Chevrolet R20 Suburban MAP Sensor: A Guide for 1987-1988 Owners
Understanding the MAP sensor in your classic '87-'88 R20 Suburban is key to maintaining engine performance and fuel economy.
- A failing MAP sensor on your '87-'88 R20 Suburban will cause rough running, poor fuel economy, and hesitation, often triggering Check Engine Code 33 or 34.
- Replacement is a simple, DIY-friendly job that takes less than 30 minutes with basic tools.
- Always inspect the vacuum hose connected to the MAP sensor for cracks or blockages, as it can cause the same symptoms as a bad sensor.
- Given the vehicle's age, a new aftermarket sensor is a reliable and cost-effective repair solution.
Diagnosing a Failing MAP Sensor in Your R20 Suburban
Because your 1987-1988 Suburban was built before modern OBD-II diagnostics, it uses an older system. You might get a "Check Engine" light on your dash. Common OBD-I trouble codes related to a failing MAP sensor on these trucks are Code 33 (voltage high, indicating low vacuum) and Code 34 (voltage low, indicating high vacuum). These codes often point directly to a bad sensor, a vacuum leak, or wiring issues.
Common Symptoms of a Bad MAP Sensor:
- Poor Engine Performance: You might feel hesitation or stumbling when you accelerate. The engine can feel sluggish or like it's bogging down.
- Rough or Unstable Idle: The engine may vibrate, idle erratically, or even stall when you come to a stop. This happens because the computer gets scrambled information about the engine load.
- Bad Fuel Economy: If the sensor fails and tells the computer the engine is under a heavy load, it will inject too much fuel, causing a rich condition and wasting gas.
- Black Smoke from Exhaust: A sign of an overly rich fuel mixture, where unburned fuel is exiting through the exhaust.
- Hard Starting: The wrong air-fuel mixture can make it difficult for the engine to start, especially when cold.
Don't Ignore the Vacuum Hose
The MAP sensor connects to the intake manifold via a rubber vacuum hose. Over decades, these hoses can become brittle, cracked, or clogged. A leaking hose will provide a false reading to the sensor, mimicking the symptoms of a failed sensor. Always inspect and, if necessary, replace the vacuum hose when you replace the MAP sensor.
Choosing the Right Aftermarket MAP Sensor
For a classic vehicle like the '87-'88 R20 Suburban, finding original OEM parts can be nearly impossible. Aftermarket parts are often the only practical choice. The key is to choose a reliable replacement that meets or exceeds original specifications.
The "Replacement" brand MAP sensor is a cost-effective solution designed to restore your engine's proper function. Since these sensors are a common failure point on older TBI systems, having an affordable and available option is crucial for keeping these trucks on the road. While OEM parts were the gold standard, a new aftermarket part is almost always a better choice than a used, junkyard sensor with an unknown history.
| Part Type | Estimated Cost | Notes |
|---|---|---|
| New OEM | $90 - $175+ | Very difficult to find new; may be discontinued. |
| New Aftermarket (Replacement) | $26.12 | Readily available and provides a cost-effective repair solution. |
| Used OEM | $15 - $40 | Risky due to age and unknown condition. Not recommended. |
Installation is DIY-Friendly
Replacing the MAP sensor on your R20 Suburban is a simple job that most owners can do themselves in under 30 minutes with basic hand tools. The sensor is typically located on a bracket near the air cleaner housing. It involves removing the air cleaner, unclipping the sensor from its bracket, disconnecting one electrical connector, and one vacuum hose. This makes it a quick and easy part to swap out during troubleshooting.
Frequently Asked Questions
Where is the MAP sensor located on a 1987-1988 R20 Suburban?
The MAP sensor is usually mounted on a bracket on the passenger side of the engine bay, near the air cleaner housing and firewall. It's a small black box with a 3-pin electrical connector and a port for a single vacuum line.
Can I drive my Suburban with a bad MAP sensor?
Yes, but it's not recommended for long. The vehicle will likely run poorly, get bad gas mileage, and could stall unexpectedly. Driving for an extended period with a bad sensor can lead to other issues like fouled spark plugs or a damaged catalytic converter from the rich fuel mixture.
How do I check for engine codes on my old Suburban?
On these OBD-I vehicles, you can often retrieve codes without a scanner. You use a paperclip or a small jumper wire to connect the 'A' and 'B' terminals on the diagnostic port under the dashboard. When you turn the key to the 'On' position (without starting the engine), the Check Engine Light will flash to indicate the stored codes. Always consult a service manual for the specific procedure for your vehicle.
Are there any recalls for the MAP sensor on this vehicle?
Based on searches of the National Highway Traffic Safety Administration (NHTSA) database, there are no specific recalls for the MAP sensor on the 1987-1988 Chevrolet R20 Suburban.
Technical Specifications
3-pin rectangular female connector, single vacuum port.
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.
- Chevrolet R20 Suburban: