The firewall side cylinders are #1, 3 and 5. The 2000 Sienna has only three coils that deliver spark to the 6 cylinders. Since the plugs in those cylinders are, putting it mildly, hard to access compared to the front plugs, there has always been a lure for unscrupulous mechanics, when given the task of replacing all six plugs, to replace the fronts and lie about replacing the firewall side plugs. I would want to pull one of the rear plugs and see if it looks the same as one of the fronts to rule that scenario out.

These vehicles have known-to-be-flakey coils. If you replaced any of your three coils with a non-Denso brand coil I would throw them away. Those 3-for-$27 Chinese coils on eBay are, by many accounts, garbage. When I had a bad coil I replaced it with a used Denso from eBay for $9. It would be nice to have a good Denso coil to swap into your vehicle to rule out bad coils, since the vast majority of misfires in these Siennas is caused by bad coils.

The notion that you can only use actual Denso brand coils with these Siennas is what I've heard over and over again to the point that using a non-Denso coil seems like a real bad idea.

Same thing with the spark plugs, I'd only use the exact ones the vehicle came with, my 2000 Sienna has a sticker that says to only use the ones with the triple electrodes, although the dealer here tried to sell me ones with only one electrode and had never heard of the sticker, but then again the service department had never heard of the well known sludge problem in these vehicles so I don't take them seriously.

Several people have solved idling problems by cleaning their IAC so I'd do that.

 

Thank iRt

I replaced those 6 spark plugs by myself.
After run the car a while, I pull those 3 firewall spark plugs out
you can see it is black. carbon deposition on it.
I hook the spark plug with the spark wire, connect the spark plug metal shell to the ground, and then run the engine.
You can see the spark between the spark plug gap, look like it is working.

I will try the DENSO ignition coil.

you know the front 3 spark plug are same as the firewall spark plug
they are all same type, if they are bad they should be all bad, right?

Thanks again

 

All the plugs are the same so the plugs should look pretty much identical when you pull them.

Bad plugs do occur, but not near as often as bad coils. If you are using aftermarket coils I'd highly suspect them. In a vehicle this old, buying three new coils from Toyota would be, to me, not wise as they are around $200 or more each. Just get three used Denso ones from a junkyard. They could be from another vehicle, like a Camry that used the same 1MZ-FE engine. How do you know they are good? You don't. Just the chances of getting three bad ones is pretty much zero, and taking the chance will save $600, about 1/2 to 1/3 of the price of the vehicle, so I'd chance it. It's a lot less risk than using new non-Denso coils.

I meant to say double electrode spark plugs, not triple in the previous post.

I've attached a pic I just took of a coil on my 2000 Sienna. It says TOYOTA DIAMOND 90080-19012 on the top. That is the correct Denso coil. I just went on eBay and there's a guy in Texas with a whole bunch of these for sale for $8.69 each and free shipping. The listing here: https://www.ebay.com/itm/Coil-Ignit...ts-96-01-LEXUS-ES300-130560/371972829711?hash=item569b4ef20f:g:vtIAAOSwDEtaQz9V If you look at the pic in the listing the part number is the correct one. You can see the send for the back plug on the coil as the 2000 Sienna, unlike the 2001 and later, uses 3 coils for the 6 cylinders.

 

You may be able to narrow down the problem by removing spark plug wires one at a time for cylinders 1, 3, and 5. If you remove a wire and it runs worse, then that cylinder was working. If you remove a wire and the idle or running does not change, then that's the bad cylinder. But if the compression test really was 120 on cylinder #5, then that's probably the problem. Rings or valves or head gasket.

 

I did the following test.



I pull out 3 ignition coils from 3 front spark plugs, still let the ignition coil drive the 3 spark plugs at firewall side through the spark wires.

I can not start the engine



I put firewall side 3 spark wire on the front side 3 spark plugs.

I can not start the engine



look like the ignition coil is strong enough to drive the front side 3 spark plugs(because it is close) but not strong enough to drive firewall side 3 spark plugs (because it is far away)
Am I right?


Another question:

2000 sienna has 2 kind of engines. 1 with VVT, another without VVT.

So the ignition coil are same for both of them?



Thanks

Harry

 

I'm not surprised your car wouldn't start with your test. Your Sienna has the non VVT engine like mine.

From what I've read the 1998 through 2000 Sienna used the non-VVT engine. After that, through 2003 they used the VVT engine. It could be that the Siennas made after August 2000 were actually 2001's. I've never heard of a 2000 Sienna with the VVT engine.

The coils are different between the non VVT and VVT engines. My non-VVT 2000 has only three coils. Each coil works for 2 cylinders. The VVT engine has 6 coils, one for each cylinder.

I've attached pics showing the coil pairs and the firing order. The firewall side cylinders is called bank 1.

