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At my wits end with this issue

Hi all, I've been trying to use this ex as a learning experience for myself, as well as to eventually use as my daily driver. Obviously, for that to be the case, it needs to be running perfectly, and i shouldn't have to worry about it being a danger to myself or others. However, with this particular issue, I'm stumped.

The ole' rough idle. Ah yes, the very bane of my existence. Starts up rough when warm, idles rough no matter what i do, and (sometimes) will stall at stoplights, or long periods of idle.

What have I done to fix it? Well, i've replaced the positive battery cable, checked for vacuum leaks, cleaned the maf, replaced the ects, replaced sparkplugs and wires, cleaned the throttle body, checked the large intake tube (plastic) for cracks, checked each vacuum line on the tree for leaks (done by plugging them simultaneously, this provided no change to the idle), and checked the iac (I unplugged it, and the engine slowly died).

At this point, the only things I HAVEN'T done, are replacing the MAF, replacing the pcv valve, replacing IAC (though it seems to be working fine), or anything relating to fuel.

Fortunately, it's annoyed me enough at this point to document it, so here's a video of a (warm) start.



Note, the oil guage ALWAYS reads high, and always "flickers" like that. When the idle is getting rough, the voltage meter also does this (because its about to stall).

Main points to take away here are the surging and rough idle. If anyone else notices anything that is ALSO an issue, or has any questions, please let me know.

Thanks in advance, and have a great day!



EDIT: UPDATE

Hi all, just got back inside from running some codes and checking a few other things people recommended. First off, I'd just like to say thank you for your support so far! This forum has one of the best communities by far.

Down to the nitty gritty:

1: I checked the PCM. Unplugged it, started the engine, plugged it back in, started the engine. No change :(

2: While looking around for the PCM (before i realized it was under the dash) I found 3 or so wiring harnesses just hanging around. This had to be something done by the previous owner, but I'm not sure what they do. Pics are posted below (or above idk)
View attachment 319130
View attachment 319131
View attachment 319132
View attachment 319133


3: I noticed that one of the main air intake hoses ( near the lower radiator hose) is just... broken. Pics posted below.

View attachment 319134
View attachment 319135

4: I used the paperclip method to run the codes, and got 3 while KOEO:

  1. 79: A/C is on or pin 10 is shorted to power
  2. 66: Vane Air Flow (VAF) or Mass Air Flow (MAF) signal low – VAF MAF (Also listed on the website: Transmission Oil Temperature (TOT) signal low (possibly grounded) – Transmissions)
  3. 63: Throttle Position Sensor (TPS) signal too low TPS
This is pretty informative! Maybe now we're on to something? Idk.

5: I took the radiator cap off and looked inside. Pics are attached. It smells off, and upon closer inspection of what dripped off the radiator cap, it seems to have some sort of dirt or particles in it. The liquid itself does seem to still have somewhat of a green-ish sheen.
View attachment 319136
View attachment 319137


That wraps up my update! I hope you all can help me, and know that I'm putting in as much effort to fix this as you all are to help me. Again, thank you so much!

the plug that you have in your hand looks like a o2 plug , i wonder if they ran some sort of bypass
 

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the plug that you have in your hand looks like a o2 plug , i wonder if they ran some sort of bypass

O2 plug(s) (in his case only one) are run down back behind the engine and are part of the transmission harness. They are also 4-pin plugs, not 2.

That plug might be for the cruise control which apparently you do not have or it was removed.

91-92 Explorer's, regardless of being sold in California, did not have EGR. 93 was the introduction of EGR for the Cali versions and in 94, Ford implemented it across all versions.

The purpose of the coolant pressure test is to check for leaks in the coolant system. If the pressure drops quickly after being pressurized or won't pressurize at all, then there is a leak somewhere. Usually if the leak is big enough you can find the source by listening for it.

