MAP sensor replacement?

[Jimmy9190]

Has anyone here who has a Manifold Absolute Pressure sensor replaced it as a maintenance item? I read on another forum that MAP sensors get carboned up and dirty and need replacing about every 60K. Mine has 111K on it and the signal wire reads 1.2 volts at idle, which is at the very low end of acceptable specs. My check engine light is not on.

I read on the other board that a new MAP sensor will improve MPG and power and make the truck run like it did when it was new. Any info is appreciated.

 

[bepperb]

MAF sensors can get gummed up. MAP sensors usually don't and don't have a hot wire. So I assume you're talking about a MAF sensor.

I certainly wouldn't replace one as preventative maintenance. Have you tried cleaning it? CRC makes a MAF sensor cleaner.

 

[StevieC]

If there is no Check Engine light and the car runs fine, leave it as it is... The computer will let you know.

 

[Jimmy9190]

My truck only has a MAP sensor, there is no MAF sensor. Truck runs OK, I am just trying to improve my gas mileage, and improve the power if I can. It's just a Dodge Dakota with a 175hp V6 and at 111K I expect it to be a little slow, but it could do better.

The guy on the Dodge Forum said he did not have a CEL either, but a new MAP sensor made his truck run like new. I have another (used) MAP sensor at home and I may just switch it out to see what happens.

Thanks.

 

[StevieC]

Give it a try and see... The only word of advice that I can offer you is if you do replace it with a brand new one make sure it's an OEM because some aftermarket ones are cheaply made and can make your problem worse IMO!

 

[Jimmy9190]

The one I have at home is from a Dodge 5.9 engine I think. It was on the V8 throttle body I put on about a year ago. I have no idea how many miles are on it or if it even works. But I can install it and check its output voltage and see what happens.

Thanks.

 

[Falcon_LS]

Prior to spending money on a new one (these can be pretty expensive), check for codes. Does your truck have any problems with poor acceleration, rough idle or excessive fuel consumption?

 

[[RT] ProjUltraZ]

i changed mine at 90K, so easy and about $30. it was kinda dirty but nothing major, might have been fine anyway

 

[Jimmy9190]

MPG is down a little from what it used to be, I used to average about 21 or 22 around town and 25 or 26 on the interstate. Now I average 18 in town, not sure about interstate yet because I haven't taken any long trips lately. Acceleration is a bit slower too. It idles fine, right at 700 RPM like it always has. The CEL is not on and I have no stored codes. I figured if the MAP was bad it will set a code. The guy on the Dodge forum just replaced his in frustration after throwing all the other parts he could think of at it (plugs, wires, cap & rotor, etc). He and a couple others said the new MAP did the trick. He is getting 20 MPG in town now, up from 15 MPG wih the old sensor.

I also thought I might need new upstream O2 sensors, but again, I have no codes so that logic says leave it alone, if the sensor fails it will set a code. I am just trying to help improve my old 3.9's performance and maybe save a little gas money.

I appreciate the help here. Thanks.

 

[StevieC]

It is possible to have bad 02 Sensors, Map sensors, plugs/wires that are breaking down and causing poor economy and still not set codes.

I would check your plug/wires/air filter first then check things like your 02 & MAP.

Now I would be more inclined to think it's your MAP if the wires/plugs/air filter check out because I have seen my dad replace many MAPS from Chrysler for friends/family.

Steve

 

[mechtech2]

The MAP sensor is connected to engine vacuum, which has vapors in in that eventually affect the sensor. [not always on vacuum, you know]
I'd replace it, but also consider that you may have a slow O2 sensor. Or a bunch of other tired stuff.
A coolant or air temp sensor can be faulty, and make you run rich or have retarded timing.

 

[Jimmy9190]

Wires have about 35K on them, I use the Belden premium set from Napa. The plugs have about 17K right now, they are NGK V-Power. Cap and rotor are the better quality Echlin parts from Napa, the ones with brass contacts and are the same age as the plugs. The air filter has about 10K on it and is clean and dry. I use ProSelect air and oil filters.

I was thinking of doing a tune-up with a new set of plugs, wires, cap and rotor, cleaning the throttle body and Idle Air Control and installing a new MAP sensor. I usually do my tune-up every 20K and replace my plug wires every 40K, and it's just about time anyway. Maybe it would help with the MPG and loss of power. Then if it still is not any better I can replace the O2's.

Thanks again for the help.

Jimmy

 

[Vizzy]

Originally Posted By: StevieC
If there is no Check Engine light and the car runs fine, leave it as it is... The computer will let you know.

Not always true .There is something called a "pending code" this is a code that is stored in the ECU but it does NOT light the check engine light because the ecu has not detected a major fault and it has not occured during enough driving cycles to light the CEL. BUT the fault could be causing drivability issues.!!!!!!!!!

You need to get your car scanned for PENDING CODES!!!!

You can get a scan done for FREE at AutoZone or AAMCO transmissions .

Check back and let us know what you find out .

 

[Jimmy9190]

I don't have any codes stored, I can turn my ignition on and off 3 times and any stored codes will display in the odometer. I don't know if that works for pending codes. Anyway I checked for codes tonight, found none. I put on the MAP sensor from the V8 throttle body and it had 1.49 volts on the output wire at idle. This is higher up in the low end of acceptable specs, and it's closer to specs than my original MAP sensor. That gave me some hope that all I need is a new MAP sensor, and I went for a test drive and could instantly tell a difference. The truck pulled harder and was easier to hold speed going up hills, acceleration from a stop was noticeably quicker and it didn't make the air-sucking sound that had been present when I would floor it, like to pass someone. The throttle response was a lot better.

I'm going to leave it as is and really test drive it on my commute to work tomorrow. But judging from how much better it is now, I will be buying a new sensor tomorrow after work. I have no idea how many miles are on this one, and if it did this much better at 1.48 volts, I think it should be even better still with a new sensor that puts out the 1.5 to 2 volt signal the MAP sensor is supposed to provide. I would think my MPG should get better too.

Thanks again for all the quick replies on this one. I'll post again after my commute tomorrow.

 

[Jimmy9190]

My truck ran a whole lot better on the way to work this morning. I'm going to install a new MAP sensor and go ahead and do a tune up with new plugs, wires, cap and rotor and clean my throttle body and intake air control pintle tomorrow. I have no idea how old the junk yard MAP sensor is, and a new one should do even better. Truck should do a lot better on power and I hope to bet getting better MPG too after I do the tune up.

I had no idea the MAP could be causing my loss of power. I thought it was just my 3.9 showing its age, because I always keep it tuned up, maintenance done ahead of schedule and I really try to keep it in the best shape possible.

Thanks for the help here.

 

[swalve]

The MAP sensor is an important part of the process- it tells the computer how much load is on the engine. Works like an electronic version of the old vacuum advance distributors. It can absolutely be wrong without being broken.

 

[mechtech2]

"it can absolutely be wrong without something being broken"
I know what you mean!

 

[StevieC]

Me too... We had this problem on my uncles 89 3.0 Litre Caravan. It was spewing fuel through the system and tons of black smoke out the pipe and the computer though it was just fine!

We replaced it and it was back to its normal self within minutes...

 

[Jimmy9190]

I put in a new set of plugs, 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 to everybody who replied. New MAP sensor made a world of difference on my truck.

 

[StevieC]

Glad you got it sorted out!