2002, 4.0, automatic

I'll try to keep things short here. Went on a 140 mile round trip on freeway back in november, gave me 15mpg. got around to scanning the ECM and found while driving the ECT leveling at 175-180F. So figured it was a thermostat issue, it's factory original and 200k+ miles I figured it would be ok to retire the t-stat, and put in a new one. Put in a motorcraft from the local dealer, $36. Now the ECT is reporting 185 and holds pretty steady there, occasionally touches 189. Still not getting good gas milage, and seems to take a while to warm up. I have some datalogs from years ago showing ECT typically 190-195 range.

Did I mention I replaced the radiator back in october? Not sure if that would have anything to do with it. e-fan set to come on at about 200F, does so when idling for periods.

Otherwise the truck-
starts fine hot or cold
idles fine hot or cold
drives fine hot or cold
no codes.
All maint up to date, oil/filter, MAF clean, PCV, plugs/wires, etc.

So, it's possible the new motorcraft t-stat is not working quite right, I guess. Are there are any bypass valves on the waterpump or climate controls I should check before swapping t-stat again?

Thanks

 

Personally, I wouldn't sweat 5 to 10 degrees. I've changed between 180F and 195F thermostats with no noticeable difference. Any change in mileage I've noticed fits within the typical variation I've seen from tank to tank. And I log every gallon of gas that goes into the tank.

With cold weather, the engine may not reach 190F - 195F. You'll notice that the big rigs in the northern states often cover most of the grill opening in the winter. This is to block air to the radiator to allow the engine to warm up when the ambient temperatures are low. Did you happen to record ambient temperature for both sets of data? How does it compare?

Also, warmup times are longer in cold weather, resulting in longer periods when the engine is running richer. That will have an impact on mileage. I used to notice a 10% decrease in mileage when the winter blend (aka oxygenated) fuel showed up at the pump, but now that alcohol is mandated year-round, the mpg reduction is permanent on my older vehicles.

200K on the motor is a lot. Surely it's a little tired and lost some effective compression ratio and efficiency via increased blowby and valves that don't seal as well.

I could see how running the heater might keep the engine cooler, especially if you use the heater heavily. On hot days over the pass, turning the heater on would lower the temperatures noticeably on my 4.0 Ranger with the single row radiator. Heater flow bypasses the thermostat, so that part of the cooling system is essentially unregulated.

 

Hi Mikeman,
Yeah, I'm not sure if the temperature is the cause for the low mpg or not. At this time it seems the most obvious thing I have to follow.

I'm used to the yearly fluctuation in mpg in winter from colder temperatures and winter blend fuel, but not this much of a decrease. Normally in winter I drop to about 19mpg so I expect that. Mpg were good in August.

I considered compression, blowby, valves - good possibilities but it seems like something changed from august to november. Pulled the tube from the PCV at idle, slight positive pressure but nothing I would consider excessive. Same with oil fill cap no chuffing sounds or any excessive exhaust exiting. Maybe I need to bump the throttle when checking. Unfortunately, no garage means I won't be pulling plugs for reading or compression checks until the weather improves, march soonest.

 

^+1 on Mikemans ideas.
Any of the bolt on mods done between Aug & Nov???
How are you measuring the ECT????
Other things that'll affect mpg that come to mind are lazy O2 sensors & with the mileage on this ride they're way past due for changing, so belong on your suspect list.
Out of calibration AIT & ECT temp sensors, larger tires, low tire air pressure, psi drops about 1psi/10deg in temp, unmetered air leaks down stream of the MAF sensor that are corrupting fuel trim, so how does your fuel trim for both cyl banks look, dirty fuel injectors with a poor spray pattern, are some other things that come to mind.
Here is a link to US & Canadian gas stations that sell non ethanol fuel, just click on your state & city, or surrounding towns. Turns out I had a neighborhood store a couple of blocks away selling no ethanol fuel from Shell, it goes into my lawn & garden equipt. http://www.pure-gas.org/index.jsp

 

I have a 2008 Ranger that was breaking the bank. I got codes about low temperature. The engine was not getting warm enough and the computer was telling it to add more fuel.

It cost me $208.00 for a stat replacement and now mpg is much better and the gauge
runs mid way.

 

All bolt on mods to engine and drivetrain were done back in 2004, shortly after purchase. Pressure in tires is good, been using the BFG 31" for years.

ECT is being measured by with ELM adapter and iphone app, also for fuel trims.

O2 sensors were at the top of my list, replaced them early december this year. I have a new fuel filter waiting on the shelf, will do that this weekend. Fuel trims are running around 1-5% at cruising speed/rpm/throttle, haven't paid much attention during acceleration.

I considered the temp sending unit might be off due to flaky sensor or aged wiring or connector contact problems. That can be checked this weekend as well. I assumed if I had a leak downstream of the MAF it would throw a code or fuel trims would be high? I can check connections between MAF and throttle body.

Also considered Injector problems or age issues. Hard to narrow down to specific injector without a code. I'm not aware of local places to test flow rate and pattern but removing all injectors again would have to wait for better weather unless it becomes an emergency.

Edit: A few people have suggested compression problems and/or injector issues. My experience has been if they are that bad you get loss of power or a rough running engine. I don't seem to have any of that. Even made a few trips to some of the steeper hill around town, seems to have plenty of power... or as much as you can expect from a Ranger with auto.