I suggest we stop throwing advice at the guy until we hear from him on the results of the diagnosis' we have suggested, just so we don't overwhelm him with "maybe's" and "possibly's" until we have some definitive answers.
 






okay reading back a bit lets clear some things up
I agree with @MrQ this thread is getting muddled with too much info and guesses

First off the air intake hose that is not hooked up to anything:
This is just a pre heater hose, it takes some warm air from near the exhaust manifold and feeds it towards the airbox. this is designed to keep your throttle body from freezing up if you live someplace like Minnesota where it is humid and freezing.... this hose is not needed and it is okay that it is not hooked up

Second the "missing wire plugs":
There are several wiring plugs that go nowhere on your truck, totally normal. Under hood light, cruiser control, diagnostics port, and others. These wires never went anywhere on your truck and they are not supposed to go anywhere now

Third "the codes":
Earlier you said you used a paper clip to test codes....Nicely done!
One of the codes you reported was Mass air flow meter voltage lower then expected.
Now that code needs to be addressed
The MAS is a vital piece of equipment as I am sure we have covered by now. If the MAS sensor is having voltage issues it will never run correctly.

still need coolant pressure and engine compression tests so you can check these off your list
 






O2 plug(s) (in his case only one) are run down back behind the engine and are part of the transmission harness.

That plug might be for the cruise control which apparently you do not have or it was removed.

91-92 Explorer's, regardless of being sold in California, did not have EGR. 93 was the introduction of EGR for the Cali versions and in 94, Ford implemented it across all versions.

The purpose of the coolant pressure test is to check for leaks in the coolant system. If the pressure drops quickly after being pressurized or won't pressurize at all, then there is a leak somewhere. Usually if the leak is big enough you can find the source by listening for it.

I suggest we stop throwing advice at the guy until we hear from him on the results of the diagnosis' we have suggested, just so we don't overwhelm him with "maybe's" and "possibly's" until we have some definitive answers.
Good Idea.
 






If you have a mulitimeter please run this simple test and get back to us.

Unplug the Throttle Position Sensor and with the Key On Engine Off measure the voltage between the two outside connections on the wiring harness connector. The Brown with a White stripe should be positive and the Grey with a Red should be negative. We are looking for 4.8 to 5 volts. This is to ensure that the PCM is sending the correct voltage to the sensors.
 






Hi! Thanks for your reply. It very well could be an IAC issue, but as stated, when i unplugged it, thew engine chugged down and died like it should, so i just figured it was fine. As for the motor mounts, no, i haven't done anything with them.

Thanks again for your reply!
No, It should not die when IAC is unplugged. When warm, unplugging IAC should result in an idle of 700. Too expensive to just buy, and I got one from Ebay (pure mantenence) that didn't work and they wouldn't take it back without a certified mechanic's report.
Compression test would be good, no colored smoke out back? steam-ok, considerable white-water, blueish-oil.
 






*sigh*
 






O2 plug(s) (in his case only one) are run down back behind the engine and are part of the transmission harness. They are also 4-pin plugs, not 2.

That plug might be for the cruise control which apparently you do not have or it was removed.

91-92 Explorer's, regardless of being sold in California, did not have EGR. 93 was the introduction of EGR for the Cali versions and in 94, Ford implemented it across all versions.

The purpose of the coolant pressure test is to check for leaks in the coolant system. If the pressure drops quickly after being pressurized or won't pressurize at all, then there is a leak somewhere. Usually if the leak is big enough you can find the source by listening for it.

I suggest we stop throwing advice at the guy until we hear from him on the results of the diagnosis' we have suggested, just so we don't overwhelm him with "maybe's" and "possibly's" until we have some definitive answers.
okay reading back a bit lets clear some things up
I agree with @MrQ this thread is getting muddled with too much info and guesses

First off the air intake hose that is not hooked up to anything:
This is just a pre heater hose, it takes some warm air from near the exhaust manifold and feeds it towards the airbox. this is designed to keep your throttle body from freezing up if you live someplace like Minnesota where it is humid and freezing.... this hose is not needed and it is okay that it is not hooked up

Second the "missing wire plugs":
There are several wiring plugs that go nowhere on your truck, totally normal. Under hood light, cruiser control, diagnostics port, and others. These wires never went anywhere on your truck and they are not supposed to go anywhere now

Third "the codes":
Earlier you said you used a paper clip to test codes....Nicely done!
One of the codes you reported was Mass air flow meter voltage lower then expected.
Now that code needs to be addressed
The MAS is a vital piece of equipment as I am sure we have covered by now. If the MAS sensor is having voltage issues it will never run correctly.

still need coolant pressure and engine compression tests so you can check these off your list
First off, just wanted to again say thank you for all the advice i've been given. While it is a bit overwhelming, I do think my priorities are somewhat in order. Later today I'll be doing the compression test, where I'll then post all results here, as well as update my original post with them. Secondly, thanks for clearing up some of my other concerns regarding the rogue hose, and missing wire plugs. I do have one question, it's about the MAF sensor voltage: It sounds as though replacing the very MAF sensor itself wouldn't solve this issue, since it's due to the actual voltage going to it... would I need to replace the wire that runs from battery to the maf?

