93 Explorer can't even complete an engine test without stalling.

[Zinith]

Last time that I ran the codes on my explorer i got a new code 412 (iac causing it to idle to low). So I used some Gumout to try and clean out the iac control valve. When I started it up after that, it seemed to start even stronger than it did before. But when I started to drive it. I got like maybe 50 feet and the engine stalled out.

When I got it parked I tried to run the codes on it, it couldn't even get to the second rev before it stalls out. And the check engine light doesn't even do anything like give me a code.

 

[Rhett]

Have the fuel pressure tested via the test port in the engine bay. You can rent a gauge at most auto parts stores, or buy one for about $30. Pressure should be about 35 psi.

Also inspect all vac lines for cracks and holes, but to me your problem sounds fuel-related.

 

[Zinith]

The fuel pressure has been tested. Its sits at 28 at idle but when its revved up to 3,000 rpms it jumps up to 40-41. The fuel filter was also changed (old one was pretty hard to blow through.) It then only rose the pressure at idle to 29-30.

I did get it to give me a KOEO code of 122 (TP low (possibly grounded or open circut)) But the only thing that changed was me attempting to clean the iac valve.

 

[Rhett]

That is a throttle position code. There is a TPS (Throttle Position Sensor) attached to the side of the throttle body (on top of the engine, front side). Are you sure your TPS is working properly?

 

[Zinith]

I'm not sure. I do remember unplugging it and plugging it back in while it was idle. And nothing seemed to change. Any idea how I could check it?

 

[Rhett]

You'll need a voltmeter (pretty cheap to buy, and useful). It's been about 15 years since I tested my TPS but as I recall the voltage should be between about 0.4v (throttle plate fully closed) up to about 4 volts (throttle plate fully open). Idle should be 0.96 volts but a little less is "ok". Here are some links that should help you know what wires to probe. The last link is a thread here with useful TPS info, even though the thread is about modding your TPS:



http://easyautodiagnostics.com/ford/4.0L/tps-multimeter-tests-1

http://www.explorerforum.com/forums/index.php?threads/adjust-your-tps-another-free-hp-mod.79362/

 

[Rhett]

Finally, there is a throttle set screw (aka throttle adjustment screw) located on the throttle body itself, on the passenger side (on a little "arm" on that side of the throttle body). This tiny screw can be turned either way with a small socket or wrench, to adjust where the throttle plate stops. If it's too closed, you can get stalling. If it's too open, you'll have a high idle.

Between adjusting the set screw, and calibrating (or replacing, if it's broken) your TPS, you should get 0.96v at idle on the TPS, and should have perfect idle. If the truck still stalls out after doing those two things, then the TPS and set screw position can be ruled out as the cause of the stalling. At least it's always worked for me.

 

[Zinith]

Alrght. I'm getting .960 at idle and 4.7 with the throttle fully opened.

And the connector itself is getting 5.03.

When I slowly open the throttle, right around 1.8 - 2.0 volts. It'll completely drop off and jump right back up.

One thing it's doing. Is that when I start it up. It'll get up and go.
But once it's been running for a little while. The engine just Boggs down really bad.
And when I'm headed down the road it'll just all the sudden loose power. And I'll get absolutely no response from the gas pedal. And it'll eventually just stall out.

 

[2stroke]

Any kind of irregularity in the voltage is a reason to replace the TPS. It should be a smooth increase from closed to open throttle.

The Ideal way to adjust the throttle plate usually involves reaming out the TPS screw holes to allow it to be adjusted. With the TPS plugged in, but IAC unplugged, and with the engine fully up to temp, adjust the throttle plate stop screw until it is idling about 500-550 rpm. The idea is that the RPM's are lower than the idle speed, but high enough that if the IAC ever fails it will not stall. Its a good idea to give the throttle body a good cleaning beforehand. After the throttle plate is adjusted, adjust the TPS so the voltage with the throttle closed is .96-.98 volts.

 

[gmbroy]

sounds like your tps has a bad spot in it . any fluctuation in voltage is not good . i would try a new tps & see how it goes .

 

[Zinith]

Alrighty. So I got a new TPS and installed it today. It will actually give me codes now. But its not fixed the reason why its barely running as it is.
The two codes it gave me this time was 116 ((O,R) Engine Coolant (ECT) sensor out of range), and 137 ((R) Oxygen sensor not switching/system rich Left or Front HO2S)
For as far as I know, the thing only has 2 o2 sensors and ive already replaced both of them now. I don't see how it could still be complaining about it. Unless your supposed to replace them at the same time. Because thats not what i did.
The first time, I replaced the left one and it ran fine for a few days and then crapped out. And then the computer was complaining about the other one, so I replaced it and it ran fine for a few days. And now I'm back to square one.

This is how its running right now. Not sure how well you guys are going to be able to hear.

