Why does my Plymouth Sundance race at idle, or why did it quit?

Short answer: If your Sundance revs high at stoplights and shuts off with a thud, one 1993 owner's fix was a new idle motor (the idle air control, which sets idle speed). Check battery cables and grounds too, since a bad connection can make the computer raise idle. If it pinged badly, lost power and puffed white smoke, suspect a blown head gasket and test before spending money, since overheating may have damaged the engine.

Symptom: The engine sounds like it's racing at lights, and the car jolts with a thud when shut off. Or it won't crank at all. Or it pinged hard, lost power, backfired and puffed white smoke.

What to check first

1. Clean and tighten the battery terminals and grounds. A new terminal clamp got the 1993 car cranking again.
2. If idle races, have the idle air control motor checked.
3. Check for coolant loss and white smoke after pinging or overheating.
4. Use a block tester (a parts-store kit that detects exhaust gases in the coolant) or watch for bubbles in the radiator with the cap off.
5. Fix the temperature gauge if it doesn't work, so you can catch overheating.

Likely causes

1. Failed idle air control motor. The confirmed fix for racing idle and the shutoff thud in the 1993 thread.
2. Corroded battery terminal or bad ground. A new terminal clamp fixed the 1993 car's no-crank.
3. Blown head gasket from overheating. A member's diagnosis for the 1991 that pinged and smoked.

What it usually costs

No prices were posted. A member said a 1991 Sundance isn't worth much now, so a head gasket or engine repair may cost more than the car is worth; test before deciding.

Is it safe to keep driving?

A racing idle makes the car harder to control at stops. If it overheated and smokes, don't drive it; you can ruin the engine. Verify with a mechanic.

DIY or shop?

DIY for battery terminals, grounds and an idle motor swap. A block test is a DIY kit; head gasket repair is a big job.

Recalls, bulletins and complaints in plain words

• Related recalls: NHTSA lists these recalls touching this area of the Plymouth Sundance: 88V105000 (1987-1987 model years, fuel system, gasoline); 89V237000 (1989-1990 model years, engine and engine cooling). Check your VIN at nhtsa.gov/recalls. If your car is part of this recall, the dealer fixes it for free.
• NHTSA complaints: 19 keyword-matched complaints for Plymouth Sundance 1987–1994 (of 315 unique complaints queried, NHTSA complaints API by model year, queried 2026-10-25; keywords: stall, dies, shut off, won't start, cut out, idle, racing, head gasket, overheating). This counts complaints that mention these words. It is not a defect finding.

What owners report

• In Dead?... my '93 plymouth sundance gone? on Car Talk, a 1993 Sundance raced at stoplights on a long trip, thudded at every shutoff, and then wouldn't crank. A member said a bad electrical connection can make the computer raise the idle, and to check battery and fuse box connections and grounds. A shop put on a new battery terminal clamp, and when the racing idle continued, replaced the idle motor, which fixed it.
• In Is my 1991 Plymouth Sundance dead? on Car Talk, a 1991 Sundance started pinging badly, lost power, backfired with a puff of white smoke, and kept running briefly after shutoff. The temperature gauge didn't work. Members suspected a blown head gasket and suggested a block tester or watching for radiator bubbles, and warned overheating may have damaged the engine.

Quick tip

If a gauge doesn't work, overheating can sneak up on you. A cheap aftermarket gauge or a fixed sender can save an engine.

Vehicle focus: 1987–1994 Plymouth Sundance (2.2L and 2.5L four), twin of the Dodge Shadow.

Safety / mechanic note

Never open a hot radiator cap. Verify with a mechanic.