Engine Smog system Q

7upmustang · Jun 6, 2021

Running with off-road h-pipe (no cats) but kept smog. Will delete it when new motor is dropped in - until then:

Question for the masses:

1) Where to plug the system (after bypass valve OR after diverter valve)?; and

2) Can I then plug & remove tube off diverter valve leading to exhaust?

Mustang5L5 · Jun 7, 2021

Here's a good pic that shows the air pump system

With the cats gone, it can all come out. I usually say to cap it at the tube that connects to the back of the heads. You'll find a metal pipe and a check valve. It's tough to pull the pipe off with the engine in the car, so where the check valve is i usually say put a short peice of pipe with a metal plug and two hose clamps. Everything else can come out, to the air pump and the pipe down to the H-pipe. You can cap it at the h-pipe the same way with some heater hose, a plug and two clamps.

If youa re keeping the EGR you need to pay attention to the vac lines to keep the EGR regulator line intact

7upmustang · Jun 7, 2021

Thanks -

I’m familiar with the system & can cap/remove/plug - I just didn’t want to throw any codes. I feared that removing the TAD/TAB solenoids would throw codes.

Like I mentioned I’m keeping the pump for now:

At what point in removing the remaining parts in the system would codes pop up?

7upmustang · Jun 7, 2021

Mustang5L5 · Jun 7, 2021

I'm unsure if the TAB/TAD solenoids are actively tested or passively. I want to say they are passive, meaning the system looks for changes in the o2 sensor readings to see if they are working properly.

The minute the air pump cannont pump air into the heads, or the h-pipe, you'll get a code. However, these codes do not trigger the CEL nor cause the ecu to change anything about how the car runs.

7upmustang · Jun 7, 2021

Mustang5L5 said:
I'm unsure if the TAB/TAD solenoids are actively tested or passively. I want to say they are passive, meaning the system looks for changes in the o2 sensor readings to see if they are working properly.

The minute the air pump cannont pump air into the heads, or the h-pipe, you'll get a code. However, these codes do not trigger the CEL nor cause the ecu to change anything about how the car runs.

Thanks for the insight.
Previous advice in this site mentioned:

“The best thing to do is to put a cap on the diverter valve or plug in the hose where it comes off the diverter valve to the crossover pipe.”

this was to avoid having “smog pump air to pass into the heads or the hpipe,if converters are no longer present,because the extra air might get measured by the O2 sensor's,causing a lean signal.”

7991LXnSHO · Jun 7, 2021

Mustang5L5 said:
I'm unsure if the TAB/TAD solenoids are actively tested or passively. I want to say they are passive, meaning the system looks for changes in the o2 sensor readings to see if they are working properly.

The minute the air pump cannont pump air into the heads, or the h-pipe, you'll get a code. However, these codes do not trigger the CEL nor cause the ecu to change anything about how the car runs.

If the solenoids are unplugged, it will throw codes. If they do not have air going through them, I do not think they can tell the computer otherwise.

jrichker · Jun 9, 2021

@7upmustang

Save your old H pipe - in the future you may net be able to sell or title your care without it...

You will make codes...

Code 81 – Secondary Air Injection Diverter Solenoid failure AM2. The solenoid valve located on the back side of the passenger side wheel well is not functional. Possible bad wiring, bad connections, missing or defective solenoid valve. Check the solenoid valve for +12 volts at the Red wire and look for the Lt Green/Black wire to switch from +12 volts to 1 volt or less. The computer controls the valve by providing a ground path on the LT Green/Black wire for the solenoid valve.

With the with the ignition on, look for 12 volts on the red wire on the solenoid connector. No 12 volts and you have wiring problems.

With the engine running, stick a safety pin in the LT Green/Black wire for the solenoid valve & ground it. That should turn the solenoid on and cause air to flow out the port that goes to the pipe connected to the cats. If it doesn't, the valve is bad. If it does cause the airflow to switch, the computer or wiring going to the computer is not signaling the solenoid valve to open.

