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smog pump system help

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Old 10-05-2012, 04:59 PM   #1
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Default smog pump system help

I recently discovered the smog pump on my '91 5.0 is bad. the motor was idling crazy which lead me to replacing the IAC valve and adjusting the TPS. after these replacements/adjustments the idle was still acting up so i pulled off the hose leading from the smog pump to the EGR valve hook up and it idled just fine-@1000 RPM. I was driving home on the highway today in 5th gear driving close to the posted speed limit and the car surged like it wanted to shut off. about ten minutes later the car actually did shut off, so i pulled to the shoulder let the car sit for a min and it fired right up. driving thru the streets i could hear what sounded like an exhaust leak(louder then usual since the smog pump line at that time was unhooked).

once i parked it i got under the hood and found that the sound was coming from the EGR valve opening, i plugged it with my finger, the sound went away but still heard the exhaust leak.....My question is would leaving the smog pump hose unhooked and both ends not plugged cause the air/fuel ratio to be off thus shutting the car off?

I dont have the $$ to replace the pump so i'm considering blocking both ends off until I can do so...
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Old 10-05-2012, 05:58 PM   #2
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I recomend throwing the entire smog pump system in the trash. You probably have a vacuum leak with all the stuff unhooked.
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Old 10-05-2012, 08:25 PM   #3
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smog delete ftw!!!
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Old 10-05-2012, 11:24 PM   #4
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smog delete ftw!!!

+1

One of the first things I did when I first got my Fox.
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Old 10-06-2012, 12:28 PM   #5
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I read on a review for the smog pump delete kit from americanmuscle.com it is only recommended for vehicles w/o catalytic converters, i recently put two cat's on for emissions, wont this mess up my emissions if i delete the smog pump?
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Old 10-06-2012, 02:00 PM   #6
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I read on a review for the smog pump delete kit from americanmuscle.com it is only recommended for vehicles w/o catalytic converters, i recently put two cat's on for emissions, wont this mess up my emissions if i delete the smog pump?
Yes it will.
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Old 10-06-2012, 02:00 PM   #7
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You shouldn't need a kit. Take the pump off, chunk it in the garbage can, and run a shorter belt.

There's lines you'll remove and things you'll need to plug and a pipe you have to cap off, maybe that's the stuff in the kit? You can get what you need for less than $5 probably. Wish I had more detailed info for you, its been a decade since I did it.

