How often do MAP sensors fail?

luftvagon · Post by **luftvagon** » Sun Nov 17, 2013 3:18 pm

I'm troubleshooting a problem which appears to be a defective MAP sensor. My local baro is 100 kpa, however my GM 1BAR MAP sensor is only registering 63.4 kpa. Once in a while it will jump to 103 kpa and stay there... Not sure if this is electrical or MAP sensor.

How does one tell besides a bench test of the MAP sensor?
If I unplug the MAP from the electrical system, I get a random reading of 12 kpa (tunerstudio) -- consistently.

Is this some kind of strange electrical problem, or MAP sensor took a well undeserved break?

luftvagon · Post by **luftvagon** » Sun Nov 17, 2013 3:51 pm

Update:

I tested the Vref,V, and resistance to ground, without the MAP sensor connected.

Vref = 4.9998
V ~ 30mV
R ~ 20 Ohm to engine block

I guess, would that constitute normal parameters?

miniman82 · Post by **miniman82** » Sun Nov 17, 2013 7:06 pm

I the software set up for the correct MAP sensor?

Post by **Piledriver** » Sun Nov 17, 2013 7:09 pm

GM sensors have been known to fail, esp if of junkyard provenance.
Fortunately they are very common.

luftvagon · Post by **luftvagon** » Mon Nov 18, 2013 4:30 am

I should have mentioned, the sensor has been set up correctly for GM 1BAR sensor and has been running for months. This is something new that just stared.
The sensor was brand new. I'll get another one.

luftvagon · Post by **luftvagon** » Mon Nov 18, 2013 8:30 am

I went to NAPA and picked up a new sensor. The sensor I bought was from Amazon, and it was $15; the NAPA part was $61 with shipping.

Steve Arndt · Post by **Steve Arndt** » Mon Nov 18, 2013 9:48 am

What were the results?

luftvagon · Post by **luftvagon** » Mon Nov 18, 2013 9:54 am

Cheap Sensors Fail often

I am back and running... did a nice tuning run today. Looks like this MAP sensor is much more precise than the old one.

dawie · Post by **dawie** » Sat Nov 23, 2013 11:38 pm

Map sensors could possibly be damaged by backfiring through the inlet. A typical map sensor has limited over-pressure rating.

By the way, on some cars, backfiring can be severe, causing the inlet plenum to explode. Even the Porsche's strongly ribbed plastic plenum often gets blown to pieces while starting the car, especially when battery is a bit low. Cold start valve, spraying upstream into the plenum seems to exaggerate the problem. Combined with unstable ignition timing at low cranking speeds/ reluctor sensor... From experience, disconnecting the cold start valve in this application may help to reduce an "exploding backfire" to just some minor "coughing" when starting.

luftvagon · Post by **luftvagon** » Mon Nov 25, 2013 5:06 pm

dawie wrote:Map sensors could possibly be damaged by backfiring through the inlet. A typical map sensor has limited over-pressure rating.

By the way, on some cars, backfiring can be severe, causing the inlet plenum to explode. Even the Porsche's strongly ribbed plastic plenum often gets blown to pieces while starting the car, especially when battery is a bit low. Cold start valve, spraying upstream into the plenum seems to exaggerate the problem. Combined with unstable ignition timing at low cranking speeds/ reluctor sensor... From experience, disconnecting the cold start valve in this application may help to reduce an "exploding backfire" to just some minor "coughing" when starting.

I think that's exactly what happened. My cold start has been disconnected for a while now, but when the fuel pump broke, it may have taken out the MAP sensor.
Or, it could've backfired during cold start, and taken out the MAP sensor.

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