lack of power and bad gas mileage

notaprob · May 30, 2014

I have a problem with my truck and it has a CEL. It lacks in HP and it shutters in any gear under 2000 rpm. It gets worse mpg than my previous ranger with the same specs. It also runs better when the engine is warmed up. The plug on CYL5 is wet and the other plugs seem a little on the lean side. In the dark, I can see a slight glow at the end of all the spark plug boots but it has new plugs and wires.

KOEO
111 o-
10-
121 cm- Closed throttle voltage higher or lower than expected
176 cm- HEGO(HO2S) sensor fault/always lean

KOER shows normal
CYL6-
111 r- system ok

It took an ohm meter to the TPS and it read smoothly. I cleaned the MAF and replaced the air filter. Changed the plugs and wires. The only noticeable difference I saw was running 4 cans of seafoam and a 28oz bottle of Lucas fuel treatment.

I`d like to do more tests and I need some guidance or opinions! Any help would be appreciated!

RonD · May 30, 2014

Common issue when things get older is a leaking Fuel Pressure Regulator(FPR).
It is located on the fuel rail and has a vacuum line attached, remove this vacuum line and check it for gas or gas smell, replace FPR it if gas is found.
The diaphragm cracks and leaks, gas is sucked into intake, MPG drops.

The computer uses it's own temp sensor to monitor engine temp, the ECT sensor, it will have two wires and be located on the top front of lower intake.
There is a similar looking SENDER(1 wire) near by, that one is for the dash board gauge.
The computer sends the ECT sensors 5volts on 1 wire, it passes thru the sensors resistor and then back to computer on the other wire.
The computer reads the return voltage to determine engine temp.
3volts is a cold engine
1 volt is a warm engine
You can test with engine cold and then engine warm

On the upper intake there is an Intake Air Temp(IAT) sensor, 2-wire, it is pretty much the same as the ECT sensor as far as testing, colder air higher voltage, warmer air lower voltage, same 5 volts in on 1 wire.
This sensor along with the MAF sensor set the base fuel/air mix.

ECT sensor sets Choke Mode: richer mix, higher idle, advanced spark.

If you have the original O2 sensors I would change them, my '94 4.0l just had that done.
My MPG started going down, everything check out OK so I figured "what the heck", 300k on them.
When I was putting in the new ones I found 1 of the original O2s had started unscrewing itself, lol, so I was sucking air in next to the O2 sensor so it was always LEAN, engine was running rich 24/7, MPG went down.

O2 sensors do not work until they get above 600degF so about 5 minutes after cold start, or 1 or 2 minutes on warm start.

If engine runs better warm if could be ECT sensor is 'telling' computer engine is always warm, so idle would be low and mix would be too lean for cold engine to run well.

notaprob · May 31, 2014

RonD said:
Common issue when things get older is a leaking Fuel Pressure Regulator(FPR).
It is located on the fuel rail and has a vacuum line attached, remove this vacuum line and check it for gas or gas smell, replace FPR it if gas is found.
The diaphragm cracks and leaks, gas is sucked into intake, MPG drops.

The computer uses it's own temp sensor to monitor engine temp, the ECT sensor, it will have two wires and be located on the top front of lower intake.
There is a similar looking SENDER(1 wire) near by, that one is for the dash board gauge.
The computer sends the ECT sensors 5volts on 1 wire, it passes thru the sensors resistor and then back to computer on the other wire.
The computer reads the return voltage to determine engine temp.
3volts is a cold engine
1 volt is a warm engine
You can test with engine cold and then engine warm

On the upper intake there is an Intake Air Temp(IAT) sensor, 2-wire, it is pretty much the same as the ECT sensor as far as testing, colder air higher voltage, warmer air lower voltage, same 5 volts in on 1 wire.
This sensor along with the MAF sensor set the base fuel/air mix.

ECT sensor sets Choke Mode: richer mix, higher idle, advanced spark.

If you have the original O2 sensors I would change them, my '94 4.0l just had that done.
My MPG started going down, everything check out OK so I figured "what the heck", 300k on them.
When I was putting in the new ones I found 1 of the original O2s had started unscrewing itself, lol, so I was sucking air in next to the O2 sensor so it was always LEAN, engine was running rich 24/7, MPG went down.

O2 sensors do not work until they get above 600degF so about 5 minutes after cold start, or 1 or 2 minutes on warm start.

If engine runs better warm if could be ECT sensor is 'telling' computer engine is always warm, so idle would be low and mix would be too lean for cold engine to run well.

I did not smell gas in the vacuum line of the FPR.

I tested the ECT and IAT and I am a little confused with the results. With the the engine cold, the ECT read 1.4v on one wire and 0.1v on the other wire. The IAT read 2.44v on one wire and the other read 0.1v. With the engine warm, the ECT went from 1.4v to 0.7v on one wire and the other wire remained 0.1v. With the IAV, one wire went from 2.44v to 1.9v and the other stayed the same at 0.9v. I did some looking around and this file:///C:/Users/Brandon/Downloads/1994%20ford%20aerostar%204.0l%20eng%20pin%20voltage%20charts.pdf is this only thing I could find that came close to my results. Is this right or should it be around 5v? Also, I saw the ECT looked brand new, so I got a new IAT because it looked old and I got a new code 113(Intake air charge temperature sensor above maximum voltage) but that could have come from the test I did. When I replaced the IAT, I noticed it was wet and smelled like fuel. Is that normal?

I went ahead and changed both of the O2 sensors because they looked old and rusted and it made me feel better

The passenger side looked dark brown and the passenger side looked orange/red. Could the passenger side be darker because of the #5 cylinder being wet?

I also took a can a carb cleaner (for the second time) and tried to find vacuum leaks. No luck. :bawling:

RonD · May 31, 2014

Set your meter to vDC

Test your meter on the battery, engine off it should be 12.4 to 12.8 volts DC.
Engine idling should be 13.6 to 14.6vDC

Just want to check if your meter is working.
With a good ground you should see 4.8v-5.1v on 1 of the wires on each of the sensors.

The 5volts comes from the computer it has a 5volt power supply.

Download the Powerpoint: wps.prenhall.com/wps/media/objects/6568/6725731/ppts/Chapter14.ppt

Your computer(PCM) could be bad, or the wires

notaprob · May 31, 2014

RonD said:
Set your meter to vDC

Test your meter on the battery, engine off it should be 12.4 to 12.8 volts DC.
Engine idling should be 13.6 to 14.6vDC

Just want to check if your meter is working.
With a good ground you should see 4.8v-5.1v on 1 of the wires on each of the sensors.

The 5volts comes from the computer it has a 5volt power supply.

Download the Powerpoint: wps.prenhall.com/wps/media/objects/6568/6725731/ppts/Chapter14.ppt

Your computer(PCM) could be bad, or the wires

As I was checking the voltage on the sensors, I tested it on the battery and it read 14.66v while the engine was running.

I read your powerpoint and it makes me lean towards the PCM...

The good news is, I have a PCM from my previous ranger. I will go try that right quick... will post results soon :icon_bounceblue:

lack of power and bad gas mileage

notaprob

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RonD

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notaprob

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notaprob

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