1996 2.3L with P1131 code

[mrchaotica]

I just bought my truck, went to register it, and found out that the previous owner didn't keep the emissions current (even though he was legally required to do so). you, previous owner! Anyway...

I scanned the truck with my ScanGauge and got three codes: P1131 and, weirdly, 0000 twice. Then I had it scanned again at the auto parts store and got only P1131.

The engine seems fine (given that I have no other I-4 Ranger experience to compare it to). It starts easily, it doesn't stall, it doesn't sound weird, it doesn't smoke, it seems to have about as much power as a 16-year-old, 112 HP engine pushing a truck should have (which is to say, not a whole lot)...

The closest thing to a symptom of a problem -- other than the light -- is that I once noticed the idle alternating up and down by 300 RPM or so at about 1Hz. It's not doing so as I sit in the cab writing this -- it's holding steady at 800 RPMs. I did just clear the code, though...

I've done some reading, and found that the P1131 can be caused by a whole bunch of things, and that an actual bad sensor isn't one of the more likely ones.

I've done the following silly n00bish things:

- the Previous Owner said he previously got it to pass emissions by filling up with a tank of premium. I'd already filled it up with regular by the time I realized the CEL was going to be an immediate problem, so I tried adding a gallon of E85. I cleared the code and drove. The CEL didn't come back for 60 miles or so, but it did come back. Then I tried filling it up with 93 octane (only about 6.5 gallons, since I still had a lot of regular/E85 left in the tank). Cleared code again; CEL came back in about 15 miles.

- I Seafoamed the intake system by removing the hose to the airbox and spraying Seafoam spray into the throttle body (mostly according to the directions, but without using the little straw it comes with or reattaching the airbox during the process). Engine seemed to run the same before and after. I haven't driven enough yet since doing so to check for ODB readiness.

- I know where the PCV valve is supposed to be, but can't figure out how to get at it.

- I've tried to look for leaky vacuum hoses, but I can't tell tell them apart from all the other wires and hoses in the engine bay (on my other car, they are easily identified by the fact that they had a braided fabric covering).

- I've bought a new upstream HO2S (supposedly direct "OEM" replacement, but Bosch instead of Motorcraft ) with the intention of testing the old one and replacing it if it's bad, but the connector is somewhere above the transmission and I can't see what I'm doing to disconnect it.

(I suck so bad at this... in my defense, I bought the truck with the intention of learning to fix it myself, but I didn't expect to need to do so this urgently! I've also fixed stuff on my other cars -- oil change, spark plugs, brake pads, etc. -- but they were hatchbacks and everything was easier to see & reach.)

 

[killj0y]

Have you checked the air filter?

 

[mrchaotica]

Have you checked the air filter?

Yes. It was moderately dirty, and I replaced it. CEL still on.

 

[killj0y]

If it ain't broke...

Seriously though if your not having adverse issues it's gonna be harder to diagnose hmm lemme look up the code

 

[mrchaotica]

If it ain't broke...

I'd be perfectly happy to not fix it, but the State won't let me drive on the roads 'till I do...

 

[JC 97]

from the chilton manual:



Trouble Code: P1131 (2.3L L4 VIN A Auto)
Lack of HO2S-11 Switching, HO2S Signal Low Input


Print this code data


Number of Trips to Set Code: 2

Trouble Code Conditions:
DTC P0300-P0310 not set, engine started, engine running in closed loop, and the PCM detected the HO2S-11 was not switching (i.e., the HO2S-11 indicated a lean A/F mixture).

Possible Causes:
■
Air intake system leaking, vacuum hoses leaking or damaged

■
Air leaks located after the MAF sensor mounting location

■
Base engine mechanical fault (i.e., compression, valve timing)

■
HO2S circuits wet or oily, corroded, or poor terminal contact

■
HO2S signal circuit open, shorted to ground, shorted to power, or the sensor has failed

■
Low fuel pressure or vehicle driven until it was out of fuel

■
Possible air leaks at the PCV valve or at the related

 

[mrchaotica]

JC 97, I appreciate your effort, but I was able to find that part out by searching the forums. The kind of help I need is more basic. Things like:

1. Of those seven possible causes, which is the easiest/most likely and should be investigated first?
2. Are there other symptoms I could look for specifically to help me narrow those possibilities down?
3. How do I check for vacuum leaks (or perhaps "how do I avoid checking my spark plug wires for vacuum leaks, since I'm so unfamiliar with the engine that I can barely tell them apart")? In other words, is there a labeled photo of the engine bay around here somewhere?
4. If I were to just replace all the vacuum hoses as preventative maintenance, what diameter hose would I need, and how many feet of it?
5. Other than the PCV valve and the hoses themselves, are there other weird places a vacuum leak could be? My other car has a vacuum hose inside the ECU, for example.
6. How do I test my oxygen sensor? Do I stick my multimeter in the plug? Do I leave it connected, or disconnect it before testing?
7. Etc...?

