Black Smoke - Minor or Major?

[moosetrek]

This is my first post, just joined after I bought a 90 Pathfinder XE auto a couple weeks back. I actually have two I'm fixing, I bought another last weekend (91 SE manual) for parts, lsd, etc. but it's in better shape than the first, except:

 

It ran fine to drive on the trailer. Upper end rattle, the PO said the oil pump went out (how hard could an oil pump be, said the new Pathfinder owner) and there may have been overheating as it was driven until it stopped running. No lower-end noise when running, just upper from no oil. Many, many, many hours later the new oil pump is installed and working fine thanks to much help from this site. Old one was rounded by the crank and shot. Changed the timing belt while I was in there, all sprockets and marks lined up, engine @TDC #1 Cyl verified with the pencil test, marked on the distributor, etc.

 

Fired it up, black smoke from exhaust and runs like @$$. Won't stay running at idle or if I let off the gas, but when I floor it it's got power. Compression is exactly 122 in five of the cyls, but 110 in cyl #3. Added oil and #3 came up to 122. Looks like maybe the ring in Cyl #3 is going, but I can live with that until a future rebuild.

 

What I can't figure out is, is 122 too low for the compression? It's consistent, so if it's low then my guess would be timing belt is off. If my timing is off would I see the black smoke? Other thoughts are coolant temp sensor, as the gauge in the dash doesn't move at all. No other symptoms of a head gasket, and I've never seen one blown where all the readings are the same - I almost thought my gauge was going out they were so close. Any help you can offer is appreciated... Thanks!

[Precise1]

from my Nissan PDF manual;

 

Standard 173 PSI

Minimum 128 PSI

Difference limit between cyl 14 PSI

 

 

Did you dry test or wet test (adding some oil to the cylinder) when checking the compression? If dry, then that would give you low numbers, if wet, that could account for the smoke, but it should be more bluish than black; black is usually to rich. Could be O2 sensor?? Have you run the ECU codes? There is a write up in the How To section...

 

there may have been overheating as it was driven until it stopped running. No lower-end noise when running, just upper from no oil.

This doesn't sound good at all!! Valves/guides trashed??

 

B

 

This is my first post, just joined after I bought a 90 Pathfinder XE auto a couple weeks back. I actually have two I'm fixing,

Welcome, BTW!!

[moosetrek]

Did you dry test or wet test (adding some oil to the cylinder) when checking the compression? If dry, then that would give you low numbers, if wet, that could account for the smoke, but it should be more bluish than black; black is usually to rich. Could be O2 sensor?? Have you run the ECU codes? There is a write up in the How To section...

This doesn't sound good at all!! Valves/guides trashed??

 

B

Welcome, BTW!!

Thanks for the help - it was a dry test, but after cranking over the first couple cylinders wouldn't the oil be up in the heads, making it a wet test? I'll try to pull the codes - the instructions look pretty easy.

 

I figured the motor was shot when I got it, but it's an SE, Sport Package, sunroof, LSD, 5-spd, new paint job, all options, I really want to get it going and sell the other. When I started it with the new oil pump I just had a slight tapping in the psgr side upper end, and it went away after a couple minutes (right when I grabbed a piece of hose to listen with of course).

[Precise1]

it was a dry test, but after cranking over the first couple cylinders wouldn't the oil be up in the heads, making it a wet test?

No, probably not that quickly. Also, did you prime the oil pump?? I swear I read something on that recently. Let me go see if i can find it...

 

Ahh, here it is. I have never done this work so I'm just parroting...

http://npora.ipbhost.com//index.php?showto...=prime+oil+pump

 

Swap the motor from the other one in it and start parting out what's left!!

The slight tap is probably the lifters, common and not a problem. If it quieted down right away, then you must have oil pressure...

 

B

Edited April 24, 2009 by Precise1

[unccpathfinder]

This is my first post, just joined after I bought a 90 Pathfinder XE auto a couple weeks back. I actually have two I'm fixing, I bought another last weekend (91 SE manual) for parts, lsd, etc. but it's in better shape than the first, except:

 

already addicted looks like...

 

Black smoke is generally rich...I have 3yr old gas in my 87 and it burns a like black esp if i rev up the engine...

 

good luck and

[moosetrek]

No, probably not that quickly. Also, did you prime the oil pump?? I swear I read something on that recently. Let me go see if i can find it...