Putting the computer into self test mode will cause the solenoid valve to toggle. If you listen carefully, you may hear it change states.

Code 82 – Secondary Air Injection Diverter Solenoid failure AM1. Possible bad wiring, bad connections, missing or defective solenoid valve. Check the solenoid valve for +12 volts at the Red wire and look for the Red/White wire to switch from +12 volts to 1 volt or less. The computer controls the valve by providing a ground path on the Red/White wire for the solenoid valve

With the engine running, stick a safety pin in the Red/White wire for the solenoid valve & ground it. That should turn the solenoid on and cause air to flow out the port that goes to the pipe connected to the heads. If it doesn't, the valve is bad. If it does cause the airflow to switch, the computer or wiring going to the computer is not signaling the solenoid valve to open.

Both 81 & 82 codes usually mean that some uneducated person removed the solenoid control valves for the Thermactor Air system in an attempt to make the car faster. It doesn't work that way: no working control valves can cause the cat converters to choke and clog. If you do not have cat converters on the car, you can ignore the 81 & 82 codes.

7upmustang · Jun 9, 2021

whelp......thanks everyone for the information; unfortunately I'm not sure what to do.....

I have the entire smog system hooked up & will keep the pump until new engine comes along.
I do not have any cats.

Do I:
1) Keep the entire system hooked up? or
2) Plug some of the system? (in which case can I remove the diverter to exhaust tubing b/c of mounting issues with the pipe?) or
3) Remove everything downwind of the pump (preserving vacuum for the ERG) & plug where necessary.

I'm tempted to just find a way to mount the pipe leading to the h-pipe & keep the system......

Mustang5L5 · Jun 9, 2021

If the easiest solution is to leave everything hooked up for now, just do that.

Best solution for the pipe to the H-pipe is to cut the pipe so there is a 3-4" gap between the two pipes where the connect. Then use a peice of 3/4" heater hose and two hose clamps to connect them. This is how a lot of aftermarket H-pipes recommend the setup be installed and they usually include the hose.

this was the hose included with my bassani x-pipe

7upmustang · Jun 9, 2021

Mustang5L5 said:
If the easiest solution is to leave everything hooked up for now, just do that.

Best solution for the pipe to the H-pipe is to cut the pipe so there is a 3-4" gap between the two pipes where the connect. Then use a peice of 3/4" heater hose and two hose clamps to connect them. This is how a lot of aftermarket H-pipes recommend the setup be installed and they usually include the hose.

this was the hose included with my bassani x-pipe

thanks....I still have the metal tube from the stock h-pipe. I removed it from the stock & welded it onto the off road h-pipe I'm now using. It's all hooked up with 3/4" heater hose as well. Here's the rub:

Because I read somewhere on this forum that: because I don't have cats I should avoid allowing smog air into the engine crossover tube from the diverter valve (for fear of causing a lean signal). I don't know the truth/veracity of that statement.

ALSO:

I have an incon 800 kit - the heater hose would've run right next to the exhaust manifold so to avoid melting I decided to use the stock metal pipe. With the passenger turbo (and perhaps damage to the metal pipe) there's nowhere to brace the metal tube other than against the firewall somewhere (it's going to rattle if I don't brace it somehow). I was just hoping to get rid of the hose & metal tube so I can drive the dang thing but I guess a mount of some sort is in order.....

Mustang5L5 · Jun 9, 2021

7upmustang said:
Because I read somewhere on this forum that: because I don't have cats I should avoid allowing smog air into the engine crossover tube from the diverter valve (for fear of causing a lean signal). I don't know the truth/veracity of that statement.

not true. During warmup on a cold engine, the diverter directs the air from the pump to the heads which would then exit the exhaust ports and flow into the upstream cats. During cold start warmup, the o2 sensors are ignored.

once warmed up, the diverter directs air to the h-pipe. The entry point is after the o2 sensors, so they have no bearing on air/fuel mixture.

