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TB - IAT - IAC - TPS - MAF ... Which one?


BTR

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Year, Model & Trim Level
2000 EXPLORER XLT 2WD
2000 4.0 SOHC 136,000 miles.

Cold Start & No Gas Pedal Applied While Cranking
Starts right up, idles smooth, accelerates properly, runs smooth and properly, no CELs.

Warm Start & No Gas Pedal Applied While Cranking
Takes 2-3 tries to start, idles smooth, accelerates properly, runs smooth and properly, no CELs.

Warm Start & 1/8-1/4 Gas Pedal Applied While Cranking
Starts right up, idles smooth, accelerates properly, runs smooth and properly, no CELs.

Before I mess with anything, I want to know - exactly - which part to work on. My choices are TB (throttle body) - IAT - IAC - TPS - MAF.

I DO NOT have the ability to read real-time data nor codes. Therefore, I'm looking for expert advice on which part to tackle first. Thanks for your help.
 

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RickOTR

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How many miles on your Explorer?. Sounds like the fuel injectors are leaking causing flooding of the engine with fuel. Common on high mileage vehicles. I had to remove mine and send them out to be professionally cleaned. No more problem after that.
 


boominXplorer

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Try when warm: Turn the key to ON for 3 seconds and do not start. Repeat. Repeat. Now crank and see if it fires on without issue. If so your issue is most likely fuel related.
 


C420sailor

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I’d hook a pressure gauge up to the fuel rail and check fuel pressure, see if it is bleeding down.
 


BTR

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How many miles on your Explorer?. Sounds like the fuel injectors are leaking causing flooding of the engine with fuel. Common on high mileage vehicles. I had to remove mine and send them out to be professionally cleaned. No more problem after that.
140,000 miles.
 
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974X4BLACKSPORT

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Without being able to see the "real time" data from the sensors, particularly the engine coolant temperature sensor (ECT) during cold and warm starts, expert advise is just not possible. If the ECT is not sending the proper coolant temperature to the PCM, the fuel mixture will be off, and it could be rich or lean, depending on the resistance of the sensor in the coolant passage, and it does not take much to flood an engine.
When you first turn the key to "ON", the PCM reads the coolant temperature and then decides how much of a "PRIME" pulse to give the engine for a clean solid start, if that prime pulse is no just right, you will have starting problems. YEs, it is also possible to have one or more leaking injectors to cause a "flooded" engine when trying to restart when the engine is warm, a fuel pressure leak down test can spot this, but it's not definitive.
I am not saying this IS the problem, just something to take into account when diagnosing, and without live sensor "data", we are throwing darts at a dart board with a blindfold on.
If you plan on doing as much of the repairs on your Explorer as possible, it would be wise to invest in some sort of diagnostic tool/s to read/clear codes, and watch the "live" sensor data.
 


410Fortune

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test fuel pressure
Check computer codes...you can have this for free, just because the light is not in does not mean there are no codes in memory that might be of help

Its likely fuel pressure related gives your symptoms.............so a fuel pressure test is the next step
 


RickOTR

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Ford recommends fuel injector replacement at 150K miles. Mine started leaking around 120K miles. Leak down test will tell you if they are leaking.
 


BTR

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Ford recommends fuel injector replacement at 150K miles. Mine started leaking around 120K miles. Leak down test will tell you if they are leaking.
What were your symptoms?
 


RickOTR

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Difficulty starting after warm restart. Needed several attempts to get it started thou it started fine when cold or left overnight. Fuel pressure was normal but pressure dropped when left for about 15 minutes. Having them professional cleaned solved the problem
 


BTR

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Try when warm: Turn the key to ON for 3 seconds and do not start. Repeat. Repeat. Now crank and see if it fires on without issue. If so your issue is most likely fuel related.
I tried your starting process on 5 different occasions. On all 5 occasions, it started right up... no stumble, no second attempt required. Given this, you indicate that my issue is fuel related. Can you be more specific? What's going on with my fuel... too much... too little... something else? Thanks for your help.
 


C420sailor

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Turning the key to ON energizes the fuel pump and the fuel injection computer commands a small priming pulse.

Usually a cold starting fix...interesting to see it work for a hot start issue.

