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Okay, I've been driving a 2005 Spyder for about two and a half years with no mechanical problems. Unfortunately, the solid engine didn't prevent the side of my car from collapsing under the momentum of a Hyundai bolting out of a parking lot and into traffic. So now I've purchased a 2001 Spyder to replace it. I had such great luck with my '05 (and with Toyotas in general), so I thought I couldn't go wrong with this one - but I'm starting to wonder. My new baby has been in the shop for two weeks now and I've been on this forum looking for some help. In the process, I'm picking up on what seem to be some pretty serious issues. I've been reading some older posts, trying to piece the information together to form an accurate picture of what I may have gotten myself into. This is what I'm seeing so far. Please let me know if I'm getting a clear picture, and please help me to fill in the blanks ...

So, apparently, the early (2000-2001) ZZW30 engines had a defective oil ring design that results in the consumption (burning) of an excessive amount of oil. This presents its own issues (running the oil level low creating lubrication problems that can damage the engine). But, aside from that, the oil vapor in the exhaust apparently has a detrimental affect on the pre-catalytic converters (causing them to disintegrate?). This in turn can result in the main catalytic converter becoming clogged, causing excessive exhaust back pressure which has its own laundry list of potential engine damage issues.

I'd appreciate any additional specific information that can help me to assess where I stand with my 2001 MR2 Spyder. And, I have some specific questions:

1.) Is the main catalytic converter affected by the oil vapor in the exhaust in the same way as the precats? (In other words, as my precats have been removed and the main cat replaced by the previous owner, do I need to be concerned about premature catalytic converter failure?)

2.) Can the oil consumption issue be controlled by closely monitoring my oil level and keeping it within the proper operating range?

3.) I've seen a lot of anecdotal information on this forum regarding adjustments to oil type/composition and viscosity to minimize consumption. This is all good food for thought and very helpful, but does anyone know of any science-based articles or papers that have been published concerning this specific issue with the ZZW30?

4.) Can the oil consumption issue be corrected by reringing the engine?

I've been scanning through some of the threads addressing this subject, but I'm sure I haven't found them all. I would appreciate links to other posts/threads within the forum that you feel I might find helpful.

Thanks!
 

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1.) Is the main catalytic converter affected by the oil vapor in the exhaust in the same way as the precats? (In other words, as my precats have been removed and the main cat replaced by the previous owner, do I need to be concerned about premature catalytic converter failure?)

I have read that burned oil is not good for the cats. My 1ZZ burned a fair amount of oil, enough to darken the tag but not leave smoke trails. My spyder currently has 160k with the original main cat. Pres where replaced with a header.

2.) Can the oil consumption issue be controlled by closely monitoring my oil level and keeping it within the proper operating range?

IMHO no.

3.) I've seen a lot of anecdotal information on this forum regarding adjustments to oil type/composition and viscosity to minimize consumption. This is all good food for thought and very helpful, but does anyone know of any science-based articles or papers that have been published concerning this specific issue with the ZZW30?

I haven't looked for any. I use a good 5w30, when the consumption got bad enough for me I replaced the block with new.

4.) Can the oil consumption issue be corrected by reringing the engine?

Depends on the condition of the cylinder walls and probably the pistons. Apparently replacement pistons have more drain holes in the ring lands.

I was able to reduce oil consumption by using BP products when the engine had 50k on it. I was happy for about 70k with the results. The internals where clean when I dissembled the engine for inspection.
 

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1.) Is the main catalytic converter affected by the oil vapor in the exhaust in the same way as the precats? (In other words, as my precats have been removed and the main cat replaced by the previous owner, do I need to be concerned about premature catalytic converter failure?)
Absolutely, yes. Not only will it prematurely lose efficiency, you’ll make hot-spots on the platinum too, which will ruin it. For the record my main cat started throwing p0420 code (efficiency loss) at about ~175k miles.

2.) Can the oil consumption issue be controlled by closely monitoring my oil level and keeping it within the proper operating range?
Close monitoring will keep you from starving your engine obviously in the short term. I would consider This “buying you some time,” more than controlling. The oil consumption will become exponential.

3.) I've seen a lot of anecdotal information on this forum regarding adjustments to oil type/composition and viscosity to minimize consumption. This is all good food for thought and very helpful, but does anyone know of any science-based articles or papers that have been published concerning this specific issue with the ZZW30?
I tried switching to a 20w50 as well as using a snake oil to free my rings up from carbon. Neither of these made any difference whatsoever with my oil consumption.

4.) Can the oil consumption issue be corrected by reringing the engine?
It sure can, but the consensus around here is to just throw in a used, 2003+ 1zz instead of rebuilding. The idea behind this is you’ll probably get more life out of a used engine than a rebuilt one. That’s what I did personally and I’m happy with my choice.
 