Thanks again for all of your help!
 






This should get you started on the MAF diagnosis.

91 MAF 1.PNG
 






eeeeeeh the second part of that test appears to be for a map sensor? We don't have no stinkin map sensors!!
 






I probably should have pulled the 92 AllData info on the MAF, was really tired when I posted this and it didn't register that I put MAP instead of MAF (for starters a MAF is a 4 pin connector, not 3).

The description of how a MAF operates is correct however.

91 is a really bad year for documentation and 92 is pretty close to 91, at least electrically, but is much better documented.

I'll pull the right info when I get home.
 






Ok maybe this will make it easier. Test the MAF connection with the key on with your multi-meter probes in the locations shown. The approximate voltage for each test is in parenthesizes.

MAF.png


This is the MAF RTN voltage chart:

MAF2.PNG
 






Ok maybe this will make it easier. Test the MAF connection with the key on with your multi-meter probes in the locations shown. The approximate voltage for each test is in parenthesizes.

View attachment 319222

This is the MAF RTN voltage chart:

View attachment 319223
Ill do this soon as i can, as well as the compression test. Unfortunately, as you all might know, theres a hurricane headed straight for us, which kinda puts a delay on me being able to go out and work on the truck. Just finished grocery shopping, but either way, best case scenario is i can have some answers tomorrow earlier in the day, worst case is it'll have to wait until tuesday. I'm sorry! I'll post any and all updates here and in the OP as soon as I can.
 






stay safe!
 






Its great to see people jumping into learning something about their vehicles, especially when it involves a first gen Explorer. These are a little near and dear to me. Like any vehicle that is pushing 30 years old, it will have it's issues from neglect and the passing of time regardless of what the odometer says. I have kinda skimmed this thread and got the basic idea of it and the advice posted is the average for the issues you have. Being uncertain of your automotive knowledge, and the arsenal of tools in your possession; this is the advise I will give until you get back with some more info on the truck.

Gasoline engines are rather simple things, they all work with the combination of 3 vital things: the proper fuel to air mixture, proper compression, and a good spark. The rest is all just fluff to keep the EPA happy. If you are certain this vehicle will be your learning tool and project, get a set of Ford service manuals for the year of the truck. You can find them on eBay. Most importantly get an Electrical and Vacuum Troubleshooting Manual for the year of your truck. If you can find one, get a full wiring schematic as well, although these are getting harder to find. These are the road map for the wiring in the truck and will give you all kinds of info about what wires go where and whats in between. You can also find Engine/Emissions Diagnosis manuals from Ford that discuss the theory of how the system works. These generally cover all Ford vehicles for a specific year. This information is handy to have if you're trying to learn these systems and troubleshoot them. Keep in mind though that these manuals are designed for someone with a basic understanding of general automotive theory and terms for the time in which it was written. Also, they reference the factory service tools and procedures which mean nothing if you don't have them.

Many people jump to trouble codes as being a flag for an electrical problem. Example being an oxygen sensor. Many inexperienced mechanics would replace the sensor because of a code when in actuality its merely doing its job by reading a lean or rich condition caused by some other possible failure. The computer just knows the exhaust has a bunch of O2 or it doesn't. If its out of range and can't be corrected for, then the computer communicates this as being an O2 fault. EEC-4 systems aren't really smart enough to determine the sensor's health. Due to the age of your truck and the fact that you probably haven't had it very long, I would be verifying the mechanical portion of things first. At this stage in the game, it would be more likely for an engine issue to arise from damaged or worn internal parts than electrical problems, not to say you don't have them.

Get some tools. Having good tools is very important. You don't have to have $50K of Snap-On stuff to do this, but you should have a good quality set of METRIC hand tools, a digital volt meter, vacuum gauge, compression tester, fuel pressure gauge, and some sort of OBD-1 scan tool. I happen to own the Super Star 2 tester that the dealers would have used on this truck, but any OBD-1 scanner will work.

Get a good place to work. If you don't have a garage or a place to tear something apart, that can get very frustrating while trying to troubleshoot or repair your vehicle. Especially when you can't leave things disassembled in between working on it due to weather, the nagging neighbors or "loved" one..

