Technical erratic revs and the MOT

[The Sultan]

My son's mk2 1.2 8v just failed cos the tester says he couldn't hold revs between 2500 and 3000.

He's right, Car drives fine but try and hold the revs when stationary in neutral and they just build up. (btw Gotta say it's damn difficult to do home mech when the bloody car hasn't got a rev counter).

I rang VOSA based on info here and they said they had no info on the problem. Fiat dealer denied there was a prob and said it should go in for 'investigation'. Unfortunately that car mechanics link no longer works. Can anyone point us in the direction of some documentation on this.

I should say we recently swapped the throttle body cos the idle stepper had failed in the old one.

Should the lambda be before or after the cat? His car has got space for either, tho only one fitted (before). Maybe that's the prob?

no it should only have one lambda as it's pre eobd cf2 emisions regulations youll find the second blocked hole is only 8mm anyway and is actally for testing exhaust temprature or something for diagnostic's

fiat contacted vosa talking about the problem who then sent a bulliten to all mot testing stations telling them they are allowed to bypass the rpm measurement

now some stations may not do this howether there is the option on all mot emistions testing equipment to bypass the rpm signal and use the cars own tachometer most sensible mot testers will use this and get round it that way

it's really intended for cars that do not have plug leads like pencil coils on and cannot use a clamp on measuring device

but because some people are anal they will go by the book and fail it as it does not hold the correct rpm

witch according to the book is the right procedure to take but as stated in the official bulliten from vosa they can use the bypass facility for puntos and should know this

another way to get them to hold rpm properly is to give the ecu a road speed signal by raising the front of the vehicle and allowing the wheels to turn wile testing the car in first gear

the reason it happens is because when the engine revs are raised without a road signal and the throttle pedal is not moved the ecu thinks it's throttle pedal position is wrong and starts using the idle control valve to bring the revs down so you push the pedal a bit more and it realises it was wrong an they shoot back up again

this is not a problem on the road as when it sees a road signal it knows it's right to see higher rpm's with no throttle input or slight

so considering it does not affect the vehicle on the road or at idle and all mot stations should by now know about it it's not a problem so fiat wont and shouldnt have to do anything about it they already have done buy informing vosa

not sure how the people at vosa denied knowledge of it they should know

so take it back to the testing station and tell them they can bypass the rpm if they say they wont tell them vosa allowed them to if they read there bullitens more often they would know this

if no joy could also ask them to try with wheels turning but this is just a trick known by fiat techs not official procedure anywhere and does intact go against more recent testing rules one of witch is wheels cannot be off the ground with engine running as some cars will log abs faults as only 2 wheels turning

but basically they should know all about this they should bypass it and they certainly should not fail your car for it that's very wrong contact the ministry if you have to and complain that you have not been given a fair mot witch you haven't and the testing station will be investigated and fined probably and you'll get your mot

edit dave also has a point

but i should think it makes no diference you car does fall directly into the affected cars early puntos with one lambda and cf2 emisions

 

[pacman]

Thanks guys.

Spent a long time on the 'phone with VOSA. Very helpful in trying to find info, lady I spoke to even said she thought she had heard this before, but after a big search through several of their databases and a call in to one of their other tech teams she could find nothing. She is going to escalate the query, but I don't hold much hope.

This topic comes up in a number of forims, and a number of people all claim it is a 'known problem' and offer a similar solution, but when you drill down to fine the crucial evidence (ie a tech bulliten, or some independent and reliable report) it can never be found. I'm not saying you're wrong, littlepip, I just cannot find the evidence that you'r right> (so please don't take offence).

On the Q about the lambda, I maybe was not clear. It actually has two fitted. One before, one after, the cat. BUT, the one after the cat is not connected, and never could be given that the cable has been chopped off. Story I have been told is that the exhaust came off a later model and the second sensor not needed for this 1.2 8v. I can certainly find no spare connector on the loom for it. Soooo, have they connected the right one? Is it pre- or post -cat?

 

[pacman]

Update - just had a voicemail left from VOSA. They have checked and also spoken to the garage that did the MOT (how did they know - I never told them?) and the garage has admitted that if it has a euro 2 engine then they may have done the wrong test!!

