Ok good feedback on the code reader. By all means use your Dads ELM scan tool & display device, or load FORScan on your viewing device choice & have it scan for codes, capture a snapshot of what's going on when connected while being driven & you cause it to misfire, as it can access All the vehicles computer / controllers PID's, so can take a in depth look at what's going on when the misfire happens.
Seeing as how we think rodents may have been munching on under hood things, inspect the ignition components closely for visual damage, especially if you get a wet down test arcs & sparks light show.
FORScan can also access & display mfgr enhanced codes & display a wealth of live data PID's of choice on its dashboard, so can help Way more than a code reader

 

Ok, that's a good idea. I'll let you know what I find out.

 

I've looked at a lot of pictures of the charcoal/fuel vapor canister online, and I don't think the gnawing makes it defective. As far as I can tell, the two holes on top are supposed to be vents, and they've just lost a bit of their "chimneys".

For now, I think I'm going to cross that off the list of possible problems.

 

Well, I have an update, but I'm not sure it sheds light on anything.
Yesterday afternoon, I took it for a drive with the ForScan attached. I got some beautiful misfires, but because I was by myself, I couldn't really monitor the gauges, and the data stream to the iPad shut off, so I wasn't really able to analyze the circumstances. All I could tell was that I had 534 misfires.

Last evening, I went for another ride, with my dad along to monitor the gauges. Going up a steep hill near my house on a 40mph road in fourth, I got it to misfire, and according to ForScan, it was misfiring on 3/4 of the cylinders. At the top of the hill though, there's a stoplight, so we didn't get any codes for the misfires.

Once we got on the freeway, with the ForScan hooked up and a focused observer, Murphy's Law kicked in. I drove that thing between 60 and 70 mph over at least 30 miles of freeway. We went to all the hills near our house, most of which I've misfired on before. Nothing. It purred like a kitten. So today I'm going to take it out again for another long drive and see if I can coax some misfires out of it when I have the ForScan.

Also, when we got back I did the wetdown test. The engine was hot, so I didn't lift the coil packs up, but I tried to spray under them, and didn't get any misfires or see any arcing.

All I've got for a theory is that something in the engine misfires only when it's cold - perhaps a small leak that seals up as the hot metal expands? But I know there are times when it's misfired with the engine warm, so that theory doesn't really work.

 

Ok good feedback on the FORScan test drive & hot wet-down test afterward, so lets think about this some more.
Might be insightful to know what parameters you had the FORScan dashboard set up to display. Last time I used mine it could display 19 parameters at once if needed.
Had you performed the battery disconnect to wipe the old fuel trim tables before the test drive???
When you got to the top of the hill at the stoplight after the misfires, what did the short & long term fuel trim numbers look like???
Could you feel the misfires as they happened & if so, did you hear any engine noise, or electrical noise in the radio speakers, or notice any dash, or other lights flickering at the time of the misfire/s?

 

I'll list the parameters I use today when I'm done. I did not wipe the fuel tables before the test drive.
I was not monitoring trim numbers. I'll do that today.
I could feel the misfires. There is a noticeable difference in engine sound. I didn't notice any lights flickering, and my radio was not on, so I didn't hear anything from it. Sometimes when it's under load, I can hear a crackling noise that to me sounds like it's behind the instrument cluster. However, my dad thought it might be unburned gas igniting in the catalytic convertor, so maybe it sounded like it was coming from under him from the passenger seat? It will happen without misfires, and sometimes it misfires without crackling, but that's one noise I have noticed.

 

When you asked, when did the previous owner say the timing belt was replaced???

 

Well... I don’t think I asked. The guy I bought it from only had it for about 6 months or so.

I took it it for another long drive today with some nice big hills, and it handled the hills fine, but on a slight incline, it misfired on cylinder 2 but not enough to trip a code. According to ForScan, it was about 60 misfires. I slacked off a bit, and it went away.

ForScan has two gauges both called Injector Fault. One of them says I have a fault, the other says I’m fine. None of the individual injector fault gauges say I have a fault, and the overall fault gauge is on all the time, not just when I have a misfire. Possibly it’s looking for a second bank I don’t have.

I did did not clear the fuel tables for this trip. My long term fuel trims were about 20% when I started it up, but dropped down to about 3% on the freeway.

I recorded the data. If you want, I can try and post it or pm you with it.

Thank you for your continued advice! It’s much appreciated.

 

By all means post up the data for All to see, as the more minds focused on this problem, likely the better.
What did the Short term fuel trim look like???

 

Here’s the data in a .cvs file. It doesn’t seem to display very well on Excel though. If there’s a better way to format it, let me know. On Excel, the misfires start at about line 7834.

When it misfires, the short term trims rise up right away to 11% and then drop down to -2% and then stays between -3% and +3%.

Let me me know if you want any more info. I have a FORScan specific file type, but FTE doesn’t support uploads of .fls files.

 

Maybe try posting screen shots of the FORScan dashboard data you had called up.

 

Will do. It misfired for about ten seconds. I’ve attached three screen shots- one when it started, one halfway through, and one at the end.

 

Screen shots are the way to go I think, as the forum is seeing what you are, without other different software interpretations mucking up the data.

On FORScan putting up Two cyl banks of data for a single bank 4banger engine, did you remember to update the FORScan initiation log with your make, year, model & engine, or did you just plug in the ELM & play what your Dad had entered when he last used it, for say, a V6 engine???

What version of FORScan is this. Good to see we now have a analog gauge display option.

 

I did not manually enter any info to FORScan, I just plugged it in. I know that it recognized the vehicle as a Ranger, but next time I drive it, I'll do a double check to make sure it doesn't think I have a v6. All the scanners I've used think it's a '96, not a '95 because they aren't programmed for the possibility of the transition year.

 

Ok, when you check / update the initiation log, make note of & post which version Number of FORScan is being used, as they're constantly updating what it'll do, fixing problems etc. The version loaded may be using the VIN # to automatically enter what the Factory shipped the vehicle with, so we need to keep that in mind because you don't have a historical account of what's been done to it over the years by previous owners. Ford Oasis will have anything done by a Dealership logged, so you could have a Dealership print you their info for your historical record.