73-87chevytrucks.com
General Site Info => General Discussion => Topic started by: gmcowner22 on October 22, 2022, 05:41:55 PM
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Ok so I have an 87 V-1500 GMC and it still has the original smog pump on the engine but it didnt have the cat. Asked my mechanic if I needed to put one back on since it had one (didnt know if PA regulations were like some other states IE WV where Im from originally) and he said no, so that leads to my question.
Ive been doing research on the site about removing it and so far I think I have a handle on the basics, the engine is a TBI 350 and from what Ive been reading I have to keep the O2 sensor. WHat Im wondering is there any other benefits to removing the smog pump and assorted "Rats" nest of pipes? (I mean besides the obvious of cleaning up the bay and having more room to work on things.) Could I use an O2 extender to move the sensor farther away from the exhaust stream, this maybe tricking it after I remove it?
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Double check regs, some states require the original set up and not all mechanics is going to give you accurate information. Check with the state laws.
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Moving the O2 sensor will do nothing but give you driveability issues. What would make you think that is something you should do? People do this on OBDII downstream sensors to get around a failed catalytic converter.
Unless the pump has failed, there is no real benefit other than cleaning up the engine compartment.
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It was only a question, my ole 1980 didnt have a computer and the pump was already removed when I got it. Since it seemed yall have more experience with it than me I just thought Id ask.
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I know this is an older post, still wondering how it turned out...
Per VZ's comment, isn't a failed Cat state going to send the same signals as a missing Cat to the O2 sensor, affecting the ECM's (sic) readings/behavior, or more concisely, input/output?
My (limited) understanding is that the air pump adds oxygen to post combustion exhaust gas, that the Cat uses to burn off
un-burned hydrocarbons.
If your truck runs well without a Cat now, the O2 sensor may be sensing a dilution of the exhaust gas from the air pump, and the ECM is not affected.
I think the only way to find out is to run her without the air pump. You can actually remove the pulley and the turbine, and use a fan belt made for a Alt-Water Pump-Crank. UNLESS that is not the setup of a '87... ::)
If she runs the same, what use is an air pump?
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The air pump on a TBI only pumps air into the exhaust when first started and until it goes into closed loop. At that time the solenoid on the diverter valve comes on and the air pump flow is diverted to the atmosphere not affecting the O2 sensor. The O2 sensor reads the AF ratio before the cat and tries to keep it the Af ratio as close to stoichiometric as possible. I have found on a TBI engines that exhaust back pressure can affect AF ratio. Too little or too much can cause the the computer system to not be able to compensate without a custom prom. Disconnecting the smog pump diverter solenoid can also turn on the check engine light.
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when I bought the truck the original cat was already gone. PO told me the o2 sensor was already missing and there is a CEL light on on the dash. Since the 02 sensor is missing it does backfire abit at higher RPMs and is abit harder to start. gues thats cause its running abit richer than normal since the sensor is missing. If removing the rest of the AIR system is gonna cause me problems Ill leave it alone.