7991LXnSHO · Jun 9, 2021

jrichker said:
@7upmustang

Save your old H pipe - in the future you may net be able to sell or title your care without it...

A coincidence, we have been getting notices about cats being cut off of trucks at night lately. If they get a jack, cars are next.

Mustang5L5 · Jun 9, 2021

7991LXnSHO said:
A coincidence, we have been getting notices about cats being cut off of trucks at night lately. If they get a jack, cars are next.

same here. Local news reports on truck cat
thefts are up

on my DD, the cats are bolted onto the manifolds. You really need to get up in there to cut them off. I don’t see it happening, although I don’t really live in a neighborhood where you see that sort of things.

btw I’ve seen stock h-pipe sell on the classified for $500ish. I’ve gotten some quotes on the cats on the one I have and it makes my jaw drop. I’ll be hanging onto it for now

Dan02gt · Jun 10, 2021

Mustang5L5 said:
same here. Local news reports on truck cat
thefts are up

on my DD, the cats are bolted onto the manifolds. You really need to get up in there to cut them off. I don’t see it happening, although I don’t really live in a neighborhood where you see that sort of things.

btw I’ve seen stock h-pipe sell on the classified for $500ish. I’ve gotten some quotes on the cats on the one I have and it makes my jaw drop. I’ll be hanging onto it for now

I have a E150 work van that only gets driven about once a week and someone stole the cats off it. We keep it in the front of our office right next to a busy road. In fact they hit every vehicle in our office complex that was left parked overnight. We ended up installing a security camera pointed at our work vehicles to at least have something to give the police if it happens again.

2000xp8 · Jun 11, 2021

In 2021 i'd keep the entire car smog legal.
In the 80's and early 90's there wasn't a whole lot of good legal, high flow options out there. Besides stupid teenagers (that includes me), just had to have the cats gone so the exhaust sound was louder and deeper.
Modern cars prove you can sound good, be powerful and still have cats (think gt350).
Deleting parts does little to no good these days.

To the OP, see if you can just get a good high flow catted pipe and keep it all intact.

7upmustang · Jun 11, 2021

Due to costs cats aren't going back on; the purpose of this thread was to see what alternatives were available (and consequences) to having no cats & the smog (or partial) system.

7991LXnSHO · Jun 11, 2021

7upmustang said:
Due to costs cats aren't going back on; the purpose of this thread was to see what alternatives were available (and consequences) to having no cats & the smog (or partial) system.

Consequences,
1. It’s getting to be more of a possibility of having your car limited to off road use or impounded while it is in off road only condition.
2. The computer will spit out irritated codes. Will the absence of all smog “ stuff” make your car run worse? I cannot say for sure. I can say my 5.0 was much more streetable by the time I restored the equipment and successfully made it through the surging Idle checklist etc. The weight of the parts, not including the cats, was not a significant amount on anything but a strip only car.
3. Options - an aftermarket ECU programmed or a chip to maximize the combo and lack of parts if you go farther than removing the cats.

If you remove the AiR system and keep the valves hooked up to the computer to avoid most codes, you probably can unhook the hoses, remove the crossover pipe, block the air tube going into the H pipe, and use either the plugs like that are at the front of the head to block the thermactor ports or get bolts and washers the right size so you can get them out later easier if needed.
Good luck.

7upmustang · Jun 11, 2021

Thanks for all the replies. Was hoping to get definitive answers about keeping the smog system with no cats but I guess I'll just have to find out when it runs.

7991LXnSHO · Jun 11, 2021

If all you do is leave off the cats, the only problem you will have (besides possibly the EPA sooner or later) is smellier exhaust. That is definite.
There is no pair of post cat O2 sensors in this generation of Mustang, so the computer does not know if your cats are spayed, neutered or euthanized.

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