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Discussion Starter #4
Thanks for the feedback, folks. I have another question ...

Beside the pistons and rings, did Toyota make any other changes to the 1ZZ engine to correct the oil consumption problem?
 

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There are several production engines that a prone to severe deterioration due to piston ring damage that appears to be started by pre-cat failure. The pre-cat is also known as the close-coupled catalytic converter and is a feature of almost every current production car engine. Mounting the catalyst really close to the exhaust ports makes a huge difference in how quickly the catalytic converter starts working to reduce emissions from a cold-start.

Here is the story based on the pre-2003 Toyota 1ZZ engine found in many Corollas, Celicas, and the MR2 Spyder: This is the most likely order of deterioration: first the little oil holes in the early piston design clog up with coked oil (because the top of the piston is hot and the oil holes are a bit too small and you didn’t use synthetic oil, or change your conventional oil enough). then the engine starts using a significant amount of oil because the top rings wear-out from insufficient lubrication. Then the oil consumption causes engine knock at high power settings which forces the knock detection system to retard ignition timing. Then running at high power with retarded timing caused the pre-cats to overheat and fail. The failed precats allow bits of ceramic to enter the combustion chamber and completely ruin the cylinder bores, pistons and the head.
 

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My understanding is the clogged piston holes prevent the oil collected by the oil ring pack from draining back into the sump, and instead the piston walls are over-lubricated so the left over oil burns in the cylinder. Also a significant amount of unburned oil ends up in the exhaust system which is then oxidised (burned) in the precats, raising their temperature further (in addition to a mild timing retard from the knock control system due to oil burning) and causing them to break apart. Reversion in the exhaust system causes the precat bits to damage the cylinder bores.

Normally an early Corolla 1ZZ with this problem can be driven for YEARS as long as the oil is kept topped up as they do not have precats. It is very difficult to clean out the piston oil ring groove holes with chemicals, but an engine that has just started burning a bit of oil (meaning the holes are constricted but not completely blocked) can be 'fixed' with some short oil change intervals, good synthetic oil, and use of oil flush chemicals right before the oil changes. Once the holes are blocked you are SOL.

The fix was to increase the number and size of the drain holes, as well as some small modifications to the ring pack to improve the oil 'wiping' performance and piston sealing. These changes occurred in late 2003. An early 1ZZ that has had short oil change intervals or good synthetic oil used (or preferably both) will never have this problem.
 

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Discussion Starter #8
rmeller, that's good to know. Thank you.

dblotii and Funkycheeze, thanks for those explanations. Very helpful.

The guy I just bought my 2001 from said he'd had trouble with the car bogging down and being unable to get above 60 mph. His mechanic (a Toyota shop) diagnosed a backed up catalytic converter and replaced the exhaust. (The precats were replaced with a header and it just has the one cat now.) The car currently has 65,000 miles on it.

Had I known the early 1ZZ engines had this issue when I was shopping, I would not have purchased this car. But, I have it now and I need to come up with a course of action going forward. Based on what I'm seeing here and in other posts and sources, I'm thinking I need to be gentle with this engine and keep a close eye on the oil level. I always run a full synthetic oil anyway, but I should probably change the oil and filter every 3000 miles or so, and possibly run some kind of flush through it just before the changes as recommended.

First chance I get, I'm thinking I should pull the engine, tear it down, and have the cylinder liners inspected. (I know a very good engine machinist who has done work for me in the past.) If they're in good enough condition that they can be cleaned up without boring them over too much, I can rebuild the engine, using the properly designed pistons and rings. Otherwise, I should probably shop for a post-2003 engine.

Does anyone see a flaw with this approach?

In the mean time, can anyone recommend a specific engine flush? (I've heard a lot of good things about SeaFoam, but I've never used it. I do use Lucas products and have been quite satisfied.) Any input is appreciated.

Thanks!
 

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AutoRX seems to be the most recommended and successful option for attempting to fix this issue without engine disassembly. There will be lots of posts on this forum if you search for AutoRX, on various methods used with it in terms of oil type/change frequency/amount of cleaner etc.
 

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...First chance I get, I'm thinking I should pull the engine, tear it down, and have the cylinder liners inspected...
I don't see a point in tearing the engine down as long as it is running well. Just treat it well and drive it while it is good. No one seems to think that rebuilding this engine is cost effective, and you seem to have been lucky with this one.
 

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There are several production engines that a prone to severe deterioration due to piston ring damage that appears to be started by pre-cat failure. The pre-cat is also known as the close-coupled catalytic converter and is a feature of almost every current production car engine. Mounting the catalyst really close to the exhaust ports makes a huge difference in how quickly the catalytic converter starts working to reduce emissions from a cold-start.

