Missing some ooomphhhh!

[Turdle]

Ok, take a look at this, is this anything like yours?

 

[Lechuga]

Sort of but not really. I recognize that to be the exhaust for an OHV engine.

This is a picture of the underside:
https://plus.google.com/photos/1164...95993389762929/5692258462298426882?banner=pwa

You will see a big catalytic converter coming from the driver side located under the transmission, and to the left of it (on the passenger side) is the passenger side catalytic converter. Each side has its own pipe into the muffler at the back and a single tail pipe. Upstream from each converter there is 1 O2 sensor (which as I've already explained are connected in the engine bay area behind cylinders #3 and #6), and zero (0) O2 sensors downstream.

Europe has very strong emission control regulations (similar to California), so I am not sure if this is the standard exhaust layout for an SOHC engine or if this is a special setup for Europe. Also I don't have access to other SOHC Ex to compare with (I really wish I did).

I don't really like the location of the driver side converter as it seems rather unprotected when offroading and dangerously close to the transmission sump. Also I have the strange suspicion this might be an aftermarket fix, so I cannot be sure if any part of it is correct.

 

[Lechuga]

Please help me

Trying to find out the source of the P0720, I noticed two things:

1. A long rubber hose coming out of the front of the tcase and going nowhere (see image item circled in red: https://picasaweb.google.com/116437049944288200919/98FordExplorerSOHC#5692618849774785746). What is this hose and where should it go?

2. At the top end of the tcase next to the rear shaft, I found this little thing with apparently no purpose but to leak a little oil (see image, item circled in red: https://picasaweb.google.com/116437049944288200919/98FordExplorerSOHC#5692619200458581922). I think it might be the OSS, but couldn't find any wires to connect to it. Can anybody shed some light?

I googled for both but couldn't find anything relevant. Please help. I am lost and stretching my knowledge here and have no other similar car to look at to compare.

 

[gmanpaint]

A rubber hose on the T-case is just the breather tube.

Your 98 has the VSS in the rear differential. My guess is someone replaced your stock T-case with a older year case such as a 97 with the same front output as the 98. 95-97 T-case had the gear driven VSS in them. There is no wire harness to connect to it on yours. If there was, it would be part of the trans harness.

Honestly, the 98 model has been gone over pretty good on this forum in all aspects. Just spend some more time reading, searching, & learning. You will find most everything you need

 

[Lechuga]

Honestly, the 98 model has been gone over pretty good on this forum in all aspects. Just spend some more time reading, searching, & learning. You will find most everything you need

Yes, and on the whole this has been the case. However I have yet to find a decent underbody shot that shows me:
1. The exhaust layout
2. Transmission and tcase layout and connections

so that I can compare. TIA

 

[Lechuga]

I removed the center console (I have the short version) and cut open the carpet to remove the panel above the transmission and this is what I saw:
https://picasaweb.google.com/116437049944288200919/98FordExplorerSOHC#5692714901502046130

No wiring loom for the O2 sensors... Sorry Turdle

And no hint as to the location of an OSS (for which I got a P0720), which I found in other posts to be at the rear of the transmission case.

 

[gmanpaint]

The rear axle has the VSS/ABS sensor. It does double duty. You will find it on the top of the rear differential. Remove it, clean it, replace it. If your still getting the code, buy a new one.

VSS/OSS on the transmissions are found in 2wd only vehicles, and that is for 95-97 only I believe. You have a tone ring in the axle that the sensor reads, and the ECM reads that signal then converts it for your speedometer/odometer.

 

[Lechuga]

Understood! Thanks gmanpaint

Going to get that done straight away

 

[rickybobby]

on my 97 there is a seperate OSS on the transmission, on the driver's side just before the trnasfer case, its a tiny connector that will be hard to see if the transmission has a bunch of dirt built up on it. The 99 ranger also had this sensor (my trans came from one) but i cant say 100% sure that the 98 explorer had it. the sensor im referring to is for trans controls only, it doesnt control the speedo or cruise control. that is why an RBV will shift through all of the gears without a vss signal. not sure this edit applies to your situation, but i thought i would add it for any future users who read through this thread looking for an answer to a similar problem.

