If You Had To Pull The Head.....

[Mike94yj]

Are your vacuum hoses all original and in good shape?
Went through this with my YJ. replaced the hoses with stock from the stealership and the problem went away.
HTH
Mike

[Allen]

The thermostat installed at the time was operating correctly.

A pot of water on my stove confirmed this.

Besides, that, I'll never believe that it suddenly went bad in my driveway while I was swapping in the new radiator?

I guarantee you that right now, if I were to swap out the clutch and fan with the lower temp unit and 7 blade fan, I'd be right back at 160.

I played around with the parts installing and removing them.

Even the 7 blade fan and stock clutch never allowed the engine to reach 195-210. Temps with that combination hovered around 180.

No, I've never replaced the O2 sensor, and all vacuum hoses are intact and in great shape.

Allen

[DanB98TJ]

Allen - I personally wouldn't be surprised if you find carbon build-up is causing the pinging. I fought the same issue starting at around 14k miles, with it progressively getting worse until it would even ocasionally ping on 92 octane. The dealer tried the chemical decarb procedure at least twice but it didn't do squat. Finally, after I had to raise a ton of hell, they pulled the head and physically removed the carbon. That cured the problem for quite a while, even on 87 octane, but it's now coming back again.

In my case, I think the problem was from me lugging the engine too much. This was my first new vehicle, and for quite a while I babied it, shifting when the idiot light told me to and keeping the RPMs down (the 3.07 gears didn't help). Now that the Jeep seldom sees pavement, I'm pretty sure all the crawling around in 4-low has allowed the carbon to build up again. I'm going to give the water trick a try and hope that takes care of things, otherwise I'll be yanking the head.

[Allen]

The dealer will see it sometime next week for a few hours of diagnostic service to see what sensors if any I have that are bad.

We'll go from there, but I have a feeling I'll be pulling the head as well.

I certainly don't baby my Jeep. I flog her pretty good.

But my 3.07s aren't helping either.

They'll soon be gone too.

Not too suprisingly, the tech I spoke with for about 45 minutes, his first question was about operating temperatures. When I told him about my cooling and overcooling issues, he kind of stared at me like he wanted to say "Well, duh you idiot."

But he didn't.

I think Blaine and I are on the right track as far as the cool engine temps causing a rich mixture and incomplete combustion leading to carbon build up.

We will see.

Thanks for everyone who's had some input. (Except for mnjeeper who suggested I trade it in.)



Allen

[truckjohn]

Certainly good luck with it.

Personally, I know I am not trying to say it *can't* be a carboned up head -- I have seen my fair share of those on vehicles owned by folks who idle them around all day in town because they are afraid to drive them... or want to look cool putting around just filling the heads up with carbon..... At that point, you can't do anything but chip it off.

If I do too much city driving, it seems like my jeep starts pinging when I really get into it. That is always my sign that I need to get it out on the highway and burn up a tank 'o gas at about 3300 RPM out on I-75.... then it is fine again for another 6-months.

I have also had it happen right after an engine service where they used some agressive fuel system cleaners. Apparently, that stuff can really knock out the trash and sometimes it sticks in the combustion chamber. Once again, a good long trip out on the interstate at high RPM's always does the trick... but we are talking about 3-4 hours at 3000 RPM..... and I usually have to wear earplugs so that I can stay sane.

Best regards from those of us hoping you don't have to pull the head.

John

[mnjeeper]

Originally posted by Allen
(Except for mnjeeper who suggested I trade it in.)



Allen

I was thinking you had wasted much more time and money than you had

[Robert J. Yates]

Hmmmm,
.....and I thought I had problems with my rig running hot. I guess at least I don't have to worry about carbon build up on my rig

[Allen]

Originally posted by mnjeeper
I was thinking you had wasted much more time and money than you had

Time?

I have all the time in the world now.

Money?

That's another story.

Allen

[Allen]

Originally posted by Robert J. Yates
Hmmmm,
.....and I thought I had problems with my rig running hot. I guess at least I don't have to worry about carbon build up on my rig

Sure.....

Rub it in.

Allen

[StealthTJ]

Allen, if you overheated the engine twice, that is to the 'redline", you've probably damaged something in/on the head itself and/or blown a head gasket.
I can't tell you how many vehicles we've had at the shop requiring "head jobs" because of overheating. I have 3 right now. A Dodge 600, a Neon, and a Mazda 626.
Pull the head and take it to a *good* machine shop that can check the valves (making sure none are bent and/or burnt), can check the head to make sure it's not warped and/or cracked.
They will redo the valves and replace the valve seals in the process.
With any sort of luck you haven't stuck any of the piston rings.
Have you run a compresson check on all of the holes ?
If not, I would highly recommend that you do.
These engines do NOT take lightly to overheating, especially twice.
The Neon we have at the shop now has a cracked head, and I suspect the machine shop will find that to be the case with the 626, as both vehicles were fried at least twice in a short period of time.




