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Discussion Starter · #1 ·
Okay, aside from dumping water/windshield wiper fluid/AFT fluid into the intake, what's the best and most effective way to remove carbon buildup?

Rebuild? Partial Rebuild? What needs to be cleaned up?

Thanks!
 

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Discussion Starter · #3 ·
What does "dunked" and rebuilt really mean?

What do they do?

Is it hard to pull the head?
(off the engine *******... <IMG SRC="smilies/rainbow.gif" border="0"> )

Thanks again!
 

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IF you haven't pulled the head, how do you *know* there is carbon buildup?


try the gas additive Techroline (sp) the stuff put in Chevron in a really heavy dose.
 

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To remove the head open you Factory Service Manual and follow the directions. If you don't have one you should buy one. A quick summary is...
1. remove valve cover
2. remove t-state
3. remove intake and exhaust header
4. remove sensors off head
5. remove head bolts
6. remove head from Jeep

There are a bunch of little things that I left out, but this should give you a good idea of what it takes.

A speed shop or engine machinist will then disassemble the valves and dunk it in a chemical tank to completely clean it. They will then put all new valves and associated pieces back in and seat the valves for you. Now you can put it back in your Jeep.

Why do you think you have a lot of carbon build up? Heve you done a compression test. Are the valves not seating? Do you have an engine tap? Too many questions??????
 

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Discussion Starter · #6 ·
Well, we haven't narrowed the problem down exactly to the carbon buildup, but I think there's a good chance that's what's causing the non-stop pinging under accelleration on the highway. A load will increase the ping.

I tried using the fuel additives, they help, but they don't cure it for long at all.

We have not done a compression test, what woudl that tell us?

Right now, the pinging is bad, real bad. 4th and 5th gear around 2600+rpm's it gets bad. If you've got a trailer on the jeep, even worse. Go up a hill, worse. Acellerate, worse...

Not sure what it is yet, but I'm just trying to figure out what all my options are depending on the problem.

Can I do a compression test?
 

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I don't think a compression test will tell you anything about your pinging problem. I am not well versed on the pinging problems. I do know it is caused by pre-ignition orf the gas. You probably have a timing issue. You may be able to have the computer adjusted to compensate. I know there are some modifications to the CPS (crank position sensor) that can help you change the timing. By design a 4.0l's timing can not be adjusted, but there are some tricks out there. BTW, the CPS controls the timing. Which engine do you have? I would post a new question specifically dealing with the ping problem. I don't think the carbon is causing it.

You may want to take this question over to JU (www.jeepsunlimited.com) because there are a much higher volume of stock 4.0l's over there and chances are someone over there has come accross this pinging problem.

[ 10-02-2001: Message edited by: DE Jeeper ]
 

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Sounds more like timing..have you checked that yet? Is your vacuum advance working correctly? Also your fuel mixture may be a little on the lean side.
Before you go and pull your head <IMG SRC="smilies/thefinger.gif" border="0"> you might want to check these out...also what do your plugs look like? nice and brown or heavy deposits?
I have found that compression tests will show you have carbon deposits if the readings on your gauge are higher than your manual calls for.

Check the plugs first though.

By the way...what have you checked so far? This might help narrow it down a little.
 

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Discussion Starter · #9 ·
I just replaced plugs and wires.

What about the vacuum thing though? The hose coming off the rear vent, the CCV? (or is that the front vent) is cracked. If that hose is cracked, could that pose a problem?

The old plugs didn't seem to have a large amout of deposits, they were just brown.

I also agree with the timing, but who can adjust it, the dealer?

What about the CPS, can I adjust/replace it?

Thanks again guys!
 

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If you've ever tried to increase compression, you will know that reducing the volume of the cylinder head only increases it slightly.

If you milled the heads down *alot* you might pick up 1/4 or at best maybe 1/2 of a point of compression (i.e from 8 to 8.5)

But carbon buildup on the intake valves can limit the amount of fuel thats getting in which can cause a lean burn detonation.

That vacuum leak could also be messing with you.

Just curious, what does that year FSM say in the trouble shooting section for detonation?

