Having problems getting a consistent idle rpm.
Thread Starter
Le Mans Master
Joined: Jan 2004
Posts: 8,295
Likes: 30
From: one night in Bangkok you are never lonely
Having problems getting a consistent idle rpm.
I have an Edelbrock 750 that has been a good carb for 3 years. But lately I have been having problems that first were a surging feeling when driving at RPMs 1000 to 2000.
I removed the carb and cleaned the all the small holes out, thinking that when the car sat for 4 months during the rainy season the gas had gummed up. This did help but now I am having problems getting it to idle. Using the idle screws I get a nice idle and no hesitation just off idle but after a few minutes the RPMs jump around and finally drop 100 RPMs. I then readjust and the same thing happens. Also when driving in low RPMs, there is a slight missing feeling.
I am thinking that there is a vacuum leak, but I have tried blocking all the vacuum hoses off the intake and carb, no difference.
Any ideas folks?
I removed the carb and cleaned the all the small holes out, thinking that when the car sat for 4 months during the rainy season the gas had gummed up. This did help but now I am having problems getting it to idle. Using the idle screws I get a nice idle and no hesitation just off idle but after a few minutes the RPMs jump around and finally drop 100 RPMs. I then readjust and the same thing happens. Also when driving in low RPMs, there is a slight missing feeling.
I am thinking that there is a vacuum leak, but I have tried blocking all the vacuum hoses off the intake and carb, no difference.
Any ideas folks?
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Get a can of brake cleaner. Install the extension tube on the nozzle. Then, with engine running, position the end of that tube very close to an area on the intake manifold and/or carb and shoot short little puffs of cleaner at them. Then listen to hear if engine revs higher (or not). If it does rev higher, then there is a leak in the manifold gasket [or carb gasket/joint] as that cleaner is getting ingested into the fuel charge.
Check all along the manifold gaskets and the end valley joints. Also check the gasketed areas of the carb and at the end points of any throttle shafts/linkage shafts.
For the condition you are describing, such a leak should be obvious when you find it. Also check the vacuum lines under the driver's dash and in the engine compartment to see if any came loose.
Check all along the manifold gaskets and the end valley joints. Also check the gasketed areas of the carb and at the end points of any throttle shafts/linkage shafts.
For the condition you are describing, such a leak should be obvious when you find it. Also check the vacuum lines under the driver's dash and in the engine compartment to see if any came loose.
