What are the benefits and/or drawbacks to removing the Secondary Air Injection system on a 1996 4.0L car?

By '96 the pump is ran by an electric motor (so the engine isn't turning it) but it still adds a lot of pluming and a bit of extra clutter under the hood, though admittedly not as bad as previous years. Seems as though it would be very easy to eliminate the system on these models so long as there are no drawbacks. Unplugging the electrical connector and driving around does not turn on the MIL light or even set a code of any kind that I can tell.

 

In theory having the pump disconnected 'should' give a CEL and code P0411 ....at least that's what happened on my '95 XJR. Oddly, once the code was cleared it never came back even though I had the pump disconnected for quite some time. But, as we know, the early OBD II wasn't all that great.

If anything bad happened from having the pump disconnected it wasn't at all apparent to me. If you have emissions testing, though, it might be a concern.

Cheers
DD

 

SouthernGypsy, I see by your other posts that you have taken the AA pump off your car. I have a question or two. When removing the large hoses off the pump I need to know if there is a need to block them off or remove them from whatever they are connected to. The same goes for the metal lines coming off the exhaust manifold. I can't see where they hook to the engine after they go around back of the engine. I have to believe they need blocked off somewhere. It would help to know all this before I start removing parts so I can determine if it is worth the trouble.

What is the pump supposed to do. I know you said removal may give an increase in MPG. That would be helpful.
Cheers, RagJag

 

I removed the hoses totally so wasn't anything left to block off. The tube running around the back of the engine does just that, it only runs around, it's not connected so nothing to block off there. All the tube does (on an AJ16 engine, the AJ6 is a little different) is to have a ribbed hose coming out of the air-box, it runs into the electric pump, then a larger hose comes out of the air-pump and into the one-way check valve, then a metal tube comes out of the one-way check valve and runs along under the intake manifold (read note below), the tube then bends around the back of the engine and connects into a fitting which splits it into the two smaller tubes which just screw into the exhaust manifold. I cut off the tubes and took those two nuts to my local welding shop who charged me $5 to cut two small pieces out of a bolt that just fit into them where the tubes came out leaving the pieces so they was a bit shorter than the tubes, then they welded up the end. These acted as caps now and was put back into the exhaust manifold. I also found a cone-shaped rubber plug that I wedged into the air-box where the hose had connected to it (that connection is AFTER the air-filter so blocking that off is important or it will suck in un-filtered air) That's all there was to the system. So all you really have to worry about blocking off is the hole left in the air-box where (#11 in the pic) connects, and welding the two nuts (#8 in the pic) so they are closed on the inside and then putting them back in as caps.

Note: there are two tabs which hold that metal tube to the block on the side under the intake manifold so you need to remove the 10mm bolts, once the tube is off put flat washers of about the same thickness the metal tabs on the rail had been on the bolts and replace them because those bolts also pass through the water-rail and you will develop a coolant drip if you don't put the bolts back in.



Here is a pic of the system;

 

Here is a pic of what the two nuts (#8) looked like after my welding shop welded them closed and I put them back in and sprayed a little high-heat black on them (since they was bright silver after the welding). My welding shop felt the holes through them was too large to "fill" with weld, So what they did was to find a regular bolt that had a smooth shank that just fit into them and cut the bolt off so they had two small pieces that was not as tall as the nuts was by a small amount. Then pushed them into the holes so the bottom was flush with the threaded end of the nuts (meaning the top was counter sunk) and then set them in a shallow metal pan of water that just came up to the top of the threads, and then welded in the top sealing it off and leaving them a little dome shaped on top. Then poured more water on them once they cooled a little so get them cold again after the welding and then they took the tops to first a bench grinder to smooth the weld off, then a polishing belt to give them a finished look. When I got home I took my Dremel tool and further rounded the edges just a little. Sprayed a little satin black BBQ & Stove paint on the threads and ran them in all the way until the shoulders bottomed out and they was snug. The sprayed a little more of the paint on them and the area of the manifold around them. The paint wont last on something as hot as an exhaust manifold but what that will do is once it cooks off it will give them an artificially aged look so they look like they have always been in the manifold. Yes, I went a little OCD with that part but I have no plans of ever needing to take them back off again. I need to clean off the stainless heat shield and polish it up again but that's a project for another day.

 

Outstanding,Sir. Thank you for this excellent post. I am going to remove mine as soon as I can get a little time and weather to suit. It will be interesting to see if the MPG improves. Even it not, I still want it gone because of the clutter.
RagJag.

 

There's little reason to think that MPG will improve. The electric air injection pump usually runs for just a minute or two after start-up. I can't see how that electric pump can influence fuel economy, and the designed function of air injection....which takes place *after combustion has already occurred* ....certainly can't.

Frankly, even the older belt-driven air injection pumps drew very little power...certainly less than an alternator or p/s pump. Claims of more power or better MPG after removal were always a bit iffy IMHO. Until, of course, the pump got old and began to seize up, that is


Cheers
DD

 

Yeah, my LT1 has an electric pump. Other than the extra "junK" under the bonnet, it is relatively harmless. Mine is there only to please the SMOG inspector.
Carl

 

Removing it for sure made difference in MPG and Power on the old belt-driven models, albeit a small one but it was there.

On the electric model pumps that are running CORRECTLY it's mainly the clutter under the hood, the pump in particular makes it a PITA to get to the alternator and belt tensioner, then you have the extra heat build-up from those pipes running around the motor and under the intake manifold, and some extra current drain when the motors running.

However they seem to fail or have other issues quite a bit, both the motors and the one-way check valve... Having a check valve that has failed or partially failed and is allowing even a little exhaust back into the fresh incoming air once the pump quits running affects gas mileage, power, proper idle, and even if your engine burns no oil it eventually carbons up your throttle-body which in turn leads to more problems, and if your engine does burn a little oil then that carbon build up is actually a wet messy black gunk and you can imagine what that would do to your performance, not to mention your sensors.

 

I believe:


the extra air at start up is detected by the O2 sensor and the mixture is enriched the rich mixture is now not fully burnt so it and the extra air from the pump help "Light off" the cat-converter


I might be wrong though...


so a little extra mpg might be seen if you take short hops in the car with out it warming up...