need help reading these plugs

[xjdriver]

Hello, im having a problem with my jeep 4.0l fouling the no2 plug, the plug will only last around a thousand miles, motor does not burn oil or smoke. Ittl start running rough at idle when the plug foules, pop in a new one and its fine for around another 1000.

 

[rbh]

Re: need help reading these plugs

I see your using a never seize type compound (threads are covered in it) are you using it on all the plugs?

Sometimes that stuff hinders in the grounding of the plug.

The plugs are not oil fouled so I would say clean the plug and seat of the goo and replace the plug wire.

 

[Boomyal]

Re: need help reading these plugs

Get rid of the Bosch Plugs and go with OEM. I bet that will cure your problem. That top plug is not oil fouled. You have a plug firing issue.

 

[robert graham]

Re: need help reading these plugs

Although there is an obvious difference in the plugs, none of them really look very fouled....best to go back to the OEM plugs so heat ranges, etc. will be correct....

 

[WIMUSKY]

Re: need help reading these plugs

Looks like the bottom plug isn't firing. Should have a nice caramel color to it. Also, don't put anything on the threads.

 

[xjdriver]

Re: need help reading these plugs

The clean looking plug is the one that is firing I just put Iit there for reference. The nasty looking one is from the problem cylinder compresion is also around 10psi lower than the rest in no2. First off it never ran all that smooth at idle, after 1000 miles it will start misfiring at idle when first started on the no2 cyl. If I just buy 1 new plug and slap it in im good for a while im just gettin tired of going around the problem. Ya I over did the anti sieze but I dont think thatsthe problem. I think I might be burning coolant in that cyl but I didnt think that would couse sparkplug to not fire. Also It doesnt misfire off idle unless I dont change the plug when It starts missing at Iidle. Cap rotor and wires are fairly new.

 

[bajaunderground]

Re: need help reading these plugs

I would replace wires/distributor cap/rotor while I'm at it?! I agree with not using the anti-seize, except with aluminum heads...I believe the 4.0L is iron-headed so the advice is sound!

The lower ones look new, the upper one looks 'burnt' (too hot) but not from oil/gas? How many miles on the motor? What year 4.0L? I know from owning 2 that they are excellent high-mileage motors (300K +, with proper maintenance). What's your compression on all 6 cylinders?

As with everything mechanical, start with the basics and go from there?!

~Brett

 

[rbh]

Re: need help reading these plugs

The clean looking plug is the one that is firing I just put Iit there for reference. The nasty looking one is from the problem cylinder compresion is also around 10psi lower than the rest in no2. First off it never ran all that smooth at idle, after 1000 miles it will start misfiring at idle when first started on the no2 cyl. If I just buy 1 new plug and slap it in im good for a while im just gettin tired of going around the problem. Ya I over did the anti sieze but I dont think thatsthe problem. I think I might be burning coolant in that cyl but I didnt think that would couse sparkplug to not fire. Also It doesnt misfire off idle unless I dont change the plug when It starts missing at Iidle. Cap rotor and wires are fairly new.

DING DING DING!!! we may have a winner here folks
All jokeing aside bud, if your compression is that far down its time for some radical rebuilding 'or maybe not' it just takes a chunk of carbon under the valve to screw up the compression and usually it is a valve problem, rings last a long time unless you yanked a piece of crud up and down enough times to gouge the cylinders.
Do a leak down test dry and wet

 

[bigdee]

Re: need help reading these plugs

Why do you think your burning coolant? 10 psi difference between cylinders is not that significant but if your losing coolant too that could indicate a leaky head gasket

 

[bruceb58]

Re: need help reading these plugs

I guess I missed the part where he is losing coolant.

 

[xjdriver]

Re: need help reading these plugs

Okay, okay. The full story 140000 on the motor ive owned it for 3 years and i really have never had any major problems, i have noticed coolant disappearing but always seem to have a coolant leak somwhere, its also been doing the missfire at idle (for about 30 sec when first started) i traced the misfire down to cyl 2 and noticed the whole wird looking plug issue so i ran compression and found it to be around 10psi lower than the rest (not critical according to Chrysler). I just wanted to see if someone could pinpoint what the condition of the plug meant. And i chose not to rebuild couse when shes completely warmed up idle oil pressure is only around 5psi if that, i think the bottom end is worn and dont want to just rebuild the top. When the time comes im going with a low mile used 4.0, couse i really like the jeep. Motor still runs strong and pulls my starcraft around no problem, so im not to worried right now.
Ive just never seen a plug look like that before.

