Running Rich Rough Idle pls HELP

[glenn_a]

Your test results indicate two things to me. Your installed MAF sensor is smaller in diameter than stock causing higher voltage readings which fools the PCM into "thinking" the engine load is greater than actual. Installing the correct size MAF sensor should correct your over rich condition. The other thing is that your MAF sensor has an unusual reading at 3,500 rpm. My test results are for my engine without VIS which shortens the intake runner length when the engine speed exceeds 3,000 rpm. However, with no load on the engine (transmission in Park or neutral) I can't see how shortening the intake runners would decrease airflow thru the MAF sensor as engine speed increases. There could be turbulence in the vicinity of the sensor at that airflow, the sensor could be dirty, or the unit could be defective. In any case, you need to replace it with the correct size unit.

What happened to your old, stock unit? If still available, I suggest installing and testing it before purchasing another one.

The MAF sensor listed on ebay linked in your post is an aftermarket unit and should probably work. I did some searching and apparently OEM stock replacements are no longer available. Perhaps because they had a metal housing. My MAF sensor housing is some type of composite material. Around 2000 the IAT sensor and the MAF sensor were integrated. The previously unused outside pin on each side of the 6 pin connector were added for the IAT sensor connections. My stock PN is XF2F-12B579-AA because pins E and F are utilized. It should have the same flow characteristics as the earlier SOHC V6 stock MAF sensor and the connector should fit. There just wouldn't be any wires/pins for the IAT sensor. Here's a link to a remanufactured unit that should also work: 97 98 99 00 Ford Ranger Explorer Mercury Mountaineer Mass Air Flow Sensor Reman
According to the fitment table the OHV & SOHC V6 and the V8 all used the same MAF sensor. Here's a link to a used one like mine: 99 00 01 02 03 04 05 Ford Explorer 4.0L MAF Mass Air Flow Meter XF2F-12B579-AA99 00 01 02 03 04 05 Ford Explorer 4.0L MAF Mass Air Flow Meter XF2F-12B579-AA The price is cheap however with your shipping being so expensive you probably should purchase a new or remanufactured unit.

I still suggest waiting on the spark plugs until you solve your MAF sensor problems but those should work fine. You could actually only buy three and replace the ones currently in bank 1 (I think but have to confirm) with the new ones singe you currently have the single platinums in both banks.

I will try to re-fit the original MAF and do the test and find out the reading too... what else could be the possibilities if i have a new MAF but still doin the same problem..?
I will try to get Autolite spark plugs or Motorcraft plugs asap but still I doubt it is my spark plugs because I replaced them again to double platinium champion and the same previous Spark plug type I used before all this problem....
BANK 1 is the Right side of the engine right?
just then since i did the MAF test on Taurus MAF, half way on the test my engine light came on and showed P0172 System too Rich (Bank 1)...
Its weird that only came up today but stilll no code for P1100 but then the P1000 still there even though I replaced th PCM already...
by the way I am sure no restriction or turbulance in the air coming into the MAF which I already checked....

 

[2000StreetRod]

same housings

The critical MAF sensor housing measurement is the internal diameter of the housing where the inlet port to the sensor is located since that's where the air mass flow is measured. My sensor does not have an inlet port tube like yours.

Therefore it senses airflow about 2 inches back from the housing inlet. Your tube port opening looks to be about 1 inch back from the housing inlet and that's where the diameters should be compared. Although from the photos your two housings appear to be identical. However, the sensor element and associated electronics may be different. Even if the units are the same there is a problem with the Taurus sensor at 3500 rpm. I'll be anxious to see the old stock sensor readings.

 

[glenn_a]

Here we go the test from the original MAF I had....

(light blue/red wire) on RED
(tan/light blue wire) on BLACK

00.1mv OFF
15.5mv Ignition ON
.822V idle @ 850rpm
1.400V @ 1,000rpm
1.555V @ 1,500rpm
1.881V @ 2,000rpm
2.080V @ 2,500rpm
2.189V @ 3,000rpm
2.340V @ 3,500rpm
2.450V @ 4,000rpm

and here was the attempt from the Taurus MAF...

