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Exhaust valve rotation and engine decarbonization

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03bluerubi

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Discussion starter · #1 ·
Chysler TSB 0900303
1999-2004 with 4.0 L enginer
Multiple Cylinder Misfire due to carbon deposits on exhaust valves.

TSB says an exhaust valve rotation and decarbonization procedure should be performed.

Has anyone done this work on their jeep, and if so, how long and involved was it? The stealership wants $1200 do to it which sounds crazy to me. I've found what seems to be good information on how to do the work here:

http://en.allexperts.com/q/Chrysler-Repair-807/2008/1/03-Grand-Cherokee-problem.htm

Thanks
 
#2 ·
Decarbonizing an engine can often be accomplished in 5-10 minutes for free using nothing more than 12-16 ounces of water. With the engine running and the air intake removed from the throttle body, SLOWLY trickle the water into the throttle body, keeping the rpms up a tad with the throttle linkage. Do it slowly enough that it will take several minutes to drain the container. No this will not (!) cause hydrolocking unless you dump the water in too quickly.

The water turns to steam and it creates millions of little shock waves that break up carbon deposits which are then sent out via the exhaust system. This is done all the time on engines that tend to develop carbon deposits when they're driven too conservatively. For example, Corvette mechanics do this all the time on engines that are babied too much by their owners.

No, done properly this will not harm the engine in the least and it's an age-old technique that can leave an engine sparkling clean internally. Engines have actually used water injection since before WWII to increase power and the mechanics quickly learned that it keeps the engines carbon free, or gets rid of existing carbon deposits once modified for water injection.

All you have to do is trickle it in slowly enough that it will take probably 2-3 minutes to drain the container... a very slow constant tiny trickle of plain tap water.

No, I'm not crazy. ;)
 
#3 ·
If you can find an Edelbrock Varajection set up you can run it all the time. I had one on my CJ5 back in the 70's to keep detonation at bay. I had high compression pistons this set up worked great. I ran a 50/50 mix of water and alcohol. It kept the engine innards sparkly clean.
 
Discussion starter · #4 ·
Yeah I have read quite a bit about decarbing using water, then decided instead to decarbonize using a type of chemical treatment which entails ingesting the chemical treatment through the throttle body, allowing a hot soak of 2-3 hours, then running the engine through its paces a few times to break any leftover carbon from the engine.

I was mostly asking about the complexity of rotating the valves themselves - apparently if there is enough carbon build-up the valves stop rotating, which leads to the valve to occasionally not open properly. I've read that the 4.0 valves will rotate slightly by themselves above ~3200 rpms, so as long as the carbon build-up isn't too bad, just taking the engine above this point should rotate the valves on its own. Because I live in a small town and drive only a couple of miles to and from work, i rarely get the engine up to these types of speeds.
 
#5 ·
The lifters rotate. The valves don't though. I haven't had a 4.0 apart and look at the valve keepers but I really don't think the valves rotate. As far as cleaning the carbon from them, once you run some water through the intake you should be good. Take it out on the highway and drive it like you stole it.
 
#6 ·
My TJ is currently misfiring on cylinder 1, 2, 3 and the dealer is performing a valve spring replacement and decarbonization. It's under a warranty, so I wasn't told the cost, but they need it all day so I'm sure there's a ton of labor involved.

I can let you know if it solves the misfiring, but other than that I don't know much about it.
 
Discussion starter · #7 ·
yeah a total valve spring replacement i believe would be much more in depth than just a rotation.

and I believe the valves to rotate. The TSB specifically says that is the valve has been rotating properly one would see a circular wear pattern, so I believe they are supposed to rotate.
 
#10 ·
Multi-groove valve keepers allow (not makes them) for some valve rotation, hence why almost every production vehicle in the world uses them. Older single groove keepers and valves put such a tight grip on the valve it won't go anywhere. That's why they're more popular with people designing hi-revving or race engines.

I've yet to have seen an automotive engine that had so much carbon buildup that it prevented valves from closing though. Even in ones that were running on the rich side and burned oil! Modern fuel has enough detergents in it to keep things from getting that bad. Combustion chamber deposits are another matter and are usually a by-product of the design of the cylinder head. Detergents or not, if there's a persistent cool spot in the cylinder, you're probably going to get deposits regardless. Usually nothing to the scale those fuel treatment bottles show though, but enough that it can cause pre-ignition problems...like in a Jeep!!
 
#15 · (Edited)
Is there a related component that's easy to inspect that would display the telltale signs of buildup in the cylinder?

For example, if I want to know whether my intake manifold is due for a cleaning on my diesel I really just need to pull the hose going into the EGR to get an idea of how much buildup I have in my intake manifold and on my EGR valve. So, 1 constant tension hose clamp to remove and I have a pretty good idea of what's going on with the intake and the egr system and know whether work needs to be done. Anything that simple on the ol yeep?
 
#19 ·
4.0l sahara said:
There is a mechanism commonly put on exhaust valves called a rotator that will help the valve slowly turn in it's seat and this helps keep the valve stay cooler.;)
Click to expand...
Do you have any examples of automotive gasoline engines that have that? I've never heard of a gasoline automotive engine that had that. :)
 
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