Another Ca Smog Question

bruno said:

It's that time again. Here's my story.

I took the car in (stock 91 GT) for smog check it came back with high HCs. My mechanic takes a look at the car and says everything else is checking out fine, so the cats need to be replaced. So instead of having them just cut and place new cats I decide to just buy a new emmisions legal h-pipe. They switch out the pipes and I fill up with 91 octane and drive the car on the highway for 60 or so miles to break in the cats then retest. HCs are now in the clear but my NOx readings are failing; they have tripled to 900s.

After some more research I find out these pipes are not CA legal; I specifically asked the guy over the phone if they were, he had said yes. At this point I just want my car to pass. Unfortunately i no longer have the stock h-pipe with 4 cats, as the shop threw it out.

So my question is if I had the shop add carb certified pre-cats and cats to my new h-pipe would that be legal?

Also anyone know of a smog testing center near Culver city in LA that would do a pretest before charging?

Thanks in advance.

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I had a similar problem with my 89 GT...I had bought and replaced my whole exhaust system with a Bassani S/S cat back and xpipe. The xpipe had only two cats and that was ok for several years...apparently the law has changed and the smog shop that failed me failed me only because I did not have the four cats on the exhaust system it.failed as tampered exhaust. this was a visual fail...all the other sniffer test the car had passed. I took it to my mechanic and we added two more cats (magnaflow) high flow cats, retested and passed. There is a slight change in sound but performance is still the same. The smog checks were performed in San Diego.

bruno said:

After some more research I find out these pipes are not CA legal; I specifically asked the guy over the phone if they were, he had said yes. At this point I just want my car to pass. Unfortunately i no longer have the stock h-pipe with 4 cats, as the shop threw it out.
Thanks in advance.

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Clue: they didn't just throw them out, they cut them up and salvaged the rare metal catalyst. That catalyst is very expensive and valuable on the scrap/recycle market. so you got ripped off coming and going.

I had no issues passing CA smog with my magnaflow catted x pipe. Granted they did not do a visual of the cats (went to a local smog shop with no lift). I think you definitely have something else going on if your nox levels are that high

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No codes at all??
I think browsing around for locations will also help. Plenty of LAZY workers that don't lift it up, but may use a quick
mirror on the ground etc. Nothing like 2 old gutted out cats inline. But the numbers have to be right on the screen, so playing with conditions rich, lean, fresh oil, lower octane, less timing may could all work together after you check codes.

No codes? If you didn't get a code 11, you have computer or wiring problems that would definitely affect the ability to pass emissions testing.

How to pass emissions testing:

High NO - high combustion temps - retard timing, check EGR for operation.
High CO – Rich condition - fuel pressure too high, check O2 sensors, replace air filter, Clean MAF element.
High HC – Lean misfire, vacuum leak, common misfire due to worn or weak ignition system components. On rare occasions, an overly rich mixture may be the cause. Do the ethanol/E10 fill up as suggested.
High CO & HC - Cat converters, smog pump, and smog pump controls. Make sure the smog pump has good air output at 1200-1700 RPM

How to pass emissions testing:

1.) Make sure all the emissions gear the car was made with is present and connected up properly. That includes a working smog pump and cats. The smog tech will do a visual check to make sure that all the original equipment is present and connected up.

2.) Make sure that you have fresh tune up with spark plugs, plug wires, cap, rotor, fuel & air filters. An oil & filter change is a good idea while you are at it.

3.) [Dumping the computer diagnostic codes on 86-95 Mustangs

Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.

Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.

Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

Post the codes you get and I will post 86-93 model 5.0 Mustang specific code definitions and fixes. I do not have a complete listing for 94-95 model 5.0 Mustangs at this time.

Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. On a manual transmission car, be sure to press the clutch to the floor.
Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.





If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.



The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.



The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and driveablity problems

Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off, and clutch (if present) is pressed to the floor, and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Your 86-88 5.0 won't have a working Check Engine Light, so you'll need a test light.
See AutoZone Part Number: 25886 , $10




Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see Equus - Digital Ford Code Reader (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.


Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off, clutch depressed to the floor and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.
Cylinder balance test
Warm the car's engine up to normal operating temperature. Use a jumper wire or paper clip to put the computer into test mode. Start the engine and let it go through the normal diagnostic tests, then quickly press the throttle to the floor. The engine RPM should exceed 2500 RPM's for a brief second. The engine RPM's will increase to about 1450-1600 RPM and hold steady. The engine will shut off power to each injector, one at a time. When it has sequenced through all 8 injectors, it will flash 9 for everything OK, or the number of the failing cylinder such as 2 for cylinder #2. Quickly pressing the throttle again up to 2500 RPM’s will cause the test to re-run with smaller qualifying figures.
Do it a third time, and if the same cylinder shows up, the cylinder is weak and isn’t putting out power like it should. See the Chilton’s Shop manual for the complete test procedure



4.) Post the codes and get help to fix them. Don’t try to pass with codes not fixed. Clearing the computer just temporarily removes them from memory, it doesn’t fix the problem that caused the code to be set.

5.) Be sure to do the testing on a hot engine. Drive for 15-20 minutes prior to taking the test to get operating temps up into the normal range. Do not shut off the engine while waiting for your turn on the test machine. An engine up to full operating temperature puts out fewer emissions.