Sensors, which one

[154466]

I bought my 1999 XLT new and it is now 25 years old and I am now 80 years old. I have visited this forum over the years but have not joined until now. I just now replaced the thermostat housing and the engine will start and then falter and quit. I suspect I did not get everything back together properly and there is likely a sensor problem. Those sensors and plug attachments on the thermostat housing I could say are on Mars and not fun to deal with. Might I look elsewhere first? I don't currently have an OBD tool or experience with one (my other vehicles I work on are 11 and 39 years older than my Explorer). I suppose I could get an OBD, but I'm not sure I could by pumping the accelerator pedal (which I last year reattached after it fell off the cracked firewall) coax enough seconds of run time from the engine to get a code. My thanks to the members here for their expertise, experience and caring.

 

[154466]

Update = it will now run smoothly & not die in park, if the RPMs are at 1500 or above.

 

[410Fortune]

So you removed the intake manifold to get to the thermostat housing and now it won’t idle?

Is the check engine light on? If so then the trouble code will Probably tell you where to look first
A obd2 scanner is cheap, or auto parts store can run the codes for you

Likely something left unplugged or unhooked check your work carefully with a brite flashlight

Good Job diy on that old sploder

 

[Turdle]

You might double check the firing order ( spark plug wires in right place) on driver side if V6. Very common to mix them up

 

[wollimann]

just now replaced the thermostat housing

New housing with new sensors? Like this one

More Information for MOTORAD CH2204

Maybe the sensor plugs twisted?

Idle air control valve plug is fully seated?
Intake air temperature sensor plug is seated?

If the upper air intake was out for the thermostat housing install, maybe there is a vacuum leak now.
(if seals are not changed)

More Information for VICTOR REINZ 111026801

 

[154466]

So you removed the intake manifold to get to the thermostat housing and now it won’t idle?

Is the check engine light on? If so then the trouble code will Probably tell you where to look first
A obd2 scanner is cheap, or auto parts store can run the codes for you

Likely something left unplugged or unhooked check your work carefully with a brite flashlight

Good Job diy on that old sploder

Thanks, 410Fortune. I replaced the thermostat housing without removing the intake manifold. The sensors in the old housing needed to come off in order to wiggle the housing out. Those sensors broke out rather than screwed out. I screwed the new ones in after the new housing was in place. I didn’t realize OBDII scanners were so cheap until I went to AutoZone to see if I could rent one. AutoZone guy said they do not rent them, but have a system to use one on your vehicle while it is right outside their door. AutoZone guy suggested I get one at Walmart for a few bucks cheaper than AutoZone low end one and quite equivalent. Did that, but haven’t been able to get the Walmart unit to work. Check engine light is on, but the OBD says no codes found. Not sure the vehicle is drivable enough to get the 2 miles to AutoZone. The sticker at the front of the engine bay near the belt routing sticker says idle cannot be adjusted as it is automatic. However, I spy a screw whereby I might MAYBE be able to adjust the air intake throttle plate resting position to raise the idle to 1500 RPM while in gear so it doesn’t shut down. Or maybe I should buy a higher grade of OBDII. I was surprised to learn those readers do their thing with the engine not running.

 

[154466]

New housing with new sensors? Like this one

More Information for MOTORAD CH2204

Maybe the sensor plugs twisted?
View attachment 457682

Idle air control valve plug is fully seated?
Intake air temperature sensor plug is seated?

If the upper air intake was out for the thermostat housing install, maybe there is a vacuum leak now.
(if seals are not changed)

More Information for VICTOR REINZ 111026801

Thanks Wollimann, and I will.check each of those things again and more.

 

[410Fortune]

The scanners work with engine running or not running

If the light is on there is a code

Adjusting the throttle
Plate Screw can only increase idle not drop it

Idle Is controlled by the iac (idle air control) valve

Good work thus far… need to get the code
Check all
Plumbing around where you were working make sure something did not come disconnected

 

[154466]

The scanners work with engine running or not running

If the light is on there is a code

Adjusting the throttle
Plate Screw can only increase idle not drop it

Idle Is controlled by the iac (idle air control) valve

Good work thus far… need to get the code
Check all
Plumbing around where you were working make sure something did not come disconnected

410Fortune, I sure appreciate your help. Check engine light is not on and no codes show up on OBD tool. With this sensor unplugged just in board of the air filter box, it idles nicely; however, as soon as I plug this sensor connector in it quits. What do I do now? BTW, I’m in a time zone where my parts stores don’t close for another 32 minutes.

 

[wollimann]

Sensor at the air filter box is the Mass Airflow Sensor. It looks like this and the Air Intake Temperature Sensor
is integrated.

The Idle Air Control valve sits on top of the air intake (under the sohc plastic cover).

Both, the MAS Sensor and the IAC valve can be cleaned, maybe that fixes the stalling.
Before cleaning disconnect the battery.

Be careful with the MAS wires, use the cleaner or some other product

CRC Mass Air Flow Sensor Cleaner 11oz

Shop for CRC Mass Air Flow Sensor Cleaner 11oz with confidence at AutoZone.com. Parts are just part of what we do. Get yours online today and pick up in store.

www.autozone.com

The IAC, mostly there is some debris inside the housing and sometimes the rod is sticking.
Cleaning with oven cleaner foam, have some good experience with. After cleaning give a drop of oil
on that rod/bushing.

Reconnect battery and thumbs up!

 

[410Fortune]

Oven cleaner!!! Genius

All these years I’ve been cleaning iac with carb cleaner and it only gets so much of it

Your mass air flow sensor maybe dirty

If it is dirty then check your airbox seal and air filter… then clean mas and try again

 

[154466]

410Fortune, I sure appreciate your help. Check engine light is not on and no codes show up on OBD tool. With this sensor unplugged just in board of the air filter box, it idles nicely; however, as soon as I plug this sensor connector in it quits. What do I do now? BTW, I’m in a time zone where my parts stores don’t close for another 32 minutes.

I cleaned the deposits off the MAF sensor with CRC brand MAF sensor cleaner and it still idles fine with the MAF unplugged, but shuts down as soon as I connect it. I now have an OBDII WHICH INDICATES THE MAF SENSOR. SO, MY NEXT MOVE IS TO REPLACE THAT SENSOR.

 

[410Fortune]

What is the code? There is a big difference between a “mas circuit failure” and a “mas reads lean” code for example

 

[154466]

What is the code? There is a big difference between a “mas circuit failure” and a “mas reads lean” code for example

I likely don’t recall the code accurately and I don’t seem able to recover it; however, I’m remembering something like “MAF circuit too hot.” A new MAF sensor is on the way and I have not yet cleaned the IAC valve as Wollimann mentioned. I am happy that the problem seems to be in the air intake area and not with the difficult to access coolant temp sensors.

 

[410Fortune]

A circuit failure does indicate that the sensor has failed or the wiring to and from