Why is my old Plymouth Valiant hard to start or missing on the highway?

Short answer: On an old Valiant that starts only sometimes, test the ballast resistor on the firewall, then check the choke and do a basic tune-up (points, plugs, condenser). A miss at highway speed with a timing mark that jumps points to worn distributor bushings or a stretched timing chain. An oil light that stays on after work is often a shorted wire to the oil sender, but check real oil pressure with a gauge before driving.

Symptom: The engine cranks but rarely starts, misses or loses power on the highway, or the oil warning light won't go out.

What to check first

1. Check the ballast resistor on the firewall. A brief jumper around it is a common test, but don't leave it bypassed.
2. Look at the choke plate with the air cleaner off. It should close on a cold engine and open as it warms.
3. Grab the distributor shaft and see if it wobbles side to side.
4. With a timing light, see if the mark jumps around.
5. Check oil pressure with a mechanical gauge, then trace the sender wire for damage.

Likely causes

1. Ballast resistor. A small ceramic resistor on the firewall feeds power to the ignition coil. When it fails, the car may start and then die, or start only now and then.
2. Choke not closing or opening right. The choke plate on the carburetor richens the mixture for a cold start. If it's stuck, cold starting gets hard.
3. Worn distributor shaft bushings. If the distributor shaft wobbles, the points gap changes as it spins, so the spark timing wanders and the engine misses.
4. Stretched timing chain. A worn chain lets the timing move around, so the engine loses power and the timing mark jumps.
5. Oil light wire shorted to ground. The oil pressure sender works by grounding the warning light. If the wire to the sender is pinched or touching metal, the light stays on even with good pressure.

What it usually costs

Owners in these threads didn't post prices. Ballast resistors, points and senders are low-cost parts.

Is it safe to keep driving?

A car that misses or dies can stall in traffic. Don't drive with the oil light on until you've confirmed real oil pressure with a gauge.

DIY or shop?

Ballast resistor, choke, tune-up and wiring checks are DIY. A timing chain is a bigger job you may want a shop for.

Recalls, bulletins and complaints in plain words

• Related recalls: NHTSA lists these recalls touching this area of the Plymouth Valiant: 73V011000 (1972-1973 model years, fuel system, gasoline:delivery); 77V242000 (1975-1976 model years, fuel system, gasoline:carburetor system). Check your VIN at nhtsa.gov/recalls. If your car is part of this recall, the dealer fixes it for free.
• Plain words: The complaint count below shows how often owners reported problems that mention these words to NHTSA. A count is not proof of a defect.
• NHTSA complaints: 0 keyword-matched complaints for Plymouth Valiant 1960–1976 (of 0 unique complaints queried, NHTSA complaints API by model year, queried 2026-10-29; keywords: start, stall, miss, ignition, oil pressure, oil light) (NHTSA returned no data for 12 model-year queries). This counts complaints that mention these words. It is not a defect finding.

What owners report

• In 65 Valiant starting problems on Car Talk, a '65 Valiant slant six started only about 1 time in 9. Members walked through bypassing the ballast resistor on the firewall to test it, checking the choke and doing a basic tune-up.
• In 1964 Valiant Missing on Car Talk, a '64 Valiant missed at highway speed and the timing mark jumped around. Members pointed to worn distributor shaft bushings or a stretched timing chain.
• In 1965 Plymouth Valiant oil pressure sensor on Car Talk, a '65 Valiant's oil light stayed on after an alternator swap, and there was no wire on the oil sender. Members explained the sender turns on the light by grounding it, so a shorted or misrouted wire can keep the light lit.

Quick tip

The ballast resistor is cheap. On these Mopars, keep a spare in the glove box.

Vehicle focus: Plymouth Valiant, 1960-1976, mostly the slant six.

Safety / mechanic note

Stalling and low oil pressure are safety and engine-damage risks. Verify with a mechanic.