Biggest thing is this will cost money. Old cars cost a lot, especially when you compare cost to value. You're upside down each and every time, I don't care what the car is. Don't be afraid to spend some jack if this is the vehicle you want to depend on for a daily. It's definitely not a cheap hobby! Have fun learning and working on your Explorer. I find it very rewarding to breathe new life into old junk and hopefully you get the same enjoyment out of it! This forum is a great place to get info and I agree there is something different about this one than others I've been on.

Attached are pics of the 91 manuals to help you ID them, and the 92 EVTM. 91 and 92 were practically the same so they interchange for the most part. The following pics show the various under hood connectors and what they do. This may help you ID some of the unplugged connectors.
IMG_20200725_144100134.jpg
IMG_20200725_144138986.jpg
IMG_20200725_144154509.jpg
 






that stuff you are seeing in the radiator looks like bars stop leak , i would do a flush , and more than likely you will have to change the thermostat
another check on radiator when hot feel over the whole radiator if you have a cold spot compared to the rest its clogged
best to put a new aftermarket one
 






Hi all, I've been trying to use this ex as a learning experience for myself, as well as to eventually use as my daily driver. Obviously, for that to be the case, it needs to be running perfectly, and i shouldn't have to worry about it being a danger to myself or others. However, with this particular issue, I'm stumped.

The ole' rough idle. Ah yes, the very bane of my existence. Starts up rough when warm, idles rough no matter what i do, and (sometimes) will stall at stoplights, or long periods of idle.

What have I done to fix it? Well, i've replaced the positive battery cable, checked for vacuum leaks, cleaned the maf, replaced the ects, replaced sparkplugs and wires, cleaned the throttle body, checked the large intake tube (plastic) for cracks, checked each vacuum line on the tree for leaks (done by plugging them simultaneously, this provided no change to the idle), and checked the iac (I unplugged it, and the engine slowly died).

At this point, the only things I HAVEN'T done, are replacing the MAF, replacing the pcv valve, replacing IAC (though it seems to be working fine), or anything relating to fuel.

Fortunately, it's annoyed me enough at this point to document it, so here's a video of a (warm) start.



Note, the oil guage ALWAYS reads high, and always "flickers" like that. When the idle is getting rough, the voltage meter also does this (because its about to stall).

Main points to take away here are the surging and rough idle. If anyone else notices anything that is ALSO an issue, or has any questions, please let me know.

Thanks in advance, and have a great day!



EDIT: UPDATE

Hi all, just got back inside from running some codes and checking a few other things people recommended. First off, I'd just like to say thank you for your support so far! This forum has one of the best communities by far.

Down to the nitty gritty:

1: I checked the PCM. Unplugged it, started the engine, plugged it back in, started the engine. No change :(

2: While looking around for the PCM (before i realized it was under the dash) I found 3 or so wiring harnesses just hanging around. This had to be something done by the previous owner, but I'm not sure what they do. Pics are posted below (or above idk)
View attachment 319130
View attachment 319131
View attachment 319132
View attachment 319133


3: I noticed that one of the main air intake hoses ( near the lower radiator hose) is just... broken. Pics posted below.

View attachment 319134
View attachment 319135

4: I used the paperclip method to run the codes, and got 3 while KOEO:

  1. 79: A/C is on or pin 10 is shorted to power
  2. 66: Vane Air Flow (VAF) or Mass Air Flow (MAF) signal low – VAF MAF (Also listed on the website: Transmission Oil Temperature (TOT) signal low (possibly grounded) – Transmissions)
  3. 63: Throttle Position Sensor (TPS) signal too low TPS
This is pretty informative! Maybe now we're on to something? Idk.

5: I took the radiator cap off and looked inside. Pics are attached. It smells off, and upon closer inspection of what dripped off the radiator cap, it seems to have some sort of dirt or particles in it. The liquid itself does seem to still have somewhat of a green-ish sheen.
View attachment 319136
View attachment 319137


That wraps up my update! I hope you all can help me, and know that I'm putting in as much effort to fix this as you all are to help me. Again, thank you so much!

Wow. One thing I would do is CLEAN the poor thing. Get rid off all that red dirt and check all the grounds. A bad ground is what caused my problems with my 93 after we did valve cover gasket replacement which of course means you have to take most of the top half of the engine off to get to. I would seriously flush that coolant too. Also helpful, Get an EVTM and shop manuals off E-bay as well as the Ford OBD1 manual and start reading. It was amazing how helpful these were when trying to fix mine.
 