I'd start there. I'd hold off pullin heads looking for a problem before I knew what I was looking for.
it could be a sensor?
 

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I like Mopar's combustion chamber cleaner. That stuff really works! What year 4.0 do you have? If it is newer than '96, there are some tsb's that deal with detination problems. These are cured by re-flashing the pcm to another part number that dosn't have quite the same spark advance. The dealer is the only one that can re-flash the pcm. I would try the combustion chamber cleaner first, then switch gas stations and try some premium fuel, it that dosn't work, re-flash.
 

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I'll second dorfs' recommendation of the Mopar combustion chamber cleaner. It isn't like the "additives" that you can find at your local Pep Boys/Checker/etc.. The pros use it and it does an excellent job as long as the correct procedure is used.
 

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The CPS mods I was speaking of have to do with modifying the mount so you can move it back and forth about 1/2" in either direction. This will trick the computer into firing the plugs slightly out of time. You have to slot the 2 mounting bolts and the plasic clip that is in the bh so the CPS can move. It is currently held in with 2 bolts and there is no adjustment. I still think a good scanner can read the engine and it will tell you if anything is screwed up. You still haven't said which year or engine you have.
 

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Discussion Starter · #14 ·
Okay, I guess I'll try that mopar stuff, where do you get it? Dealer?

This is a '93 4.0 with 146K miles...

I'll also try and get that vacuum line replaced...
 

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Carbon build-up can certainly be a cause of pinging. Carbon can continue glowing after the combustion stroke enough to prematurely ignite the fuel mixture on the next compression stroke.

Personally, I like the idea of SLOWLY adding a trickle of water to the intake while you keep the engine rpms up a little to keep the engine from stalling. ATF works well too but it has a habit of annoying/scaring the wife and neighbors with the huge clouds of smoke.

Repeated HARD revving of the engine can often blow the carbon out too. I watched a Corvette mechanic at a Chevy dealer do this to a near-new 427 engine that was running poorly and pinging. He commented that the owner wasn't driving the engine hard enough which was causing carbon build-up. While he was revving the engine, all kinds of soot was blowing out of the exaust which he said was the carbon. After he was done, the engine was fine again but he had to caution the owner to drive it harder so the carbon wouldn't build back up again. I imagine that's a bigger problem with higher-performance engines and not Jeep engines but it illustrates the point that carbon build-up doesn't necessarily mean the engine needs to be torn down or the heads removed.

If you do the water treatment, just make sure you have the water under control so not too much is dumped in all at once accidentally. 8-12 ounces, maybe a Coke-can worth, is usually about right. This method really cleans things up inside, that's for sure. Just be careful to feed the water in as slowly as possible and just a small trickle at a time.
 

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A build up of carbon can be a big cause for pinging. ATF works great to get it off of there but tends to make great big scary clouds of smoke. Unless you live in a unpopulated area use some clean tap water. When you feed the motor the water make sure to do it slowely and keep the RPM up a little so it doesn't stall. You only need to run a cup or two through the motor at the most. I have always followed this up with racing the throuttle a little to help clear the rest of it out.
 

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Discussion Starter · #17 ·
Okay, maybe I'll try the water route to see what happens.

When you say a steady trickle, you mean like just enough so that it's running, and not dripping out of the cup?

I just pull the air hose off and drop it into the opening by the throttle body correct...just checking... <IMG SRC="smilies/wink.gif" border="0">

By the way, I tried the aft route once, NO SMOKE at all. I just trickled a very small amount in a few times...no smoke...
 

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The Mopar stuff is 80% water, and some real powerful amonoia. It comes out of the can in a foam so you won't hydro lock the engine. Using water will work, but if you dump too much, it's knock knock. The principle is slowly injecting water, which turns into steam, and cleans off the deposites. The big advantage of using the Mopar stuff is the cleaning action of the amonoia. It also super cleans the throttle plates and idle air passages. This stuff melts off any oliphin deposties better than any carb cleaner. Oliphin is the unwanted waxy substance that looks like tar on the bottom of the plates that is not refined out of us crude.
 
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