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EGR question

9

97vulcan

CEG'er
Joined
May 22, 2007
Messages
456
Location
Wisconsin
When I start my car and its cold out, there is a miss in the idle around 1300, and I can hear a vacuum leak when controlling the throttle under the hood. I disconnect the tube going to the top of the EGR valve and the rough idle stops. This only happens when the engine is cold, so I really don't know what exactly to think of this. Once the engine is warm, the rough idle around that approximate RPM disappears. :shrug:

Thanks,
Adam
 
You have a plugged exhaust. Either Bank 1 (firewall side) or main catalytic converter.
 
Ur right. I have gotten a code for Catalist below threshold on the firewall side. Why does the idle get screwy when cold, and is fine when the engine warms up? Is it not my EGR thats faulty? or my O2 sensor on that bank?

Thanks,
Adam
 
twocontours said:
Tony,

Interesting diagnosis, care to explain? (not being sarcastic just interested)
Click to expand...
OP previously posted about a catalyst code and other issues like a leaky exhaust sound (or an engine knocking sound). When the engine warmed up, the metal near the leak expanded and sealed the leak (sometimes it is the other way around :shrug: ).

When the EGR tube was connected, there was no way for the exhaust to leave the system. When he disconnected the EGR tube, there exhaust left through the top of Precat 1 (if Precat 1 was plugged or if the main cat was plugged). The EGR tube goes from the EGR to the top of Precat 1 (next to the Bank 1 Upper O2 sensor). There is a good picture in the Haynes manual showing the location.
 
97vulcan said:
...Is it not my EGR thats faulty? or my O2 sensor on that bank?

Thanks,
Adam
Click to expand...
If your EGR is faulty, you will get a P0401 or other code. In addition, EGR valves seldom malfunction. If it is the O2 sensor, you should also get a O2 sensor code.
 
When I say disconnected the tube to the EGR, I am talking about the vacuum hose that connects to the EGR valve. Is this different?

-Adam
 
Would it be ok for me to leave the vacuum hose off the EGR valve at all times since I have an exhaust leak or plugged up CAT? Will this affect drivability or MPG?

Thanks,
Adam
 
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