Emissions advice

[TM99]

Hi

Looking for some emissions advice here. Friend has a car that has repeatedly failed MOT on emissions (CO). Lost faith in his mechanic and we're going to try and take a look at the weekend. 2001 VW Golf 1.4 16v.

Known issues that might be involved- EGR valve, and coolant temperature sensor (Dash gague never moves >0)

Test #1- Failed, high CO
EGR cleaned. MIL lamp lit, according to mechanic "nothing to worry about". hmm.
Test #2- Failed, high CO
O2 Sensor replaced.
Test #3- Failed, high CO
Mechanic advises replacement CAT. Quotes £350.
Friend sources new CAT from GSF for £150.
Mechanic fits new GSF CAT, says emissions are "all over the place".
States that the £350 CAT he has will definately correct emissions.
GSF response: puzzled but willing to send CAT off to supplier if its suspected faulty. Apparently no signs from looking at the CAT to show that it was ever fitted.

So, I'll have a chance to have a look at this at the weekend and I'd really like to get my hands on a CO tester.
Is there anything worth buying (<£200 ish), that would allow us to measure CO at the exhaust?
I noticed http://www.amazon.co.uk/Gunson-G4125-Gastester-Dig...
But- I'm concerned that the accuracy is +- 0.5%. The pass rate is <0.5%....

And also- any immediate thoughts on coolant temp sensor? I assume as long as OBD2 shows the correct temperature, we can rule this out... for these purposes.. right?
Thanks!

[stevieturbo]

All that and you leave out the most important information. The actual emissions levels !!

[TM99]

Ah indeed.

Engine/Oil Temp 89C
Low Idle- 600rpm- CO 1.46%. HC 182ppm.
High Idle- 2770rpm- CO 0.54%. HC 79ppm.
Lambda 1.02


The main worry is that if we can't measure, we can't know if we're going in the right direction.

[stevieturbo]

Coolant temp sensor and gauge sensor are not the same ( although they may be combined in a single unit )

So if the OBD data says correct temperature, you're fine.

Given the readings, and it's hard to imagine how even the dumbest mechanic alive wouldnt suggest or at least check, is the lambda sensor.

Either test or replace it. No idea if whatever OBD reader you are using gives it's output or not.
Although it is possible your's uses a 5 wire wideband sensor, so testing will be limited to viewing it's output on a diagnostic scanner if the OBD doesnt offer anything

And sometimes even then, the readings may appear ok, but it's still a duff sensor.

[stevieturbo]

And that tester would be a waste of money.

Fine for older cars where a simple 3.5% CO was required for MOT. But no use for modern cat equipped cars.

You'd need a proper gas analyser costing hundreds of pounds at least

[TM99]

Tester is Autel Maxidiag EU702. So I think it'll show both sensors ok.

Thanks for the confirmation on the Gunson.