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Old 07-11-2010, 11:03 PM   #1
ChickenRammit
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what are symptoms of a bad EGR valve?

i've done a TBI swap on my '86 350. i'm having some issues that i can't quite figure out.

there are no codes to speak of.

i'm wondering what the engine would act like with a bad EGR valve? it's not stuck. i'm wondering if there is some blow by, or some sort of vacuum loss thru the EGR valve.
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Old 07-11-2010, 11:09 PM   #2
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You can disconnect the vacuum to the EGR valve to see if it changes anything. Assuming you know for sure that the valve isn't leaking and causing the engine to idle rough or die if whatever issue you're having changes when you disconnect the EGR then you probably have found your problem.

A bad EGR usually causes a rough idle or won't stay running or even a stumble off idle when trying to accelerate.
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Old 07-11-2010, 11:23 PM
Posted in reply to 4X4HIGH's post starting "You can disconnect the vacuum to the..."
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Quote:
Originally Posted by 4X4HIGH View Post
You can disconnect the vacuum to the EGR valve to see if it changes anything. Assuming you know for sure that the valve isn't leaking and causing the engine to idle rough or die if whatever issue you're having changes when you disconnect the EGR then you probably have found your problem.

A bad EGR usually causes a rough idle or won't stay running or even a stumble off idle when trying to accelerate.

it seems to idle pretty well. its when i'm trying to accelerate that i have the most problems. it has a bit of a stumble. then after acceleration the idle stays at a higher RPM than normal.

if the egr valve was leaking, would that cause a loss in manifold vacuum pressure? i can hear a hissing sound coming from the IAC, and i think it is trying to compensate for a loss of vacuum somewhere. just don't know where. i starting to suspect the EGR valve.
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Old 07-12-2010, 04:42 AM   #4
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when my EGR crapped out, that was it's symptom... poor off idle performance, stumbling, etc... held an idle decent, but fell on it's face....
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Old 07-13-2010, 01:41 PM   #5
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I agree with 4X4High & Ryoken. Mine would idle a bit rough and then die when taking off from a dead stop...forcing me to hold the brake while giving it gas so as to not die in the intersection. Replaced the EGR and all was good.
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Old 07-14-2010, 01:53 PM
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To test, plug the vac line going into the egr solenoid. Don't just plug the line going from solenoid to EGR valve, that will isolate the valve but not hte solenoid.

I had a bad solenoid that took me FOREVER to diagnose, as i just swapped hte valve and thought i was good.
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Old 07-22-2010, 11:23 AM
Posted in reply to dhcomp's post starting "To test, plug the vac line going into..."
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I'm having the same issue now. Idles fine, but when I give it just a little throttle it will stumble and then clear up. Replaced egr, but I'm going to go check the solenoid and see what that does.

Well dhcomp you hit the nail on the head, solenoid is bad. Thanks for the info.

Last edited by zombiyjay76; 07-22-2010 at 11:28 AM. Reason: found problem
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Old 07-22-2010, 01:15 PM
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Quote:
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Well dhcomp you hit the nail on the head, solenoid is bad. Thanks for the info.
Awesome! Took me MONTHS to diagnose mine, glad i could help!
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Old 08-04-2010, 08:50 AM
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What solenoid are u guys referring too. Is it an egr solenoid. I'm having a very simiar problem and have had a helluva time trying to figure it out when its not throwin any codes. Thanks
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Old 08-04-2010, 10:25 AM
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Quote:
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What solenoid are u guys referring too. Is it an egr solenoid. I'm having a very simiar problem and have had a helluva time trying to figure it out when its not throwin any codes. Thanks
Not sure on yours, but on my 91 350, there is a bracket on the passenger side of the top of the motor at a 45 degree angle, with a goofy little black box thing on it. Couple wire connections in a weather pack connector, a vac line to the throttle body, and a vac line to the egr valve. Follow the vac line from the egr valve, you should find it. Plug the line going from the solenoid to the throttle body, and see if your problem goes away. When they fail, they fail open, and basically become a vacuum leak.
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