 

[gmbroy]

I am at a loss at the moment . it is really running bad . If the tps didnt help id try to return it . id clean the mass air flow , clean the throttle body , try plugs & wires . Or you could bite the bullet & send it to a good shop . might be cheaper than just throwing stuff at it . I am going to think on this some . hopefully one of the other guys will have something for you . but keep us informed it will help us all .

 

[gmbroy]

could be a bad connection on the eec or the eec could be bad . just tossing it out there .

 

[gmbroy]

it is possible your injectors are dirty & clogged up .

 

[Zinith]

Got new spark plug wires on it today. And drove it around a little while it was cold. Until it stalled out and started driving like crap. After about 20 mins of getting it back across my town which is only like 2 square miles to get it parked. Looking through my haynes repair manual and takin video (of which ill post later). Tomorow im going to go out and test the maf sensor and see what voltages its giving me.

When you change o2 sensors, should you do them all, at the same time? Or would it be alright if you did one at a time over the course of multiple days. Like change one and have it run fine for a few days until it craps out, and then change the other one and have it run fine for a few more days and crap out again. The engine test is still giving me a code of 137 (and 177-memory) (heated oxygen sensor indicates rich condition, left side) which is the one i changed first. Its also still giving me 159 (Mass Air Flow Sensor out of self-test range)

But that's all the codes it gave me today.

 

[gmbroy]

darn i hate to see you throwing money at this . you could try both 02 sensors but i am not sure about having to change them both at same time . that doesnt make sense to me . try testing the mass air flow . i will keep thinking on this , just keep us informed .

 

[Rhett]

When you change o2 sensors, should you do them all, at the same time? Or would it be alright if you did one at a time over the course of multiple days. Like change one and have it run fine for a few days until it craps out, and then change the other one and have it run fine for a few more days and crap out again. The engine test is still giving me a code of 137 (and 177-memory) (heated oxygen sensor indicates rich condition, left side) which is the one i changed first. Its also still giving me 159 (Mass Air Flow Sensor out of self-test range)

But that's all the codes it gave me today.

I am a believer in changing both O2s at the same time -- only because that way I will know how old the O2s are- - I won't have to guess, "...well, the driver's side one I changed in 2014 and the pass side one I changed in 2007". Also, once I'm in there, working on one, I might as well do the other one.

That said, I don't see how it should matter if you change one O2 last week, and the other one this week. Then you'll have 2 new ones anyway.

Are you sure your FPR (fuel pressure regulator) is working properly? Stalling and rich (flooding) are pretty common with a malfunctioning FPR. Your fuel pressure should be 35-40 psi at the rail. If you're getting 60-70-80 psi you can bet the FPR isn't doing its job. A bad FPR can foul your O2 sensors too.

 

[Zinith]

The fuel pressure was checked and was at 29 at idle and 41 at 3k rpm. and once it was turned off it stayed at idle pressure for 15 mins.

Here's the video for today.
Just ordered a new MAF sensor since cleaning it clearly did nothing.



After I finished this I took it for a drive without the MAF sensor connected, and it did alright. Just that it was a little confused because it was going off of default guessing.

 

[Zinith]

So I got that new MAF sensor today and put it on. And its driving just fine now. checked the voltage it was sending back to the computer. And at idle it was .7, which is good news.

Should I be too worried about the gasket that was between the MAF sensor housing and the air box. At first I thought I was going to be able to reuse it. But it ended up coming off broken.

Quick question, what does the hose that runs from the tube (you put oil in) to the big black plastic air thing? For the first year I had it, it wasn't even connected. Once I was trying to figure out what was wrong with it in general, I noticed that it wasn't connected, so I put it back on. But I don't notice any difference at all. And now I'm noticing a line of oil running from it, into the air intake manifold. (inside that big black plastic thing.) What does it even do? And should I be worried about it? Is it supposed to act as a sort of vacuum to keep bubbles out of the oil? Lil confused with it.

 

[Rhett]

Should I be too worried about the gasket that was between the MAF sensor housing and the air box. At first I thought I was going to be able to reuse it. But it ended up coming off broken.

You can buy gasket material at any auto parts store (the cork stuff is not very good -- they should be able to sell you some vinyl-rubberized gasket material in a small roll - cut to fit).

Quick question, what does the hose that runs from the tube (you put oil in) to the big black plastic air thing? For the first year I had it, it wasn't even connected. Once I was trying to figure out what was wrong with it in general, I noticed that it wasn't connected, so I put it back on. But I don't notice any difference at all. And now I'm noticing a line of oil running from it, into the air intake manifold. (inside that big black plastic thing.) What does it even do? And should I be worried about it? Is it supposed to act as a sort of vacuum to keep bubbles out of the oil? Lil confused with it.

That's called the "air breather hose" and it should be connected. Has to do with equalizing crankcase pressure. If you were running with it off then you were getting unmetered air into the engine, which can cause lean condition and other problems.