440 emissions

[vicpool]

I have a 1995 1.8 Si 440 with emission problems. Last summer I had a new down tube fitted between engine and CAT by a well known company. They had to fit a new oxygen sensor as they could not remove the old one. From that time on petrol consumption went from 28-30 mpg to 22-23 and the plugs were coating up with carbon. On taking the car for MOT in Sept it failed on emissions 0.8 Lambda and hydrocarbons way over. One garage wouldn't touch it the other had it for over 3 weeks and were vague and having obvious trouble. Eventually I got it back 'fixed' with MOT cert (and new oxygen sensor!) no emissions record. Result? no improvement in over-rich mixture. I have just had it checked for emissions. As bad as before. No faults were shown on diagnostic check. Any suggestions before it is scrapped even though it runs well and is in good nick?

[veegard]

I don't know, we don't have emission checks here I think.. But mine runs on 1.4l / 10km gas. So I guess I have the same problem as you :p

[Baffler]

I have a 1995 1.8 Si 440 with emission problems. Last summer I had a new down tube fitted between engine and CAT by a well known company. They had to fit a new oxygen sensor as they could not remove the old one. From that time on petrol consumption went from 28-30 mpg to 22-23 and the plugs were coating up with carbon.

Did this "well known company" fit the correct sensor? They should have guaranteed the work for six months or so. You might be able to take it back to have them check the sensor. Shame to scrap a good car...

[B20F]

The original lambda is needed from Bosch. General lambda's cause problems or won't work at all. Here' s an interesting thread about testing the lambda:
http://volvo480.dragons.org.uk/forum/viewtopic.php?t=14683

[vicpool]

Thanks folks. I disconnected the sensor at the point where the three wires enter the wiring loom, ran the engine after warming it up, measured the voltage at the output of the sensor as suggested. Result not a millivolt at any revs! I double checked before ordering the proper lambda sensor (at £97 with club discount!). I am about to install it and will let you know progress. I only hope the CAT isn't ruined. I suspect the worst after running rich for so long. Watch this space for further news.

[vicpool]

I have fitted the new Bosch lambda sensor and eureka! it seems to have solved the problem as the fuel consumption is back to about 30 mpg. The moral? As pointed out on the forum, get the proper one. To Veegard I suggest measuring the sensor output voltage. 'B20F' has a link on this.

[jlgrosvenor]

Vicpool, what readings did you get when you measured the lambda?

I am interested because I have had the lambda light come on my dash a coupe of times in the past few months after a long run, so I am going to change my sensor - I don't want to risk the CAT and the sensor has been on since new (115,000 miles).

I have just checked my sensor and it starts at 0.375V with the ignition ready to start from cold, then when warm fluctuates between 0.048V and 0.869V. This lower reading may be causing the problem, and I can check this against the readings with the new sensor.

I opted for an NTK (lambda department of NGK) sensor because it was £28 delivered off ebay rather than £41 for the bosch (search part number on ebay for 16444), hoping that NGK is still a respected brand and should do the same job as the bosch. I was not considering an unbranded universal jobby.

B18U engine by the way.

[jlgrosvenor]

After a bit more reading, I am wondering if it is actually the CAT that could be causing this.

That said, it just scraped by emissions at MOT time, although if the engine is running really well (i.e. I have stripped and rebuilt the engine) could it manage with a nearly dead CAT?

[B20F]

could it manage with a nearly dead CAT?
Depends on the year of the car. Before '93 the MOT only checks the CO level, so a bad cat won't be noticed. You can even get a MOT without a cat if the Lambda is ok. If the car is from +93 the MOT takes a 4way measurement for CO, COx NOx, SOx and then a bad (or no cat) will be noticed. At least thats the situation in NL, believe it's the same in GB. The cat influences the NOx and SOx output levels, not the COx levels.

[vicpool]

I took the car for an emissions test with the new sensor and it passed with flying colours. lambda 1.005 etc. when I came to measure the output I got no reading! This happened with the old sensor. I believe it may be necessary to connect up the 12v supply to the sensor heater. This is the multicoloured wire in the two pin connector and only energises when the engine is running. The other (brown) wire is the common earth for the sensor and the heater. As everything seems ok I have left well alone. Incidetally during the six months it was running rich it does not seem to have affected the cat. Also the lambda light never came on and no fault codes appeared. Any observations?