Here is the story based on the pre-2003 Toyota 1ZZ engine found in many Corollas, Celicas, and the MR2 Spyder: This is the most likely order of deterioration: first the little oil holes in the early piston design clog up with coked oil (because the top of the piston is hot and the oil holes are a bit too small and you didn’t use synthetic oil, or change your conventional oil enough). then the engine starts using a significant amount of oil because the top rings wear-out from insufficient lubrication. Then the oil consumption causes engine knock at high power settings which forces the knock detection system to retard ignition timing. Then running at high power with retarded timing caused the pre-cats to overheat and fail. The failed precats allow bits of ceramic to enter the combustion chamber and completely ruin the cylinder bores, pistons and the head.
This is a good write up. The only thing I would like to add is a rumor I heard many many years ago. That the 1ZZ was designed to run on either low-ppm sulfur or even a completely sulfur-free gasoline, which the majority of the free world was supposed to switch to around the time this engine was conceived. Of course this changeover didn’t happen, and the higher sulfur content of gasoline is why the oiling holes get clogged so quickly.

Again, I have no idea if this is true or not, but it would certainly explain how Toyota managed to make such a colossal design mistake on the 1ZZ, which as an engine family goes back decades from my understanding.
 

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Everyone has an engine story, so here is mine..

I got 300K Miles out of my Org 1zz.. Synthetic Oil from 80K Mi when I got it. Up till 200K it was 1Qt Oil per ~3to5K miles.. I was changine oil every ~4 Months at ~ 15K miles.. Commute Car.
After 200 K I started to see oil consumption rise, and at 300K I was able to Blow a Smoke Cloud if I wanted to..

I grabbed another 'Junk' 1ZZ that was an oil Burner, and Re-d it.. Same Bore..

'03 Pistons
'05 Rings
Had the Head 'Touched' lightly as the Seats almost do not exist..
All New Bearings/Seals/Chains rubbing Block/Oil Pump/
Stage 1 Cams
Lightweight Flywheel

That motor has ~65K miles on it now.. Running fine.. I no longer do that insane Commute.. but it is still my 'Primary' Commute Car.

The problem with Opening up an Old Motor, is all the things are worn out.. Like Crank.. The Journals are a little Small, and the 'Tightest' Crank/Rod bearings were still 'too loose', and I had to shim them tighter.. ( Old Skool ).. Normally people would just Grind the Crank, but I don't lik the Finish on ' Consumer Reground' Cranks.. and the Hard Face is now thinner.. I'm Picky..

Generally I spent ~+$2k on the Rebuilt Motor.. and it's still an Old Motor that has Aluminum Foil Shims behind ALL of the Engine Bearings..

A running +03 Engine is the Slick Easy way to go.. do a little pressure washing and toss it in.. Or that 2ZZ Engine all the People are talking about..

Cap
 

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This is a good write up. The only thing I would like to add is a rumor I heard many many years ago. That the 1ZZ was designed to run on either low-ppm sulfur or even a completely sulfur-free gasoline, which the majority of the free world was supposed to switch to around the time this engine was conceived. Of course this changeover didn’t happen, and the higher sulfur content of gasoline is why the oiling holes get clogged so quickly.

Again, I have no idea if this is true or not, but it would certainly explain how Toyota managed to make such a colossal design mistake on the 1ZZ, which as an engine family goes back decades from my understanding.
it was either 2000 or 2004 that the US dramatically lowered the regulated sulfur content of gasoline and Diesel, and it was lowered again in 2017. The only thing that sulfur content significantly effects is the life of the catalytic converter and particulate emissions.
 

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if you are really worried about carbon buildup you need something like ACEA C1 C2 oil - that is rated low SAPS for engines with catalysts.

"The post-treatment systems, sensitive to the lubricants used and expensive to maintain, are also protected over the long-term thanks to the “Low SAPS” formulation (low content of sulphated ash, phosphorus and sulphur contents)"

Modern euro spec (ACEA) direct injection engines like the Mini (DS3, RCZ etc) have problems where recirculated oil can cause problems on inlet valve stems (buildup) - so using the lowest SAPS content will have less problems.

Like API, the specific formulations balance variables wanted for emmission, economy, and wear protect protection against each other.

So while there are many synthetic 5w30 out there they dont burn the same way. Switching brands over consecute changes or changing driving style may affect your consumption.

Between changes top up with 5w40 and see if consumption improves.

I am new to ZZW ownership - only done 2000km. My 104,000km (65k mile) motor currently using perhaps 100ml per 100km ! Previous owners partner claimed used no oil
 
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