I just bought an '85 K2500 with a 350 engine that has all of it's original emissions "clutter" still in use (except there is no catalyic converter). I have a '79 that has everything removed and plugged off. Would engine function be hampered in any way if I removed the air pump and all associated vacuum lines and plugged the egr valve and just ran a vaccum line to the vaccum advance on the distributor? It is a 24 year old truck in Arkansas where there are no smog police or checks. I posted this on another board but this one seems to be much more knowledgeable and active. Thanks
CK5
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'85 Emissions?
- Thread starter Mule man
- Start date
Fabrimacator21
1/2 ton status
I know you won't throw a code if you remove air but not sure about egr... IIRC theres no plugs associated with the egr so you'll probably be fine without it. I believe theres a block off plate you can buy to remove the egr completly.
apache
1/2 ton status
We have a couple 84 C20 3/4 ton chevys pickups/350 carbed full smog with pump,egr etc but neither had cats from the factory. If you look at the vin theres probably a M or L desigination which stands for heavy duty and over 6800 GVW I believe which dosent require them. 85 and up, not sure but it should say on the door sticker or under the hood onthe emission lable.
Fabrimacator21
1/2 ton status
Sorry I misread your post... the short answer is no. Air and egr aren't doing anything but making your exhaust cleaner. It'll run fine and probaly have a little more power without them.
No, it won't run right if you pull them. EGR displaces air/fuel, and the carb will run LEAN if you pull it.
I am afraid of this. I had a mid 80's Jeep with an "electronic carb" and it didn't run as well. Does egr gasses control the fuel mixture? and if so how? I thought that the air pump basically took exhaust gasses and then burned them again to make it a cleaner burn?
On all Q-jets, the primary needles/jets are calibrated for light throttle/cruise conditions, as well as other throttle positions/engine loads of course. The needles are tapered (or stepped) to correspond to their depth in the jets with engine vacuum at X.
When EGR is applied, fuel is taken out (via the needle taper/step) because vacuum sets them in that position. When you remove EGR, the needle/jet relationship stays the same (so fueling is the same as when EGR was being introduced), meaning the engine now runs lean, because there is no EGR displacing the now increased quantity of oxygen that is entering the cylinders.
I'm not making this stuff up, I've been there and done that, at light throttle cruise (35MPH+) the vehicle would surge from the lean condition. Richening up the mixture via replacing the needles and/or jets "solved" the problem, however without wideband O2, it's still not right. People severely overestimate how much modification the Q-jets can handle without being tuned again. They may or may not notice it, but as with any improperly tuned engine, economy or power is being lost.
When EGR is applied, fuel is taken out (via the needle taper/step) because vacuum sets them in that position. When you remove EGR, the needle/jet relationship stays the same (so fueling is the same as when EGR was being introduced), meaning the engine now runs lean, because there is no EGR displacing the now increased quantity of oxygen that is entering the cylinders.
I'm not making this stuff up, I've been there and done that, at light throttle cruise (35MPH+) the vehicle would surge from the lean condition. Richening up the mixture via replacing the needles and/or jets "solved" the problem, however without wideband O2, it's still not right. People severely overestimate how much modification the Q-jets can handle without being tuned again. They may or may not notice it, but as with any improperly tuned engine, economy or power is being lost.
Fabrimacator21
1/2 ton status
Even with the lines plugged?
apache
1/2 ton status
Couldent have said it better,every stock engine Ive disabled the EGR on ended in massive pinging from a lean condition. If your gonna go different intake and card then have at it,otherwise it wont run right.
