Chevrolet Impala Manifold Absolute Pressure (MAP) Sensor Guide: 1985-1993
Diagnose and replace the MAP sensor on your 1985-1993 Chevrolet Impala to restore engine power and fuel economy.
- A bad MAP sensor on a 1985-1993 Impala causes poor fuel economy, rough idle, and lack of power.
- Replacement is very easy, requiring basic tools and less than 30 minutes.
- Choose premium brands like ACDelco or Delphi for OEM quality, or trusted aftermarket brands like Standard Ignition for a balance of price and reliability.
- Look for OBD-I trouble codes 33 or 34, which point directly to a MAP sensor circuit failure.
Is Your Impala Running Rough? It Could Be the MAP Sensor
If your 1985-1993 Chevrolet Impala is experiencing issues like poor fuel mileage, rough idling, or a lack of power, a failing Manifold Absolute Pressure (MAP) sensor is a common culprit. This sensor provides critical engine load information to the main computer. When it fails, the computer can't properly calculate the right air-fuel mixture, leading to a host of driveability problems. Fortunately, this is a part that is easy to diagnose and replace for most owners.
Symptoms of a Bad MAP Sensor on a 1985-1993 Impala
A bad MAP sensor sends incorrect information to the engine computer, which can result in either too much or too little fuel being injected. Watch for these signs:
- Poor Fuel Economy: If the sensor incorrectly signals a high engine load, the computer will inject too much fuel, causing your gas mileage to drop.
- Rough or Stumbling Idle: The engine may shake, vibrate, or struggle to maintain a steady RPM at a stop.
- Lack of Power & Hesitation: When you press the gas, the car may feel sluggish or hesitate before accelerating. This can happen if the sensor incorrectly signals a low engine load, starving the engine of needed fuel.
- Black Smoke from Exhaust: This is a clear sign of a rich fuel mixture (too much fuel, not enough air), which can be caused by a faulty MAP sensor telling the computer the engine is under more load than it is.
- Hard Starting: The engine may take longer than usual to start or may not start at all.
- Check Engine Light: On these OBD-I vehicles, a failing MAP sensor will typically trigger a Code 33 or Code 34.
Choosing the Right Aftermarket MAP Sensor
While an OEM part from the dealer is an option, the aftermarket offers a wide range of quality replacements. For a critical sensor like this, brand quality matters. Here’s how the available brands generally stack up for your Impala.
OEM vs. Aftermarket Quality
For GM vehicles of this era, ACDelco is the original equipment manufacturer. Delphi was part of GM and is also considered an OEM-level supplier for electronics. These brands ensure a perfect fit and performance identical to the original part. High-quality aftermarket brands like Standard Ignition and Walker Products are also excellent choices that often meet or exceed original specifications. Budget-friendly brands can be a good value, but may have a shorter service life or less consistent quality control.
Brand Tiers
- Premium Aftermarket (OEM-Equivalent): Choose ACDelco or Delphi if you want the closest thing to the original factory part. They are trusted by professional mechanics for their reliability and precise calibration.
- Quality Aftermarket: Brands like Standard Ignition (SMP) and Walker Products have a strong reputation for producing reliable sensors that are a direct fit. They offer a great balance of quality and price.
- Standard Aftermarket: Brands such as Facet, Global Parts, Hella, Spectra, and True Tech provide functional replacements that can get your car back on the road at a lower cost. These are suitable for budget-conscious repairs.
| Part Type | Estimated Cost |
|---|---|
| New OEM (ACDelco) | $100 - $150 |
| New Aftermarket | $44.66 - $99.57 |
| Used OEM | $15 - $40 |
| Shop Labor | $50 - $100 |
A Note on Used Parts
While a used MAP sensor from a salvage yard is inexpensive, it's a gamble. The part's history is unknown, and it could fail shortly after installation. Given the low cost of new aftermarket parts and the importance of this sensor, a new part is strongly recommended.
Frequently Asked Questions (FAQ)
Where is the MAP sensor located on my 1985-1993 Impala?
The MAP sensor is typically mounted on a bracket on the intake manifold, near the throttle body and distributor. It's a small, black plastic part with an electrical connector and a single vacuum hose attached to it. You will likely need to remove the air cleaner assembly to see and access it.
Can I clean my MAP sensor?
While some sensors like the Mass Airflow (MAF) sensor can be cleaned, it is generally not effective for a MAP sensor. The failure is usually internal to the electronics. Given the low cost of a new sensor and the ease of replacement, replacing a faulty MAP sensor is the best course of action.
What happens if I ignore a bad MAP sensor?
Driving with a bad MAP sensor will cause persistently poor engine performance, terrible fuel economy, and increased emissions. A very rich fuel mixture can lead to fouled spark plugs and eventually damage the catalytic converter, leading to more expensive repairs down the road.
Are there any recalls for the Impala MAP sensor?
No, there are no specific recalls or technical service bulletins (TSBs) from Chevrolet or the NHTSA for the Manifold Absolute Pressure sensor on the 1985-1993 Impala model years.
Technical Specifications
OEM Part Numbers: 16187556 12219931 16006835 AS5
This is a 3-pin sensor that operates on a 5-volt reference from the ECU and measures pressure changes in the intake manifold via a vacuum hose.
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The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
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