00.1mv OFF
16.2mv Ignition ON
.943V idle @ 850rpm
1.200V @ 1,000rpm
1.630V @ 1,500rpm
1.920V @ 2,000rpm
2.130V @ 2,500rpm
2.370V @ 3,000rpm
2.000V @ 3,500rpm
2.450V @ 4,000rpm

the difference I have noticed from the original MAF was it runs rough (runs rich) within 5secs but the other Taurus MAF took about more than 2mins tilll the engine kinda warmed up then it runs rough...

just thinking if I have a new Explorer MAF but still same problem what else it could be...? 'just need to think ahead'


2000StreetRod quoted: the right reading for a perfect MAF is:

Monitor the MAF sensor output voltage while increasing engine speed. The voltage should increase smoothly with no dropouts as the engine speed increases. Listed below are representative values.

Voltage/RPM

0.8 @ 500
1.0 @ 1000
1.25 @ 1500
1.4 @ 2000
1.55 @ 2500
1.65 @ 3000
1.9 @ 3500
2.1 @ 4000

 

[2000StreetRod]

MAF sensor plots

I plotted your MAF sensor voltages vs rpm and mine for comparison. Notice that my stock MAF sensor plot is fairly linear from idle to 4,000 rpm:

The Taurus plot shows a drop out at 3,500 rpm. The voltage readings generally are considerably greater than mine but the slope of the graph rapidly decreases at higher engine speeds indicating that the sensor is approaching its limit or measuring airflow.

Your stock MAF sensor voltage jumps from idle and then is fairly linear but at a smaller slope than mine and is shifted upwards.

Your voltage readings could be higher than mine because of denser air (altitude and temperature differences) than mine during the measurements.

Have you cleaned your MAF sensor element with MAF sensor cleaner or an electronics aerosol cleaner?

What is the configuration of your intake system? Your plot indicates air may be entering your engine that is not being measured by the MAF sensor. Do you have a breather installed on the valve cover instead of a hose connecting the valve cover port to the main intake tube downstream of the MAF sensor? Does the IAC valve inlet air come from a hose connected to the main intake tube downstream of the MAF sensor? Are any vacuum hoses disconnected or broken: VIS vacuum regulator, EGR vacuum regulator, power brake booster, PCV valve, crankcase breather, fuel vapor management valve, vacuum reservoir below air filter enclosure, fuel pressure damper, evaporative emission canister purge valve? Have you replaced the upper and lower intake manifold gaskets? If so, did you also replace the EGR tube O ring?

 

[2000StreetRod]

intake mods

I searched thru your registry type thread and found the photo below.

When you added the snorkel did you just plumb it to the air filter box enclosure without making any modifications to the intake system?

 

[glenn_a]

I searched thru your registry type thread and found the photo below.
View attachment 76910
When you added the snorkel did you just plumb it to the air filter box enclosure without making any modifications to the intake system?

Woah that graph looks good...!
Yes i have checked all the above you just mentioned i even took off the top intake to make sure for leaks and i sprayed to double checked for vacuum leaks. The EGR pipe was re-sealed twice and all the vacuum hose are checked for cracks and leakage... The VIS is working properly...
About the snorkle, i fitted that long before this problem nd I highly doubt it cannot be the snorkle causing the problem. I even took off the airfilter box and left the top cover with MAF hangging just to make sure for air restriction but made no difference...
Its very weird whats happening right now and me as a qualified mechanic this made me so speechless....

Been thinking deeply over christmas till now and still scratching my head where and what to look for....

Do you think my MAF is not looking good? Im sure it cannot be the spark plugs cos' i already change that again but the Autolite plugs its way from online shop...
I dont think the coil pack would do this problem right? I pulled the leads one by one and all has a good strong spark but I just remembered since i replaced the spark plugs to double platinum it went better for a day and it lasted hours of driving and I thought its all good. Then i started feeling the hesistation after few hours and then it got worst and back again happened after few minutes starting....

 

[2000StreetRod]

replace the MAF sensor if TPS good

I suggest that you test the TPS since a defective one can result in the PCM doing weird things: Ford Explorer - Ranger TPS Test Procedure
If the TPS tests good then I guess if it were me I would replace the MAF sensor since it indicates a significant increase in voltage for a minor increase in rpms and you're confident there are no vacuum leaks. Also, with the Taurus MAF sensor there was no corresponding jump in airflow.

