1986 c4 vacuum leak
04-14-2014, 10:27 AM
#1
Cruising
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1986 c4 vacuum leak
1986 C4.
I was at the store a couple of days ago and an older man told me I have a vacuum leak, without even looking at it.
I have no idea if he's right or not. so,
1.Where would a vacuum leak be?
2.Hard to fix?
3.Expensive to fix?
Thanks!
I was at the store a couple of days ago and an older man told me I have a vacuum leak, without even looking at it.
I have no idea if he's right or not. so,
1.Where would a vacuum leak be?
2.Hard to fix?
3.Expensive to fix?
Thanks!
Last edited by MarcusWrenn; 04-14-2014 at 10:28 AM. Reason: Forgot year and model.
04-14-2014, 11:21 AM
#2
Safety Car
Vacuum Leak
Could be as simple as a vacuum hose came off a fitting, could be a crack or cut in a hose etc. I had one that was the hose that goes to the cruise control unit, it had a crack in the hose. It was where the hose went between the battery and that brace above it.
If something isn't working, if the idle is off, things like that can be an indicator. Try listening and you may hear it. If not, just start following hoses and see if you can find it. Others sometimes use a unlit torch and take some propane alone the hoses and see if the idle changes (usually when the torch end is near the crack or break - unlit).
I take no responsibility if you try that one, but if you do then definitely do it outside and be careful.
If something isn't working, if the idle is off, things like that can be an indicator. Try listening and you may hear it. If not, just start following hoses and see if you can find it. Others sometimes use a unlit torch and take some propane alone the hoses and see if the idle changes (usually when the torch end is near the crack or break - unlit).
I take no responsibility if you try that one, but if you do then definitely do it outside and be careful.
04-14-2014, 01:10 PM
#3
Cruising
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Could be as simple as a vacuum hose came off a fitting, could be a crack or cut in a hose etc. I had one that was the hose that goes to the cruise control unit, it had a crack in the hose. It was where the hose went between the battery and that brace above it.
If something isn't working, if the idle is off, things like that can be an indicator. Try listening and you may hear it. If not, just start following hoses and see if you can find it. Others sometimes use a unlit torch and take some propane alone the hoses and see if the idle changes (usually when the torch end is near the crack or break - unlit).
I take no responsibility if you try that one, but if you do then definitely do it outside and be careful.
If something isn't working, if the idle is off, things like that can be an indicator. Try listening and you may hear it. If not, just start following hoses and see if you can find it. Others sometimes use a unlit torch and take some propane alone the hoses and see if the idle changes (usually when the torch end is near the crack or break - unlit).
I take no responsibility if you try that one, but if you do then definitely do it outside and be careful.
04-14-2014, 01:52 PM
#5
Are you sure his hearing aid wasnt whistling?
04-15-2014, 03:54 AM
#6
Race Director
Usually a vacuum leak will cause a rough idle and/or off-idle stumbling.
You should have a vacuum routing diagram label on the radiator shroud, but just in case it's missing it looks like this:
Note the "TO HVAC" vacuum port on the rear of the plenum. There are vacuum lines attached there that go to the cruise control, vacuum reservoir and into the cabin to control the HVAC system.
You should have a vacuum routing diagram label on the radiator shroud, but just in case it's missing it looks like this:
Note the "TO HVAC" vacuum port on the rear of the plenum. There are vacuum lines attached there that go to the cruise control, vacuum reservoir and into the cabin to control the HVAC system.
04-18-2014, 04:36 PM
#7
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Not a vacuum leak?
Usually a vacuum leak will cause a rough idle and/or off-idle stumbling.
You should have a vacuum routing diagram label on the radiator shroud, but just in case it's missing it looks like this:
Note the "TO HVAC" vacuum port on the rear of the plenum. There are vacuum lines attached there that go to the cruise control, vacuum reservoir and into the cabin to control the HVAC system.
You should have a vacuum routing diagram label on the radiator shroud, but just in case it's missing it looks like this:
Note the "TO HVAC" vacuum port on the rear of the plenum. There are vacuum lines attached there that go to the cruise control, vacuum reservoir and into the cabin to control the HVAC system.
However,
Symptoms: Rough Idling, When it DOES idle. She likes to start and die before idling can happen. I've noticed alot of smoke coming out of the pipes now (black). Strange popping sound when I press on the gas to help the car start.
Help
And thanks for the replies!
04-19-2014, 03:38 AM
#9
Race Director
Sounds like you have fuel problems. Possibly a hole in your FPR (Fuel Pressure Regulator) diaphragm.
Take the vacuum hose off the FPR and turn on the ignition (don't start the engine). Check for fuel coming out of the vacuum port on the FPR.
If the FPR diaphragm has a hole the fuel will go through the vacuum line and into the plenum. That will cause a rough idle and running rich. In my case it caused a fire.
Take the vacuum hose off the FPR and turn on the ignition (don't start the engine). Check for fuel coming out of the vacuum port on the FPR.
If the FPR diaphragm has a hole the fuel will go through the vacuum line and into the plenum. That will cause a rough idle and running rich. In my case it caused a fire.