Lean codes after fixes

[Bradley0770]

2003 4.6L XLT
I recently turned 18 and purchased my explorer for a really good price, only problem I noticed at the time was a faulty alternator, I replaced that along with spark plugs. Soon after, I discovered a coolant leak. Took me a good while to discover exactly what and where it is. I bought a new intake manifold and swapped it out. Fixed the leak. After that, I've been getting lean codes on a small scanner I bought. I lived with it for a while while trying to figure it out. I had a coolant hose pop off at one point, I put it back on and put a hose clamp on it instead. The rebuilt alternator failed so then I but a new one instead and put it in. I blew smoke through the vacuum system and saw smoke coming out between the egr and throttle body. I bought a metal gasket, but it didn't solve any codes. I decided to just go for it and swap the oxygen sensors. Was a hassle but I got at 4 swapped out for new ones. Sadly, not a thing changed. Also swapped the brake pads. The car drives, symptoms are horrible gas mileage, rough idle after 5 minutes warming up, and only recently, the car jerks back and forth as if the throttle was being tapped, rarely when holding a medium speed.

Current codes I have right now:
P0059
H02s heater resistance ban 2 sensor 1

P0135
O2 sensor heater circuit ban 1 sensor 1

P0155
O2 sensor heater circuit ban 2 sensor 1

P0171
System too lean bank 1

P2197
O2 sensor signal biased/stuck lean bank 2 sensor 1

I'm speculating that the coolant explosion cause something to go wrong in the wiring harness or there is still a vacuum leak.

If anyone has ideas, I would be very happy to discuss any solutions!

 

[Davies0202]

2003 4.6L XLT
I recently turned 18 and purchased my explorer for a really good price, only problem I noticed at the time was a faulty alternator, I replaced that along with spark plugs. Soon after, I discovered a coolant leak. Took me a good while to discover exactly what and where it is. I bought a new intake manifold and swapped it out. Fixed the leak. After that, I've been getting lean codes on a small scanner I bought. I lived with it for a while while trying to figure it out. I had a coolant hose pop off at one point, I put it back on and put a hose clamp on it instead. The rebuilt alternator failed so then I but a new one instead and put it in. I blew smoke through the vacuum system and saw smoke coming out between the egr and throttle body. I bought a metal gasket, but it didn't solve any codes. I decided to just go for it and swap the oxygen sensors. Was a hassle but I got at 4 swapped out for new ones. Sadly, not a thing changed. Also swapped the brake pads. The car drives, symptoms are horrible gas mileage, rough idle after 5 minutes warming up, and only recently, the car jerks back and forth as if the throttle was being tapped, rarely when holding a medium speed.

Current codes I have right now:
P0059
H02s heater resistance ban 2 sensor 1

P0135
O2 sensor heater circuit ban 1 sensor 1

P0155
O2 sensor heater circuit ban 2 sensor 1

P0171
System too lean bank 1

P2197
O2 sensor signal biased/stuck lean bank 2 sensor 1

I'm speculating that the coolant explosion cause something to go wrong in the wiring harness or there is still a vacuum leak.

If anyone has ideas, I would be very happy to discuss any solutions!

Did you entirely reset the system after you installed all the new parts to allow it to adjust to everything you changed?

 

[Hank102938]

Edit: Davies0202 has a good point, reset would be the place to start.

—

You might try cleaning the mass airflow sensor with some electronic parts cleaner if you haven’t already. Double check the rubber intake tube and smaller hoses on it between the MAF sensor and throttle body for leaks.

However, if either those were the issue I think you’d be getting a bank 2 lean as well.

If it started immediately after the intake swap it could be a bad gasket or it’s improperly seated.

I wouldn’t rule out an electrical issue, esp since some of those codes could arise from a bad connections, but those items above are more likely IMO.

By the way, where was your intake leaking coolant? My 03 V8 is currently leaking somewhere...

 

[Bradley0770]

Did you entirely reset the system after you installed all the new parts to allow it to adjust to everything you changed?

By reset the system, do you mean resetting the codes? There are about 7 codes that pop up awhile after I clear them. I've also unplugged the battery for awhile while doing the alternator but I can try to do it again tomorrow.

 

[Bradley0770]

Edit: Davies0202 has a good point, reset would be the place to start.

