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Discussion Starter · #1 ·
My air pump recently died, with the car throwing P0410. While clearing the code (I'll likely program it out later), I checked my long-term fuel trims (LTFTs) and noticed that Bank 2 was significantly higher than bank 1: at idle, bank 2 pegged at 25% while cold, eventually getting down to 17% at idle after a 60 km jaunt. While at cruising speeds (throttle position > 6%), Bank 2 behaved perfetly normal. Bank 1 is "normal" at all times (±5%).

My question is, is this "LTFT 2 high" condition related to the loss of my air pump? Could the Bank 2 check-valve be stuck open, thereby allowing too much air into that side, which the motor then compensates for by adding more fuel?

Thanks for any help!
 

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I guess it's possible.
Remove the tube and put a plug in the manifold. It the LTFT's still act the same, look for another exhaust leak upstream of front O2 sensor.
 

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Why do you even still have the AIR system?
 

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Discussion Starter · #4 · (Edited)
Why do you even still have the AIR system?
Not really the point, but...

a.) The car's all stock, and it was working, so there was no incentive for me to remove it: why pay $200 for a retune?

b.) In Canada, all emissions equipment that is installed on a car must remain on the car, even if it technically passes a "Drive Clean" test without it.


Personally, I don't really care if it's there or not, but until now, it didn't bother me, so I didn't bother it :).
 

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Discussion Starter · #5 ·
I guess it's possible.
Remove the tube and put a plug in the manifold. It the LTFT's still act the same, look for another exhaust leak upstream of front O2 sensor.
When my PCV was leaking, both banks gave me high LTFTs, as expected; is there any Bank 2-exclusive vacuum system that could be contributing to the hight LTFT, rather than an exhaust leak? Just trying to cover my bases before looking too deep.
 

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... is there any Bank 2-exclusive vacuum system that could be contributing to the hight LTFT, rather than an exhaust leak? ...
No .
 

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Possibly an individual injector issue. Even if the AIR system isn't removed,I'd still disable/plug it. It will always be suspect,and eliminating this possibility permanently would strike me as a cost effective thing to do anyway.
 

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Discussion Starter · #8 ·
Agreed, and with the pump dead my car is much quieter at start-up, no groaning and grinding as it tries to work!

Good thought about the injector, too.
 

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Agreed, and with the pump dead my car is much quieter at start-up, no groaning and grinding as it tries to work!

Good thought about the injector, too.
the air pump has 3 check valves. these when working prevent exhaust gases from going into the air pump. when the exhaust gases do go into the pump this means that these check valves are defective . the air pump with this then rapidly fails. the other problem is the exhaust gases then get into the maf. since the pump is not working remove the connector to the pump . block off the 2 check valves , remove the check valves and get a pipe fitting end cap. 1/2 in I think..

on a cold start the air pump operates 5 min . this is to provide added air so the converters can better remove un burned fuel.

since this was a high failure GM got the feds to allow removal of this air pump system on the 1996 models.............
 

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Any broken rear manifold bolts??? Maybe just a defective o2 itself. Ever replace it?
 

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... Since this was a high failure GM got the feds to allow removal of this air pump system on the 1996 models.............
The GM TSB allows the AIR pump to be "disabled".

'Red', why are you ruling out the common possibility of broken bank 2 exhaust manifold studs or a bad O2?

.
 

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Discussion Starter · #12 ·
The O2 sensors are all giving normal readings, so I don't suspect those. The fact that this LTFT issue started when the air pump died really leads me to believe it is related.

I haven't checked the manifold bolts, but it's a worthwhile thought.

Although I know the pump can be disabled and still be emissions-compliant, I really didn't want to have to pay for a tune :). However, I've read that our emissions testing only requires 1997 and newer vehicles to be checked with an OBDII scan, while older cars get away with the tailpipe test. I'd still pass that as the car would already be warmed up.

Interestingly, my CEL hasn't come on in the last 500 km of driving, and by now I figured the system would have tested the pump.

I did notice today that acceleration seemed a big sluggish, so the thought of exhaust gas getting back into the MAF has me a bit worried. I'll deal with that this weekend.

Thanks for all the brainstorming, guys!
 

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The O2 sensors are all giving normal readings, so I don't suspect those. The fact that this LTFT issue started when the air pump died really leads me to believe it is related.

I haven't checked the manifold bolts, but it's a worthwhile thought.

Although I know the pump can be disabled and still be emissions-compliant, I really didn't want to have to pay for a tune :). However, I've read that our emissions testing only requires 1997 and newer vehicles to be checked with an OBDII scan, while older cars get away with the tailpipe test. I'd still pass that as the car would already be warmed up.

Interestingly, my CEL hasn't come on in the last 500 km of driving, and by now I figured the system would have tested the pump.

I did notice today that acceleration seemed a big sluggish, so the thought of exhaust gas getting back into the MAF has me a bit worried. I'll deal with that this weekend.

Thanks for all the brainstorming, guys!

I would disconnect those air injection manifold check valves, clean the MAF and see how it runs. dirty maf will give poor take off power..

makes it slow responding to air flow changes !
 
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