SMOG cheating

[SpeedinIan]

When I rebuilt my '88 454 TBI I tossed the A.I.R. pump. Now I have a constant check engine light (code 13 for oxygen sensor...despite replacement). I'm convinsed it due to the lack of artifical air in the exhaust causing a constant false "rich" reading and constantly leaning the mixture. How do I fool the system or get the computer to think it is a non A.I.R. truck?

Thanks

[GreaseDog]

did you use a quality o2 sensor?

[cancritter]

not shure how l did that to my 88..ditched airpump but didnt realy do anything short of putting shorties on it...never had a code or prob...new o2 and that was about it,,,left egr alone...my 91 came with airpump ect already gone

[modular93fox]

there is a wire that tells the dist. to advance and retard when the idle changes... the place i went to (after i failed) he unpluged it (one wire connector by the dist... i believe its round) and it makes the signal null @ 0 regardless of rpm. passed just fine after that. then i ditched it and put a 496cid :) passed everytime after that

[SpeedinIan]

Hum...Yes it's a quality O2 sensor. Voltage check on the last one showed it to be ok too. But it's the only light I get so I changed it anyway.

I'll try disconecting the ignition control modual but then I won't get any advancement... anywhere right? I don't need to pass a emissions idle check. However on the topic of timing I do run a extra 4 degrees bdc (8 total) and it still struggles to tow a trialer at over 2500 rpm. Also the engine dies at the stop sign if I suddenly step on it to Wide open throttle.

I'll let you know what happens.

[doublelow49]

When I rebuilt my '88 454 TBI I tossed the A.I.R. pump. Now I have a constant check engine light (code 13 for oxygen sensor...despite replacement). I'm convinsed it due to the lack of artifical air in the exhaust causing a constant false "rich" reading and constantly leaning the mixture. How do I fool the system or get the computer to think it is a non A.I.R. truck?

Speedin,

I ditched the pump on my 87 350. Just left the elec wires hanging and plugged the vaccum line that goes to the tbi. Didn't seem to have any problems. Not sure how this compares to your 454 setup, but you may want to make sure you got the vac line plugged. There may be some codes in the ecm that could be changed but don't know of or familar with any in the 7747 ecm.

It is my understanding the AIR Pump functions primarily during deceleration mode and pumps air in to help burn leftover combustion gases. With no pump, I could see this richening up the exhaust a little when decelerating but don't understand how it could cause problems at other times. You may want to do some datalogging to see how the O2 is functioning. May be grounding out or have intermittant connection.

Let us know what you find.

Good luck,
Buddy