Question about 1987 Pontiac Bonneville
I have the 3.8 v6 in my car. When I scan the car for codes it comes back with a MAP sensor voltage low. When I call part shacks, they all say they don't list a map sensor for my car. The car bucks and tries to die out unless I really stay on the throttle. So is it going to be a dealer only part? And if so where the heck is the sensor at on my car? Thanks in advance
tough one this, but you never know. The MAP sensor is usually located on the inlet maniforld, however, if the car shacks say they don't have one listed, i suspect this is because the MAP will be integral with the ECU. To test this theory, locate your ECU, and if it's got a vacuum pipe going to it (from the inlet man), thats where your MAP is. Could be bad news if it is, but often the problem is gunge in the pipe leading to the MAP or gunge in the map.
Before you go off to the dealer with a fat wallet, its worth considering having a go at DIY.
First check the pipe, and if it is blocked or partially blocked suspect the MAP is dirty too. These sensors vary in design, but all are essentially the same. Remove ECU and carefully take it apart to check the MAP. Its not rocket science (as the dealers would have you believe) and any fault should be "findable" using a bit of common sence. Remember that most faults of this kind (>90%) are mechanical.
Forgot to mention, also check if the pipe is leaking or split etc.
All the best, and good luck....Dave
Posted on Jun 14, 2008
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First, using your scan tool with the Key on and engine running, monitor the MAP Sensor voltage. If it is reading less than 5 volts, turn engine off, unplug the MAP sensor and, using a DVOM (Digital Volt/Ohm Meter) check for 5Volts on the 5 Volt reference circuit.
1. If there is not 5 Volts on the reference circuit, then check for the reference voltage at the PCM connector. If it is present at the PCM connector but not the MAP connector, repair the open in the wiring loom between the PCM and MAP harness connector.
If 5 Volt reference is NOT present at the PCM connector, check powers and grounds of PCM and repair/replace as needed.
2. If you have a 5 Volt reference at the MAP connector, jumper the 5 volt reference circuit to the signal circuit. Now check the MAP voltage on the scan tool. It should be 4.5 to 5 Volts. If it is, replace MAP sensor. If not, repair open/short in the signal circuit wiring and re-check.
3. If all appears okay, perform a wiggle test. Start engine and manipulate the harness, connector and tap on the MAP sensor. Note any changes in voltage or engine speed. Repair connector, harness, or sensor as needed.
4. If the wiggle test checks out, use a vacuum pump (or just use your lungs) to draw a vacuum on the MAP sensor vacuum port. As you add vacuum the voltage should decrease. With no vacuum, the MAP sensor should read approximately 4.5 volts. If there is no change in MAP sensor reading on the scan tool, replace MAP sensor.
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