I just bought a 1994 Z28 and the service engine light is on. The tech told me he pulled a code 29 air system????? Help please!!!!! thanks

Steve

 

Don't worry about it. All it does is recirculate exhaust gasses for about 2 min after startup. I removed mine. If you have emissions, you might want to get it fixed depending on what they look for.

 

AIR pump doesn't 'recirculate exhaust gases' unless it is running backwards..
It takes fresh air, and pumps it into the exhaust manifolds, to heat the cats up..

 

The usual cause of DTC 29 is a blown fuse for the AIR pump. Check the fuse, and if its blown, replace it. It may continue to blow, in which case you will either need to replace the AIR pump (they rust and seize up), or simply disconnect the harness connector from the pump and put a good fuse in the circuit. That will eliminate the SES light.

 

That's funny right there I don't care who you are.

It's true that the air pump brings in fresh air (from the intake elbow after the air filter) and blows into the exhaust manifold. BUT it can NOT suck exhaust if it runs backwards because.... Those funny looking doodads on the exhaust manifold are check valves. They have to be there otherwise, the exhaust would go into the pump. If the pump ran backwards, it would immediately die and probably blow a fuse to boot.

BTW, the EGR system is behind the intake manifold and is hard piped from the passenger side exhaust manifold to the back of the intake below the FPR area.

EGR and the air injection system are 2 different systems. Both help with emissions but work entirely differently. One helps with Catalyst efficiency and the other puts a small amount of exhaust back into the cylinders.

Not making fun of anyone, just enjoying the conversation.

Dave

 

You may want to check a dealer, because I had my air pump fixed for free due to a recall on it.

 

Recall was only for 95's and newer. 94's were not included.

 

Well I didn't mean it literally.. it was the easiest [and shortest] way to post that he had it 'backwards'... [and if it COULD run backward it WOULD recirculate exhaust gases..]and yes I know the diff between AIR and EGR.. and what AIR check valves are, etc..

 

thanks everyone!!!!! I just unplugged it and replaced the fuse. will it cause any performance loss or will it hurt my engine? Can I just keep it this way since i'm in north dakota and we don't have emisions?? thanks

Steve

 

A good fuse, and having it unplugged is OK for OBDI[your 94]
No performance loss, nor will it hurt the engine..
You can leave it that way..

 

Oh so hostile........ (Barbara Walters)

(Indian Chief replys)...... Hostile, Dog style, any style me don't care.

Oh dear......BW

No Deer, A$$ too high, run too fast.

Chill out buddy, Slopok was replying to the other person more so than you.

 

When the engine is cold it needs more fuel to run. As it warms up it needs less fuel. Air pumped to the exhaust manifold in front of the O2 sensor is called "upstream." Air pumped after the O2 or into the cat is called "downstream." On the LT1, the air is only pumped when it's cold into the exhaust manifold. With a rich mixture the O2 can become contaminated. The air is pumped to dilute the mixture before it gets to the O2. After the engine is warmed up, the air shuts off or is pumped after the O2 to allow the O2 to control the air/fuel mixture.

 

Every technical document I have ever read on the secondary AIR system indicates that the extra air (21% O2) is provided during intial startup/cold conditions to help oxidize the excess HC and CO from the rich cold-start mixture. The oxidation of the HC and CO is an exothermic reaction, providing heat to heat up the catalytic convertor, so it starts operating sooner.

 

Upstream air is to keep the O2 clean until the engine goes into closed loop. Once into closed loop the air is cut off to allow the O2 to control fuel. If the system has downstream air, the air is diverted after the O2 to allow the cat to be more efficient. The cat doesn't become 100% efficient until the engine is warmed up, anyway. The ability of the O2 to work quickly is more important than a few minutes of cat non-efficientcy.

 

Again, you are contradicting every technical document I have ever seen. 90% of the emissions from a modern computer controlled vehicle are generated on cold start. Getting the cats up to operating temperature quickly, while also reducing the HC and CO content is extremely important - at least in the eyes of the EPA.

Unlike your 3rd Gen, the LT1 cat is a mixed bed, and does not require the injection of air between the beds to provide oxidizing air for the second catalyst bed. That part of the discussion is a moot point.