Deleting the pump shouldn't affect your emissions enough that you wouldn't pass a sniff test, but I'm not positive. Maybe someone else will know for sure. I didn't have cats on mine so it wasn't a concern.
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Old 10-06-2012, 03:43 PM   #8
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re-connected the smog lines, adjusted TPS til idle was at 1500 RPM then backed it down to 900 idled great for about ten minutes then started acting up again...i just ordered the new pump and TPS(just to be safe) i'll let y'all know how it goes after the replacement tomorrow.
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Old 10-07-2012, 12:35 PM   #9
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quick update, i replaced the TPS first to double check and see if it wasn't the pump. I let the motor warm up to operating temp, idled it to mimic the car driving down the street and the idle was still irregular so it is confirmed that the smog pump indeed needs to be replaced. when i replace the pump and reapply the belt do i need to re-tension the belt or will it be good?
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Old 10-07-2012, 12:58 PM   #10
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The smog pump shouldnt have anything to do with your idle at all. I have a 94 gt and I eliminated it all together. I also could be wrong about the 91 but the hoses from the smog pump should not go to the egr . One should go to the back of the heads and one should go to the cats. The egr and smog systems are completly seperate entitys. The egr should have a tube connected to the exhaust manifold or header, and also a vacuum line to operate it.
Now if your egr is sticking open it will cause an erradic or stumbling idle. I may be wrong on the 91 But im pretty sure they all work the same up to 95.
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Old 10-07-2012, 04:58 PM   #11
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Smog delete is dumb.
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Old 10-07-2012, 05:26 PM   #12
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smog delete is not dumb.........I took mine off cause I dont run any cats and my heads dont accept the tube . So how is it dumb exactly??
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Old 10-07-2012, 05:57 PM   #13
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I'm going to disagree with the dumb comment also. It's like saying driving a fox Mustang over a prius is dumb. The Smog pump is for polution control. Nothin more. It injects air into the hot exhaust before the cats. This reduces the amount of hydrocarbons emitted out the exhaust. The burning produces more oxides of carbon and nitrogen than unburned fuel, simply because it is burnt. I'm more interested in the horse power gain and weight saving off the nose of the car than saving the rain forrest. But thats just me.
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Old 10-07-2012, 06:10 PM   #14
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I'm going to disagree with the dumb comment also. It's like saying driving a fox Mustang over a prius is dumb. The Smog pump is for polution control. Nothin more. It injects air into the hot exhaust before the cats. This reduces the amount of hydrocarbons emitted out the exhaust. The burning produces more oxides of carbon and nitrogen than unburned fuel, simply because it is burnt. I'm more interested in the horse power gain and weight saving off the nose of the car than saving the rain forrest. But thats just me.
exactly ....our govment makes more pollution in a day than my little pony makes all year . And when I went to no cats I didnt see a reason to drag that anchor around under the hood anymore. Of course Im in ohio and they dont do smog checks in my county or safty inspections for that matter. I think the smog pump delete kit is a waste of time though as I just got a smaller belt to bypass the pump and ac unit.
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Old 10-07-2012, 07:30 PM   #15
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The smog pump shouldnt have anything to do with your idle at all. I have a 94 gt and I eliminated it all together. I also could be wrong about the 91 but the hoses from the smog pump should not go to the egr . One should go to the back of the heads and one should go to the cats. The egr and smog systems are completly seperate entitys. The egr should have a tube connected to the exhaust manifold or header, and also a vacuum line to operate it.
Now if your egr is sticking open it will cause an erradic or stumbling idle. I may be wrong on the 91 But im pretty sure they all work the same up to 95.
that's what i thought as well until i unhooked the pump hose to the connector line that leads to the back of the block, drove it around and the idle stayed normal. I then hooked it back up and did the same process and the idle started acting up again, which lead me to believe that the smog pump is some how causing it to act stupid. I figured the whole reason for the pump is to aid the catalytic converters in well converting unwanted particles by supplying more air to them and if it isn't doing it properly while hooked up then it needs to be replaced. I would love to delete it all together but i'm gonna need it for emissions.
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Old 10-07-2012, 07:56 PM   #16
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that's what i thought as well until i unhooked the pump hose to the connector line that leads to the back of the block, drove it around and the idle stayed normal. I then hooked it back up and did the same process and the idle started acting up again, which lead me to believe that the smog pump is some how causing it to act stupid. I figured the whole reason for the pump is to aid the catalytic converters in well converting unwanted particles by supplying more air to them and if it isn't doing it properly while hooked up then it needs to be replaced. I would love to delete it all together but i'm gonna need it for emissions.
Well thats a different area than the egr..... Your pump is probly working fine it sounds like it may be the valve that supplys air to the heads could be stuck open. Have you checked for any codes on the computer? The smog pump should only supply air to the heads for a short time at startup after that the valves close and the air is dumped into the atmospere. If the valve is stuck open it will pump air into the exhaust ahead of the o2 sensors causing the computer to think its running lean and it will richen up the air/fuel mix.
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Old 10-07-2012, 10:48 PM   #17
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Well thats a different area than the egr..... Your pump is probly working fine it sounds like it may be the valve that supplys air to the heads could be stuck open. Have you checked for any codes on the computer? The smog pump should only supply air to the heads for a short time at startup after that the valves close and the air is dumped into the atmospere. If the valve is stuck open it will pump air into the exhaust ahead of the o2 sensors causing the computer to think its running lean and it will richen up the air/fuel mix.
To be honest I didn't even think about checking for codes. I figured the check engine light isn't on so it should be good. Which vavle should I be checking?
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Old 10-07-2012, 11:36 PM   #18
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There should be one valve with some wires going to it its a solenoid that opens and closes a valve when its open it sends air to both the cats and heads for the first miniute or 2 then it closes and dumps the air. Im not sure what codes the computer will store but if i remember right it will be a code 44 for the Thermactor Air Control System or diverter valve. The check engine light doesnt come on for every code . Before I eliminated my pump the diverter valve was stuck and when I ran a KOER test I got a lean code from my o2s . One of the valves is a diverter and one is Thermactor Air Bypass Im not sure but If i remember the diverter is operated by a solenoid controlled by the ecu and the other is controlled by a vacuum line that goes threw the fender on the passanger side, this vacuum line goes to a vacuum control solenoid . And I cant remember witch one does what any more but Im alomost sure the diverter is the one that controls air to the heads.
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Old 10-08-2012, 03:06 PM   #19
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There should be one valve with some wires going to it its a solenoid that opens and closes a valve when its open it sends air to both the cats and heads for the first miniute or 2 then it closes and dumps the air. Im not sure what codes the computer will store but if i remember right it will be a code 44 for the Thermactor Air Control System or diverter valve. The check engine light doesnt come on for every code . Before I eliminated my pump the diverter valve was stuck and when I ran a KOER test I got a lean code from my o2s . One of the valves is a diverter and one is Thermactor Air Bypass Im not sure but If i remember the diverter is operated by a solenoid controlled by the ecu and the other is controlled by a vacuum line that goes threw the fender on the passanger side, this vacuum line goes to a vacuum control solenoid . And I cant remember witch one does what any more but Im alomost sure the diverter is the one that controls air to the heads.
Ok thanks, ill check it out and let you know what turns up
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Old 10-08-2012, 05:51 PM   #20
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Air Bypass Valve

Air flows down the hose from the smog pump to the Air Bypass Valve.

With no vacuum at the valve, air is diverted out the bottom of the valve to the atmosphere. The air is directed to the atmosphere under deceleration.

With vacuum at the valve, air continues down the hose to the Air Diverter Valve.


Air Diverter Valve

As the air enters the Air Diverter Valve it has two choices, it either flows to the back of the heads or to the catalytic converters.

With no vacuum at the valve, air flows downward in the valve toward the catalytic converters.

With vacuum at the valve, air continues to the back of the heads.
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Old 10-08-2012, 05:51 PM
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