Engine Running-On Check

Check for engine running-on before you buy an older petrol car. Ask the seller to show the correct equipment while parked, using the instructions for this vehicle.

I reviewed How a Car Works running-on guide for this November 6, 2026 checklist. The example helps identify the relevant instruction, but your vehicle manual and accessory documentation control the actual fit and procedure. So, keep the inspection within a safe stationary demonstration and stop when damage or an uncertain part makes further testing inappropriate.

Know what running-on means

Check for engine running-on before you buy an older petrol car. The How a Car Works guide cited here says running-on is when the engine keeps turning after the ignition is switched off, because a hot spot in the combustion chamber ignites the mixture, and that it can cause serious damage if left to go on.

Switch off after a warm drive

After the test drive, with the engine fully warm, switch off and listen. The cited guide says the engine may jerk and rock on its mountings, sometimes backfire, and in bad cases run on for a minute or more. Note what you hear and ask the seller whether it happens often.

Ask about plugs, fuel grade and tune

The guide says the simplest causes are the wrong grade of petrol, faulty or wrong-grade spark plugs, a carburettor badly out of tune or wrong ignition timing, with carbon build-up a more serious cause. Ask when the plugs were changed and the timing and mixture were set.

Have air leaks and carbon checked

The guide says a weak mixture from air leaking into the inlet manifold can make the engine run hotter. Ask the inspector to check for vacuum leaks and to look at plug condition for signs of overheating. Get any needed work priced before you pay.

Put the missing item in the purchase agreement

Write down the engine running on condition, the pieces missing and the supplier identification you still need. Ask whether the seller will provide the correct replacement or agree a price adjustment for you to obtain it. Keep any promised correction in the purchase agreement with a clear description of what must be supplied. A generic online price cannot establish that mounting parts or the correct fit are included, so ask the supplier for a current quote.

Keep the accessory check inside a wider inspection

The condition of one accessory cannot establish the state of the whole vehicle. Our pre-purchase inspection checklist helps specify the work an independent shop will undertake. NYC used-car guidance recommends that independent examination. Ask the inspector to record related damage and explain inaccessible areas. Look, a fake PDF or a polished seller checklist can conceal an unresolved problem.

Separate history records from equipment present today

A report may contain reported events without listing every accessory that has been lost or replaced. Our VIN verification guide helps match the car to its documents; our tire-replacement reporting guide shows the gap between records and current equipment. NMVTIS concerns U.S. title history rather than certifying this item. Keep condition and documents as separate findings.

Note who supplied the current item

Ask whether the engine running on is the original part or a later replacement, and who supplied it. A dealer invoice or parts receipt helps confirm the right fit. If the seller bought a generic version online, check it against the instructions for this vehicle before relying on it. Record the part number where one is visible. That small detail saves time if you later need a matching piece or a warranty claim on the item.

Decide how much the gap matters to you

A missing or damaged engine running on rarely decides a car purchase alone, but it tells you something about how the car was kept. Weigh it with the rest of the inspection. If several small items are missing, ask the seller for a written list of what is and is not included. Agree the price with that list in front of you rather than discovering gaps after you drive away. A short written note from the seller about known faults also helps if a dispute comes up later, because it shows what was disclosed before you paid.

Take your time with this check. If the seller hurries you past it, ask why. Small faults are easier to price in before you pay than to argue about after you drive away.

We are a licensed CARFAX and AutoCheck reseller, not affiliated with CARFAX, AutoCheck or Experian. Wholesale reports cost a few dollars; confirm current coverage and the total at checkout. A quiet report can miss unreported repairs. Keep the independent inspection even if the seller sends an impressive PDF.

Sources

• How a Car Works running-on guide
• U.S. DOJ NMVTIS
• NYC used-car buying guidance