The Toyota sludging problem--a theory

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I have a 200 Camry V6, which I haev just learned is known for its sludging. I believe 1999-2002 are the years? My car has three coils. On each coil fire, two spark plugs actually fire. These engines use a strategy whereby each cylinder is sparked not once but twice per cycle--one for the power stroke and one in the exhaust stroke, to burn off any unburned fuel. My mom has a 2003 or 4 Avalon with the exact same engine, but with 6 coils. Could it be that the years known for sludging coincide with the exhaust scavenging spark technology? Could the extra heat generated by the extra spark be the culprit? It's a stretch I know.
 
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No. From what I have read it was an issue of cylinder head temperatures combined with environmental, driving and oil change interval factors. Toyota redesigned the heads to change their temperature at certain spots. Nothing to do with multi-spark. John
 
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I heard from a reliable source it was a redesign of the cylinder heads to lower emissions that caused the problem (or was it's biggest contributor). It took another redesign of the cylinder heads to solve the problem.
 
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quote:
Originally posted by jthorner: No. From what I have read it was an issue of cylinder head temperatures combined with environmental, driving and oil change interval factors. Toyota redesigned the heads to change their temperature at certain spots. Nothing to do with multi-spark. John
Heaven forbid, John and I absolutely agree on something!!! [Big Grin] I've also heard that the "waste spark" thing went away when actual distributors made their exit, although candidly, I have NO evidence to back this up, just something I heard without any way to assess reliability.
 
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Maybe it's the combination of: 1.87 octane gas leading to higher cylinder head temperatures. 2.Oil changes that went too long. 3.PCV system maybe not up to snuff. I've also heard the redesigned cylinder head caused lower emissions but increased head temperatures.
 
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They way I heard it was they increased cylinder head temperatures to decrease emissions. Which kinda' leads into another thing. I heard many people here say that with modern FI engines there shouldn't be any dilution on the oil with gasoline. When in reality, one of the things engineers are reseaching is how to solve the problem of fuel wetting of the fuel spray onto cylinder head ports, valves, combustion chambers and pistons. I've special research engines with quartz window ports actually showing the wetting of the fuel on these surfaces. That's one of the reasons you see researchers looking again at stratafied charged engines Ford made a big stink about 25 years ago. [ May 20, 2004, 07:49 AM: Message edited by: 427Z06 ]
 

Lumberg

Thread starter
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quote:
Originally posted by ekpolk:
quote:
Originally posted by jthorner: No. From what I have read it was an issue of cylinder head temperatures combined with environmental, driving and oil change interval factors. Toyota redesigned the heads to change their temperature at certain spots. Nothing to do with multi-spark. John
Heaven forbid, John and I absolutely agree on something!!! [Big Grin] I've also heard that the "waste spark" thing went away when actual distributors made their exit, although candidly, I have NO evidence to back this up, just something I heard without any way to assess reliability.

ePolk, The waste spark thing uses coil packs on top of the cylinders. It just uses half the number of coil packs (for example on my car there are just coil packs on teh front bank), and each coil always fires two cylinders simultaneously.
 
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GM uses wasted spark designs on many of its engines, including the venerable 3800 V6. You never hear of any sludge problems there. There's no way the wasted spark on the exhaust stroke will catch fire to anything, as it's pretty much all already burnt at that point. The only heat you'll get, therefore, is from the spark itself, which is inconsequential compared to the combustion heat. So, basically, I'd agree with John and ekpolk that it's much more a matter of cylinder head design. In fact, the most credible thing I've heard is that they changed the design back in '98 or '99 to make the head run at hotter temperatures. This made for a cleaner burn to comply with tighter emissions regulations. The problem happened because they didn't compensate with larger oil passages and higher oil volumes. This lead to coking in the oil passages, especially when the owner got careless about oil changes, and lead to oil starvation. That has, supposedly, been fixed now. I've heard inconsistent stories, though, about how Toyota has treated customers with this problem. If this were my car, you could be darn sure I'd be using a full synthetic, due to better heat resistance.
 
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335
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Detroit (Rock City)
quote:
Originally posted by ekpolk: I've also heard that the "waste spark" thing went away when actual distributors made their exit, although candidly, I have NO evidence to back this up, just something I heard without any way to assess reliability.
Nah, my '94 Miata has two coil packs for four cylinders, uses waste spark, and has no distributor.
 
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562
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Austin, TX
I would lean on the crankcase breathing side. The gases just aren't scavenged at high enough volume or rate. One of our cars is an older Range Rover. They are known to sludge up quickly if the breathing is clogged. In our Isuzu Trooper the PCV system is very restricted leading to increased crankcase pressure, sludge, piston ring deposits and high oil consumption. In both cases in addition to the PCV system it is crucial to maintain a clean air filter so that overall crankcase pressure is in spec.
 
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Austin, TX
quote:
Originally posted by Geoff: I would lean on the crankcase breathing side. The gases just aren't scavenged at high enough volume or rate. One of our cars is an older Range Rover. They are known to sludge up quickly if the breathing is clogged. In our Isuzu Trooper the PCV system is very restricted leading to increased crankcase pressure, sludge, piston ring deposits and high oil consumption. In both cases in addition to the PCV system it is crucial to maintain a clean air filter so that overall crankcase pressure is in spec.
Nice theory, however, one of the regulars here has a Toyota Sludgemonster. His evidence, doesn't support your theory. In the general sense, yes, I agree with you.
 
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