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1999 2.5V6 CF2 Emissions Failure

1185 Views 7 Replies 2 Participants Last post by  gibot123
Exhaust has a couple of leaks on joints post cat. The cat is a recently fitted used pattern one that doesn't rattle and "seems OK", the lambda is 6 years old (only 15K miles) but not sure if it's Bosch.

What do these figures suggest? (apart from failing the MOT)

Fast Idle
CO 0.30 (or below) 0.74 (actual) FAIL
HC 200 (or below) 90 (actual) PASS
Lambda 0.97 to 1.03 - 1.27 (actual) PASS

2nd Fast Idle
CO 0.30 (or below) 0.31 (actual) FAIL
HC 200 (or below) 58 (actual) PASS
Lambda 0.97 to 1.03 - 1.082 (actual) FAIL

Natural Idle
CO 0.50 (or below) 0.26 (actual) PASS

1 - 8 of 8 Posts

No expert but looks a bit like a air leak or running a bit lean ?
First step would be to check your intake pipe is fitted properly and check for leaks in it.
How does it run otherwise.

· Registered
418 Posts
Discussion Starter · #3 ·
replaced induction pipe. There are no (visible) air leaks pre-combustion. I've tried to fix the post cat exhaust leaks , but the pipes are not all original and the joints are not marrying as well as they should.... still, pre-cat, no obvious leaks.

Not sure in that case . As for the pipes did you try fitting them with an exhaust paste at the joints see if that helps.
You need someone who understands the figures moe than I do I'm affraid.
looked similar to my 3.0 results that turned out to be a lean mixture due to the bypass screw but not the same set up as the 156 . have you checked the maf or injectors you will need to hook it up to the diagnostics to see whats going on.
If he's about Grahameo may know he really good with the v6 but might not be on till later.

· Registered
Alfa Mito, 2010, 1.4NA, 6-speed
9,362 Posts
Was it hot enough? Sometimes an "Italian Tune-up" before the MOT is necessary to get get the cat hot.

If the lambda isn't a Bosch, you could have problems as the alternatives don't appear to be exactly the same and send spurious errors to the ecu ... I had an NTK for years that was a PITA for the MOT and once replaced with a Bosch sales through now.

Just for info my last mot results were:
Fast Idle
HC 18ppm
Lambda 1.02

Natural idle
CO 0.03%

The car got a good workout on the way to the MOT with a longer route including three sections of unrestricted dual carriageway
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