MOT next week

[mojobaby]

Just getting my car ready for her MOT next week and as I usually have an issue with my emissions I might need to do some adjustments.

A few weeks ago I saw a comment by someone who said that before their MOT they screw the mixture screw all the way in and also remove their air filter.

Does that actually work? I've looked again for the comment but can't remember who wrote it

 

[JdeW]

Think this might be the topic mojo https://www.renault4.co.uk/forum/threads/costs.10173/#post-69619
For the Dutch MOT I visited our village local garagists, who are Renault car fans for many years (R4, R5, R8 Gordini, and only an Alpine 310 still in showroom). Never any problem with emission rates whatever, because those garagist knows what it is to drive oldtimers and they just turn a blind eye when it comes to a certain emission "inconvenience", and that's the real spirit for those few who still love to drive an oldtimer, and what's the difference when a certain emission rate differs by a tenth or onehundred?

 

[mojobaby]

Thanks JdeW, might give it a try I wish we had guys like that. My last inspector looked like he was still in school

 

[JdeW]

Thanks JdeW, might give it a try I wish we had guys like that. My last inspector looked like he was still in school

I know what you mean Mojo nowadays youngschool nerd garagists only know how to read a fault code of an engine analyzer, hardly interpreting it, switch the presumably faulthy part(s), realising after a week it wasn't wright etc. etc. instead of using the knowledge of real oldschool garagist who will dig in the real problem and repair it.
But surely in that large country France there will be garagists with the same mentality like living in my village

 

[laxeian]

When I took my 4 to its 1st ITV(mot) here in Spain in my ownership I did not adjust the mixture screw, the readings for the emmisions initially failed ( carbon dioxide levels were way above the limit here {iirc 3.5 for year or under was whats required, 1985 car, it was initially reading 9+!, I was thinking Oh no!}), the tester allowed me to turn mixture screw in whilst in test, with it fully turned in it watched the carbon dioxide drop from 9+ down to a sail pass of 1.7, this was with lead replacement additive, next ITV ran the car to make sure it was hot, turned mixture screw in for test with a hot engine and the levels were 1.19 pass, these tests were all with air cleaner on with filter. ( forgot to add 1108cc)

 

[angel]

What MOT / CT test takes into account is CO (carbon monoxide, not dioxide).
If acceptable CO levels in your country aren't ridiculously low (below 1,0%), any R4 will be able to pass the test - in fact, with idle CO at over 5% you would probably already have other issues (poor running, hard hot starting, plug fouling).
Do they check hydrocarbons (HC) emissions, too? If yes, excessively leaning idle mixture will increase HC emissions and your R4 will fail on this.

 

[laxeian]

Totally correct Angel,my post should of read monoxide not dioxide, brain was a bit short of oxygen!

 

[mojobaby]

Thanks for the comments......
@JdeW , there are still reliable garagists in the smaller villages, but the MOT guys seem to be quite young and don't "question" their computers and analyzers. If you remember the last time I went in 2018, I was failed because I had a tear in my seat!!

Only once, as in Laxeians case, did an inspector screw in the mixture screw. The CO reading went from 8% down to 4%. When I got home I took out the mixture screw and noticed that the point was crooked and damaged. I don't know if he did that or if it was like that already.

Angel, according to my print out its only CO that is measured. It has to be less that 4,5% and the last time I went for an MOT in 2018, the reading was 4,42% so I only just made it.

 

[angel]

Wow, I wonder why many French people complain about the strictness of the new CT. In Greece emissions test measures CO and HC at idle, and HC at 2500rpm and must be performed annually.

 

[mojobaby]

Angel, there are 3 Failure Catagories, Minor, Major and Critical

With a Minor Failure, your repair has to be made before your next visit. (2 years)
Major Failure, your repair has to be made within 2 months
Critical Failure, you are not allowed to drive your car until the repair has been done. You can drive it home or to a garage for the repair, but no more.

I don't think the French are too happy with the Critical Failure category.
The last time I did the test, I failed because my car seat was torn and also because the seat didn't slide on its rails very easily. This was classified as "critical"!
I've just realised that I haven't repaired my brake lights yet. One is red and the other is faded red, more orange-like actually. This was a "minor" failure.
I agree, I don't know why they complain so much

 

[JdeW]

I remember the torn and difficult sliding seat critical car failure, as I may say "to stupid for words". Maybe its critical for some grandchild who might injure their little hands rubbing the seat, but then again.....
Good luck on this CT mojo

 

[ecurb.renots]

Wow, I wonder why many French people complain about the strictness of the new CT. In Greece emissions test measures CO and HC at idle, and HC at 2500rpm and must be performed annually.

 

[ecurb.renots]

My R4 is due for its French CT next Saturday and the worries have already started. The emissions test is the concern and after following this thread and links i screwed the mixture screw on the Zenith 281f right in to weaken the mixture but there was no discernable difference to running. I had expected it to run lumpy. I took the mixture screw out and it looks fine so have screwed it right back in and backed it off 1.5 turns. Running and starting is fine.

Do I potentially have a problem or is it quite normal to have good running with the mixture screw fully home.

 

[laxeian]

Mine ticked over surprising well with the mixture screw turned full in, as said this was the engine hot, I literally turned it in 200m from test centre, then immediately back out just out of the test centres gate!, so unsure of on the road running, I did leave it running even when parked to keep temp up once in test centre, I did find it would go to stall if left running for over 5 min but started OK, then a blipped throttle would save stalling when in line for test, which would settle it, it only seemed to happen with prolonged period of tickover) and passed (result is in photo in project thread ‘ now in gaicia), Best of Luck.

 

[angel]

Do I potentially have a problem or is it quite normal to have good running with the mixture screw fully home.

You may have turned the throttle stop screw too much inwards, so that you have bypassed the idle mixture screw circuit, and now the engine is idling on the progression circuit. Normally the engine should stall when idle mixture screw is turned fully inwards.

 

[mojobaby]

Well, I failed my MOT.
I expected the issue to be with the emissions but it was the brakes this time.
If you have a look at the results below, AVANT means front. A little way down you can see "force de freinage" which is brake force, and the 146 is the left hand front brake and 67 is the right hand front brake. So quite a difference.

The inspector told me that the right hand brake does not maintain the pressure. By this I would assume that there is something wrong with the brake cylinder or perhaps there's air in the brake line. Any thoughts please??

2 years ago my emissions test was 4,4% and this time it was only 3,11%. I've haven't touched or adjusted the carb in this time. Two months ago I stopped adding the lead additive for unleaded fuel. Do you think that this could have made a difference.??

 

[angel]

It seems that one piston of the right front wheel cylinder is seized. With such unequal braking performance up front, I would expect the car to pull when braking, have you noticed it? Brake performance on the "good" wheel seems low, too. I remember that my '75 R1123 with 200mm drum brakes would put out 180-200 daN of braking force, back in the days when the actual force was printed on the test result sheet. So it may also be air in the lines.
CO content has nothing to do with lead substitute, in fact it does not affect any of the measured pollutants.

 

[mojobaby]

Just the advice I was looking for, thanks Angel!!

The car does pull to the left when I brake ; the harder I brake the stronger it pulls. So I will start off with a brake bleed (you helped me with the last one) and if the problem persists I will replace the brake cylinders.
thanks again!

I wasn't too sure about the lead substitute. As far as I know, its some sort of lubricant to help the valves. I can't think of any reason why the CO reading would drop so much, unless the inspector was just doing me a favour. He seemed quite fascinated with the car and actually found the button to open the bonnet all by himself