Hey all,

Just wanted you guys to know that i am in fact not dead, I've just been extremely busy with work, and am on a new schedule that pretty severely limits my ability to work on the truck. To add to that, unfortunately the time i DO have to work on it, it's like mid day in the hawaiian summer and is 90+ degrees with humidity in the 90%'s as well. If only i had a garage to work in! At any rate, I've been able to make it outside and do a few cosmetic improvements, like cleaning the engine bay. While not completely necessary, it'll certainly be easier to work on with it now clean. Finally, look for an update post coming likely this Sunday or Monday, where I should have the findings from the compression test. Again, thank you all for your support through this, hopefully someday soon we'll have it all figured out!

-TwistedFish
 









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Elite Explorer members see no advertisements, no banner ads, no double underlined links,.
Add an avatar, upload photo attachments, and more!
.





Its great to see people jumping into learning something about their vehicles, especially when it involves a first gen Explorer. These are a little near and dear to me. Like any vehicle that is pushing 30 years old, it will have it's issues from neglect and the passing of time regardless of what the odometer says. I have kinda skimmed this thread and got the basic idea of it and the advice posted is the average for the issues you have. Being uncertain of your automotive knowledge, and the arsenal of tools in your possession; this is the advise I will give until you get back with some more info on the truck.

Gasoline engines are rather simple things, they all work with the combination of 3 vital things: the proper fuel to air mixture, proper compression, and a good spark. The rest is all just fluff to keep the EPA happy. If you are certain this vehicle will be your learning tool and project, get a set of Ford service manuals for the year of the truck. You can find them on eBay. Most importantly get an Electrical and Vacuum Troubleshooting Manual for the year of your truck. If you can find one, get a full wiring schematic as well, although these are getting harder to find. These are the road map for the wiring in the truck and will give you all kinds of info about what wires go where and whats in between. You can also find Engine/Emissions Diagnosis manuals from Ford that discuss the theory of how the system works. These generally cover all Ford vehicles for a specific year. This information is handy to have if you're trying to learn these systems and troubleshoot them. Keep in mind though that these manuals are designed for someone with a basic understanding of general automotive theory and terms for the time in which it was written. Also, they reference the factory service tools and procedures which mean nothing if you don't have them.

Many people jump to trouble codes as being a flag for an electrical problem. Example being an oxygen sensor. Many inexperienced mechanics would replace the sensor because of a code when in actuality its merely doing its job by reading a lean or rich condition caused by some other possible failure. The computer just knows the exhaust has a bunch of O2 or it doesn't. If its out of range and can't be corrected for, then the computer communicates this as being an O2 fault. EEC-4 systems aren't really smart enough to determine the sensor's health. Due to the age of your truck and the fact that you probably haven't had it very long, I would be verifying the mechanical portion of things first. At this stage in the game, it would be more likely for an engine issue to arise from damaged or worn internal parts than electrical problems, not to say you don't have them.

Get some tools. Having good tools is very important. You don't have to have $50K of Snap-On stuff to do this, but you should have a good quality set of METRIC hand tools, a digital volt meter, vacuum gauge, compression tester, fuel pressure gauge, and some sort of OBD-1 scan tool. I happen to own the Super Star 2 tester that the dealers would have used on this truck, but any OBD-1 scanner will work.

Get a good place to work. If you don't have a garage or a place to tear something apart, that can get very frustrating while trying to troubleshoot or repair your vehicle. Especially when you can't leave things disassembled in between working on it due to weather, the nagging neighbors or "loved" one..

Biggest thing is this will cost money. Old cars cost a lot, especially when you compare cost to value. You're upside down each and every time, I don't care what the car is. Don't be afraid to spend some jack if this is the vehicle you want to depend on for a daily. It's definitely not a cheap hobby! Have fun learning and working on your Explorer. I find it very rewarding to breathe new life into old junk and hopefully you get the same enjoyment out of it! This forum is a great place to get info and I agree there is something different about this one than others I've been on.

Attached are pics of the 91 manuals to help you ID them, and the 92 EVTM. 91 and 92 were practically the same so they interchange for the most part. The following pics show the various under hood connectors and what they do. This may help you ID some of the unplugged connectors.
View attachment 319294View attachment 319295View attachment 319296
Hi, not sure if you get notifications for it, but i made an update on the compression test, check it out if you could and let me know what you think!
 






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