High emissions. How to cure?

[frehol]

Hi,

Just had my -95 Blazer V6 CPI in for the annual testing and it faild the emission test. Too high CO and HC... Does anyone have any input on how to fix it? I have one month to fix it or I may not drive it anymore.

CO is 0.8 (0.5 is limmit)
HC is 240 (100 is limmit)
Lambda is 1.01 (OK)

//Freddy

[old_master]

A rich mixture will cause HC and CO to be high. Is the SES light on? A misfire or leaking "nut kit" or fuel pressure regulator would be the first thing to check. How does the engine run? With those numbers it probably runs fairly well. Check fuel pressure and check for excessive leakdown. Cheap and easy to test it. Lambda, (Oxygen sensor) voltage is high also, indicating a rich condition. Post your results.

[frehol]

Hi OM!
No, the SES light is not lit. And it is running fine. But exhausts smells like it is rich mixture. I think it drinks more petrol than usuall, ca 13,5 litre per 100 km, used to be 12,5 l/100km. Not much difference, but still a diff...

Maybe I will open it up this weekend and check the fuel spider/regulator for leaks. Seen a good guide to that in this site.

Will also try to get hold of a fuel pressure gauge...


The Lambda value is not from the Blazers O2 sensors, its calculated in the external emission analyzer, but it should be at 1 if good combustion, and so it is.

//Freddy

[old_master]

Originally Posted by frehol

...Maybe I will open it up this weekend and check the fuel spider/regulator for leaks. Seen a good guide to that in this site.

Will also try to get hold of a fuel pressure gauge.

Hey Freddy,

Checking for fuel pressure leakdown will tell you if that's the problem. Might save you from taking the plenum all apart needlessly.

Cheers

[frehol]

Hello,

I havn't had time to try to find out whats wrong, have not got hold of any fuel pressure gauge to check leakdown.
But I booked time at the local GM-shop so they can look at it,( next year!)
First he asked me was if the cat is rattling, suggesting that is the problem. And it rattlig a lot!

Any thougts?
//Freddy

[old_master]

Freddy,
If the converter is rattling, and you have OBDII, the SES light should be on with a P0420 DTC set in memory. If it has OBDI it may or may not set a code for the converter. With the numbers that you posted, a deteriorated converter might contribute the high HC & CO, but it would be best to check fuel pressure and leakdown also. Please post the results of what they find.

[frehol]

Hi again,
It has OBDII and ses light is off. I had about a year ago problem with power loss at high load, pulling a horse trailer uphill or accelerating going on the highway. Then I had a ses light pointing to O2 sensor before cat. Might have been that the cat choked... ?

Anyway, I will ask them to check fuel pressure. How long should it normaly keep pressure?
It starts fine, does not seem to be "soaked" in fuel in mainfold.

//Freddy

[old_master]

Fuel pressure must not drop below 55psi for 3 to 5 minutes after the pump shuts off.

[frehol]

Hi,

Just had the ratteling Cat replaced and I think it might have been the problem

Have a look inside the old cat:


Not much left in there! You see right through it...

Problem solved!
//Freddy

[MT-2500]

Thanks for posting back how it is going.
Has it been retested and a pass on emissions?

Yes cat may be part or most of the problem but you need to check for things that would make the cat fail.
As always a good tune up and engine running check for a log life of cat.
Good luck MT

[frehol]

Originally Posted by MT-2500

Thanks for posting back how it is going.
Has it been retested and a pass on emissions?

Yes cat may be part or most of the problem but you need to check for things that would make the cat fail.
As always a good tune up and engine running check for a log life of cat.
Good luck MT

It has not been retested yet, will do it tomorrow. If it don't go well I have to look in to the fuel system...

Cat has been ratteling for some years but I never thought it was this bad! What I don't get is why I did not get a SES light indicating post cat O2 sensor!

Next to fix is probably the AC compressor that also rattles, and it's pully whines... but it will have to wait some time.


Thanks for all help and input!
//Freddy

[MT-2500]

Originally Posted by frehol

It has not been retested yet, will do it tomorrow. If it don't go well I have to look in to the fuel system...

Cat has been ratteling for some years but I never thought it was this bad! What I don't get is why I did not get a SES light indicating post cat O2 sensor!

Next to fix is probably the AC compressor that also rattles, and it's pully whines... but it will have to wait some time.


Thanks for all help and input!
//Freddy

Is it the W code engine?
OBD11 vcm compter?
Two or three pcm systems were used in 95.
Some do not set cat codes or use the rear 02 sensor to test and watch cat.
Good luck with the testing.
And let us know how it goes.
MT

[frehol]

It passed!

CO 0.1 (0.5)
CO@2500rpm 0.1 (0.3)
HC 089 (100)
LAMBDA 1.01 (0.96-1.25)

HC is a bit high, but it passed this year too...

Originally Posted by MT-2500

Is it the W code engine?
OBD11 vcm compter?
Two or three pcm systems were used in 95.
Some do not set cat codes or use the rear 02 sensor to test and watch cat.
Good luck with the testing.
And let us know how it goes.
MT

Yes it's a W code engine and OBDII (connector and VCM). Have no scanner and dont want to put up 800SEK (about $100) to get it scanned at a shop when I don't even have a SES light lit... (it's expensive here in Sweden... )


//Freddy

[MT-2500]

Thanks for posting back how it went.
Glad it made the grade.
Keep it tuned up good and it should be good for a long tiime.
MT