Explorer Swaped suddenly has no power, had to limp home

[71BroncoSport]

I've been fighting a problem where it runs rough between 1k and 2k rpm's. Once over 2k, it runs strong. I figured it was running too rich. I hooked a Scan Gauge into the ODBII port, and it's NOT throwing a CEL, but in the history it had a P0102 code suggesting "Insufficient air flor through the air filter". I have a new K+N and it's still clean. So I put a new MAF housing and meter on and instantly it is running so much better. However, I can still feel a SMALL hint of it chocking out, but can definitely live with it.

A few days ago I was heading out on a big 75 mile trip and I could tell the engine was struggling, specifically up a hill. I made it up, but could tell something wasn't quite right. When I merged onto the highway, I couldn't get over 40mph and it quickly started going slower and slower. I pulled off and checked the Scan Gauge. Now it had either a P1151 or P1152. I don't exactly remember and it's not in the history anymore. This is suggesting something with the O2 sensors, but I'm guessing that's not the source of the problem.

Pretty much every sensor is new on this thing. I checked to make sure the O2 wiring wasn't burned and everything was fine.

I start to limp home and I can't go over 2,500 rpm in 1st. Running like garbage. Then, like someone flipped a switch, it runs strong. I shift into 2nd and it's strong. I'm thinking I can merge on, but eventually it runs bad again. It did that 2 more times before I was able to limp home.

Any thoughts? I'm going to try and program this scan gauge to look at the fuel pressure. I also ordered a Idle Air Control valve as a shot in the dark, but I think the one on there is new within the year.

Is it possible to foul up O2 sensors in a five hundred miles??

Any input would be appreciated!!

 

[DirtDonk]

A part that is “new“ no longer guarantees that that part is any good.
So don’t assume anything just yet. And don’t throw away the old ones yet either!
I don’t see how the idle air control can cause this kind of a problem personally. But I’ve been wrong on EFI stuff before.
The air filter being new, you didn’t add oil to it by any chance, did you?
And generally speaking, they don’t have so much oil on them from the factory that it hurts the MAF. But I believe I have heard of oil, the air filters, causing this kind of a problem years ago. It’s not a common issue, but I seem to remember it coming up now, and then Wayback win.
But if it did, and that’s what caused the previous MAF to act up, it could also have messed up the O2 sensors.
if you have O2 sensor codes, I would personally replace them. Even though I hate to change parts out as a test. And I hate recommending it even more! But I’m not sure of the proper testing procedures for O2 sensors. If there are any.
I would also keep the old ones just in case.
If it turns out not to be the problem, you will eventually use them down the road anyway.

Good luck. Curious what the EFI experts say.

 

[71BroncoSport]

A part that is “new“ no longer guarantees that that part is any good.
So don’t assume anything just yet. And don’t throw away the old ones yet either!
I don’t see how the idle air control can cause this kind of a problem personally. But I’ve been wrong on EFI stuff before.

I 100% agree, but I saw a thread that someone said this fixed a similar problem and it was only $20 I'm not expecting this to work.

The air filter being new, you didn’t add oil to it by any chance, did you?
And generally speaking, they don’t have so much oil on them from the factory that it hurts the MAF. But I believe I have heard of oil, the air filters, causing this kind of a problem years ago. It’s not a common issue, but I seem to remember it coming up now, and then Wayback win.
But if it did, and that’s what caused the previous MAF to act up, it could also have messed up the O2 sensors.

Interesting... I didn't add any oil, but I bought a cleaning/oil kit but haven't used it yet. It looks dry to my naked eye, but I'm sure that's not a good measure.

if you have O2 sensor codes, I would personally replace them. Even though I hate to change parts out as a test. And I hate recommending it even more! But I’m not sure of the proper testing procedures for O2 sensors. If there are any.
I would also keep the old ones just in case.
If it turns out not to be the problem, you will eventually use them down the road anyway.

I'm at the point where I'll throw $$$ at it in hopes that it works. I am a novice at this EFI stuff, but I don't think we can measure the voltage output from the O2 sensors with this PCM version. I heard 2003+ can do that, but that's just from reading the interwebs. Replacing both O2 sensors will be happening in the next few days.

When I pushed together the Driver side O2 plug, it went in a tiny bit, but I can't imagine it was enough to make a difference. It seemed all within the push pin area, if that makes any sense.

Good luck. Curious what the EFI experts say.

I really appreciate your feedback, as always.

 

[Timmy390]

P0102 is mass air sensor circuit low

Make sure you have the correct sensor. Check for bad connections. Clean it with proper mass air sensor cleaner.

Tim

 

[73azbronco]

Everyone here is going get tired of me asking, what is your fuel pressure during these events?

 

[71BroncoSport]

I pulled the O2 sensors and the drivers side was caked in carbon. Passenger side was fine.

I cleaned it and it's still running bad, but only when warmed up, which makes me think it's a faulty O2 sensor.

I measured the volts from the O2 sensors and the passenger side (The good side) is .99 volts and the Drivers side (Bad side) only got up to .6 volts

To me, those are good O2 sensors. Something is making the drivers side run rich.

