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Hey All,

I recently was trying to diagnose a P0411 MIL on my 1997 Mustang Cobra and had ZERO luck finding solutions on the forums. So after painstakingly going over this super obscure emissions system, I figured I'd cover my process as well as include a diagram of the airlines that make up the Secondary Air Injector System.

So I bought a 97 Cobra at the beginning of August down in South Alabama. When I purchased it, the only outstanding issue that the car had was a P0411 MIL which I quickly learned was a Secondary Air Injector System Fault. Here's how the system works, the pump pulls in fresh air when the car cold starts and feeds it through the lines and the vacuum controlled diverter valves and eventually goes into a port on the exhaust manifolds ( one on each cylinder bank) Thr purpose of this air is to help the catalytic converters heat up quicker and start working more efficiently.

( In reality, this system does not affect the performance of the car and In a market where emissions aren't required, I probably would just remove the system altogether. However, I live in an emissions required to market and thus have to comply until the car is at least 25 years old. )

Now there are several parts to a SAIS system.

1. The Secondary Air Injection Pump
2. Hoses between the valves and the pump
3 The Air Diverter Valves ( two, one of each cylinder bank)
4. Vacuum lines that control the valves
5. Valve Control solenoid that controls the opening and closing of the valves.

First things first, I knew that the pump was not working at all. I knew this because when I would start the car, the pump would make zero noise whatsoever. (It's actually pretty loud) Once I was able to pull the pump off, I tested it and was not able to get any power out of it what so ever. No the next piece here is the connecting hose. I replaced this as it was severely cracked and dry rotted. Once that was done, I pulled the Diverter Valves off and found that they were full of soot and carbon build-up. i cleaned and them with brake cleaner. ( we will come back to this) After that, i snaked out the air injection ports with a literal plumbing snake as this is a commonplace for carbon to build up and block the air from moving. Lastly, I went down to autozone and bought a new vacuum control solenoid for $30 and replaced it.

After I did all of this, I reset my engine computer and went to start her up. Immediately, I could see on my code reader that I already had a pending P0411 code in the system. So I went back out and started pulling parts apart to find out where I had flow in the system....Ultimately, I pulled the valves back off and realized that the vacuum seal on one was completely shot and that the other one was only opening slightly.

Now the problem here is that Ford no longer makes these valves. This means that the few parts that are out there, run about $300 per valve. Now the good news here is that ford did not change the design of this valve very much over the years so you can actually pull from other vehicles to satisfy the need for new valves.

Below is the part number for my 97 Cobra as well as the part number that I substituted for it.

1997 Ford Mustang Cobra - F6ZE -9F491-DA
1999 Ford Mustang GT - XR3Z-9F491-EB

The important part when choosing a substitute part is that it must have the same size valve stem on it for the vacuum line and it must have the same bolt pattern for the mounts. Other than that, Ford left the design for these basically the same all the way up until 2009 .
Once I changed out the valve, I reset my computer and tried again, this time I did not have any pending codes whatsoever and did not have any further issues with the SAIS system. Also, one thing to note here, this code will not throw officially until about 4 failed pump turnons so its super important that you have a computer monitor or a code reader of some kind so that you can efficiently see if you have a problem rather than waiting until you have driven 60-70 miles.

I hope all of this helps...this was a giant pain in the butt and I hope I can provide some insight into someone dealing with a similar issue.
 

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I've been chasing this problem on my 97 Cobra for 5 years. When it first happened it was the vac solenoid. No vac...pulled it and it was all gunked up and corroded. Replaced it. Good for about a year.
Found your idea of snaking the tubes intriguing. I've had a related carbon clog on my truck... so ripped it apart today. Used an old control cable off a heater control and a drill (on slow) got all the way to the manifolds on both sides. No clogs. Ran compressed air down both tubes and have air out both exhaust pipes.
The air system cycles on initial startup for about 30 seconds. The vac solinoid opens, diverter valve opens and I get strong air blowing out the diverter (tube disconnected to check). All hoses intact/air tight. If I put my hand over the diverter output its pretty strong pressure. No leaks
Last year I replaced ALL four o2 sensors with motocraft replacement parts.
Still throwing p0411.
If anyone has any idea whatsoever please post. I've asked a couple knowledgable friends if the cats could be causing this? Im told no. It has stock original Cat pipe. No other codes.
Runs great. Please help.
 

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Hey All,

I recently was trying to diagnose a P0411 MIL on my 1997 Mustang Cobra and had ZERO luck finding solutions on the forums. So after painstakingly going over this super obscure emissions system, I figured I'd cover my process as well as include a diagram of the airlines that make up the Secondary Air Injector System.

So I bought a 97 Cobra at the beginning of August down in South Alabama. When I purchased it, the only outstanding issue that the car had was a P0411 MIL which I quickly learned was a Secondary Air Injector System Fault. Here's how the system works, the pump pulls in fresh air when the car cold starts and feeds it through the lines and the vacuum controlled diverter valves and eventually goes into a port on the exhaust manifolds ( one on each cylinder bank) Thr purpose of this air is to help the catalytic converters heat up quicker and start working more efficiently.

