Thread: Low engine vacuum but no vacuum leaks.

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In addition to what every one else has offered.
Don't hesitate to open the exhaust at the manifolds and re-do a vacuum test. It's not seen much anymore but exhaust pipe sometimes had a interior pipe that would swell and kink closing off the pipe. This would effectively choke the motor airflow/vacuum. Like I said, you don't see this anymore but it should be easy (relatively speaking) to open the headers/manifolds and double check the vacuum.

I bought a Dodge D-100 for 200 bucks 'cause after throwing some 1200 bucks at a local garage this thing wouldn't run! It had new ignition, carb, pcv etc. etc. and it would barely idle. After getting it to my shop - I dropped the pipe at the manifold and it ran perfect. I determined the cat converter had plugged 'cause they were running leaded fuel in a unleaded vehicle. swapped in a cat from a wreck and sold the truck for 1500 2 days after I bought it. There's other examples of course, it does happen and is easy to check. Ya never know.

Originally Posted by 34_40

In addition to what every one else has offered.
Don't hesitate to open the exhaust at the manifolds and re-do a vacuum test. It's not seen much anymore but exhaust pipe sometimes had a interior pipe that would swell and kink closing off the pipe. This would effectively choke the motor airflow/vacuum. Like I said, you don't see this anymore but it should be easy (relatively speaking) to open the headers/manifolds and double check the vacuum.

Could you please specify what you mean by opening the exhaust at the manifold ? Do you mean to remove the exhaust manifold to check for obstruction? Thanks