First Post. After reading some 200 hundred pages from the Aerostar section of the forum, feel I know my new machine better. It is a garage queen 1994 4.0 AWD with 42,000 miles in nearly perfect shape. Except for the dent in the rear on the passenger side. Remembering Jurassic Park...

I have posted a picture of the dash when going down the road. As you see the engine light is on. It comes on intermittently, pulled the codes, indicated MAF, 02 sensor, running lean/rich. Runs like a champ, no hesitation, still gets up and goes, gets the appropriate gas mileage. I replaced the 02 sensor with the original Ford Part. Didn't cause the engine light to stop going on after about 20 to 60 minutes driving, sometimes it doesn't come on at all.

Could this thermostat be running too cool and causing the engine to throw those codes? Would gladly take it to a mechanic, but seems like it might be a fishing trip with my dollars for them. Next I was going to replace the MAS myself, easily done with the original remanufactured part at a cost of 150.00, 70 for the core, but don't want to chase my tail with these engine lights on when it runs nearly perfect.

Have sprayed the MAF. Checked for air leaks anywhere. Done all the things I could do by just lifting the hood.

So the picture shows the Temp gauge barely touching the N flying down the road at 70 on a level surface, outside temp about 60. Reading the posts says they all run in the cool section of the temp gauge.

So the question is, do they run this cool? Heater works fine and the gauge goes up past the N resting before the O when going up hills on the way to Tahoe. Is this a thermostat problem on a 20 year vehicle with low mileage, or am I going to have to bite the bullet and let the mechanic go wandering through the vehicle?

Whew, that was winded. TIA.

BRGDS,

patrick

 

Yes, the 4.0L is notorious for reading at the low end of the scale. Dummy fake soccer mom gauge system. But the real engine coolant sensor that drives the PCM will show 195d F coolant temperature rock solid on a correctly operating cooling system
Just watch the gauge and if it starts running over on the right side 3/4 or more, pull over.
The "oil pressure" gauge also gives pie in the sky false soccer mom readings to keep them out of the service managers hair.
Both of these fake cheap gauge circuit designs are common across the 90s Ford lineup, Rangers, Explores ad naseum.
Most of us Aero-affectionados put on real sensors and gauges. Don't be surprised when you see only 10 psi oil pressure on hot idle.

Need to clean the MAF sensor, located in the air flow tube by the air filter housing. Remove and soak the element, dirt cooks and cakes on. Lots of good threads on here about cleaning the MAF. Use an electronic component cleaner, no harsh brake cleaner.

Check the air filter and box for any leaks, dirt/dust ingress coats the MAF sensor

 

Amazing that a car that was driven around a small city all it's life in a non dusty environment with such low mileage would have the MAF sensor gummed up. Have sprayed it thoroughly and checked for leaks around the air filter box nada.

I guess these intermittent check engine lights even with the codes can be a bear to troubleshoot, especially if the car is running near perfect. The guy who said in one of the posts, "just stick tape over it, had something there.

Of course the mechanic would be happy to troubleshoot. Getting some ideas on where to tell him to look.

TIA, BRGDS,

patrick

 

did you reset the CEL by disconnecting the negative battery terminal after replacing the O2 Sensor?

my 1997 4.0 runs the same way, but the heater works fine, no overheating, nada. Just keep the coolant level checked.

 

cleaning the MAF sensor:

get a clean spray bottle.

put about 1 inch of rubbing alcohol in the bottle,

disconnect the plenum tube assembly from the air filter box and the intake butterfly, remove from vehicle.

remove two bolts from the air filter box cover, remove from vehicle.

spray alcohol on MAF sensor from both sides, allow to drain, alcohol will dry in seconds, inspect, re-spray if needed.

reassemble.

 

Pretty sure I did reset the CEL.. Wondering how the CEL works then. If I reset the CEL and it throws the codes after 20-60 minutes of driving, sometimes not at all, what to think. If I didn't and the light comes on as above after 20-60 minutes driving, wouldn't the CEL throw the engine light on when first starting as it is an unresolved error?

TIA, BRGDS,

Patrick

 

if the cell came back in only 1 hour after doing a reset, you must have driven at least 15+ miles, on the average that's how much it takes for the computer to read codes again.

if the light goes off by itself and then comes back on, you have a bad sensor somewhere. The question is where.

just disconnect the negative battery cable and leave it disconnected for 1 hour, then drive the van again; When the light comes back on, read the codes again to see what code(s) it shows. Then replace the part in question and make sure the replacement part has the correct calibration for your year and engine.

 

City streets have lots of MAF contaminating particles. All the worn off tire rubber dust and asphalt particles, heat from the MAF element, road oil/grease from all the vehicles dripping and we have shoe goo on the MAF.
Even the most expensive air filter is not 100% filtration.

Rubbing alcohol contains 30% water, not something to clean caked on oily debris.
Some try to shortcut and use a soaked Q tip, most of these attempts fail and damage the fragile sensor elements.
I use a shot glass with MAF cleaner or acetone or paint thinner in it. Soak the elements and their support only. None of the plastic housing in back. Mine is still OEM factory MAF, 190,000 miles on an OBD-II 96 4.0L which are even more sensitive to a slightly dirty MAF.


How to retrieve codes from an OBD-I system(85-95) - Ford Truck Club Forum

To clear codes, during the KOEO test remove the jumper wire before all codes are displayed. Or as an alternate method you may disconnect the battery to clear them. Disconnecting the battery will cause the loss of the computer memory that adapts to your driving style, so this method will cause a different running condition until the computer relearns your driving style. This isn't a big deal, most people clear codes by disconnecting the battery. It is important to remember to clear codes any time work has been done so old codes aren't present.

 

Okay. Will reset and post the codes (hopefully none to post) after installing a Ford rebuilt MAF. I had cleaned both sides of the element with the recommend MAF sensor cleaner spray purchased ar O'teilly's. Didn't have the right torx set to lift the sensor out of the housing. So for about 80 bucks can rule out the sensor and the assembly, could have had the mechanic do a resistance check for probably 50 bucks, but bit the bullitt should have the new sensor and housing in in a coupla days.

Then the next round of questions. Thanks again for the help. I really love this vehicle while gas prices are cheap. Getting it ready to put some serious miles on it traveling. Any 20 year old vehicle low mileage or not is going to have "things" crop up. TIA. BRGDS.

patrick

 

there are videos on YouTube showing how to clean the MAF and stating that "MAF Cleaners" sold at autoparts stores are nothing but alcohol.

I have had no problems spraying rubbing alcohol over the MAF sensing "bulb", it leaves it clean. Same for the secondary Air Temp Sensor after the MAF.

 

SAFETY DATA SHEETS | CRC Industries

1. Identification
Product identifier Mass Air Flow Sensor Cleaner
Other means of identification
Product code 05110, 05610
Recommended use Mass air flow sensor cleaner

3. Composition/information on ingredients
Mixtures
Chemical name Common name and synonyms CAS number %
Naphtha (petroleum), hydrotreated 64742-49-0
light
80 - 90
Carbon dioxide 124-38-9 5 - 10
2,2,4-Trimethylpentane 540-84-1 3 - 5
n-Hexane 110-54-3 3 - 5
Methanol 67-56-1 < 1
Specific


Naphtha is used primarily as feedstock for producing high octane gasoline (via the catalytic reforming process). It is also used in the bitumen mining industry as a diluent, the petrochemical industry for producing olefins in steam crackers, and the chemical industry for solvent (cleaning) applications. Common products made with it include lighter fluid, fuel for camp stoves, and some cleaning solvents. Light naphtha is also used directly as a blending component in the production of gasoline.

 

Replaced the MAF sensor with one from the ford dealer, unplugged the + side of the battery, waited awhile, put 500 miles on it, no engine light popping on, runs like a chanp.

Later up in the hills around here, taking friends out smoke began pouring out of the left wheel well with brakes getting mushy. Friends bailed, they thinking it was on fire. (no check engine light haha..)

Troubleshooting revealed driver side outboard transaxle boot cracked spraying gear grease onto brake rotor. Replaced same at local mechanic for 95.00 dollar part, 95.00 dollar labor. Back to running like a champ. Still runs on the low of N on temp, but with the reassurance and help from fellow members no worries for now..

Thanks for all the help.

BRGDS,

patrick

 

with the temp in the 20's in my area, the Temp Gauge in my 4.0 liter has been going crazy, it quickly rises to the M in normal while driving 70 mph then inmediately drops to between the N and the O, then does it again and again.

Never done that before. this is the first time I see that gauge move so high so rapidly.

I am starting to suspect the Ford thermostat.

 

Followed this thread with interest. Answer comes at the end of thread. Maybe your culprit for the fluctuating gauge..

BRGDS,

patrick

 

in my case, when I bought the van, the owner had replaced the radiator and water pump because they told him it could be either.
It did not cure the low reading temp gauge.

that was in May 2012. I have kept it flushed and with fresh Prestone. Then I replaced the Thermostat and both the Temp Sensor
and the Temp Sender, and Same thing. If anything it started running colder.

there is no overheating , no coolant leaks, a/c works, heater works, so I have concluded that the 4.0 runs cold even in traffic.

if the gauge was totally bad, I would have had some incident already with the cooling system, This is my third Aerostar since 1986,
I know them well. I am just puzzled at how cold this engine runs even in Summer. The two 3.0 engines I had were a lot hotter
in temperature. Maybe he installed a bigger capacity radiator? I don't know.