 

[bigdee]

Re: need help reading these plugs

Okay, okay. The full story 140000 on the motor ive owned it for 3 years and i really have never had any major problems, i have noticed coolant disappearing but always seem to have a coolant leak somwhere, its also been doing the missfire at idle (for about 30 sec when first started) i traced the misfire down to cyl 2 and noticed the whole wird looking plug issue so i ran compression and found it to be around 10psi lower than the rest (not critical according to Chrysler). I just wanted to see if someone could pinpoint what the condition of the plug meant. And i chose not to rebuild couse when shes completely warmed up idle oil pressure is only around 5psi if that, i think the bottom end is worn and dont want to just rebuild the top. When the time comes im going with a low mile used 4.0, couse i really like the jeep. Motor still runs strong and pulls my starcraft around no problem, so im not to worried right now.
Ive just never seen a plug look like that before.

What year? 1999-2001? Sounds like coolant got in oil and washed out the bearings. That was a major issue with the 4.0 for a couple of years. BTW mine has been running on 5psi or less for years.

 

[xjdriver]

Re: need help reading these plugs

What year? 1999-2001? Sounds like coolant got in oil and washed out the bearings. That was a major issue with the 4.0 for a couple of years. BTW mine has been running on 5psi or less for years.

Its 1998 cherokee, it could have happened before i owned it i suppose but as far as i owned it it never had coolant in the oil. I do believe its probably been overheated, the cooling systems on these Cherokees are a pretty bad design.

 

[WIMUSKY]

Re: need help reading these plugs

I thought a coolant leak would clean the plug so it looks new (steaming it clean)?

That's my thoughts too. I had a boat with a blown head gasket. The cylinder that was taking on water was clean as a whistle, including the plug. Just like the clean looking plug in the pic above. That plug is too clean unless the pic is deceiving..... It looks like a new plug that's never been fired(understanding that it is firing)......

 

[bigdee]

Re: need help reading these plugs

I thought a coolant leak would clean the plug so it looks new (steaming it clean)?

What condition is the coolant? Is it brown or oily? That color is close to what IAT coolant looks like when it breaks down.

 

[bruceb58]

Re: need help reading these plugs

To me, that plug looks fine and I would be suspecting a weak ignition for that plug.

I know the OP says fairly new for the plug/wires but have they been changed since this started occurring.

 

[xjdriver]

Re: need help reading these plugs

To me, that plug looks fine and I would be suspecting a weak ignition for that plug.

I know the OP says fairly new for the plug/wires but have they been changed since this started occurring.

Yes thats why I changed them in the first place couse the wires didnt look b ad when I first got it, then it started idling rough so I did a tune up, then a little while after same problem. Ive just*been changing that one plug out since then. Coolant is green, I have to top off the bottle every few weeks.

 

[bigdee]

Re: need help reading these plugs

I have to top off the bottle every few weeks.

That still throws up a flag. How long has it been losing coolant? Have you or previous owner ever added stop leak? It does not make sense that spark would be weak on only one cylinder if wires and distributor cap have been replaced.
The unexplained coolant loss,overheating and low oil pressure are the classic signs of a Jeep 4.0 with a cracked head or bad head gasket.

Where is oldjeep? He knows what I'm talking about.

 

[xjdriver]

Re: need help reading these plugs

Ya im thinkin either cracked head or somethin with head gasket on no2 cyl.im not gona tear into it couse mainly of the low oil pressure, lower end is also a little noisy. Its my dd so if it dies im going with a used motor as long as I hear it run first.

 

[bigdee]

Re: need help reading these plugs

Ya im thinkin either cracked head or somethin with head gasket on no2 cyl.im not gona tear into it couse mainly of the low oil pressure, lower end is also a little noisy. Its my dd so if it dies im going with a used motor as long as I hear it run first.

Yeah that is the same decision I made over two years ago and it it still running. I am going to get criticism for saying this but if the motor is already worn out and your just trying to buy time add some brown Bars stop leak pellets. Mine has not used a drop of coolant since I flushed the cooling system and added one jar of stop leak about 14 months ago.
A motor that has had antifreeze-in-the-oil-damage is not a good candidate to rebuild so my advice is drive it until it quits and then buy a salvage or rebuilt engine. Mine had low oil pressure (5psi) at 80k miles and it now has 110k miles and it still runs like new. That 4.0 is one tough engine!