—

You might try cleaning the mass airflow sensor with some electronic parts cleaner if you haven’t already. Double check the rubber intake tube and smaller hoses on it between the MAF sensor and throttle body for leaks.

However, if either those were the issue I think you’d be getting a bank 2 lean as well.

If it started immediately after the intake swap it could be a bad gasket or it’s improperly seated.

I wouldn’t rule out an electrical issue, esp since some of those codes could arise from a bad connections, but those items above are more likely IMO.

By the way, where was your intake leaking coolant? My 03 V8 is currently leaking somewhere...

I'll pickup some cleaner for sure! How should I go about cleaning the tubes? I did take a look at the MAF sensor and it looked pretty good. When I did the intake swap, the intake came with pre installed gaskets in the actual intake, but I bought the full gaskets and put the on anyway. I went back in a bit later and took em out to see if they were actually causing problem, but nothing changed when I did.

The really common coolant leak on this generation ford explorers is located in the bottom of the thermostat housing, just to the right of the alternator. It's a metal houaing on top of the plastic intake. Just under the metal housing is plastic which is the intake manifold, that's where mine cracked at. But it can really crack anywhere on the coolant line on the Intake manifold. I attached an image showing where mine did. (This was my process picture for when I took that new blue gasket out)

I'll try some of those fixes when I get the cleaner! If you or anyone else has any more ideas, that'd be great! Thankyou so much!

 

[Explorer75]

Which oxygen sensors did you buy? OEM or aftermarket? are 100% sure they are the ones for this engine?

For lean codes you only need the front sensors (pre cat converter) to be working good. The back sensors are just catalytic converter monitors.

 

[Hank102938]

I'll pickup some cleaner for sure! How should I go about cleaning the tubes? I did take a look at the MAF sensor and it looked pretty good. When I did the intake swap, the intake came with pre installed gaskets in the actual intake, but I bought the full gaskets and put the on anyway. I went back in a bit later and took em out to see if they were actually causing problem, but nothing changed when I did.

The really common coolant leak on this generation ford explorers is located in the bottom of the thermostat housing, just to the right of the alternator. It's a metal houaing on top of the plastic intake. Just under the metal housing is plastic which is the intake manifold, that's where mine cracked at. But it can really crack anywhere on the coolant line on the Intake manifold. I attached an image showing where mine did. (This was my process picture for when I took that new blue gasket out)

I'll try some of those fixes when I get the cleaner! If you or anyone else has any more ideas, that'd be great! Thankyou so much!

​

​

I usually unbolt the MAF housing from the air box and just spray the cleaner at the sensor in the direction of air flow from 4-5 inches away for a second or so. Let it dry, repeat, let it dry, and reassemble. A “dirty” MAF sensor may simply be a bit of dust, hard to see, no visible dirt, but the cleaner blows it away safely.

I wasn’t clear on the tubes, don’t clean them, I was suggesting you check for cracks in the rubber that might open up and allow air in under vacuum but didn’t show up in your smoke test.

As long as you didn’t double up the gaskets and the ones you used mated with the manifold properly. I haven’t replaced an intake manifold on the ex before so I don’t have any other suggestions there. But looks like I might be doing that soon to solve my coolant leak. Thanks for the picture.

 

[Bradley0770]

I'll pickup some cleaner for sure! How should I go about cleaning the tubes? I did take a look at the MAF sensor and it looked pretty good. When I did the intake swap, the intake came with pre installed gaskets in the actual intake, but I bought the full gaskets and put the on anyway. I went back in a bit later and took em out to see if they were actually causing problem, but nothing changed when I did.

The really common coolant leak on this generation ford explorers is located in the bottom of the thermostat housing, just to the right of the alternator. It's a metal houaing on top of the plastic intake. Just under the metal housing is plastic which is the intake manifold, that's where mine cracked at. But it can really crack anywhere on the coolant line on the Intake manifold. I attached an image showing where mine did. (This was my process picture for when I took that new blue gasket out)

I'll try some of those fixes when I get the cleaner! If you or anyone else has any more ideas, that'd be great! Thankyou so much!

View attachment 327461

​

Just too add on real quick, the MAF sensor reads about .80lb/min at idle and the rpm is between 650 and 700

Which oxygen sensors did you buy? OEM or aftermarket? are 100% sure they are the ones for this engine?