I may just buy a new O2 sensor anyway.

Thoughts?

 

[71BroncoSport]

Everyone here is going get tired of me asking, what is your fuel pressure during these events?

I can't tell you that. I read up on how to make the scan gauge show fuel pressure through entering codes, but I haven't tried it yet.

I think only the drivers side is running rich based on what my O2 sensors look like, so my guess is my fuel pressure is good. But that's just my guess.

 

[73azbronco]

You may have to much pressure, fuel pressure is step one in diagnosing any efi issue, its a cheap step.

 

[904Bronco]

Fuel pressure, confirm what it is... Early or late Explorer EFI? 19 lbs orange injectors or white 17 lbs injectors
K and N oiled filters are JUNK. My Humble Opinion based on MAF issues years ago with Fox Body Mustangs.
Buy a new O2 sensor for the one that was carboned up. Clean MAF with EFI cleaner, don't soak the snot out of it. Don't put the KN filter back on.
Disconnect the battery for 20 mins to start fresh.
Who did the harness and ECU programing?

 

[71BroncoSport]

Fuel pressure, confirm what it is... Early or late Explorer EFI? 19 lbs orange injectors or white 17 lbs injectors
K and N oiled filters are JUNK. My Humble Opinion based on MAF issues years ago with Fox Body Mustangs.
Buy a new O2 sensor for the one that was carboned up. Clean MAF with EFI cleaner, don't soak the snot out of it. Don't put the KN filter back on.
Disconnect the battery for 20 mins to start fresh.
Who did the harness and ECU programing?

What's the best way to put a fuel pressure gauge on it? The one I got with the fuel lines didn't fit. Can I put one on rail?

It's a 1996 motor, completely stock so it has the orange injectors. They've been sent off to have them tested and cleaned already.

I hear ya on the K+N, but I can't imagine it would make it do all of this.

The MAP is brand new a week ago. A new O2 sensor should be here in a day. If that doesn't fix it, I'm putting the old MAF on.

10-4 on the battery disconnect.

Thanks

 

[73azbronco]

Oil filters will gum up a MAF sensor. They are a filter designed for carbs.

You can get a fuel press gauge for $15 at HF. There should be a schrader valve on the fuel rail. Be careful, this is 60-90psi fuel, very explosive combination, i never did this checking inside.

 

[EPB72]

Fuel pressure, confirm what it is... Early or late Explorer EFI? 19 lbs orange injectors or white 17 lbs injectors
K and N oiled filters are JUNK. My Humble Opinion based on MAF issues years ago with Fox Body Mustangs.
Buy a new O2 sensor for the one that was carboned up. Clean MAF with EFI cleaner, don't soak the snot out of it. Don't put the KN filter back on.
Disconnect the battery for 20 mins to start fresh.
Who did the harness and ECU programing?

this///\\\............also are you able to see Fuel Trim data on your scan tool.. .normal o2 operation switching voltage about .180-.800v for closed loop ..

 

[Timmy390]

I've been running an oiless AME filter for 5 plus years. No issues.........

Tim

 

[71BroncoSport]

I swear there's always a "But..." with this truck.

I put the new O2 sensor on and it's running sooo good. Never ran better.

However... I noticed that the exhaust bolts connecting the O2 flange to the header was a little loose on both sides, but more loose on the Driver side, the side I was having troubles with.

So I'll never know if it was a bad O2 sensor or an exhaust leak. I will say I never heard an exhaust leak, so not sure if it was enough to foul up the O2 reading or not.

I thank everyone that took the time to help me out.

-Dave

 

[DirtDonk]

If there’s even a small leak close to the O2 sensor, I would say there’s a distinct possibility that it was skewing its readings.

 

[71BroncoSport]

If there’s even a small leak close to the O2 sensor, I would say there’s a distinct possibility that it was skewing its readings.

That's what I'm thinking. User error

 

[904Bronco]

We all learn from our mistakes/experiences and from others who are willing (brave enough) to share theirs. With any project there is a learning curve, in time you will become somewhat of an expert, just remember to share your knowledge with others... Glad you were able get your Bronco back on the road!

 

[garberz]

If there’s even a small leak close to the O2 sensor, I would say there’s a distinct possibility that it was skewing its readings.

Yup, the possibility is that it’ll suck in air and create a false lean condition for the O2 sensor to read, resulting in an overly rich mixture that will kill the life of the sensor.

Mark

 

[71BroncoSport]

I spoke too soon. Still running rough, but not as bad as before. I'm going to look for more exhaust leaks tomorrow

 

[71BroncoSport]

I've been replacing parts (Idle air valve, O2's again) and it's to the point where it's slightly driveable, but still running rich.

When I go WOT (Open loop) it runs good. I bought starter spray and I can't find any vacuum leaks.

Question to the group: Could my O2 sensors be too close to the engine? They're right after the shorty header.

I'm thinking of having an exhaust shop weld in some bungs about a foot back.

Thoughts? I'm at a loss here. Thanks