2000 Toyota Sienna Multiple Error Codes - Might they suggest a particular problem?

@db4690, Indeed, those A/F ratio sensors were perfect fit. Many thanks for the insights. I will be back with the next results (from spark plug replacement).

I changed plugs 1 and 4 as planned. I had the mind of changing them all, but that # 1 was more fun than I was ready to triplicate unnecessarily. I did not remove any parts to get to #1. I just worked with the little space … no fun at all for my above average-sized (putting it very mildly) hands. I took it out for a test. Runs great, no “check engine light”, no error codes!

Thank you all.

@Kimland congratulations!

Are you holding off on coils unless they are needed?
If so, that was smart thinking.

@db4690, Yes, I decided to hold on the coils and replace only if the car “complains.” By the way, there was a bit of dark formation in the housing for spark 4 (of course I could not see anything to do with spark 1’s housing). This formation has me concerned. Any idea what would have caused that? I cleaned it up as much as I could, using a rug moistened with Wd 40. The housing tube is deep though, so I could not clean it as thoroughly as I would have wished. I cleaned it just as well as I could. Any idea what could have caused this build-up? Just wondering whether it might be an indication of something fundamental that could just repeat with the new plug.

@Kimland is there any chance the formation was in fact engine oil? If so, that would seem to indicated that the spark plug tube seals may be faulty.

I’ll go a little off-topic now . . . I recently replaced a plastic intake manifold on an engine because of a misfire. The old manifold became brittle and broke, allowing oil and coolant to seep into a spark plug hole, eventually fouling the plug and causing a misfire.

I hope this isn’t the cause of that dark formation. In the case mentioned above, someone else had recently replaced the visually fouled plug, without bothering to ask how all that oil and coolant got in there.

If you do have an intake manifold or gasket problem, you should know soon enough.

@db4690, I cannot tell if it was oil, but I suspect it is not. I think you would see much more carbon on the tip of the plug if it was oil. How did the plug look in the case you describe?

@Kimland the plug was actually still wet with oil. And the spark plug hole had still visible coolant in it.

I believe you’ll be fine.

Just my 2 cents, but plugs should be changed in one shot even if it is a distasteful job. Aged plugs can be coil killers to boot.

Any deposit on the plug boot or plug shank from inside the plug well could be fresh and/or coked engine oil and sometimes blackish debris can be due to the spark exiting the side of the plug boot into the cylinder head. If a spark can’t jump the gap on an old plug it’s going to look for the next easiest path to ground and that’s usually through the boot.

@Ok4450, my thoughts exactly. If the sparkplugs on 1 and 4 were bad enough to cause misfires, 2, 3, 5, and 6 are not that far behind. Do the rest, and don’t worry about it for another 100,000 miles. Misfires risk expensive damage to expensive catalytic converters, a/f senors, and coils. Why risk that on cheaper spark plugs, even if they are hard to get to?

I appreciate that logic. I will go ahead and change the rest of them.

Great people, after I replaced all 6 spark plugs I went several days without any indication of problem but then the car started having intermittent check engine light shortly. Code reader was not picking anything up for a long time, till there was a major misfire today.

Code reader picked up cylinder 1 & 4 misfires. I was ready to replace these again, but reviewing this thread I realize those 2 were the same ones that were the problem to begin with. This suggests to me that the problem is not the spark plugs, rather damage on spark plugs is a secondary effect. The spark plug wires are in very good shape. What’s the likely culprit?

Oh, I think I forgot the attack plan here: next I need to replace ignition coils. I wonder whether plug 1 & 4 share the same ignition coil. I am going to educate myself on this first. Any help will be appreciated.

@Kimland I believe each plug has its own coil

Didn’t I send you a link to a TSB with part numbers for the new and improved coils?

@Kimland here’s that TSB again

I highly recommend you go to the Toyota dealer and buy the specific coils from the TSB

Sometimes the aftermarket parts don’t have all the latest upgrades.

Sometimes the aftermarket parts are a “copy” of the original design which will eventually fail.

Look at it like this: a coil is easier to change than a plug.

Anyways, @db4690, thanks for the guide. I ordered an original coil (90080-19012) from Toyota Parts.

It seems to me that this engine has only 3 coils, with cylinder 1 & 4 sharing one coil. I can trace a wire running from the coil that is in front of cylinder 4 to cylinder 1. I see only 3 coils, all on the front bank. Please let me know if you find other info, or if you confirm this.

@Kimland

I have a 2005 Camry with the same engine as your car. I have one coil for each plug. I (apparently) wrongly assumed that was the case for your car, as well.

Here is the cylinder bank layout, according to Toyota. Unfortunately, it doesn’t picture the coils.
But at least you’ll know where the cylinders are located. Unfortunately, not every manufacturer has the same layout.

@Kimland

With all due respect, is it possible you got the cylinder bank mixed up and wound up replacing the “wrong” plugs?