Thanks

Items done since August:
Front end alignment
front brake rotors and pads
read shoes and drums
PCV valve
HID headlights/LED turn sigs, running and brake lights
Replaced radiator
New Battery
Oil/Filter, Clean MAF, air filter
New upstream o2 sensors, both

 

I wish it would throw a code, it would at least point me in some direction.

$208.00? new housing?

 

OK, good feedback. With the ELM scantool you have access to lots of different controller data inputs.
With fuel trim seeming to be in range it kinda answers a lot of my questions about the fuel injectors, AIT, ECT, O2 sensors, MAF sensor & fuel trim in general.....maybe. Post the short & long term fuel trim Numbers for Both cyl banks.
Also since you have an auto tranny, have the ELM take a look at the tranny controller to see if it can spot something going on with slip, or unexpected load numbers.
31's won't do anything to improve mpg. Was the computer recalibrated for the larger tires????
Of the things done since Aug, the only thing that stands out that the ELM may not monitor, maybe, would be dragging front or rear brakes, or a messed up alignment, but then you'd likely be fussing about an alignment if it was bad enough to seriously affect mpg. If you have dragging brakes, hop out after a drive & see if you can detect any abnormal heat at any particular wheel.
Make sure the emergency brake is fully releasing.
More thoughts for consideration, keep the forum posted on your trouble shoot.

 

The PCM/ECM should be calibrated for the larger tires since it came from the factory with the 31". I checked for codes, nothing, also checked for pending or history, nothing found. Still figuring out the app I'm using. Wishing forscan for the iphone would work with bluetooth.

I'm having trouble getting the data logs into usable format but generally the trims are bouncing between -4% and +4%, usually on the positive side, same with the long term trims, from what I saw.

Thought about the brakes hanging up. My driveway has a slight incline, when cold in the morning in neutral it rolls, same after a 30 mile drive. Also pondered if the transfer case wasn't disengaging but I would notice that in parking lots on dry pavement.

Checked transmission fluid level as well, fine.

It's like there's a hole in the gas tank.

Thanks

 

I don't know if I'd bother checking compression if it idles well. I was just mentioning the lower effective compression as a natural part of aging. At 200k miles, it's no spring chicken. However, pulling the plugs might give you some clues as to which cylinders might be running rich. But, you always run the risk of breaking a plug wire.

As usual, pawpaw threw out a very comprehensive list, and I'm running low on additional ideas, but here are a couple more. Not sure how likely they are.

How about the fuel pressure regulator and fuel pressure? I would have expected the ECM to have been clamping down on injector pulse width if either were bad, but it's easy to check.

Does the spark advance look reasonable?

By the way, what is the app that you're using with your iphone? My PC laptop went off to college but the ipad didn't and I'm looking for a recommendation for an app (or even a recommendation of which apps to avoid) that will provide me live data viewing and data recording.

 

I'm using an app called Engine Link, it's ok, so far. The data logs aren't exactly in the format I would like so trying to figure out an easy way to fix that. Also there's some peculiarities to the logging I'm finding as well. Not much tech info available online from the developer although I've read they are good with email support. I chose it because it will use bluetooth, whereas forscan for the iphone will not. I think it's probably a decent app and tool once I figure out how to use the full capabilities.

Engine Link - OBD II vehicle monitoring and diagnosis

 

OK, finally got some data to look at. The long term trim is in red, it came out weird color in the legend. Short term in green.





At this point I'm out of ideas and guess maybe it's just the cold weather and winter blend E10. But I've never sen the MPG's drop this low, still makes me nervous.

 

OK, good feedback on the graph. Short term fuel trim spikes up to a +10% a few times, but for the most part stays below 5% & the long term trim looks ok.
What is the Trh pos dark blue line??? For some reason I just can't get my mind wrapped around that abbreviation????

 

Put up graphs of both cyl banks up stream O2 sensors & fuel trims, to see how they're tracking over time & to see how the O2 sensors are switching.
Edit: Also graph both cyl banks fuel injectors squirt time, to see if you can catch one acting out in time with the short term + fuel trim spikes.

I don't know what to make of the ECT still indicating low after the thermostat replacement. I suppose it could be a calibration problem with the ECT sensor after 200K miles. The engine & lubes are set up for 190-200F operating temp, so not sure how much difference 10 deg or so lower operating temp would make.
Are you using the specified 5W-30 crankcase lube in your 4.0L????

 

LOL, "trh pos" was my dyslexia kicking in, was supposed to be "thr. pos", aka throttle position. Didn't notice until after I posted.

On the subject of the ECT, I pulled the t-stat yesterday and put it in a pot of hot water on the stove. Started opening around 195F, open full at boil, and closed at around 195. Should have done that before I installed. I was expecting it to be on the low end of the specifications, but it wasn't. I used a digital thermometer I use for homebrewing and put high priority on calibration so I know it's reading accurate within +/- 2F.

I was going to replace the ECT while I was in there but I couldn't pull the connector off as it was hitting bottom of the intake, and I wasn't going to pull the t-stat housing apart. Maybe in spring.

And... with my screwing around with it yesterday I now have a leak in the t-stat housing so I'll be out in my driveway this morning, in the snow, trying a new t-stat o-ring. I shoulda left it alone.

I'm also thinking to pull the battery cable for 10-15 minutes and re-connect, thinking maybe there's just some corrupted data in the PCM.