88 Suburban TBI Smog pump question

[BR@NDON]

Please let me know the pro's and con's to removing the smog pump and a.i.r. system components.

Will removing these things throw a CEL code or burn the Cats?

 

[v2500burb]

I've wondered the same thing
The move useless parts I remove the better


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[Senck243]

I've also have been wondering the same on my 87


Sent from hell

 

[89Suburban]

I don't have the answer but I have read that lack of a certain amount of exhaust back pressure can affect operation of the TBI and throw a code. Not sure if that is true or not. If the A.I.R. system does not inject into the manifold with the O2 sensor then I would say it should not affect anything removing and plugging off the A.I.R. system.

 

[chengny]

Consider doing a simulated test.

Remove the belt from the air pump(s), pull the supply hose off check valve inlet nipple (also plug/cap the nipple to prevent any air from being sucked in to the exhaust) and then drive normally for a couple of weeks.

If you don't throw any codes (or notice a decrease in performance), you can feel confident that removing the entire system will not cause any problems.

As far as the catalytic converters; they are designed to operate at extremely high temperatures anyway. Eliminating the small quantity air that is injected by the AIR system certainly won't cause them to fail.

 

[BR@NDON]

Thanks for the replies guys

 

[bucket]

I removed the smog pump and related hardware from my '88 years ago and never looked back. There has never been a check engine light because of it. I've removed it on TBI equipped cars too, with no trouble.

 

[89Suburban]

I removed the smog pump and related hardware from my '88 years ago and never looked back. There has never been a check engine light because of it. I've removed it on TBI equipped cars too, with no trouble.

Yeah but we already know you an outlaw.

 

[anubisani]

I removed mines on my 88 last year with no chk eng lights or problems

 

[bucket]

Yeah but we already know you an outlaw.

Yep, I'm a rebel without a cause

 

[rich weyand]

Removing the AIR pump will actually decrease the temperature of the catalytic converters. The AIR pump exists to continue combustion in the exhaust manifold, in order to get rid of unburned hydrocarbons in the exhaust at idle. The vacuum advance on these engines was connected to ported vacuum, which defeated the vacuum advance at idle. The late firing of the charge at idle caused the mixture to be still burning when it passed through the exhaust runners into the manifold. With fresh air being pumped in, the exhaust gasses continued burning. This caused the primitive cats then in use to run very hot as well, which helped them operate effectively.

Removing the AIR pump will increase your unburned hydrocarbons at idle, which is an issue if you still need to be smog checked.

If you remove the pump, you should move the vacuum advance vacuum line to a manifold vacuum port to get correct timing at idle. This will make your engine idle much better (you will probably have to adjust the idle speed back down), kill any off-idle hesitation that sometimes results from ported vacuum (because the distributor has to advance to the correct position when you crack the throttle), and reduce engine heat at idle (because you aren't dumping a late-fired mixture through the exhaust runners in the heads).

 

[bucket]

Removing the AIR pump will actually decrease the temperature of the catalytic converters. The AIR pump exists to continue combustion in the exhaust manifold, in order to get rid of unburned hydrocarbons in the exhaust at idle. The vacuum advance on these engines was connected to ported vacuum, which defeated the vacuum advance at idle. The late firing of the charge at idle caused the mixture to be still burning when it passed through the exhaust runners into the manifold. With fresh air being pumped in, the exhaust gasses continued burning. This caused the primitive cats then in use to run very hot as well, which helped them operate effectively.

Removing the AIR pump will increase your unburned hydrocarbons at idle, which is an issue if you still need to be smog checked.

If you remove the pump, you should move the vacuum advance vacuum line to a manifold vacuum port to get correct timing at idle. This will make your engine idle much better (you will probably have to adjust the idle speed back down), kill any off-idle hesitation that sometimes results from ported vacuum (because the distributor has to advance to the correct position when you crack the throttle), and reduce engine heat at idle (because you aren't dumping a late-fired mixture through the exhaust runners in the heads).

I've often removed those pesky converters too

In the case of the TBI with no vacuum advance, does the same result apply? I don't remember if air was pumped into both manifolds or just the passenger side. The O2 sensor was on the driver's side.

 

[rich weyand]

Should be pumped into both sides.

The TBI computer control will run the timing per the factory ignition curve. Not sure if there is a vacuum sensor for the computer or not.

 

[BR@NDON]

Thanks for that information - makes sense.

 

[Derick C.]

My 90 burb has had the smog pump removed by previous owner. He put headers and aftermarket cat on it. I will have to look and see where the vacuum advance is hooked up. it runs great but it does surge a little at idle. Idles fine until its warmed up and then it will idle around 700 rpm for 10 seconds or so and jump up to 950 for about the same time and only does this in park.