Question about air flow and cats
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Yep, I've got a vaccum guage. It just feels like it's bogging down and I can't seem to find any other issues; air/fuel mixture, etc. I don't know how to explain it, it just feels like it's not gettin' enough air through the exhaust. Also, I pulled all the carpet so I can Line-x the floor and now I can hear a faint rattle coming from the passenger side right where the cats are and I'm pretty sure it's the screen rattling.
#6
Yep, I've got a vaccum guage. It just feels like it's bogging down and I can't seem to find any other issues; air/fuel mixture, etc. I don't know how to explain it, it just feels like it's not gettin' enough air through the exhaust. Also, I pulled all the carpet so I can Line-x the floor and now I can hear a faint rattle coming from the passenger side right where the cats are and I'm pretty sure it's the screen rattling.
#7
I've checked every wire and everything else I can think of, so I started suspecting the cats. They look OLD and are covered in rust deposits, so I just started thinking they might be clogged. I hit 'em with a rubber mallet and I don't hear anything loose, but I can't find anything else wrong with this thing. I did look at the engine running in the dark the other night and saw that the ignition module was glowing a little bit, but I just replaced it a few months ago, so that shouldn't be going bad already.
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#8
With a vacuum gauge, there are two easy tests you can run to determine if your exhaust is restricted (cats clogged).
First test:
1) Attach vacuum gauge to manifold vacuum source.
2) Observe vacuum at idle.
3) Snap throttle to WOT and release, while watching the gauge.
The vacuum gauge should drop to almost zero when you hit WOT. When the throttle snaps closed immediately after, the vacuum should read 4" to 6" higher than what it did at idle. It should then settle back at the same reading it was at idle before the WOT snap. This whole exchange should go from idle reading to idle reading in 2-3 seconds, tops. If it takes longer for the gauge to return to the same idle reading, your exhaust is restricted. The longer it takes, the worse the restriction.
Second test:
1) Attach vacuum gauge to manifold vacuum source.
2) Warm up engine.
3) Observe vacuum at idle.
4) Leave engine idling for 10 minutes. Do not touch anything on the car during this time. In fact, go inside and fix some coffee.
5) After 10 minutes, observe the vacuum.
If the vacuum is the same or higher, you don't have any resctrictions. If the vacuum gauge has dropped, you do have a restriction. The more it drops, the greater the restriction. If it drops 1" or more, you have a serious restriction. 2" or more and you might as well have the exhaust welded shut. Keep in mind that a rich exhaust will clog up cats in a hurry.
First test:
1) Attach vacuum gauge to manifold vacuum source.
2) Observe vacuum at idle.
3) Snap throttle to WOT and release, while watching the gauge.
The vacuum gauge should drop to almost zero when you hit WOT. When the throttle snaps closed immediately after, the vacuum should read 4" to 6" higher than what it did at idle. It should then settle back at the same reading it was at idle before the WOT snap. This whole exchange should go from idle reading to idle reading in 2-3 seconds, tops. If it takes longer for the gauge to return to the same idle reading, your exhaust is restricted. The longer it takes, the worse the restriction.
Second test:
1) Attach vacuum gauge to manifold vacuum source.
2) Warm up engine.
3) Observe vacuum at idle.
4) Leave engine idling for 10 minutes. Do not touch anything on the car during this time. In fact, go inside and fix some coffee.
5) After 10 minutes, observe the vacuum.
If the vacuum is the same or higher, you don't have any resctrictions. If the vacuum gauge has dropped, you do have a restriction. The more it drops, the greater the restriction. If it drops 1" or more, you have a serious restriction. 2" or more and you might as well have the exhaust welded shut. Keep in mind that a rich exhaust will clog up cats in a hurry.
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Another test that seems bizzare but I've seen several on other forums confirm that it works:
Remove the O2 sensor and run the truck. You'll throw a code for the mixture, but just the hole in the exhaust will reduce the restriction (if it exists) enough to tell there is an exhaust restriction.
And BTW Pkrwud,
Per the second test, step 4. What if you don't drink coffee?
Remove the O2 sensor and run the truck. You'll throw a code for the mixture, but just the hole in the exhaust will reduce the restriction (if it exists) enough to tell there is an exhaust restriction.
And BTW Pkrwud,
Per the second test, step 4. What if you don't drink coffee?
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I finally got a CEL this morning on the way to work. I put the code scanner on it and I'm getting a 31 and a 32, which I got a couple of weeks ago. I already replaced the EGR, the EGR sensor, all of the vaccum lines and the little actuator that the vaccum line goes to when I got the codes the last time. At least that explains the bad gas mileage. Any ideas?
#15
I finally got a CEL this morning on the way to work. I put the code scanner on it and I'm getting a 31 and a 32, which I got a couple of weeks ago. I already replaced the EGR, the EGR sensor, all of the vaccum lines and the little actuator that the vaccum line goes to when I got the codes the last time. At least that explains the bad gas mileage. Any ideas?
Still the smarta$$, I see.