My 90 sentra oil on spark plug question

[ahardb0dy]

So, on my 90 sentra sometimes when I come to a stop and step on the clutch the RPM's will drop to about 400 and the engine will run rough, if I rev it one time it will idle normally. This only happens once in a while.

 

The last week I noticed the idle will do this every time I come to a stop and the engine also feels like it is running rough.

 

I had to add oil about 2 weeks ago and than again 2 days ago, no leaks under the car no smoke out of the exhaust.

 

Today I pulled the plugs and all four were out of range on the gap, they have just over 11K miles on them right now, I re-gapped them and cleaned them , 3 of the 4 were dry but the 4th had oil on the threads and around the electrode, no oil on the outer ceramic area so don't think the valve cover is leaking. I re-installed them and took the car for a drive and it seemed like it was better, the RPM did not drop when I stopped.

 

So does oil on the electrode area indicate oil is leaking by the rings? Engine has never been worked on internally and has 244K on it.

 

Thanks

[devonianwalk]

Wow! That is a lot of mileage. Did you happen to look at the top of the piston to see if there is any "wet" residue on it? I would suspect blue smoke if it was leaking that badly though.

[ahardb0dy]

No, I didn't. I drove the car about 30 miles after I re-installed the plugs so tomorrow I'm going to pull out the one plug that was wet to check it again, I'll see if I can see anything inside when I do that.

 

A lot of mileage what?

[ahardb0dy]

forum won't let me edit my post for some reason so I'll just reply this is what I was going to say:

 

 

 

I bought this car on 11/02/03 with 117K on it, which works out to about 9000 miles a year which I thought was low. Paid $580 for it.

 

So far I have replaced the crank seal (twice), oil pan gasket, distributor (was leaking internally and got real good deal on a surplus OEM part), valve cover gasket, just recently replaced water pump ( wasn't leaking just figured after 22 years may be good to replace was having cooling issues that turned out not to be caused by the water pump), replaced the original 4 speed manual trans with a surplus new OEM 5 speed, replaced the clutch, clutch cable, speedometer cable, fuel injector and all normal maintenance items (plugs, wires, all filters, all vacuum hoses, thermostat, O2 sensor, oil, coolant, etc)

 

But nothing internal, still has the same timing chain which I assume is original.

Edited December 16, 2012 by ahardb0dy

[devonianwalk]

A lot of mileage what?

 

244k

[ahardb0dy]

Oh, ok

[ahardb0dy]

Pulled the plug today, it was a little wet but not like it was yesterday, smelled like oil. Looked down the hole and didn't see anything wet just very black.

[ahardb0dy]

So I was doing some research online about this and found where someone said oil on the plug could be caused from a bad valve seal? I guess there is no easy way to determine where the oil is coming from?

 

How hard is it to replace the valve seals? Does the head have to be removed?

 

Thanks

[Alkorahil]

If you do not have any oil leaks, then it sounds like you have oil consumption from somewhere which a valve seal can/will cause.

You can redo the valve without removing the head, but if you have one that is gone the other intake or exhaust are probably not far behind, esp with the miles we are talking. Many times the cost of doing all the valves in parts/labor is the same or more as getting a new/reman complete head and slapping it on there. I would look into both options.

 

Keep in mind you can have internal oil consumption and not be billowing smoke out the back. Smoke is BAD/excessive oil consumption.

Yes you could have a ring or rings that are old as well, but the statment that you revi ti and it recovers makes me think valve seat like you said. (in that you get some oil on the plug, rev it and burn it off)

[ahardb0dy]

I was checking out some video's last night and also looked in the FSM on how to replace them, doesn't look that hard to do, Rockauto has the intake and exhaust seals n a kit from FelPro for about $21

 

I wouldn't think of replacing just the one that may be leaking, have to do them all like you said with the mileage approaching 250K, I pulled the plug out Saturday and there wasn't much oil on it and the car is running pretty good.

 

From what I have seen it looks like I would need to remove the valve cover, rocker arm assembly, and than the valve springs for each cylinder, remove and replace the seal and reassemble. Of course have to remove each plug one at a time and maybe use compressed air to hold the valves up . Or I could have my buddy do it and just pay him.

 

Rockauto has one head left in stock for $360 but out of my budget, I would try to find a JDM GA15 engine and swap the engines for that price.

Edited December 24, 2012 by ahardb0dy

[nismothunder]

Valve seal, guide. Does it Puff on start up?

[ahardb0dy]

Not that I know of

[nismothunder]

I've been thinking, my 91 RS Camaro has 277k on its 5.0 and it has needed valve seals since roughly 150k. What I notice is it'll puff on start up and blow a little smoke if I sit and rev it. I have never had enough oil on the plugs too cause a mis fire like what your saying. But yet again its a 8 cylinder so I may just not be noticing a mis on start up. Well acutally I it does have a miss buts that's from the dizzy and I do notice that.

 

I wouldn't count on it being simply one bad seal, I think you may have 1 cylinder with low compression.

[ahardb0dy]

I think I'll pick up a cheap compression tester, or rent one and check the pressure, The car runs fine after I clean the one plug. The first time I pulled the plugs and found the oil on the one, there was a lot of oil on it, it had been running badly and after I cleaned the oil off and re-gapped the plugs it ran good again.