 

Ahh, here it is. I have never done this work so I'm just parroting...

http://npora.ipbhost.com//index.php?showto...=prime+oil+pump

 

Swap the motor from the other one in it and start parting out what's left!!

The slight tap is probably the lifters, common and not a problem. If it quieted down right away, then you must have oil pressure...

 

B

Thanks for the info, and the reminder about priming the pump... I almost missed that step, and after all the work just to get to the dang thing I was driving around to every local truck stop (the only places nearby and open on a Sunday evening) looking for Vaseline - got a couple of strange looks. Packed it full and the idiot light went out right away; I was sweating for a second there since getting the differential out (and in) by myself SUCKED...

 

I'm thinking it might be the coolant temp sensor, I don't think the T-Stat is opening. Gotta pull the codes and check, but there's no water circulation right now. Had the new one and forgot to put it in when I did the timing belt (kicking self...). Lots of carbon coming out the tailpipe when I rev it. I'm wondering if the exhaust might be a little plugged too, I'm guessing the O2 sensor should throwa code though?

 

Swapping motors is the last resort, the plan is to sell the XE to pay for the parts on this one.

 

Thanks again for the help-

[moosetrek]

Learned a valuable lesson yesterday: CHECK THE CODES FIRST!

 

I was all set to write the motor off, pull heads and check the valves, etc., and I finally read the how-to and checked the codes. Code 12: MAF. The entire problem was the ground wire to the MAF was pinched in the distributor cover, and had broken. One wire nut, 2 mins later, and I fired it up; smooth as anything. Hard to believe all that from one little wire... Changed plugs/cap/rotor yesterday, I'll change the filter and oil again to make sure no metal filings from old oil pump are in there, and off we go (I hope) onto the next problem - brakes, custom bumper, stereo, the fun stuff.

 

Anyone try Lucas Oil Stabilizer? My plan is to Sea-Foam the upper end, then change oil and filter, then add some Lucas to treat the upper end after running without oil.

 

Thanks for everyone's help on the Forum, without it I'd probably be posting a cheap SE on Craigslist for parts! Now just got to get the other one going and sell it. (or maybe a offroad-only trail rig...?)

[OldSlowReliable]

(or maybe a offroad-only trail rig...?)

SAS!!!!!!!

[Precise1]

Learned a valuable lesson yesterday: CHECK THE CODES FIRST!

 

I was all set to write the motor off, pull heads and check the valves, etc., and I finally read the how-to and checked the codes. Code 12: MAF. The entire problem was the ground wire to the MAF was pinched in the distributor cover, and had broken. One wire nut, 2 mins later, and I fired it up; smooth as anything. Hard to believe all that from one little wire... Changed plugs/cap/rotor yesterday, I'll change the filter and oil again to make sure no metal filings from old oil pump are in there, and off we go (I hope) onto the next problem - brakes, custom bumper, stereo, the fun stuff.

 

Anyone try Lucas Oil Stabilizer? My plan is to Sea-Foam the upper end, then change oil and filter, then add some Lucas to treat the upper end after running without oil.

 

Thanks for everyone's help on the Forum, without it I'd probably be posting a cheap SE on Craigslist for parts! Now just got to get the other one going and sell it. (or maybe a offroad-only trail rig...?)

 

LOL I'm not going to say "I told you so...".

Many people forget that important step. I generally consider it the second thing to do after a visual inspection. Glad to hear that it was so simple to fix!!

 

Lucas OS is good stuff. I ran it in my tranny and diffs, but never in the motor. After flushing the motor and a few oil changes, even the lifter tap it had when I bought it is gone. Maybe I'll try some next oil change...

 

B

[moosetrek]

Yep - I did the Seafoam the other day, and am out of town this week for work. When I get back I'll do the oil change, and the Lucas. Still debating sellgin or keeping the other Pathfinder, depends how bad a set of new tires sets me back I think, the BFGs on it are almost shot.

 

And I need to start the bumper build... All this fixing is fine, but my welder is sitting in the corner feeling neglected and I miss the smell of hot steel in the morning:) Got some cheap scrap from the local shop, and am going to build up a custom deal for the front since we have so many deer and antelope on the roads. Most of the aftermarket ones seem a little delicate, and pricey too. Any suggestions on design are welcome, or I'll just make it up as I go as usual.