I put in a new set of 3923's, wires, cap and rotor today and I replaced the MAP sensor with a new one. At a cold idle in my carport it had 1.9 volts from the new sensor, it started quicker and had a much smoother idle. I test drove it and again it had much better power and throttle response. It was really good to climb hills in 5th gear at 65 mph again. Truck is running ten times better than it was. I need to drive it a while to see how it affects the MPG, but even since yesterday, I am pretty sure it's using less gas. If I can get even just 3 or 4 more MPG I will be glad.

Thanks for posting this and to everybody who replied. New MAP sensor made a world of difference on my truck.

Jimmy

 

so which wire did you backprobe to test?

 

middle wire, its the signal back to the PCM.. grab a chilton manual if you havent. everything you need to know to test the map and various other sensors are in that manual.

 

nope I'm good, just verifying that it tests the same as the TPS.

 

I noticed right away that my trucks idle was smoother

and it climbed the rpm's better as well

 

Can some one tell me what the limits for the map sensor are. Finally got a chance to test mine and it shows 1.42 volts at idle, is that acceptable? this is a 2004 with a 4.7, The cheapest I can find is at autozone and its app. $90.

Thanks Ron

 

Not sure on 4.7. On my 3.9 the acceptable range is 1.5 to 2.0 volts at idle. I'll check my manual at home when I get there. 4.7 is probably the same I bet.

Jimmy

 

Check a couple local dealers. I got my map sensor from Dodge for $23 and I have a 2003 4.7 so it should be the same.

 

My books don't differentiate between 3.9's and 4.7's for the output voltage. 1.4 is in specs, but low on the scale of acceptable. Lowest it should be is 1.3. Highest at idle with throttle plates closed should be 2.0. If it was mine I would replace it.

I already picked up almost another 3 MPG around town since I replaced my MAP sensor. I got a tank last weekend and filled up again today and divided the mileage by the gallons, it was 19.23. I'm pretty happy with that. I ordered 2 new upstream O2's from NGK Monday and they should be here tomorrow. When I get those installed this weekend I hope to gain another couple MPG's.

Jimmy

 

Thanks for the replies, now got to find time to get to the dealer.

Ron