Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Trapped Vacuum Spark
When engine temperature is below pre-set specified value, manifold vacuum signal is routed through check valve to distributor. Ports on TVS are blocked. Check valve will keep distributor vacuum at levels higher than manifold depression during vehicle acceleration.
Small sintered iron bleed orifice is provided in check valve to allow for leak-down to enable engine to be restarted if it stalls. This applies to all models except Light Duty California and High Altitude emissions, 5.7L V8 with Heavy Duty emissions, and all 7.4L V8 engines.
When engine temperature is above pre-set value, TVS ports will be open to allow manifold vacuum to distributor. During this mode of operation, check valve will act as a connector.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
Rather have a pro handle this?
A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.
No obligation. See pricing before you book.