arios56
Forum Newbie
Posts: 1
Loc: San Diego, Ca.
Reg: 07-13-12
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 07-13-12 05:11 PM - Post#2247924
I have an 85' C-10 with a 350....went to get ice cream one night and all of a sudden i get MAJOR loss of power....next thing you know i had to keep revving it up to keep it alive....very rough idle. i pulled over and turned it off then turned it back on but i had to keep the accelerator down to keep it from shutting off...got home...and a couple days later i took home a pcv valve and a couple feet of hoses...she started running great like before then the next day it began to act up again....im confused???
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 62chevy427
"7th Year" Silver Supporting Member
Posts: 1499
Loc: laurens sc
Reg: 04-13-06
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07-13-12 07:57 PM - Post#2247970
In response to arios56
check the egr valve to see if it is sticking open.
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 Vaughn
"11th Year" Gold Supporting Member
Posts: 13562
Loc: Colorado Springs, CO
Reg: 08-08-04
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07-14-12 12:10 PM - Post#2248158
In response to 62chevy427
If you unplug a PCV valve hose, the motor won't idle well and you will have to rev it up a bit to keep it running. When the PCV line is disconnected, it introduces a very large vacuum leak into the base of the carb. That was all it was.
If you replaced the hose, you need to make sure it is high pressure hose versus the standard vacuum hose, otherwise the hose will collapse and your PCV valve won't work. Look at the cut end of the hose - if you see braiding embedded in the cross section of the cut end of the hose, you have the right hose. If you see no braiding, you need to get the right hose.
Traditionally, vacuum hose is OK for most things - but if you use it in this application, the hose will collapse due to the high vacuum signal.
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 gchemist
Senior Chevytalk Moderator
Posts: 20830
Loc: Austin, TX 78748
Reg: 05-09-00
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07-16-12 06:13 AM - Post#2248652
In response to Vaughn
Check the PVC again. Next take a hammer and bang on the catalyst converter. If is sounds like a full sandbox, it's collapsed. Check the sound of the exhaust. Does it sound muffled? Does the exhaust sound very low and forced? When the cat falls apart, exhaust is forced out and you loose power.
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS |
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Brad30
Forum Newbie
Posts: 7
Reg: 07-27-12
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08-11-12 03:12 PM - Post#2258204
In response to gchemist
This brings up another question. At idle is the PVC valve blocking vacuum or allowing it to pass thru? Which type of port should the PCV valve be connected to? One that is active at idle or one that is active with opening the throttle? An answer might help me with the idle of my truck? 
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gchemist
Senior Chevytalk Moderator
Posts: 20830
Loc: Austin, TX 78748
Reg: 05-09-00
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08-11-12 03:21 PM - Post#2258208
In response to Brad30
Do you have a stock Qjet or aftermarket carb on it?
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS |
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Brad30
Forum Newbie
Posts: 7
Reg: 07-27-12
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08-11-12 03:26 PM - Post#2258209
In response to gchemist
A number of years ago I changed to a throttle body system, Recently I changed the intake manifold from a four barrell model that required an adapter plate to a two barrell intake. Just got the truck running again after a long time in the body shop for rust repair. Now at idle the vacuum fluxuates about 1 1/2 inches at idle and the rpm varies as well.
Edited by Brad30 on 08-11-12 03:36 PM. Reason for edit: No reason given.
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Vaughn
"11th Year" Gold Supporting Member
Posts: 13562
Loc: Colorado Springs, CO
Reg: 08-08-04
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08-11-12 06:05 PM - Post#2258263
In response to Brad30
PCV must be connected to manifold vacuum. It will be a large sized nipple at the base of the TBI.
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