Surging & stalling @ idle when warm

[fastskier]

I did a search on this and got a few threads that seemed like they covered some of the issues but I wanted to see if anyone out there had any other ideas.

 

94 4x4 SE Pathy. 216K km's.

 

Problem: Today I first noticed a lack of power. Didn't think too much of it at first. ThenI noticed the idle getting really low when warm and loping between 200-500 rpm. Watching the tail pipe while it was idling and stepping on the gas I could see black smoke coming out (I could smell the unburnt gas too). Engine stalled a couple of times @ idle. Also would stutter below 1500 when I stepped on it but once above that it would run fine (lack of power though)

 

Truck history: tune up 2 years ago (40K km's). new plugs, fuel filter, egr valve.

Brand new air filter. Cleaned the MAF last month. I have not changed the o2 sensor.

 

I have tried the mode III diagnostic but it says every thing is fine (55).

 

Any ideas??

 

Thanks,

 

Paul

[94extreme]

o2 would be my guess. my truck ran like crap when it was going out...

[Guest pathman]

The engine check light should come on if the o2 sensor is bad or sensing a rich mixture.

[fastskier]

update:

 

no engine check light has come on.

 

I started to notice a black fluid being blown out of the tail pipe when I started the engine. Kind of oil/water mixture. I then checked the oil late last night and thought I noticed gas in it. Changed the oil and had to start it up again to move it forwards to get the garage door closed. Checked the oil again and still thought I noticed gas in it.

 

At this point I am scared to drive it and I think its either a blown injector or a dropped ring.

 

Any other suggestions?

[94extreme]

The engine check light should come on if the o2 sensor is bad or sensing a rich mixture.

not necessarily.

[94extreme]

update:

 

no engine check light has come on.

 

I started to notice a black fluid being blown out of the tail pipe when I started the engine. Kind of oil/water mixture. I then checked the oil late last night and thought I noticed gas in it. Changed the oil and had to start it up again to move it forwards to get the garage door closed. Checked the oil again and still thought I noticed gas in it.

 

At this point I am scared to drive it and I think its either a blown injector or a dropped ring.

 

Any other suggestions?

if you dropped a ring then you'd get a lot of blow from the oil fill access and your dipstick wouldn't wanna stay down in its tube...

 

leaky injector ought to give you a light and code but sometimes they just don't

 

good luck

[fastskier]

After taking it to the shop they determined nothing was wrong with it. I drove it for awhile and it just seemed like the ECU needed to adjust to what the engine required. This took some time. Lately I've been noticing that if I take the battery cable off the battery (which resets the ecu) my pathfinder will have a lag when accelerating from stop for awhile. It seems like it needs time for the ECU to adjust to what the engine actually needs.

[GhostPath]

These trucks have learning ECUs - they do actually "learn" the engine characteristics; it takes them about 10 minutes or 10 miles (or so) to relearn if they've "forgotten".