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90 Mustang GT w/ 306 gt40 heads,intake
Ive been searching for a couple days for info on the two bolt sizes to mount the smog pump and cant find the info anywhere.The picture at the bottom,from LMR are the bolts Im asking about.Does anyone have a clue of their size?? The other question relates to the tab/tad valves,crossover pipe and the pipe that runs to the hpipe.Im aware that if the thermactor system is deleted completely, codes may be present for those components,but driveability issues will not be caused by their removal.Now what if everything was left in place,but the smog pump was bypassed with a shorter belt and the cats were still in place.Could this cause a backfiring issue if the cats were beginning to become partially clogged,due to smog pump air not being present?? Or if everything was left in place,including a functional smog pump,but the cats had been removed already?? If smog pump air is still being sent to the hpipe,but the cats have been removed.Would the smog pump air being pumped to the hpipe cause the o2 sensors to read a lean condition,if the cats were no longer present to consume/
use up the smog pump air?? What if the smog pump had been bypassed,but one of the hoses or pipes was leaking.Could engine vacuum pull unmetered air in through this leak and cause a lean condition that could trigger backfiring?? I guess all of the previous questions could be summed up into just one question. What scenario would have to exist within the system,solely due to a thermactor system cause,to cause backfiring??
A friend of mine is having an issue where the car runs fine when the smog pump is connected,but as soon as its bypassed,it begins to run bad and backfires.Thanks for any help you can give.
 

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are your 02 sensors in the stock location and do you have stock headers?

backfires in the exhaust are usually a sign that unconsumed fuel is entering the exhaust and then ignites in the presence of oxygen, like having a combustion event in the exhaust

are the only thing changed from stock are heads and intake?
 
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