I know this is pricey, but if this were my car, I would make sure all the plugs were new and the correct type (I believe you’ve already done this), and I’d replace all the coils with the ones called for in the TSB (it sounds like you have 3 coils, all on the “front” bank).

Since that other TSB I provided for the oxygen sensors (a few months back, if I recall) actually worked (I’m assuming, because you would have mentioned those codes reoccurring), I am going to assume to that the TSB for the coils will, in all likelihood, fix your misfire problem.

@db4690, No, I cannot have replaced the wrong plugs. Actually I replaced all 6. At first I replaced these #1 & #4, but after your (and others) suggestion, I dug back and replaced the rest.

I was also under the impression that the Camry engine and Sienna were the same. May I ask the following:

(1) What year is your Camry?

(2) Are its banks arranged one behind the other (as you look at them from the front of the car), or are they parallel (left line and right line)?

Mine are arranged one behind the other. Bank 1 is at the back; bank 2 at front (and with the coils, per my understanding), i.e. as in Figure 2 at http://www.toyotapart.com/Engine_Bank_1_and_Bank_2A-F_and_O2_Identification_T-SB-0398-09.pdf . I imagine yours must be a parallel arrangement as in Figure 1, or you would have to go through hell to replace coils in the “back” bank.

You said you know it is pricey, but you would replace all plugs. I will have to replace the plugs again anyway (and I am using the original Densos only, just like last time) - this time though I do not think there is reason to replace the ones that are not in faulty, as they are new from the previous replacement.

For the faulty ones though, they have to be replaced again. I pulled out #4 and it is worse than the #4 I pulled out a couple of months ago. It has the residue that the previous one had, but in addition there is oil on the shaft. I must assume the same is the case with #1.

Oh yes, the oxygen sensor problem is put to rest. THANKS!

I am thinking there is something fishy about Toyota’s coverage of these coils; first, they do not provide diagrams for the layout (at least not one that is easily accessible as we would have gotten to it now), but then, and this is critical in my view, when a dealer (at least in my experience) replaces a coil they do not indicate on their records what coil they replaced. They only indicate how many coils they replaced. I plan to call the dealer before I do this job, at least to see how forthcoming they are in detailing the replacements they made. At the same time I will try to get their word on the arrangement of these coils.

I was going through my paperwork and I find that 2 ignition coils have been replaced - one in 2006 and the other in 2007. In each case they say something like “… checked problem. Replaced 1 faulty coil, ignition.” In one of the cases a coil was replaced along with the plug for Cylinder 6 - so I assume it was the coil serving cylinder 6 (which seems to be also serving cylinder 3.

I attach a frontal clip of assembly, showing what i believe are all the coils. Under these coils, from left to right, are plugs for cylinder 2, 4, 6. I have unthreaded #4, as you can see. Bank 1, with plugs 1, 3 and 5, is far back on the other side, deep behind the windshield and many other things. The plugs on bank 1 don’t have the knuckles you see on the frontal 3, rather each is a simple tube for the plug.

@Kimland

My 2005 Camry has the same 3.0 liter 1MZ-FE engine as yours.

I have coil on plug = 1 coil per plug . . . so I have 6 coils

Same cylinder bank layout

Transverse layout, just like in your Sienna

Yes, it IS hell to work on the back (firewall) bank!

@db4690, I know this can be tiring now, but you have me concerned that I may not know these coils as much as I think I do. I have found a posting by someone who removed the plenum to be able to expose bank 1 and its spark plug tops:

http://i269.photobucket.com/albums/jj53/Fortune50/99%20Camry%20V6%20Spark%20plug%20and%20wire%20replacement/Untitled-4.jpg

There you can see plug 3 & 5. On those you can see what I meant that there are no knuckles on top of the plug. Do your plugs look like that, if they do, where then are the bank 1 coils placed?

@Kimland

All 6 of my plugs have their own dedicated coil

All of my plugs have a coil sitting on top of them

YOU only have 3 coils. Each of your coils is “feeding” two plugs

You don’t have coils on bank 1. You only have coils on bank 2. The plugs on bank 1 are “fed” by the bank 2 coils.

Bank 1 has cylinder 1 on it

I believe your firing order is 1-2-3-4-5-6
On systems where one coil is responsible for 2 cylinders (like yours), the coil should fire the plug it’s sitting on top of AND the companion cylinder’s plug as well.

Here are the companions, as far as a I know

1 and 4
2 and 5
3 and 6

Cylinder 2 has a coil, with a wire feeding cylinder 5
Cylinder 4 has a coil, with a wire feeding cylinder 1
Cylinder 6 has a coil, with a wire feeding cylinder 3

You have
P0301 cylinder 1 misfire
P0304 cylinder 4 misfire

So I recommend replacing the #4 coil. That should be the middle coil on the front bank.

Of course, I also recommend replacing all the coils with those updated parts, so that this problem will disappear once and for all.

Since 1 and 4 are both fired from the same coil, that leads me to believe the coil itself is the problem.

Hopefully this has helped.