 

[glenn_a]

Did some test on the TPS and heres the reading:

0.36mv @ IGN OFF
1.06V @ IGN ON
4.69V @ FULL THROTTLE

 

[2000StreetRod]

TPS test results

The voltage range of your TPS looks good. The voltage should increase smoothly (no drop outs) as the throttle plate is moved from idle to WOT. Is there a friend (mate) in your local area with an Explorer that would be willing to let you try his MAF sensor for 30 minutes of testing on your vehicle?

 

[glenn_a]

The voltage range of your TPS looks good. The voltage should increase smoothly (no drop outs) as the throttle plate is moved from idle to WOT. Is there a friend (mate) in your local area with an Explorer that would be willing to let you try his MAF sensor for 30 minutes of testing on your vehicle?

I wish I have a friend or neighbour have an Explorer but Explorer here in Aust. not that popular and rare...

I have found in the ad that there was a guy selling the whole explorer in good running engine for $900 and thinking just buy that for spares...

I just had a look over again into my Explorer and checked all the wiring and vacuum leaks but nothing I could find, I am sure maybe some electrical sensor or switches....

I ran the engine and for first minute when its first cold start, it runs perfect and then soon it warmed up a little the idle drops just a little and then almost a minute the idle kinda goes up and down slightly and few seconds again it stable and back up and down again then I started to smell rich exhaust fumes and slightly black smoke. If i leave it for too long the engine stalls but then it was easy to start and few seconds the idle goes up and down again....

second try, I started to raise the rpm and I feel the engine flooded with fuel (splatters and pop noise comes from the exhaust pipe) till it reaches around 3,000 then it feels it cleared out and when I let go the accelerator pedal it goes back into normal idle and few seconds later started to goes up and down the idle again....

 

[glenn_a]

Now Im thinking maybe my Oxygen Sensor could be faulty, my gut feeling it could be the Oxygen Sensor but I'm thinking that was new and replaced just more than a year now...
It reminded me back 6mths ago I had a engine light came on multiple times saying running rich but cannot remember which bank. but always in my mind it maybe a glitch because it was new...
but now I dont get an engine light, is there any way I could check manually if my 02 Sensor is good working order...?

 

[2000StreetRod]

Fuel trims?

After pondering your recent post describing symptoms I've come up with two other possibilities. If you have a defective engine coolant temperature (ECT) sensor that reports to the PCM the engine temperature is always cold then the fuel mixture will be rich after the engine starts to warm up. The ECT sensor has a wide resistance range making it difficult for the PCM to determine if its faulty. Its resistance vs temperature are posted elsewhere but it is difficult to measure with a meter because of inaccessiblity. If I were in your situation (an Explorer in a foreign country with limited dealer/auto shop support) I would invest in a device allowing access to the PCM internal data via the OBD-II port. That way you could read what the PCM has available (ECT temperature, fuel trims, mass airflow, ignition advance, etc.). If you have a laptop or other smart device there are modestly priced applications available to purchase.

Your symptoms indicate that the engine is running better when using pre-stored fuel ratio settings (happens when under moderate to max load) than when in closed loop using the O2 sensor outputs. You can monitor the O2 sensor voltages with a meter but once again they are not very accessible. An OBD-II scanner application would tell you when the PCM is in open or closed loop and the O2 sensor voltages.

 

[glenn_a]

After pondering your recent post describing symptoms I've come up with two other possibilities. If you have a defective engine coolant temperature (ECT) sensor that reports to the PCM the engine temperature is always cold then the fuel mixture will be rich after the engine starts to warm up. The ECT sensor has a wide resistance range making it difficult for the PCM to determine if its faulty. Its resistance vs temperature are posted elsewhere but it is difficult to measure with a meter because of inaccessiblity. If I were in your situation (an Explorer in a foreign country with limited dealer/auto shop support) I would invest in a device allowing access to the PCM internal data via the OBD-II port. That way you could read what the PCM has available (ECT temperature, fuel trims, mass airflow, ignition advance, etc.). If you have a laptop or other smart device there are modestly priced applications available to purchase.

Your symptoms indicate that the engine is running better when using pre-stored fuel ratio settings (happens when under moderate to max load) than when in closed loop using the O2 sensor outputs. You can monitor the O2 sensor voltages with a meter but once again they are not very accessible. An OBD-II scanner application would tell you when the PCM is in open or closed loop and the O2 sensor voltages.