Now, how do I know if we have a euro 2 engine (1.2 Mk2 on a W plate) ?

 

[Most Easterly Pandas]

A bit worrying if they did do the wrong MOT

 

[The Sultan]

Update - just had a voicemail left from VOSA. They have checked and also spoken to the garage that did the MOT (how did they know - I never told them?) and the garage has admitted that if it has a euro 2 engine then they may have done the wrong test!!

Now, how do I know if we have a euro 2 engine (1.2 Mk2 on a W plate) ?

ok the pre cat reads the engine runing and adjusts mixture

the post cat simply checks the cat is working on euro 3/4 models

if it had been cut off the engine light would be on for sure

so i think the story about wrong exhaust is correct and you do indeed only have one lambda euro2

on a w plate yours is definitely euro 2 as it also has no cam sensor and uses grouped injection

the mot emisions is done buy year ie w plate so don't know how they could have made a mistake the machine wil set the limits for that year

i am seriously confused at how vosa dont have a clue about the things

they knew about your failed mot as it will be on database as it's all computerised now

anyway keep complaining to vosa someone somewhere will know about it and you will get your car passed at no extra cost eventually we mot puntos regularly with this charicteristic always bypass them never had a problem

changing the lambda will not make a difference to holding revs i have already explained why that happens so don't let anyone talk you into buying one of those

i should think the only way to proseed in your case is to fill in an official mot complaints form ask any mot station they are required to give you one straight away no questions then a man from vosa will be out very quickly to see what's going and he will know about them

is your car still at the testing station or did you take it away

if you think about it to put things into perspective

as i have said there is no way to stop these things wondering out side the rev range required for the mot equipment to measure within the mot rules

you car has been doing this it's hole life up to now it's nothing new and it's passed every other time

so what are you spose to do really right your car off cos of something you cant and will never fix that ludicrouse really

also it's not just punto's

allot of cars do it some with similar injection systems made buy the same company one that pops to mind is early vauxhall corsa's

also some cars just have dodgy throttle pedal that makes it hard to test

in all cases testers should use the bypass function

edit: my dad is a tester i just asked him a car cannot fail it's mot for not holding revs there is no fail for that

so if you get right along with that apeals form and the ministry come and investigate as soon as they read the fail sheet they'll fall about laughting and the garage will more than ikelly get fined and told off excetera and you'll get your mot for free pluss refund of original costs

any chance you can post up the actual fail sheet and i'll tell you if it kosher witch it quite obviously is not if you can post you can send to me ill let my dad have a look

 

[pacman]

They failed it on two counts:

1. Nearside CV boot loose at one end (easy fix, with a zip tie).
2. Inability to maintain steady revs at high idle meaning the emissions test could not be carried out.

They charged the full test fee and said we'd get a free retest if we took it back in 14 days.

Ok, going to give the station a call now. Update to follow.

 

[The Sultan]

yep asked a hole bunch more testers about it today

that is simply not a fail

that testing station should be investigated

 

[Richie_81mk]

Could this be the reason when I put my car in neutral and hold my foot down on the accelerator the RPM counter bobs up and down between 500RPM. Even when I'm holding my foot perfectly still? Because I just noticed this problem yesterday.

Say I put my foot down and bring the needle up to 2000 and try to hold it there, it stops at 2000 for half a second, then falls to 1500 for half a second, then back up to 2000 and so on.

Bit dodgey if you ask me.

I have the same problem. What should I do?

 

[Mr Wild]

You don't need to do anything, it is not a fault and not an MOT failure.

 

[Richie_81mk]

You don't need to do anything, it is not a fault and not an MOT failure.

Are you saying that its normal?

 

[oseibonsu]

This problem is sometimes due to a dodgy Lamba sensor . I replaced mine with a new one, and the revving is fine now.

 

[oseibonsu]

I have the same problem. What should I do?

Guys check out the following thread on this website : https://www.fiatforum.com/punto/126278-disconnecting-lambda-sensor.html