MOT Failure - CO2 emissions help! - UPDATE NOW PASSED

[timmaaah 0]

Hi all - just got the car back from the (failed) mot (local place near where I work)! Got inner rear (front wishbone) suspension arm bushed deteriorated resulting in excessive movment in both sides :roll: being fixed tomorrow, but also got failed on emissions as below

Fast idle:

CO 6.416%

HC 149ppm

Lambda .805

2nd fast idle

CO 6.062%

HC 163ppm

Lambda .811

Natural idle

CO 7.23%

A while ago, on it's last service, I informed the dealer (who no longer has anything to do with the car coz they're a bunch of chimps!)that the fuel consumption had got really bad. They said they'd have a look, and came back with 'intermittant fault with the lambda and an intermittant fault with the electric throttle(?)' Seeing as they wanted more cash to look into it further, I thought I'd just live with the poor mpg. I have noticed that there is a fair amount of sooty residue around the exhaust, and if you boot it, a small black cloud come out the rear. Coupled with the poo mpg, I guess the car is running rich. Is it likely to be the lambda prob borked, or the tps (wich is what the dealer thought the 'electric throttle' was!)? Cash is tight - especially with the above suspension work to be done, and the place doing the mot work can't say it's definately the lambda. Any ideas? Want to sort tomorrow, so a quick response would be really great.

 

tia Tim

('94 VR6)

On a side note, sometimes get a bad missfire in 1st and 2nd gears whilst accelerating hard - coil pack?

 

(*free beer offered with both parents, parents parents and parents parents parents being present at time of disclosure!)

 

I really need help with this tonight as my beer tokens are gonna run out!!!

[timmaaah 0]

Free beer now offered (please read terms and conditions!!!)

[thetino 0]

It seems you have answered most of the questions yourself.

Rich running can be caused by various things, including lambda sensors, MAF, air leaks, etc.

I think you need someone with VAG-COM to give ou some ideas.

[corozin 0]

Well it looks like the garage have indicated that there's a lamda problem, or a problem with it's wiring. That's the first place to start as the ECU will be fuelling all over the place if it's getting funny info from Lamda, or may even put the car into safe mode.

 

The other thing you might consider is that if the car has been very rich for a long time you may have damaged your cat convertor to an extent, and that won't help your CO2 readout much either. Good news is that there are aftermarket options available from some tyre/exhaust places. I was able to get a cat made up to order about three months ago locally for around £350. I think they were a powerflow agent, so it might be worth seeking one of those out locally if you find your cat's been snuffed out.

 

HTH

John

[Kevin Bacon 5]

Natural idle - CO 7.23%

 

Yikes!

 

Should be around 1.5% ! IIRC, 4% is the max permissable for a car of that age!

 

Chief suspects -

 

Cam sensor dead - Switches injection to batch mode and retards ignition = BAAAAAD fuel economy and lack of power.

 

Ancient spark plugs = Plenty of missed sparks and therefore lots of unburned fuel.

 

Knackered coil pack = Similar to above

 

MAF sensor knackered = Throttle angle sensor and lambda guesstimating the fuelling.

 

Throttle angle sensor = MAF and lambda guesstimating the fuelling.

 

Lambda sensor dead - Poor part throttle economy, no change under wide open throttle.

 

I notice your MOT report showed a lambda of 0.8V, which is a lean condition around 15 AF. If it were dead, it would not move off 0.45V, so yours appears to be working.

 

VAG-COM codes can often point to a lambda failure as a result of a failure of something else.....usually when the lamdba runs out of adaptation options.

 

Is your car gutless past 4000rpm? If so, my money's on a dead cam sensor.....as said already, you need VAG-COM on it to be sure.

[Jon_vr6 1]

Heres my results from my MOT which passed so to give you an idea!

 

Fast Idle Test

 

CO %vol

Max limit = 0.200

Actual = 0.177

 

HC ppm Vol

Max limit = 200

Actual = 15

 

Lambda

Min = 0.970

Max = 1.030

Actual = 1.004

 

Natual Idle Test

 

CO %vol

Max limit = 0.300

Actual = 0.013

 

Hope that gives you some help fella!

Jon

[timmaaah 0]

Right - cheers for all the above help - you'll all be pleased another rado has passed the dreaded mot for another year!! Lambda was replaced and gave readings as below

fast idle

co 0.027%

hc 14 ppm

Lambda 1.030

Natural idle

0.018%

 

Woohoo!!!!!

......but, she's running really rough - got a nice steady idle, but if you blip the thottle, it'll missfire and the exhaust will pop - got a small leak being sorted on the zorst in a couple of weeks - really need to run it up on vag-com like you guys say - anyone near me? I'll pop over to the sticky and see who's near me and give them a pm - thanks all for your help - just got to get the beast running better now!!!

 

Tim

[renson 0]

sholuld have a scan tool that will work, did on my 16v. i'm in Kings Lynn. Need to check if i have one set up, PM me if you need help

[Yandards 0]

I think you still need to look at everything Kev said above.

 

The car is obviously still running badly so I would replace the HT leads and spark plugs (Go to a Ford dealer and ask for the leads for a Galaxy V6 - its the VR6 engine and the leads will be the same as the VW ones but half the price.)

 

The lambda change 'fix' has worked because the old one was probably covered in soot and was not able to add as much adaption as the new one. Given some mileage on the car the new lambda probe will head the same way as the old one.