 

[Lechuga]

Update time. I've replaced the O2 sensor on the passenger side (it was missing 2 pins and couldn't have worked in any way) and now the car seems to run smoother (wonder if it will improve my MPG?). Still can't get any live O2 or fuel trim data (or speed for that matter) from the OBDII connector. I've read elsewhere this may be because Ford in 98 didn't fully comply with the OBDII specifications and I should be able to find this data in the extended PIDs (apparently ScannerXL software has an enhanced module for Fords that can read this data, so there may be others). The other option would be a PCM SW upgrade, but here in Europe coaxing Ford for that is like asking for lemons from an apple tree.

Any ideas? TIA
Chris

 

[ScottRT]

Some of the eagerness of your newer truck to downshift when ascending a grade is due to the fact it is a 5 speed where your older Explorer had a 4 speed. The 5 speed is designed to drop out of OD with less load than the 4 speed.

Scott T.

 

[Lechuga]

Thanks Scott, however I feel the car is just simply underpowered. Going up even the slightest hint of a hill causes it to struggle, quickly losing speed and popping out of O/D (all with cruise control on). On heavier inclines, sometimes O/D will disengage itself entirely (which frightened me the first time as I thought it was going to leave me stranded in the middle of nowhere). I think the catalytic converters are done as the exhaust smells of sulphur and they may be creating back pressure, which in turn is reducing power.

Next on my list is 2 cats (meow-purr)

 

[rickybobby]

before you go out and spend a bunch of money on the cats, cut a slit in the pipe (about halfway through) with a sawzall or hack saw, then drive and see if the problem improves or goes away all together. the 2nd step if the cats are bad is to figure out why. cats dont typicly fail with age, at some point it was running too rich or too lean, which causes the cats to get hot enough to melt or break down. the original cause may have been repaired previously, but you want to be sure that your investment isnt gonna be wasted

 

[rickybobby]

http://www.explorerforum.com/forums//showthread.php?t=177366
Look at this thread, item 15 in the pic on the 2nd post is the OSS. from my reading, a faulty oss will cause odd shift points, and could cause it to seem like there is a lack of power due to it being in the wrong gear. a quick search of ebay may find you one, but if you go to the parts store or dealer it will be special order

 

[Lechuga]

Ricky that is sound advice. I know that bank1 has been running rich as the O2 sensor was broken (missing 1 pin for the heater wire and 1 pin for voltage output) so I'm guessing that the cat on bank1 is pretty much done. The cat on bank2 is all dented and things rattle inside...

As for the OSS in your second post: my Ex doesn't have one. Gmanpaint suggested that only 2wd had those and I should look at the VSS on the rear diff.

EDIT: After replacing the O2 sensors I have noticed an MPG improvement of 1-2 MPG more

 

[Lechuga]

UPDATE: I replaced the OSS/ABS sensor on the rear diff but I've still got the same P0720 code. I've checked the wiring into the sensor and all the along the fuel tank until it goes up into the body under the driver seat (the wiring looked just fine). I also removed the radio (I think that's where the ECU is) and pushed every connector I could find in the space into its socket on anything that looked like an ECU. Is there anything I am missing? What else could it be?

TIA
Chris

 

[drbenz]

The computer behind the radio is the gem module/body control module, the ecm you want plugs up under the hood at the firewall. Since I am not sure if the EOBDII spec is exactly the same as OBDII there is some room for guessing but my recommendation would be to try another scanner to see if it would give you more info. If you don't have access to one you might try asking a nearby shop to try theirs, sometimes us techs are curious enough to help just to see if there is a difference. On another note, while this is a long shot, you might try disconnecting the battery cable for ten minutes and reconnect to reboot the system to see if it will make any difference in the way the engine runs (won't help your scanner issues though).

 

[Lechuga]

Ok. So then I am lost. Whereabouts is the ECM under the hood and how do I get to it? EDIT: Found it! Going to push all connectors and make sure they are fitting snugly and clean, both in the Firewall top center towards the passenger side and behind the cowl in the passenger footwell. We'll see if it makes any difference and post back.

It is definitely ODB2 and I always disconnect the battery everytime I'm about to do any electrical work on the car. The only DTC I have is the P0720. Nothing else. Other workshop scanners have provided the same result in the recent past.

Mechanically I noticed that 4x4 is permanently engaged, and so is the torque lock-up.

TIA,
Chris

 

[Lechuga]

Definitely all connectors are snugly in their sockets. I am starting to think of refurbishing the rear axle differential. Am I barking up the wrong tree? Should I try with another sensor? Are these known to go duff? How can I test them?

 

[SB98UKexplorer]

its possible the egr is staying open during full throttle or open too much during cruise speeds. you can try blocking the egr and taking it for test run to see if it improves.