Will Idling Too Fast Result in an MOT Failure?
18 May 2005, 05:44 PM
#1
Scooby Regular
Thread Starter
Join Date: Jul 2003
Posts: 478
Likes: 0
Received 0 Likes
on
0 Posts
Will Idling Too Fast Result in an MOT Failure?
Anyone familiar with the detailed ins-and-outs of teh MOT test?
I am about to flog the wife's ageing Seat Ibiza 1.6S, and want to get a new MOT first. The car is generally ok, but the idle speed actuator is pooped (stuck in one position, and costs nearly as much as the car is worth to replace). The result is that it runs a bit slowly when cold but, more importantly, idles too fast (about 1200 RPM) when hot.
I have plugged a diagnostic PC into the car (using VAG-COM), and the CO2 emissions should be fine, even with the fast idle, but will it fail on the basis of the high idle speed alone?
I am about to flog the wife's ageing Seat Ibiza 1.6S, and want to get a new MOT first. The car is generally ok, but the idle speed actuator is pooped (stuck in one position, and costs nearly as much as the car is worth to replace). The result is that it runs a bit slowly when cold but, more importantly, idles too fast (about 1200 RPM) when hot.
I have plugged a diagnostic PC into the car (using VAG-COM), and the CO2 emissions should be fine, even with the fast idle, but will it fail on the basis of the high idle speed alone?
18 May 2005, 06:18 PM
#3
Scooby Senior
Join Date: Mar 2003
Location: Next door to the WiFi connection
Posts: 16,293
Likes: 0
Received 0 Likes
on
0 Posts
yes, the more a car revs the higher the CO2 level will be and hence a fail..... although high idling will probably be easy to cure, take it intot he MOT station, explain the prob and tell them to sort it for the MOT 
job done.....
job done.....
18 May 2005, 06:55 PM
#4
Scooby Regular
Join Date: Jun 1999
Posts: 1,496
Likes: 0
Received 0 Likes
on
0 Posts
Yes - IIRC the emissions test has to be done at the manufacturers specified idle speed.
If it won't do that, a strict MOT station will refuse to do the test and hence you will fail.
If it won't do that, a strict MOT station will refuse to do the test and hence you will fail.
18 May 2005, 08:09 PM
#5
Scooby Regular
Thread Starter
Join Date: Jul 2003
Posts: 478
Likes: 0
Received 0 Likes
on
0 Posts
Thanks for the replies.
The diagnostics report that the lambda value (air/fuel ratio) is fine even at 1200RPM - if anything, it's a bit lean - so the CO2 level should be ok, as this only increases significantly with a rich mixture.
Unfortunately, the car has Bosch Mono-Motronic single point fuel injection, which has (like most EFI systems) no means of adjusting the idle speed. Is is indeed simple to fix (replace the broken actuator), but not cheap (>£150!).
The diagnostics report that the lambda value (air/fuel ratio) is fine even at 1200RPM - if anything, it's a bit lean - so the CO2 level should be ok, as this only increases significantly with a rich mixture.
Unfortunately, the car has Bosch Mono-Motronic single point fuel injection, which has (like most EFI systems) no means of adjusting the idle speed. Is is indeed simple to fix (replace the broken actuator), but not cheap (>£150!).
08 June 2005, 05:45 PM
#7
Scooby Regular
Thread Starter
Join Date: Jul 2003
Posts: 478
Likes: 0
Received 0 Likes
on
0 Posts
MoT Passed!
Sopke to someone at the DoT, and it transpires that the MoT test does not specifically check idle speed. However, the automated emissions testers will only take measurements (and hence pass the car) if the idle speed falls between specified limits, which are different for each car.
The limits for the Seat were 450 RPM to 1500 RPM, so it passed no problem at 1197 RPM!
The limits for the Seat were 450 RPM to 1500 RPM, so it passed no problem at 1197 RPM!
Thread
Thread Starter
Forum
Replies
Last Post
fatboy_coach
General Technical
15
18 June 2016 03:48 PM
Mattybr5@MB Developments
Full Cars Breaking For Spares
28
28 December 2015 11:07 PM