For lean codes you only need the front sensors (pre cat converter) to be working good. The back sensors are just catalytic converter monitors.

I bought aftermarket ones and replaced all four, the performance of the car went a bit up as the idle became a tad bit smoother and I think the fuel efficiency also went up some. But nothing too drastic.

 

[Bradley0770]

I usually unbolt the MAF housing from the air box and just spray the cleaner at the sensor in the direction of air flow from 4-5 inches away for a second or so. Let it dry, repeat, let it dry, and reassemble. A “dirty” MAF sensor may simply be a bit of dust, hard to see, no visible dirt, but the cleaner blows it away safely.

I wasn’t clear on the tubes, don’t clean them, I was suggesting you check for cracks in the rubber that might open up and allow air in under vacuum but didn’t show up in your smoke test.

As long as you didn’t double up the gaskets and the ones you used mated with the manifold properly. I haven’t replaced an intake manifold on the ex before so I don’t have any other suggestions there. But looks like I might be doing that soon to solve my coolant leak. Thanks for the picture.

Thankyou! It is raining today so I'll start to try new things tomorrow. I will still be open to any ideas if anyone has had experience with this type of situation, thankyou so much!

 

[fireftr]

Edit: Davies0202 has a good point, reset would be the place to start.

—

You might try cleaning the mass airflow sensor with some electronic parts cleaner if you haven’t already. Double check the rubber intake tube and smaller hoses on it between the MAF sensor and throttle body for leaks.

However, if either those were the issue I think you’d be getting a bank 2 lean as well.

If it started immediately after the intake swap it could be a bad gasket or it’s improperly seated.

I wouldn’t rule out an electrical issue, esp since some of those codes could arise from a bad connections, but those items above are more likely IMO.

By the way, where was your intake leaking coolant? My 03 V8 is currently leaking somewhere...

Replying to your intake leak, they are plastic, and are prone to crack and leak around the thermostat housing. I found one “used” on Amazon for around $100. Took a chance on ordering a “used” one, but figured it was worth the savings, and Amazon has a no-hassle return policy. It was never used, came in the original plastic bag, and the instructions! Apparently, it was ordered, not used, and returned for whatever reason! Couldn’t match that price anywhere!

 

[Bradley0770]

2003 4.6L XLT
I recently turned 18 and purchased my explorer for a really good price, only problem I noticed at the time was a faulty alternator, I replaced that along with spark plugs. Soon after, I discovered a coolant leak. Took me a good while to discover exactly what and where it is. I bought a new intake manifold and swapped it out. Fixed the leak. After that, I've been getting lean codes on a small scanner I bought. I lived with it for a while while trying to figure it out. I had a coolant hose pop off at one point, I put it back on and put a hose clamp on it instead. The rebuilt alternator failed so then I but a new one instead and put it in. I blew smoke through the vacuum system and saw smoke coming out between the egr and throttle body. I bought a metal gasket, but it didn't solve any codes. I decided to just go for it and swap the oxygen sensors. Was a hassle but I got at 4 swapped out for new ones. Sadly, not a thing changed. Also swapped the brake pads. The car drives, symptoms are horrible gas mileage, rough idle after 5 minutes warming up, and only recently, the car jerks back and forth as if the throttle was being tapped, rarely when holding a medium speed.

Current codes I have right now:
P0059
H02s heater resistance ban 2 sensor 1

P0135
O2 sensor heater circuit ban 1 sensor 1

P0155
O2 sensor heater circuit ban 2 sensor 1

P0171
System too lean bank 1

P2197
O2 sensor signal biased/stuck lean bank 2 sensor 1

I'm speculating that the coolant explosion cause something to go wrong in the wiring harness or there is still a vacuum leak.

If anyone has ideas, I would be very happy to discuss any solutions!

So after a long time of figuring it out, I finally got my service engine light to stay dormant. I went to a junkyard and picked up a wiring harness and an original intake manifold. The wiring harness just had one incompatibility which was the egr sensor so I went to AutoZone and pick up one that would be the right socket for the harness. The OEM manifold I got wasn't cracked but it looks like it had maintenance to prevent it from happening. Put it all together and have never had a problem since. Also cut a hole in the floor to replace the fuel pump and everything feels in pretty good order! Thankyou to all that helped me with this process! Hope this can help some in the future.