1999 Mountaineer “Miss Fire” without codes. Not your typical question.

[97-5.0]

Too much Vaccum dude! ide look into it!

 

[Kage.]

Move that ground to the metal bracket the packs bolt too, at the front remove that black plastic clip and hook it there , remove the jumper between packs as not needed, bigger wire if possible and test again

You do realize that the top of the coil packs (where I have those wires jumping) are a ground right? The top of the pack where the bolt mounts too has a metal plate under it that is a common ground. By running a direct ground from the Drivers side to the battery, and then adding the jumper between packs I was able to see if it was just one pack with a bad ground or both. I want to say that there was a slight change in adding those wires, but it might just be wishful thinking on my part.

I did add an additional large wire (Spare battery cable, ground all the paint under the bracket so we have a good connection) as suggested just to see if it did anything for me. No change:

At this point the only way this thing can be more grounded is if I drive a copper rod into the Earth So it looks like it is time to tear into the harness, or throw a Crank sensor at it just for a whim.

Too much Vaccum dude! ide look into it!

So I should I wear the motor out a bit more, or add forced induction to lower the vacuum?

 

[Kage.]

Still plugging away here. I'd like to say that it is getting better, but it might just be wishful thinking on my part. It seems like the miss is getting less severe and less frequent, but it is still present.

So updates to date:
- Swapped out the alternator as it was on the bottom end of the output, no change in behavior, but it is charging better :lol:
- Pulled the PCM and popped the case open, no nasty burnt smells, and the capacitors look to be in good shape (no leaks or bulging)
- Pulled the easily accessible part of the harness apart that runs to the coil packs. Looks good there
- Swapped out the Crank Sensor and pulled that harness apart, looks good there as well, and the new sensor didn't make a difference.

So yeah. Next step is to pull the upper intake and start looking into the injector harness. Not overly motivated to do that right now, so it'll be awhile before that update.

If I stumble across something else, I'll let the class know.

 

[Stealthbowl]

i would look into the injector harness i have had many a nissan 300zx that would at random give me multiple miss fire and just generally run like dog piss and come back to normal and it was resolved by replacing the injector harness, at least you have a new fuel lol if i hang a left too hard/quick my truck ***** the bed and comes right back lol so thats on my 2 mile list

 

[Kage.]

Sooo... I had some more time to dig into this, and managed to make things much worse. This round...

- Went through more of the harness, didn't find any obvious issues. Every wire that was in the plastic shrouding is like new, the stuff outside of the shrouding (near the connectors) was stiffer, but nowhere near brittle.

- Slapped it all back together, and had a real bad miss, but it wasn't on one cylinder. Backfired through the exhaust frequently and just plain smelled wrong. Really rough idle. I dare say it seemed like it acted like it was out of time?

- Checked the spark, and all was good there (even got hit a few times just to make sure!!!)

- No new codes on the ECU.

So I shut it down and walked away from it for a bit (5-10 minutes) when I came back it'll crank but won't start. Won't try to hit at all, no fuel smell. Check engine light no longer comes on, but the anti theft light comes on like normal. But the biggie is that I can no longer connect to the ECU via the OBDII port. Either my reader just happened to die, or the ECU might have finally died.

Either way, I just walked away from it very frustrated again tonight. I would think that if the ECU was dead, it wouldn't let me crank it, but maybe that isn't the case? Not really sure where to go from here, and I'm quickly getting tipped towards the scales of just parting the damn thing out since I'm getting tired of spending more time in the garage with it rather than wheeling.

Thoughts?

 

[Centaurus5.0]

I fried a ECU once. It would start and run for about 15 seconds then shut off and couldn't start it again until it set for awhile. Ran rough too. Got a new one and had it programmed at the dealer and then it was back to normal.

A bad coil pack will also do funny things intermittently but I don't think that is the case here.

Might be worth getting it to knowledgeable mechanic and paying $70 or so to hook it to a high dollar scanner a have him tell you what he sees.

Sorry about your bad luck.

 

[Dono]

You did the right thing... Walk away.

I wish I could remember what pin on the odb2 connector has power. I remember something about a fuse blowing that would stop the odb2 port from working.

 

[Kage.]

Might be worth getting it to knowledgeable mechanic and paying $70 or so to hook it to a high dollar scanner a have him tell you what he sees..

If I had a shop I could trust, I would drop it off today. Compounding the matter is the 5 gear swap. As soon as I mention that, the price goes up, or the shop isn't interested in dealing with "What I've hacked together". And I can understand their point on that matter as I wouldn't want to deal with that if I was on the other side of the counter.

You did the right thing... Walk away.

I wish I could remember what pin on the odb2 connector has power. I remember something about a fuse blowing that would stop the odb2 port from working.

I'll dig into the wiring/fuse diagrams tonight, but the port appears to have power as the reader has juice.

Adding to the fun, I kicked the key over on the way out the door this morning and now the fuel pump doesn't even do its initial prime. So yeah.. Looking very likely that the ECU is toast. Now I just have to worry about whether or not it just happened to die at this point in time, or if I still have a bad wire in the loom that shorted and killed it somewhere.

Fun fun fun...

 

[Dono]

Sorry. I understand your absolute frustration completely.

 

[Kage.]

So it’s back alive again. I’m my own worst enemy at times…

Turns out I popped fuse 19 (Power to the PCM). My best guess is that it happened while I was dicking around with the Ignition interference Capacitor circuit as I was working on cleaning that connection up, so it is entirely likely that I grounded that out while playing with motor running swapping plug wires around. That’s my best guess anyway.

I also had # 1 and # 3 wires swapped, once I had that fixed, it started running much better :homer:

So now I’m back to square one again that it still runs fine, except for the intermitting misfires that I’m dealing with, which is better than being dead in the garage.

I’m playing phone tag with the EFI guy to see if he can help it out. Maybe the damn thing just needs a tune after all....

 

[Centaurus5.0]

Right On!

If it makes you feel any better, I've been trying to find the miss in mine now and have had it since 57,000. Put all new motorcraft ignition parts, grounding wires, just put new injectors in, checked/cleaned all the sensor. While it runs great, that bit of miss is still there... so it feels like every other explorer i've ever owned. I'm wondering if its just the sloppy factory valve train causing it or maybe the crap headers. Maybe better valvesprings and a valve job will help but will do that with a fresh motor. A spun balancer could also make the engine feel goofy.

 

[Kage.]

Yeah, there is a definite trend of misses on these trucks. Which gives me confidence that it is unlikely to just randomly die on me, but it is annoying as hell still.

I am really starting to wonder if all of all of these had a miss from the showroom floor but the 'slush' of the automatic just managed to hide things that are revealed with the less give of the manual.

 

[Kage.]

So closing this out. Even though everywhere I read said you don’t “need” a tune when swapping in a manual. It turns out that you do.

I got a recommendation to contact the “EFI Guy” over on Classic Broncos (His profile LINK). I called him up and picked his brain for an hour or so. In the end I wound up shipping out the PCM to have it reflashed by Gary. He got it turned around very quickly to me so that I could get a few miles on it before heading west. After 120 miles, I can safely say the thing hasn’t missed a bit, and the drivability has improved greatly (not that it was that bad before).

So lesson learned, if you plan on swapping in a 5 gear into one of these, plan on spending the money on a tune of some sort as well.

I hope that helps someone in the future!

 

[Dono]

wow! I wouldn't have thought that could cause a miss.

Congratulations on seeing this thru.