Why does my Plymouth Laser idle too high, or run rich and flood out?

Short answer: On the Laser, a warm idle stuck around 2,000 rpm and an engine that runs rich and floods both point to the parts that control idle air and fuel mixture. Read the stored codes first. Then check the idle air control valve, the fuel pressure regulator (gas in its vacuum hose means it's leaking), and the wiring to the coolant temperature sensor. An open wire there can make the computer pour in fuel.

Symptom: When warm, the engine idles too fast, sometimes near 2,100 rpm, and turning on the A/C brings it back down. Or it runs rich, smells of gas and floods out, even after the owner replaced several sensors.

What to check first

1. Read stored trouble codes before buying more parts. These are OBD-I cars; a shop or a code chart can help.
2. Pull the vacuum hose off the fuel pressure regulator. If there's gas in it, the regulator is leaking and flooding the engine.
3. Check the coolant temperature sensor and its wire. An open wire to the computer can make the engine run very rich.
4. Clean or test the idle air control valve if the warm idle is high.
5. Look for vacuum leaks and check the air filter.

Likely causes

1. Idle air control valve or vacuum leak. The usual cause of a high warm idle that changes when the A/C kicks on.
2. Leaking fuel pressure regulator. Suggested for the car that floods: gas in the regulator's vacuum hose is the giveaway.
3. Open wire or bad coolant temperature sensor. A member said a broken wire from the computer to the sensor can cause this, and even a new sensor can be bad.
4. Clogged catalytic converter. Also mentioned for the rich, flooding car.

What it usually costs

No owner posted prices in these threads. A regulator, idle air valve or sensor is a modest part; most of the cost is diagnosis.

Is it safe to keep driving?

A high idle makes the car want to creep forward and work the brakes harder. A flooding engine can stall in traffic. Fuel smell means get it checked soon. Verify with a mechanic.

DIY or shop?

DIY for the regulator hose check, cleaning the idle air valve and testing the sensor wire. Fuel pressure and converter checks are easier at a shop.

Recalls, bulletins and complaints in plain words

• Recalls: NHTSA lists no recall for idle, stalling or fuel on the Plymouth Laser for these model years (checked 2026-10-27). Other recalls may exist for your car, so check your VIN at nhtsa.gov/recalls. If your car is part of a recall, the dealer fixes it for free.
• Plain words: No recall we found matches this problem, so it's a normal repair, not a free recall fix. Still run your VIN, since other recalls may be open.
• NHTSA complaints: 9 keyword-matched complaints for Plymouth Laser 1990–1994 (of 119 unique complaints queried, NHTSA complaints API by model year, queried 2026-10-27; keywords: stall, dies, no start, cut out, idle, rich, flood, rpm, surge, hesitation). This counts complaints that mention these words. It is not a defect finding.

What owners report

• In 1990 Plymouth Laser - Dies at 1200 RPM on Car Talk, the original owner of a 1990 Laser Turbo said it idled around 2,100 rpm once warm, and that turning on the A/C brought the idle back to normal. A member's advice was to read the stored trouble codes first.
• In 1990 plymouth laser runs rich then floods out on Car Talk, an owner had already replaced the mass airflow sensor, coolant temp sensor, oxygen sensor, fuel pressure regulator and plugs. Members suggested checking the regulator's vacuum hose for fuel, the idle air control valve, a clogged converter, fuel pressure with a gauge, and the wire from the computer to the coolant temp sensor. No final fix was posted.

Quick tip

Replacing sensors one after another gets expensive. A fuel pressure gauge and a meter on the coolant sensor wire answer the question for less money.

Vehicle focus: 1990–1994 Plymouth Laser (Eagle Talon and Mitsubishi Eclipse twin), turbo and non-turbo.

Safety / mechanic note

Raw fuel in a vacuum hose is a fire risk. Work with the engine off and cool, and wipe up any gas. Verify with a mechanic.