My other car failed smog

[minifridge1138]

Hello everyone,

I recently moved to an area that requires a smog test and my other car failed.
It is a 1995 5.0L Mustang.

The CEL is not on, so the computer thinks everything is fine.

It failed Hydrocarbons, carbon monoxide, and nitrous oxide.

I've never lived in a place that did smog, so I'm not even sure where to start.

I don't want to throw random parts at it, so how do I find just the trouble areas and focus on those?

I guess this doesn't belong in the C3 forum, but this is the best place I've found for advice so I decided to start here.

Thanks everyone,

-David

 

[Rex S]

Need the readings from the test to know where to start.

 

[minifridge1138]

My Numbers? No problem...


------------RPM | HC PPM | CO (%) | NO PPM
15 mph | 1842 | 139 (59) | 0.76 (.34)| 933 (484)
25 mph | 1830 | 117 (34) | 0.62 (.32)| 915 (498)

key: MyValue (Max allowed)

 

[duke94]

How many miles on the car? Try throttle body and fuel injector cleaner, set of plugs.

 

[Hib Halverson]

Is the car trying to pass the CA enhanced test or a test in another state?

Were the cats good an hot before the test?

If the car modified?

How many miles since the last time the cat converters were replaced?

Do you have the factory service manual for the vehicle?

Keep in mind that with a preOBD II car just because the engine light is not on, does not mean all is well with engine controls.

 

[minifridge1138]

California enhanced test.

The car is stock other than the air cleaner, which has a CARB#.

I have only owned the car for two years, 20k miles. I haven't replaced the cats. Anything before that time is unknown.

I have service manuals, but not factory ones (Chilton).

I had driven the car about 5 miles before the test.

The car has 153,000 miles on it.

 

[Peer81]

When I go to our test, first thing I'll go is get the oil temp up to the right temperature (takes longer then the coolant). I don't say the engine was still in open loop but with the engine up to temp around 190F it will burn the air/fuel mixture much better.

Btw. Do you know what the max CO test reading is in California for a 81 car? Overhere (got the test last week) the max is 4.5% for CO and I got between 1.8 and 2.2%.

Greetings Peter

 

[Hib Halverson]

California enhanced test.

The car is stock other than the air cleaner, which has a CARB#.

I have only owned the car for two years, 20k miles. I haven't replaced the cats. Anything before that time is unknown.

I have service manuals, but not factory ones (Chilton).

I had driven the car about 5 miles before the test.

The car has 153,000 miles on it.

Well...check the air filter to make sure it's clean. I say that because your numbers say "rich".

Next, I'd go for a retest and ask for a "pretest" first. Before you go drive the car 20 miles with a least half of that on the freeway in drive rather than overdrive. If the smog station is not close to the freeway, drive the car around the block in first gear a couple of times then pull into the station. This ensures the cats are hot, hot, hot.

If it still flunks with similar numbers then, I'd be looking for the FSM for that car. You also may need a scan tester which supports Fords OBD sysetms.

You'll need to go through everything (ign, fuel, engine mechanical problems) that would cause high emissions. If you find trouble which would cause flunking (say a bad injector or something like that) go for a retest.

If you don't find anything, replace the cats then go for a retest.

Lastly, unless you have the tools, diagnostic equipment and the FSM, you might be better to find someone who works on old Mustangs.

 

[minifridge1138]

I gave the car a once over looking for something that was plugged, stuck, or broken. Lots of things are old, but they were all working.

New cats and I passed smog.

Thanks for your help everyone.

 

[keith6469]

When were the O2 sensors replaced.

 

[minifridge1138]

I had replaced them about a year ago.
Increased my gas mileage 4 mpg when I did.