irv

Anyone else get this? On engine braking/deceleration there is a bit of an obnoxious continuous popping/backfiring that comes from the exhaust. I have a muffler and catalytic converter of course but have eliminated most other emissions equipment. I have been thinking that it's perhaps a result of removing the air injection system which takes fresh air from the intake and sends it into the exhaust manifold. If I can determine exactly what emissions equipment to add back into the equation to eliminate this I would do it.

scope103

Yes, that is one of the symptoms of a non-working PAIR system. http://www.cygnusx1.net/Media/Supra/...taTech/h65.pdf It can also be caused by a defective throttle damper (dashpot).

The only way to assure good vehicle operation is put back all of the equipment you removed. Unless, of course, you're a much better automotive designer than the engineers who built your truck.

irv

Sometimes on new rebuilds and restores on old trucks it makes very good sense to a particular individual not to add certain emissions items back into the mix. Check out any manual for these old Toyotas and look at the literally dozens of emissions diagrams. Toyota set these trucks up in many many different ways. Toyota, and every other company, devised different equipment for many states, countries, etc simply based on what laws existed where. There are certain mid 80s Canada models that didn't even have the PAIR system. Some models had almost near zero of this extra equipment directly from the factory. In setting up the emissions system on a new rebuild of a 1980s or earlier truck it makes perfect sense to look through these diagrams and pick and choose for yourself which items you will have on your vehicle. To simply add back in all of the original equipment because that's just what was there is a very robotic and unfree thinking thing to do. Especially if you bought the truck in a different state/country and especially if you now live in a state or area where there are no laws regulating the same things. These factory setups were not simply the result of Toyota engineering. It is government regulation convoluting and over complicating their designs. Some items made more sense than others. Some items are great. I may choose to take a couple hours and reinstall the PAIR system if I decide that the slight backfiring on deceleration is a nuisance. It is definitely slight but it's enough that I see good sense behind controlling it. From what I understand the air injection system simply adds some fresh air to the outgoing exhaust as to combust unburnt fumes before reaching your tailpipe - to make your exhaust a little more quiet. A few items I decided to keep in my setup are the HAI(Hot Air Intake), MC(Mixture Control Valve, Deceleration Fuel Cut System, and I of course also left the automatic choke and other various items for the carb. I'm running the stock Aisin carb.

Anyway, If anyone else has any thoughts on the slight backfiring on deceleration, let me know! Are there any items you added back into your setup to control it? Or did you decide it wasn't a big deal to you?