I apologize for being so pathetic, but please humor me...!

 

[JC 97]

This is basic mechanical knowledge.You should probably find someone who has knowledge show you around the engine bay.What you are doing is like saying" hey I want to try my own surgery but I know nothing about being a doctor.How do I do it? Where exactly is my spleen and what does it do?" I applaud your effort to learn.I would get a manual and start reading.Learn as much as you can from the book.Good luck.

 

[mrchaotica]

You should probably find someone who has knowledge show you around the engine bay.

No kidding; why did you think I was asking you?!

Apparently the fine folks here at "The Ranger Station" either know nothing about Rangers or are willfully unhelpful. I guess I need to go find a Ranger forum that doesn't suck...

By the way, I am planning on getting a manual. I asked for advice about which one is best in my other thread and have so far received a whopping zero replies.

 

[adsm08]

Despite what you have found that says the sensor isn't high on the suspect list, given the age of the truck it would be FIRST on my list.

The plug can be a bugger to get at from the ground, but you may be able to reach down from the top and grab it given that it's only a 4-cly engine.

 

[mrchaotica]

Despite what you have found that says the sensor isn't high on the suspect list, given the age of the truck it would be FIRST on my list.

The plug can be a bugger to get at from the ground, but you may be able to reach down from the top and grab it given that it's only a 4-cly engine.

Thank you; I hadn't thought to try reaching down from the top.

 

[JC 97]

Apparently the fine folks here at "The Ranger Station" either know nothing about Rangers or are willfully unhelpful. I guess I need to go find a Ranger forum that doesn't suck...

By the way, I am planning on getting a manual.

The folks here do know alot about rangers,but damn put some effort into helping yourself.You should of got a manual to start with.You yourself said "I don't know the differance between a plug wire or a vacuum hose." So over an internet forum we are supposed to hold your hand and walk you threw everything? If not you get offended? Learn the basics. I posted what to test but you don't know how to test anything.So good luck.

 

[mrchaotica]

The folks here do know alot about rangers,but damn put some effort into helping yourself.You should of got a manual to start with.

Which one? For the VWs I'm familiar with, there's huge difference in quality between different manuals (and both the Haynes and Chilton are crap).

You yourself said "I don't know the differance between a plug wire or a vacuum hose."

First, that's not an accurate quote. Second, ever hear of a concept called "exaggeration?!" All I was looking for was a labeled photo of the engine; I just tried to ask in a funny way. Clearly, that was a bad idea.

Just for the record, I can tell which things are spark plug wires! (In fairness, however, both the plug wires and the vacuum hoses are apparently covered in black rubber and are similar in diameter... my VW's vacuum hoses are braided fabric and it doesn't have spark plug wires.)

 

[adsm08]

Which one? For the VWs I'm familiar with, there's huge difference in quality between different manuals (and both the Haynes and Chilton are crap).

I would advise you troll Amazon and Ebay and try to find the Ford workshop manual, EVTM, and PC/ED books.

 

[mrchaotica]

Despite what you have found that says the sensor isn't high on the suspect list, given the age of the truck it would be FIRST on my list.

The plug can be a bugger to get at from the ground, but you may be able to reach down from the top and grab it given that it's only a 4-cly engine.

I managed to get the O2 sensor changed. Installed, the plug is pretty inaccessible because it hangs above the transmission. Apparently, the trick is to unscrew the sensor from the exhaust first and pull it up over the transmission so that it hangs down on the driver's side. Then the plug becomes easy to reach.

I've driven the truck about 100 miles this afternoon/evening since replacing the sensor. The good news is, the CEL hasn't come back on. The bad news is, I keep getting "not ready" when I scan it. Do I need to just keep driving around some more, or is there something wrong?