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10-19-2012, 10:27 PM
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#1 |
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Registered User
Join Date: Aug 2012
Location: Derry, PA
Posts: 63
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Idle Problems
I'm not savoy with mechanical things but I bought this truck to teach myself what i could as I went along fixing it up. So anyway here is my problem maybe someone could shine some light on whats going on.
I have a 1970 C20 with a stock 307. I changed the oil yesterday and since I live in Pa and its getting into the colder months I used 10w-30. I couldn't get the oil filter off so I just left it on there till I can get a tool to take it off. Also while the oil was draining I decided to take off the air filter holder and sand some of the surface rust off and give it a little black spray to put some color back on it. After it dried I connected everything the way it came off and finished with the oil change. Now here is the problem the Truck before all this ran great and idled really good. On Cold start i just had to feather the gas like 3 or 4 times and the engine would stay at a decent idle till I was ready to drive. Now when I start it i have to continuously feather the gas to keep it from stalling out. I sat there for 10 mins yesterday, to see at what point it would idle on its own without stalling and it never happened. When I let go of the gas it just stalls out. So I decided to take it for a drive (now having a 4 speed and not being able to idle in my little town of low speed limits and tons of stop signs was a blast trying to keep the truck from stalling), after i got it on the highway and drove about 10 mins down the road at about 45-50 i pulled over. It finally idled on its own but very low and sounded like it wanted to stall but it didn't. So any help here would be great. Also should note that the oil pressure gauge drops all the way down when I don't press the gas. I know you cant trust the gauges on these trucks and honestly i never paid attention to it when the truck was running good so not sure if it did it before this or not. |
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10-19-2012, 10:35 PM
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#2 |
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Registered User
Join Date: Mar 2010
Location: Shawnee, OK
Posts: 63
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Re: Idle Problems
Check and make sure you didnt disconect a vacuum line on accident when you took off the breather lid.
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71 GMC long bed 70 Chevy short step 71 Chevy K10 long bed |
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10-19-2012, 10:47 PM
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#3 |
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Registered User
Join Date: Aug 2012
Location: Derry, PA
Posts: 63
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Re: Idle Problems
This is a picture of the engine compartment when I first got the truck.
Is this the tube you are talking about? If it is, I made sure it was connected back up like it was when I took it off. |
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10-19-2012, 11:21 PM
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#4 |
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Registered User
Join Date: Mar 2010
Location: Shawnee, OK
Posts: 63
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Re: Idle Problems
thats one. im not 100% sure, but there could be a smaller one on there as well. i havent messed with the factory setup on one these old trucks, but some of the newer trucks have a smaller vacuum line on them as well that connects on the bottom somewhere.
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71 GMC long bed 70 Chevy short step 71 Chevy K10 long bed |
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10-19-2012, 11:53 PM
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#5 | |
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Registered User
 
Join Date: Oct 2011
Location: Victoria, B.C
Posts: 3,794
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Re: Idle Problems
Quote:
It sounds like you might have a gas line/filter problem. If it was my truck I'd remove the gas line at the carb and replace the filter for starters. Question: do you have a 'vacuum' gauge for doing a little diagnostic testing? Coley
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....for some men, there is experience, skill and effort....for the others...there is visa and UPS LOL 1966 Chevy 1/2 ton (Florida- Red/white) 1972 Chevy 1/2 ton (California- Blue/white) 2005 Chevy Silverado HD2500/Duramax 2000 Dodge Ram 1500 |
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10-20-2012, 12:06 AM
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#6 |
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Registered User
Join Date: Aug 2012
Location: Derry, PA
Posts: 63
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Re: Idle Problems
No I do not have a vacuum gauge.
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10-20-2012, 01:43 AM
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#7 |
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Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,731
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Re: Idle Problems
That is incorrect Coley.
That line is to let air into the motor. Filtered air. THe pcv on the driver's side draws air from it thru the motor and that air mixes with the crankcase vapours to be burned back in the motor. |
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10-20-2012, 01:45 AM
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#8 |
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Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,731
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Re: Idle Problems
Pull the air cleaner off RxPx and see how it runs. You might have put the cleaner back on slightly crooked and are limiting the accelerator pump arm movement.
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10-20-2012, 01:58 AM
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#9 |
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Registered User
Join Date: Aug 2012
Location: Derry, PA
Posts: 63
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Re: Idle Problems
Thanks geezer. Ill try that in the morning and let you know how it goes.
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10-20-2012, 08:15 AM
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#10 |
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Registered User
Join Date: Jul 2012
Location: Ft Wayne Indiana
Posts: 1,204
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Re: Idle Problems
Another thing to consider is that the PCV valve itself is bad.
You can unplug it from the valve cover, and put your finger over the hole and see if it runs better. If it does, the PCV valve is bad.
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71 K20 64 GMC mud truck |
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10-20-2012, 10:05 AM
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#11 |
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Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,731
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Re: Idle Problems
Another thing on the air cleaner. It sits close to the distributor so you might have moved a plug wire or have a bad wire shorting out on the cleaner.
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10-20-2012, 10:44 PM
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#12 |
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Registered User
Join Date: Aug 2012
Location: Derry, PA
Posts: 63
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Re: Idle Problems
Okay so I was going to check on this today but got called into work early this morning and just got home. I decided to start it up and see what it would do after sitting cold for a day and a half. After about 30 secs of feathering the gas (like usual) it idled just fine and my oil pressure gauge stayed in the middle even when i took my foot off the gas.
So not sure what happened but I guess for now all is well again. Thanks again everyone for your suggestions, just glad its working again. |
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