Hi all. Above vehicle drives fine but failed MOT on emissions. Very high CO at 10%, HC's at 600 ish, Lambda around 0.6-0.7

I pulled the gas analyser out.

No fault codes present.

Idle test results
manifold vac = 18.5-19.5 in Hg
fuel pressure = 2.15 bar
O2 sensor = 800-900mv constant
inj pulse = 3.7ms-4.5mS, 3.7mS most of the time
O2 integrator = -50

Fast idle test results
manifold vac = 20-21 in Hg
fuel pressure = 2 bar
O2 sensor = 800-900mv
inj pulse = 3.7mS
O2 integrator = -50

The O2 sensor will move down below 50mV if you open the throttle suddenly or give it an air leak, and the O2 sensor status does indicate the lean and rich mixture, but at a steady throttle position the mixture always stays on rich and 800-900mV. Basically the O2 sensor is telling the truth.

Going to try blanking the EVAP and probably check the cam timing during the week.

hi Ian

I think this will have a MAP sensor, Make sure ECU live reading cross checks with measured manifold vacuum. If remote mounted check pipe for leak and blockage.

Is coolant sensor OK ?

Cheers Aidan

Hiya

Coolant sensor is good, as was the air temp sensor. The vac pipes appear good as well.

I took the vac reading with a tee on the MAP sensor line at the manifold. I did compare the MAP reading with the vac reading but i cant recall it now so im gonna have to measure it again, i think it was 600-700 mBar which does convert to the vac readings i was getting, but i will double check them.

Hi Ian,

>>> i think it was 600-700 mBar which does convert to the vac readings i was getting,<<<

If this was taken at idle looking at live readings then you have problems. HTH

Regards Mark

Hi Ian this is almost indentical to the sharan that i am having prolems with(see further up on this forum)Looking forward to a fix
regards, Steve Sneap

All my vac readings are done in "hg. How does one convert mbar to "hg?

Thanks

Pete M

Try this.

http://www.csgnetwork.com/pressinmbcvt.html

Hi all, please don't forget that you are reading from two different ends of the scale. HTH

regards Mark.

Thanks Bryan...nice link. Mark: Now I am confused (easy I know!) but I make Ian's readings equating to about 19 - 20 "hg which I make quite reasonable. Do not understand the "two different ends of the scale". Mind you as soon as I hit the "send" button it might come to me!

Regards

Pete M

Pete,

<<< I make Ian's readings equating to about 19 - 20 "hg which I make quite reasonable. Do not understand the "two different ends of the scale". Mind you as soon as I hit the "send" button it might come to me! >>>

The clue is the use of the word “absolute” in Manifold Absolute Pressure. This could take the thread way off topic though. There could be something in the archives as this was discussed in detail years ago, back when such discussions were common place. Should be loads of info on google as well.

A correct MAP at idle for that car should be approx 300Mbar.

HTH

Alan

Hi Pete, as Alan says the clue is in the name.

The MAP sensor reading that you are seeing in live data is reading from Zero(absolute pressure) UP to a positive pressure, whereas the Vac gauge that most people use to take manifold readings will start at a positive reading(atmopheric pressure) and go DOWN towards absolute zero.

So when the MAP reading is at 350 Mb, the vac gauge reading would be at 650 Mb allowing for nominal atmospheric pressure being about 1 Bar at sea level.

It is this that can confuse people and thats before you start to bring conversion tables to the party.HTH

Regards Mark

Thanks Alan and Mark,

Thanks for that. Something new I have learnt.

Regards

Pete M

Hi all. Wow, this carried on well without me, made interesting reading. I am really sorry i didnt follow this post up, had a bad past month. Had a spot of trouble with someone breaking in and stealing all my customers keys, took a few weeks but got most of them back, luckily the cars were not at my garage, they were dotted about. Then had a minor electrical melt down at home which i fixed and then a nice water leak at home which i fixed, then just had some time off work with a chest infection which i didnt fix but some pills did. So work wasnt top of my list.

Anyway, enough of that. I have fixed this one, bit limited with measurements after fixing as the customer was pressuring me to have the car back, but i do have some. It was the small vac hose on the MAP sensor at fault, couldnt see anything wrong until i gave it a good hard bend around and little cracks opened up. I found it when i checked the MAP sensor with the vac tester and it failed. Replaced the vac hose and all ok. Funny thing is though im still getting similar vac readings, 18-20"Hg idle and 20.5-22.5"Hg fast idle.