The 2001 -03 engines say "VVT-i" on the plastic cover on top of the engine, and have 6 coils.

 

I went to the DENSO website and they list the spark plug wires and state that you need to buy the 3 boots (for the non-coil plugs) also.
The DENSO website does not list the actual coil nor do I seem to be able to find DENSO brand online for this, so perhaps it was only sold under the Toyota brand name?
I had no luck under the DENSO brand name at auto part store websites..... I got some that picture the wrong part.....so you would want to see in person to make sure it is correct.

Have you tried replacing the wires? OEM coils and wires is not a bad investment after all these years.

They are listed at $97.70 each at metrotoyotapartsnow website for Genuine Toyota Brand.
It looks like, if you want NEW OEM you may need to shop online dealership part sites for the best price.

 

I think the coils were made by Denso for Toyota. I don't see "Denso" printed on them, just what's in the pic I posted earlier. Try searching for "Toyota 90080-19012". I was surprised to see them at what appears to be legitimate Toyota parts places for about $90, much lower than I'd seen on previous searches.
Just make sure they say "TOYOTA DIAMOND 90080-19012 on them.
Since the wires don't carry high voltage like cars did in the past they don't really wear out or change a whole lot over time I don't think.

I've attached the technical service bulletin Toyota sent out in 2004 admitting that the coils were funky and that they were giving away a free one to Sienna owners, unfortunately that offer is long gone.

 

Thank you very much!

I changed lots of parts which could cause the misfire.
Never think about the coil because they are new.
I think the coil I used is for VVT engine,

This time I can resolve this problem very likely.
If not , The car destination is the junk yard.

Harry

 

DO NOT SHOCK YOURSELF !! Here is what I do. I don't recommend you do it. Sienna has 3 coils on the front cover. Each fires 2 plugs.
1. Use a small screw driver and carefully loosen the clips that hold on the wire on the top of the coil pack.
2. Do not remove the wires.
3. Start the car.
4. Wear gloves, use rag and insulated pliers pull the one wire off one coil at a time and see how long the arc is.
Wear a long sleeve coat, and don't rest bare arms against the car.
- The wire will continue to arc and spark maybe 1 or 2 inches away from the coil.
- A failing coil will arc less than the other two coils.
If you drive long enough with a bad coil, the spark plug won't fire right and will get sludge on it.
If you drive long enough with a bad coil, you can damage your catalytic converter from unburned gas.
Denso brand coils are better than some after market ones.

 

That's a good idea Tom, old school visible spark test. I used to have a spark plug mounted on my '69 Impala's inner wheel well that I could plug a spark plug wire into and see the spark from the driver's seat. That and a see-through glass gas filter and you could check for gas and spark in less than 30 seconds. There was nothing that could stump me with those cars, and I got better gas mileage than the Sienna with engines that were twice the size. So much for technology.

As far as Harry's Sienna, another thought I had was the the gaskets in the firewall side valve cover were leaking oil into those plugs thus making them fail.

Yesterday I helped a neighbor putting in all new coils into his V6 F-150 that has only 36k miles. In the last 45 years I've owned about 35 vehicles, mostly GM land yachts. In all those vehicles I only replaced one coil. We are living in an epidemic of dishonesty.

 

That's a good idea Tom, old school visible spark test.Yesterday I helped a neighbor putting in all new coils into his V6 F-150 that has only 36k miles. In the last 45 years I've owned about 35 vehicles, mostly GM land yachts. In all those vehicles I only replaced one coil. We are living in an epidemic of dishonesty.

I'd like to argue with you about "epidemic of dishonesty", except you are absolutely right. The ignorant and the people trying to make money off them, or tell them what to think, are overwhelming objective communication. Guys here deserve a lot of credit for trying to develop their basic troubleshooting skills they were never taught.

 

Maybe the rear plug wires aren't on the correct plug, and they're firing at the wrong time ?

 

Put 3 used TOYOTA DIAMOND 90080-19012 on it.
Wire spark plug in the right order.
No misfire anymore!

Thanks your guys!

 

Your spark plugs - being black - give a hint to a condition you have:
A rich fuel mixture can result in carbon fouling.

There are several potential reasons the fuel mixture is rich and these reasons range from a leaky fuel injector (a misfire generally would expel fuel into the exhaust), to problems with vehicle oxygen , MAF or coolant sensors.
I would venture with those misfires that your CEL had a P0430 code as well. Your Bank 1 [ O2 - A/F ] Sensor (Rear - firewall side) might be defective - you should see it switching positive to negative and your fuel trim should be opposite on a graph - when A/F sensor is high positive- short term fuel trim should be low.

Your old coil packs may have worked and been too weak to handle the abnormal A/F ratio mixture. You might want to check your Short Term and Long Term fuel trims - High Short Terms and Low Long terms could indicate a vacuum leak.