1988 GMC Sierra Air injection?

[A-2 ace]

How exactly does this work? And is there anyway it can be deleted?

 

[someotherguy]

Injects air into the exhaust stream to help the cat burn off pollutants, or some such sorcery. It was determined to not be needed to meet emissions requirements on the TBI engines and was omitted after just a couple years. If it's not required in your state to pass a visual inspection, you can ditch it. I do understand parts for it may be tricky to obtain. I don't know NM's smog laws so you should research before removal. Here in TX your '88 would already be exempt due to age.

The first TBI engines to omit the pump retained the bracket for it and just used a different belt; you *should* be able to do the same. Just look up a belt for one without the A.I.R. pump and see if it will fit. The routing may be slightly different, but try this example from a '94 5.7 TBI:

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Then you can plug the holes in the manifolds, I do believe they are NPT (national pipe taper, aka pipe thread) with simple inexpensive plugs from the hardware store. If you don't care about looks or retaining the original parts for later if needed, you can cut the lines off with some excess sticking out, and crimp them over firmly to prevent leaks. You'll need to do the same with the other end at the cat.

You may have a diverter valve in your system that has a vacuum connection to the TBI so you'll need to cap the vacuum source at the TBI, of course.

If any of this is off-base I apologize; it's been YEARS since I've seen a TBI with that setup - though I'll also bet there are threads if you search a little bit where people have done this, and posted pics.

Richard

 

[Dover]

NM does not do inspections so unless your in Albuquerque or Santa Fe, or work on on base and need an emissions test no one will ever know you removed it. Thankfuly my 90 does not have one so I have no advice on removing it.


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[PlayingWithTBI]

My 88 5.7L was a CA truck so, of course, it has the A.I.R. pump and we do have emissions here in Maricopa County so, I'm stuck with it. I really don't think there is a lot of parasitic drag from it though. The pipes going in the exhaust manifolds are the only ones you need to cap off, you can disconnect the wire plug to it and, like Richard said, plug off the vacuum hose going to it. I had to modify mine a little to work with the headers and intake, the little blue filter is for the inlet to the pump.

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The tube goes around the back of the engine and connects to the other side. The little black bell looking thing in line with the tube is a check valve so exhaust doesn't back feed into the pump.

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[A-2 ace]

Awesome thanks a bunch guys!!! I'll have to take a look at it once o get out of work... Is there a wired plug that goes to the system?

 

[PlayingWithTBI]

Is there a wired plug that goes to the system?

Yes, it's a 2-wire plug that activates the solenoid to actuate the vacuum and make it pump, otherwise it just free-wheels (hence the check valves), that's why I don't think it pulls too much HP. FWIU it only activates when the engine is cold, to help fire off the cat. The ECM doesn't even get any feed back if it's there or not so, no SES to worry about.

 

[A-2 ace]

Ok cool that makes sense.. my ride don't have cats, true dual exhaust... The motor sounds great and sounds good to, just at idle it has a slight misfire.. my cousin was saying it's nothing to worry about it's just cuz of the cats being deleted?

 

[Supercharged111]

Its sole purpose was to light off the cats for a cold start so of they're gone there is zero reason to keep the air setup. On a carb setup, the air helped during warm running with the 2 way cats.

 

[Schurkey]

1. The fittings in the exhaust manifold are very unlikely to be pipe thread. Mine are long gone, but similar systems used inverted-taper fittings, same as brake tubing but much larger.
2. The pump runs all the time. When cold (open loop) it pumps air into the exhaust manifolds as stated, to help "light off" the catalyst.
3. When the vehicle gets to "closed loop" operation, the diverter valve directs the air into the air cleaner, otherwise the added air would provide false "lean" operation of the O2 sensor because of pumping additional oxygen into the driver-side manifold.
4. The pump takes little power to run, if the thing works, leave it the hell alone.
5. Sure, it's possible to have a failed pump, or failed diverter valve, or failed check-valves. The AIR pump on my '88 K1500 failed at approx. 315,000 miles. I found another used-but-usable one to replace it with.

 

[someotherguy]

1. The fittings in the exhaust manifold are very unlikely to be pipe thread. Mine are long gone, but similar systems used inverted-taper fittings, same as brake tubing but much larger.
2. The pump runs all the time. When cold (open loop) it pumps air into the exhaust manifolds as stated, to help "light off" the catalyst.
3. When the vehicle gets to "closed loop" operation, the diverter valve directs the air into the air cleaner, otherwise the added air would provide false "lean" operation of the O2 sensor because of pumping additional oxygen into the driver-side manifold.
4. The pump takes little power to run, if the thing works, leave it the hell alone.
5. Sure, it's possible to have a failed pump, or failed diverter valve, or failed check-valves. The AIR pump on my '88 K1500 failed at approx. 315,000 miles. I found another used-but-usable one to replace it with.

You may be right on the threads. I'm thinking early TBI big block, which IIRC, are npt - but it's been years and years.

Anyhow reason for deleting the pump is I've heard of several that have seized up. If it's not required to pass smog, I say, delete it...

Richard