How to test MAP sensor?? - Diesel Forum

amberjax · 02-13-2008, 04:22 PM

Anyone have the skinny on how to test a MAP sensor?? I've seen several posts talking about the MAP sensors causing the mpg to drop. Mine seems to be doing the same thing for no obvious reason. Like to know how to test it before buying one.

**action4478** · 02-13-2008, 04:38 PM

Quote:

Originally Posted by amberjax

Anyone have the skinny on how to test a MAP sensor?? I've seen several posts talking about the MAP sensors causing the mpg to drop. Mine seems to be doing the same thing for no obvious reason. Like to know how to test it before buying one.

If you don't have a scanner ,, try unpugging it ...Have you checked the fuel pressure ?...

amberjax · 02-13-2008, 05:30 PM

No, haven't checked the fuel pressure. Have a new pump (less than a month old) and have shimmed the fpr.
If I unplug the sensor will it set a code??

blageurt · 02-13-2008, 05:41 PM

Try spraying some electric contact cleaner inside the Map sensor where the hose goes on. It seemed to have decreased the black smoke on mine. I don't know about Mpg's yet because Its been so cold here lately there's no point driving around wasting fuel just to test it out. I might buy one too. I priced them at Powerstroke shop for $ 127 plus shipping. I will look in a junkyard too apparantly the I-6 Econoline has the same sensor as me. part # F4TZ-9F479-A

**action4478** · 02-13-2008, 06:01 PM

Quote:

Originally Posted by amberjax

No, haven't checked the fuel pressure. Have a new pump (less than a month old) and have shimmed the fpr.
If I unplug the sensor will it set a code??

Yes , but it won't hurt anything while testing

Patrick Feeley · 02-13-2008, 06:53 PM

Quote:

Originally Posted by blageurt

I will look in a junkyard too apparantly the I-6 Econoline has the same sensor as me. part # F4TZ-9F479-A

Before rushing out to your local boneyard to find the Econoline version (or just another MAP sensor), you might want to read this: "TSB 94-23-15, LOSS OF POWER - 7.3L DIRECT INJECTION TURBO DIESEL - INCORRECT MAP SENSOR".

Cheers!

MX_STROKER · 02-13-2008, 08:52 PM

Quote:

Originally Posted by action4478

If you don't have a scanner ,, try unpugging it

And what are the symptoms if you unplugging it to see that it is bad? changes something in the idle, WOT, or what?

STurbo90 · 02-14-2008, 12:21 AM

Quote:

Originally Posted by MX_STROKER

And what are the symptoms if you unplugging it to see that it is bad? changes something in the idle, WOT, or what?

The drivability should be different.
If the map sensor is unplugged the pcm will default to a set value.
If the map is bad and sending the wrong data to the pcm it usually shows in poor acceleration.

Usually when complaints about poor acceleration came up testing the map sensor was one of the things most checked. It seems just recently that people are saying the mpg improved when they replaced the map sensor, but they were not complaining about any drivability issues. So I don't know if its a direct relation, or they just didn't notice any poorer performance.

MX_STROKER · 02-15-2008, 08:24 PM

Quote:

Originally Posted by STurbo90

The drivability should be different.
If the map sensor is unplugged the pcm will default to a set value.
If the map is bad and sending the wrong data to the pcm it usually shows in poor acceleration.

Usually when complaints about poor acceleration came up testing the map sensor was one of the things most checked. It seems just recently that people are saying the mpg improved when they replaced the map sensor, but they were not complaining about any drivability issues. So I don't know if its a direct relation, or they just didn't notice any poorer performance.

Thanks a lot, and yes I have read that about the MPG, and Im having poor MPG and not any poorer performance, thats why asked that. Im going a try, unplugg the MAP sensor and let see what happens.