( In reality, this system does not affect the performance of the car and In a market where emissions aren't required, I probably would just remove the system altogether. However, I live in an emissions required to market and thus have to comply until the car is at least 25 years old. )

Now there are several parts to a SAIS system.

1. The Secondary Air Injection Pump
2. Hoses between the valves and the pump
3 The Air Diverter Valves ( two, one of each cylinder bank)
4. Vacuum lines that control the valves
5. Valve Control solenoid that controls the opening and closing of the valves.

First things first, I knew that the pump was not working at all. I knew this because when I would start the car, the pump would make zero noise whatsoever. (It's actually pretty loud) Once I was able to pull the pump off, I tested it and was not able to get any power out of it what so ever. No the next piece here is the connecting hose. I replaced this as it was severely cracked and dry rotted. Once that was done, I pulled the Diverter Valves off and found that they were full of soot and carbon build-up. i cleaned and them with brake cleaner. ( we will come back to this) After that, i snaked out the air injection ports with a literal plumbing snake as this is a commonplace for carbon to build up and block the air from moving. Lastly, I went down to autozone and bought a new vacuum control solenoid for $30 and replaced it.

After I did all of this, I reset my engine computer and went to start her up. Immediately, I could see on my code reader that I already had a pending P0411 code in the system. So I went back out and started pulling parts apart to find out where I had flow in the system....Ultimately, I pulled the valves back off and realized that the vacuum seal on one was completely shot and that the other one was only opening slightly.

Now the problem here is that Ford no longer makes these valves. This means that the few parts that are out there, run about $300 per valve. Now the good news here is that ford did not change the design of this valve very much over the years so you can actually pull from other vehicles to satisfy the need for new valves.

Below is the part number for my 97 Cobra as well as the part number that I substituted for it.

1997 Ford Mustang Cobra - F6ZE -9F491-DA
1999 Ford Mustang GT - XR3Z-9F491-EB

The important part when choosing a substitute part is that it must have the same size valve stem on it for the vacuum line and it must have the same bolt pattern for the mounts. Other than that, Ford left the design for these basically the same all the way up until 2009 .
Once I changed out the valve, I reset my computer and tried again, this time I did not have any pending codes whatsoever and did not have any further issues with the SAIS system. Also, one thing to note here, this code will not throw officially until about 4 failed pump turnons so its super important that you have a computer monitor or a code reader of some kind so that you can efficiently see if you have a problem rather than waiting until you have driven 60-70 miles.

I hope all of this helps...this was a giant pain in the butt and I hope I can provide some insight into someone dealing with a similar issue.
This is really good information. I'm having the same persistent problem on my 1998 3.8L v6. I'll go through these components to see what else I can find wrong. Thanks for posting this.
 

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I've been chasing this problem on my 97 Cobra for 5 years. When it first happened it was the vac solenoid. No vac...pulled it and it was all gunked up and corroded. Replaced it. Good for about a year.
Found your idea of snaking the tubes intriguing. I've had a related carbon clog on my truck... so ripped it apart today. Used an old control cable off a heater control and a drill (on slow) got all the way to the manifolds on both sides. No clogs. Ran compressed air down both tubes and have air out both exhaust pipes.
The air system cycles on initial startup for about 30 seconds. The vac solinoid opens, diverter valve opens and I get strong air blowing out the diverter (tube disconnected to check). All hoses intact/air tight. If I put my hand over the diverter output its pretty strong pressure. No leaks
Last year I replaced ALL four o2 sensors with motocraft replacement parts.
Still throwing p0411.
If anyone has any idea whatsoever please post. I've asked a couple knowledgable friends if the cats could be causing this? Im told no. It has stock original Cat pipe. No other codes.
Runs great. Please help.
I have a 97 Cobra as well. Followed this guide and my air pump looked good, the hoses from it looked good, the vac solenoid which has the vacuum hoses tracing to the valves looked good. I didn't want to take the valves off and find a replacement if I didn't have to.

Here's what fixed it for me: trace the vacuum hoses coming from the two valves. The one from he left goes up to a three way junction. From that junction, one of those hoses goes to what looks like a second vacuum control solenoid.

I don't know how it tall works, but it looks like all of these vacuum hoses are shared by another system. At that junction one of my vacuum tubes broke off.

If one of them brakes, none of them will pull a vacuum.

To remove the old piece of tube from that junction I twisted a screw into it and pulled it out like a wine cork. Because the remaining hose was shorter and I didn't want more tension on it, I inserted it into the junction and used a zip tie to firmly hold it in. Hopefully next time it will slip out and not break off.

Hope that all makes sense. Good luck.

Edit: If your diverter valves work then this is not relevant. This is what I did to get my diverter valves to function.
 
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