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egr vacuum solenoid

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Old 04-10-2006, 12:39 PM   #1
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egr vacuum solenoid

Well I may have found the culprit for my rough idling, motor surges. I unplugged the vac line and all the problems went away. This would be the third vac solenoid I have replaced on the two S10s I have owned and a friends TBI V8. I was thinking about just plugging the vac line or better off, putting a plate infront of the valve itself. I have always been a believer of leaving it there if it came from the factory philosophy. Well now I want to get rid of it. My question is, has anyone hear had any problems with blocking off their EGR valves? The chances are detenation are greater I know, but has anyone ever had problems with power, or MPGs? Solenoids cost around 60 bucks
Old 04-10-2006, 01:25 PM   #2
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Re: egr vacuum solenoid

i doubt you will have any problems from disabling the egr valve.
the egr is just a necessary evil for the factory to comply with EPA mandates.

there are some engines that have problems with detonation, because of factory ign. timing curves that have been advanced to compensate for the effects of EGR, but most cars i have disabled them on, have had no problems with detonation...
Old 04-10-2006, 01:27 PM   #3
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Re: egr vacuum solenoid

will blocking cause any computer codes?
Old 04-10-2006, 02:43 PM   #4
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Re: egr vacuum solenoid

on a 91 4.3, i`m not certain, but i dont think so.
if there is no thermal or position sensor on the egr, and the vac solenoid remains plugged into the wire harness, probably not.

most of the 80`s-early 90`s GM std. style vac operated EGR valves used no means of verifying the presence, or proper operation of the EGR system to the ECM.

Last edited by Crew Cab Sonoma; 04-10-2006 at 02:49 PM.
Old 04-10-2006, 04:06 PM   #5
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Re: egr vacuum solenoid

Quote: Originally Posted by Crew Cab Sonoma
on a 91 4.3, i`m not certain, but i dont think so.
if there is no thermal or position sensor on the egr, and the vac solenoid remains plugged into the wire harness, probably not.

most of the 80`s-early 90`s GM std. style vac operated EGR valves used no means of verifying the presence, or proper operation of the EGR system to the ECM.
isn't it the job of the solenoid to tell the computer how much EGR is flowing?
Old 04-11-2006, 08:55 AM   #6
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Re: egr vacuum solenoid

Quote: Originally Posted by 91S104x4
isn't it the job of the solenoid to tell the computer how much EGR is flowing?
no. its job is to regulate vac. to the EGR. the solenoid itself has no way of confirming the operation of the EGR valve to the ECM.

but the ECM might be able to determine if the solenoid itself is connected, by monitoring voltage drop/resistance on this circuit.
Old 04-11-2006, 10:56 AM   #7
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Re: egr vacuum solenoid

well now I have more issues. Last night I was standing outside talking with my truck idling in the driveway. All of a sudden it started spittin and sputteren and then DIED!! No codes yet. Started it back up waited a few seconds then it throws CODE 42-The timing bypass code? I checked the timing wire and its plugged in? The way it died did soound like to much EGR the way it sputtered then died. Now Im really confused.
Old 04-11-2006, 05:55 PM   #8
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Re: egr vacuum solenoid

Quote: Originally Posted by 91S104x4
well now I have more issues. Last night I was standing outside talking with my truck idling in the driveway. All of a sudden it started spittin and sputteren and then DIED!! No codes yet. Started it back up waited a few seconds then it throws CODE 42-The timing bypass code? I checked the timing wire and its plugged in? The way it died did soound like to much EGR the way it sputtered then died. Now Im really confused.
Now it just stalls out even with no codes. Before it starts pitin and sputtern, if you try to rev it, it revs really crappy and blows some black smoke. This is EXACTLY what happened when my last EGR solenoid took a crap. Instead of buying a new solenoid, will pluging the valve casue it to still idle down and die?
Old 04-12-2006, 12:15 AM   #9
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Re: egr vacuum solenoid

ok: even though the vac line was unplugged and open, it still stalled once again today. Im starting to think to myself now how plugging the valve itself is going to solve anything? The last time my truck did this I put on a nother used solenoid and it ran fine for about 8 months till this day. So somehow I think the solenoid is sending bad signals to the ecm to make it stall out? Then again while its spitten and sputtern while you try to rev it up it has a hard time building RPMs like it has TO much EGR flow? It also some black smoke while i rev it during the stalling? So Its somewhere in the EGR system? Either find another solenoid or block off the valve itself? The only reason why I would block off the valve to fix it not for HP. Sorry Im a redneck mechanic.

Basically will blocking off the EGR fix the problem or even with the EGR blocked will the solenoid still cause the engine to run bad?

Last edited by 91S104x4; 04-12-2006 at 12:32 AM.
Old 04-12-2006, 12:12 PM   #10
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Re: egr vacuum solenoid

if the EGR valve itself is disabled and acually closed, then the solenoid isnt going to affect how the engine runs.

you may want to verify that the EGR valve isnt sticking open. if it is fully closed, then you may have another issue not related to the EGR causing your problems...
Old 04-12-2006, 01:27 PM   #11
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Re: egr vacuum solenoid

Quote: Originally Posted by Crew Cab Sonoma
if the EGR valve itself is disabled and acually closed, then the solenoid isnt going to affect how the engine runs.

you may want to verify that the EGR valve isnt sticking open. if it is fully closed, then you may have another issue not related to the EGR causing your problems...
but what im confused about is even when the solenoid is unplugged from the EGR valve, it still has spontaneous idling trouble. When I replaced the solenoid 9 months ago it fixed it until this day?
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