Fred

[Allen]

Originally posted by StealthTJ
Allen, if you overheated the engine twice, that is to the 'redline", you've probably damaged something in/on the head itself and/or blown a head gasket.
I can't tell you how many vehicles we've had at the shop requiring "head jobs" because of overheating. I have 3 right now. A Dodge 600, a Neon, and a Mazda 626.
Pull the head and take it to a *good* machine shop that can check the valves (making sure none are bent and/or burnt), can check the head to make sure it's not warped and/or cracked.
They will redo the valves and replace the valve seals in the process.
With any sort of luck you haven't stuck any of the piston rings.
Have you run a compresson check on all of the holes ?
If not, I would highly recommend that you do.
These engines do NOT take lightly to overheating, especially twice.
The Neon we have at the shop now has a cracked head, and I suspect the machine shop will find that to be the case with the 626, as both vehicles were fried at least twice in a short period of time.




Fred

Fred,

I only overheated into the red once, and yes, I know that once is enough. The heat immediately went on, and I pulled over to the shoulder. It wasn't hot long, and the needle came down quickly. I was lucky in that regard.

I used to work in a machine shop, and saw plenty of warped and cracked heads, so I'm familiar with what needs to be checked out. The head gasket is good as far as keeping water and oil seperate, but that's all I can say for sure. No smoke out the back end, so if anything is hurt, it can't be hurt too badly. Especially given the fact that I've got 15,000 or more miles on it since it happened.

No compression check yet, but one will be done.

I'm interested to see what I'll find, and will report back the results.

Allen

[Chuck K.]

Update??? I am still in awe that the fan was doing such an efficient job that the engine stayed as cool as it did with the thermostat closed .. Let us know what you find, inquiring minds want to know

[JLemieux]

Are you running the stock air box or some type of intake tube that does not ingest cool air when running?

[Allen]

Originally posted by JLemieux
Are you running the stock air box or some type of intake tube that does not ingest cool air when running?

Stock airbox with an OEM filter.

It goes into the dealership this afternoon for a diagnostic scan.

Will update Monday morning.

Allen

[Allen]

Went to the dealer Friday, and after I coughed up $325.77, I walked out the door to hopefully a fixed TJ. It certainly was peppier and ran better.

I say hopefully because I'm still running out a tank of 93 octane. I'll fill up with a half tank of 87 after work today to finally test it out.

All sensors and the PCM checked out normal.

What wasn't normal was the fuel injectors, or their timing sequence.

They were running out of sync.

Seems that there is a problem with the oil pump drive shaft and gear, specifically the gear which runs off the camshaft, which also turns the fuel injector sensor.....that's where the distributor used to be on the older TJs.

The gear wears abnormally, and can even cock sideways a bit on the shaft, throwing off the fuel injector sequence. They've seen it fairly often. Ford uses a similar design.

It has to be fixed at the dealer, because when setting the injector sequence, the Jeep must be hooked up to their computer. The sensor is rotated by hand while the engine is running, and locked down when their computer shows the injector sequence "In Range". Mine was well out of range.

So if the injectors are spraying when they shouldn't be.....that could certainly cause some detonation.

Allen

[Croaker]

Wow -- who'da thunk? Here's hoping it's finally fixed!

Do you know if that's a problem only on the newer "distributorless" models, or should those of us with older TJs also be on the lookout?

[PK99TJ]

I am thinking that it wouldn't be a problem in older models? Since the cam sensor in the distributor controls the injector timing (right?)... so the timing of the spark and injectors should be in sync because any variances in the gear on the cam would be irrelevant to the sync of the spark/injectors which occurs "downstream".

However, its probably a lot more complicated than that.

That's really quite an unusual end to the story, hopefully that will take care of it.

[Allen]

As far as I know, it's just on the newer distributorless models.

What is utterly stupid, is that the PCM doesn't throw the "Check Engine" light. How could the fuel injector pulse be so far off, and there be no warning.....

The tech told me he's seen one so bad, that the gear had actually welded itself into the block. Which would be a disaster.....

The factory service manual definately states that both ignition timing and injector timing are completely seperate. The sensor is not to be disturbed for any reason, other wise it's off to the dealer for re-adjustment. It also says not to attempt to set ignition timing by moving the device, as it has no effect on ignition timing what so ever.

Allen