1998 4.0 MAP Sensor

[Idaho Mountainman]

I have a 1998 Ranger 4X4, manual, with a 4.0 in it.

Does it have a MAP sensor & if so where is it located?

On a schematic from ford it shows it in the cab, located around the heater. But it doesn't say if I have one or not. There isn't one located there on my Ranger & I don't understand why it would be in the cab in the first place.

On the vacuum hose routing decal under the hood it doesn't show a vacuum line going to a MAP Sensor.

I'm told that my Ranger has one & most auto parts websites show two different ones for my Ranger. BUT. I can't find it on my Ranger & can't find anyone who can tell me where it is located.

Any help in letting me know IF I have one & if so, where it is located?

Thanks in advance!!!

 

[RonD]

It does have a MAP sensor but it is used for the EGR system, MAP sensor is inside the DPFE(Differential Pressure Feedback Exhaust) sensor

MAP = manifold absolute pressure, in newer vehicles it is used to read exhaust manifold pressure to detect EGR valve opening and closing.

On older vehicles, pre-MAF sensor days, it was used to detect engine load via vacuum pressure in intake manifold for computer to set air/fuel mix.

 

[Idaho Mountainman]

So if I replaced the DPFE Sensor that would be the same has replacing the MAP sensor? Just making sure.

Thanks for your information Ron!!

 

[adsm08]

No, I don't think so. You don't have a MAP sensor, you have a baro sensor, and it is most likely part of the MAF sensor.

The 4.0 did not use a MAP sensor, ever, EXCEPT for the 2002+ Explorer SOHC engine, with had it integrated into the "EGR system module" which encompassed the valve, DPFE, and MAP, and is the part that Ron referenced.



Generally speaking MAF systems don't use a MAP sensor, unless they are boosted applications, and for the most part Ford has been going to a Baro, two MAP speed-density system for the Ecoboost engines.


In your application the DPFE is used to determine EGR flow, and not a MAP. The DPFE has two hoses, one placed on either side of a restriction in the EGR tube, and it measures the pressure drop from one side to the other to determine actual EGR flow.

 

[RonD]

Sorry about the confusion.

What trouble code did you get that referenced the "MAP", that may help clear up the confusion.

 

[shane96ranger]

A bad DPFE will give you an excessive or insufficient EGR flow code (P0401 or P0402, IIRC). There is a DPFE specific code as well which is P1401 - but that may not be a code in 1998.

 

[adsm08]

Sorry about the confusion.

What trouble code did you get that referenced the "MAP", that may help clear up the confusion.

Haha, I edited my post 3 times to add stuff and still forgot to ask why are looking for the MAP.

A bad DPFE will give you an excessive or insufficient EGR flow code (P0401 or P0402, IIRC). There is a DPFE specific code as well which is P1401 - but that may not be a code in 1998.

No, I think they would all have been there in 1998.

Many codes that make reference to the MAP sensor give it as MAP/Baro.

 

[shane96ranger]

No, I think they would all have been there in 1998.

Just looked it up and it became a code in 96. I knew some of the early OBD-II systems were lacking this code, but couldn't remember the year it was implemented.

 

[Idaho Mountainman]

It’s a longer story but here goes.

This engine has 171,000 on it. I’ve had it since 124,000. Never used any oil & has never smoked or anything unusual. Put a new cat & oxygen sensors in about a year ago. Put head gaskets in about 8 or 10 thousand ago. Started getting a noise sounding lower in the engine. It is now a knocking sound. When driving there is the knocking sound, then around 2500 RPM it sounds like the valves are starting to float. Like the timing way advances all of a sudden. Soon as the rpms drop the valve sound goes away. I haven’t reved it any higher to see what happens.

A guy at work hooked up a reader to check codes. No codes but it said the coolant sensor & the EGR weren’t in specs. He down loaded all the information & sent it to a tech he knew, this tech said a bad MAP Sensor could cause these symptoms without throwing a code. So I think I’ve been on a wild goose chase trying to track down all my vacuum lines to see if a MAP sensor would be hiding on the other end.

