[markblock]

1991 Caprice Classic 132,000

these are the IM240 results


Reading Units Limit Result
HC: 25.9048 GPM 1.2000 Fail

Co: 124.1811 GPM 20.0000 Fail

NOX: 1.6089 GPM 2.5000 Pass


any advice?????

[oldbogie]

Originally Posted by markblock

1991 Caprice Classic 132,000

these are the IM240 results


Reading Units Limit Result
HC: 25.9048 GPM 1.2000 Fail

Co: 124.1811 GPM 20.0000 Fail

NOX: 1.6089 GPM 2.5000 Pass


any advice?????

Mixture is way too rich this is causing the high HC number which in turn is causing the CO number as well. The latter because the excess fuel uses up the available oxygen trying to burn all the gas (which it can't) before the chemical reaction of the burn can go to completion which makes the CO into CO2.

- What is the engine?
- Does it have an AIR air injection system that pumps air into the exhaust?
- Has the catalytic converter ever been serviced or replaced?
- When was the last tune up?
- Has the cam timing been checked to see if it still tracks the crankshaft?
- Has a compression or leak down test been performed?
- Has the fuel pressure test at the injector body inlet been performed?
- When was the air filter replaced?
- Does the thermostat work, engine needs to be at least 180 degrees when tested?

Bogie

[T-bucket23]

O2 ever been changed?
The numbers show there is both excess unburnt fuel HC and overly rich burnt fuel CO. Looks like the cat is working as the NOX is ok. I would check the operation of the O2 sensors and the MAF if it has one. Also if you have access to a scanner see what the fuel trims look like.
I am guessing your fuel mileage is horrible as well.

One other item is ignition timing. Overly advanced timing will show hight numbers at idle

Edit: Coolant temperature sensor, if it is not working the car will always think it is cold and will dump more fuel than a warm engine needs.
This can also be checked with a scan tool