Thanks heaps for all your help 2000StreetRod but the ECT has been checked and its working fine plus 02 sensor not showing any codes in my scanner and that made it harder for me to look around for faults...
I tried using our workshop Snap On scanner and the Auto Electrician Scanner and both dont show anymore faulty codes...

now trying to figure what make the car run rich and ill work on it manually and see how it goes...

 

[glenn_a]

Could be a bad FUEL make my Explorer play up' like this...?

 

[2000StreetRod]

rich not due to bad fuel

I can't imagine a way that bad fuel would make the fuel mixture rich. It's too bad that you can't read your fuel trims, the O2 sensor outputs or if the PCM is in closed loop. Your cold start description sounds like the engine idles fine when cold when it needs a rich mixture. Then as the engine warms up the mixture stays rich and the IAC valve has trouble maintaining the desired idle speed. It takes my engine about a minute at idle for the O2 sensors to heat up and the PCM to switch from open to closed loop. A possible experiment would be to disconnect both pre-cat O2 sensors so the PCM has to stay in open loop. Then disconnect the battery, turn on the headlights for 3 minutes to erase the PCM volatile memory forcing the fuel trims to revert to factory settings. Reconnect the battery and cold start the engine and let it warm up at idle. Note any differences from the previous cold start symptoms. If the vehicle drives significantly better without the O2 sensors then they are at least part of your problem. You posted that you have no DTCs so I assume the O2 heaters were working correctly. When you replaced the sensors did you install the correct part? Do they happen to be cross connected - left sensor to right bank and right sensor to left bank? That usually results in a lean code for one bank and a rich code for the other bank.

 

[glenn_a]

It's too bad that you can't read your fuel trims, the O2 sensor outputs or if the PCM is in closed loop.

I already booked it to City Ford nearby but need to wait in 2weeks time...

Hoping to solve the mystery....!

 

[glenn_a]

I have found this thread one saying:

"Symptoms of bad fuel"

((((Hey guys i had a **** fuel in my car and my car made a terrible burbling/popping noise from the exhaust and the revs had trouble climbing between 1000rpm and 3000rpm. its still able to reach redline but just has trouble getting there.))))

((((I filled up last night, made it home just fine. Started it up this morning once just fine and drove about 10 miles. Then went to start it again and now it is sputtering/knocking and backfired plus when I hold steady on the gas it revs then slows the revs then slows and so on))))

Sound similar but ill try to drain the old petrol and fill up a new/fresh ones while i wait for the Ford Company....

 

[glenn_a]

this is kinda weird....

I tried to start the Explorer but then the battery went flat, I tried to jumpstart the Explorer with another spare battery and after it started I hold the rev for a minute and it seems the hesitation disappeared....
after few minute I took my foot off from the gas pedal and the idle was fine but I can still smell a strong smell from the exhaust being rich and I heare popping sound time to time from the exhaust tip...
Then I tried to accelerate and i can hardly feel the hesitation... But its still there

Just needed to share this, thats all....

This coming wednesday is the day for a good scan from CITY FORD....'

I'll give you an update soon!

 

[2000StreetRod]

keep alive voltage

Even when the ignition is off power is still supplied to the volatile memory in the PCM that stores the fuel trims among other things. When you switched batteries the volatile memory was cleared and the PCM reverted to factory settings. When you connect to the scanner monitor the fuel trims and the open/closed loop parameter. Also monitor the pre-cat O2 sensor output voltages.

 

[glenn_a]

Even when the ignition is off power is still supplied to the volatile memory in the PCM that stores the fuel trims among other things. When you switched batteries the volatile memory was cleared and the PCM reverted to factory settings. When you connect to the scanner monitor the fuel trims and the open/closed loop parameter. Also monitor the pre-cat O2 sensor output voltages.

thanks mate! My Explorer is in City Ford at the moment for full Scan, I'll update you later what is the verdict...

just a few questions my friend, I always want to upgrade my Fuel Pump + Ignition Coil + High Tension leads could you please let me know what you think about this item and I need your Expertise... thanks!

FUEL PUMP
http://www.ebay.com.au/itm/300828367701?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

IGNITION COIL
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=331107603565

HIGH TENSION LEADS
http://www.ebay.com.au/itm/310440123899?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649