted any removed multi block connectors. Please let us know if you cure it and what was the fault.Cheers Ray

[clarky]

Well thanks for that - for the record I didnt suggest touching the cable - I suggested that it might have become loose...

I did indeed say that my idle rate had been adjusted and fair play re-reading the post it looks like I implied it was me ... apologies it wasnt - it was a mechanic.

Maybe 'learn' isnt the right word for the follow on from a Battery disconnection - but many of us have experienced the 'change' in performance that occurs after the Battery has been reconnected. The cars feels and responds in a different more restricted way for a couple of days then settles back to normal.

Im not trying to get anyone to harm their car in any way - I was trying to be helpful - apologies if this want clear.

[YarisGLS]

Thanks for the reply guys! Sorry that my question started an argument... :(

I will try and investigate on the topic today and will let you guys know the reason behind :) Shouldn't be anything bad, I hope :P

BTW, the new computerised ECUs may run on Fuzzy logic, hence "learning" is not entirely incorrect, as the ECU will compare the input of fuel/ air/ throttle angle (caused by the driver)...etc with the output of the engine and try to get an optimum. So the driver will afterall affect how the ECU of that particular car runs.

Well, that's just my guess... still learning from the lecture notes from Uni :P Let me know if I am wrong though!

[clarky]

Bo arguments - maybe I wasnt clear enough - let us know how you get on