The silver bullet here is going to be monitoring your fuel pressure with a fuel pressure gauge. Without investing in the right diagnostic tools, you’re simply going to have to guess and throw parts at it until you accidentally fix it.
 


boominXplorer

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Most commonly it's the check valve not holding the fuel in the lines in the sending unit. You have to replace the whole unit as it's not sold separately and best to do so anyway. You could also have a leaking down injector.
 


Cpl. Opey

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Buy a elm327 obd2 reader. It'll give you real time readouts. I like my Vgate. Around 10-12 bucks on Amazon. Then download a free app. I like Car Scanner.

Screenshot_20200209-131218_Google Play Store.jpg
 


BTR

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Regarding "engine temperature" data being sent to the PCM, is there only one source of data, or are there two sources of data?

1. The ECT Sensor (Engine Coolant Temperature Sensor) sends coolant temperature data to the PCM.
2. There's something that sends temperature data to the engine temperature gauge (the red colored "C---H" needle located on the dashboard). I don't know what the "something" is.

Question: Are 1 and 2 the same sensor... or are 1 and 2 different sensors?
Question: If 1 and 2 are different sensors, then does the "something" sensor send its data to the PCM?
 


C420sailor

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Depends on the year. Early models had two separate sensors. Later on, Ford went to a single sensor in the t-stat housing.
 


BTR

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The year is 2000. 4.0L SOHC. 5-Speed Automatic. 2WD.
 


C420sailor

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Should be two sensors on that.

Some years use thread-in sensors, others use clip-in. Not sure how that’s broken down by model/year. You’ll have to look for yourself.
 


BTR

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Without being able to see "real time" data from the sensors, particularly the engine coolant temperature sensor (ECT), during cold and warm starts, expert advise is just not possible. If the ECT is not sending the proper temperature to the PCM, then the fuel mixture will be off, and it could be rich or lean depending on the resistance of the sensor in the coolant passage, and it does not take much to flood an engine.
If you plan on doing as much of the repairs on your Explorer as possible, it would be wise to invest in some sort of diagnostic tool/s to read/clear codes, and watch "live" sensor data.
UPDATE FROM THE OP

I now have the ability to watch and log real-time data. 2000 4.0 SOHC JOB1 5-SPEED AUTOMATIC 140,000 MILES.

Cold Start & No Gas Pedal Applied While Cranking
Starts right up, idles smooth, accelerates properly, runs smooth and properly, no CELs.

Warm Start & No Gas Pedal Applied While Cranking
Takes 2-3 tries to start, stumbles to start, idles smooth, accelerates properly, runs smooth and properly, no CELs.

Warm Start & 1/8-1/4 Gas Pedal Applied While Cranking
Starts right up, idles smooth, accelerates properly, runs smooth and properly, no CELs.

Q1 - In addition to engine coolant temperature, what other real-time data should I log? Specifically (there are lots of choices)?

Q2 - Once I have the data, what am I looking to decipher/determine? Specifically?

Thanks for your help.
 

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Explorer Forum has probably saved you that much already, and will continue to save you money as you learn how to diagnose fix problems yourself and learn which modifications work without having to experiment on your own. Elite Explorer members see no advertisements, no banner ads, no double underlined links, can add their own profile photo, upload photo attachments in all forums, and Media Gallery, create and save more private Conversations, and more. Join Today. Your support is greatly appreciated.




BTR

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UPDATE FROM THE OP

2000, 4.0 SOHC Job1, 5-Speed Automatic, 140,000 miles. Here's the real-time data I gathered:

COLD ENGINE START ATTEMPT
Coolant temp - 32 F
Pre-start short-term fuel trims - 85
Outcome - Successful start on first attempt; proper idle; runs smooth. When cold, it always starts on the first attempt; 100% of the time.

WARM ENGINE START ATTEMPT #1
Coolant temp - 167 F
Pre-start short-term fuel trims - 24
Outcome - Did not start on this attempt.

WARM ENGINE START ATTEMPT #2 (6 seconds after the first warm attempt)
Coolant temp - 167 F
Pre-start short-term fuel trims - 24
Outcome - Successful start, proper idle; runs smooth.

Sometimes, with a warm engine, I attempt to start it 2-3 times and all attempts fail. Then, I give it a little gas pedal and hold the pedal, and then I start it and it fires right up.

What are your thoughts on the root cause of the warm no-start problem?
 


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