I originally was thinking bearing, rod problem, but that is even funny. This engine has always had very good oil pressure & still does. The pressure has never dropped, never flinched. It’s got clean oil in it with no sign of bearing wear. Never have heard a sound like a bearing trying to spin.

That’s where I’m at. Trying to see if I’ve got any other options before pulling an engine.

Any ideas?

 

[shane96ranger]

Well, that tech is wrong. Sometimes it will throw codes like EGR and Temp Sensors if the engine is cold and been sitting for a while (I.e. overnight).

Did you replace the lifters when you did the head gaskets? The 4.0 is pretty famous for having noisy lifters. My 91 Explorer would develop a slight knock every time I changed the oil - but it would go away after a day or three. Kind of a finicky motor.

 

[Idaho Mountainman]

Didn't replace the lifters, the engine was running quiet then.

 

[dczerny90]

Have you done any type of compression or cylinder leak down tests? if you have a bad rod or bearing, you would have a weak hole. I would start there, and if everything is fine, it's going to be something top side causing the issue at which point I would pull the valve covers and check tension on the rockers.

 

[Idaho Mountainman]

Looks like I need to find the time to do a compression test. Thanks for the help!!

 

[RonD]

It’s a longer story but here goes.

This engine has 171,000 on it. I’ve had it since 124,000. Never used any oil & has never smoked or anything unusual. Put a new cat & oxygen sensors in about a year ago. Put head gaskets in about 8 or 10 thousand ago. Started getting a noise sounding lower in the engine. It is now a knocking sound. When driving there is the knocking sound, then around 2500 RPM it sounds like the valves are starting to float. Like the timing way advances all of a sudden. Soon as the rpms drop the valve sound goes away. I haven’t reved it any higher to see what happens.

A guy at work hooked up a reader to check codes. No codes but it said the coolant sensor & the EGR weren’t in specs. He down loaded all the information & sent it to a tech he knew, this tech said a bad MAP Sensor could cause these symptoms without throwing a code. So I think I’ve been on a wild goose chase trying to track down all my vacuum lines to see if a MAP sensor would be hiding on the other end.

I originally was thinking bearing, rod problem, but that is even funny. This engine has always had very good oil pressure & still does. The pressure has never dropped, never flinched. It’s got clean oil in it with no sign of bearing wear. Never have heard a sound like a bearing trying to spin.

That’s where I’m at. Trying to see if I’ve got any other options before pulling an engine.

Any ideas?

Why new head gaskets?

I had a Fan Clutch going bad, it gave a noise and vibration above 2,000rpms.
With engine cold I would rev engine and see if you can duplicate any noises in the driveway.
Then remove serpentine belt, or loosen it, restart engine and repeat test, without the fan noise you should be able to hear better but also see if any noises were coming from pulleys or fan that are no longer moving.
Battery light will come on, that's ok, and a few minutes without water pump won't hurt anything on cold engine.

Knock noise can be an exhaust leak at manifold.
To check Rod bearing issue, make sure you can hear knock, then unplug one spark plug wire at a time, if a rod is knocking that noise will disappear when that cylinder stops firing, the "Knock" is from the rod slapping the crank when cylinder fires.

Just FYI, Oil pressure on Fords after about 1986 is shown as either on or off, the sender on the engine is a switch, below 5psi of pressure the switch is off, above 5psi is on.
So gauge shows low(0) or mid-range, any movement of the gauge, is from alternator voltage fluctuating, so can be RPM based, but it's not oil pressure based.
IMO, this "faux gauge" setup is worse than an idiot light because people think it is reading actual pressure.


The expression "it sounds like valves were floating" is odd, floating valves wouldn't make a noise, you feel the engine power curve drop when valves float, but there would be no noise just the lack of power since valves are not closing all the way.

When you replaced the Cats, was the muffler replaced?
Collapsed/clogged exhaust system limits RPMs