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P0303 on a 2004 Sienna. Any most likely causes? UPDATE: not plug or coil Login/Join 
Team Apathy
posted
My wife’s Sienna started chucking this code yesterday, misfire in #3. You can feel it missing when it starts up but it seems to smooth out with a few seconds and I couldn’t honestly say if it is still missing. I think not. It is smooth and acceleration seems normal.

Of course #3 is on the demon side of the engine. I was hoping I could relatively easily swap coils with another cylinder and hopefully confirm a bad coil. When I pulled the engine cover off I knew I was in trouble. It appears to me that the whole intake manifold needs to come off to even see the area in question?

My new obd scanner has freeze frame data, I just don’t know how to use the data. If I share can anyone help pinpoint the problem? Is there something that typically goes wrong? The van has over 130k and I don’t know when the plugs were changed last, if ever. We bought it used recently.

Any hints?? Confused

This message has been edited. Last edited by: thumperfbc,
 
Posts: 5325 | Location: Modesto, CA | Registered: January 27, 2005Reply With QuoteReport This Post
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You need to remove the cowl and intake manifold to get to the rear coil packs. The van may have never had a tune up since it’s difficult to get to them. The problem is more than likely a bad plug or coil pack.

https://m.youtube.com/watch?v=HugulBElvtM


———————————————-
Those who can, do. Those who can’t, manage.
 
Posts: 806 | Location: North And East Of The Big Chicken | Registered: November 18, 2017Reply With QuoteReport This Post
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A misfire of that type is usually an ignition coil. Also check the spark plug for carbon tracking.



The rest of them are probably due for replacement, this being a 2004. They are 105,000 mile iridium.

When the spark plugs are more accessible Roll Eyes I will often swap the coils with a different cylinder and see if the miss follows the coil. Sometimes, a miss only right after startup can be a head gasket leaking coolant into the cylinder, but head gasket failure is rare on this engine. This is the kind of crap that makes me wish for early retirement.
 
Posts: 21991 | Location: Johnson City/Elizabethton, TN | Registered: April 28, 2012Reply With QuoteReport This Post
Team Apathy
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quote:
Originally posted by egregore:
A misfire of that type is usually an ignition coil. Also check the spark plug for carbon tracking.



The rest of them are probably due for replacement, this being a 2004. They are 105,000 mile iridium.

When the spark plugs are more accessible Roll Eyes I will often swap the coils with a different cylinder and see if the miss follows the coil. Sometimes, a miss only right after startup can be a head gasket leaking coolant into the cylinder, but head gasket failure is rare on this engine. This is the kind of crap that makes me wish for early retirement.


Yea, the coil swap game was my intention, until I removed the engine cover. My spirit deflated quickly.

Is it normal to replace all coil packs if one goes out? Or just the 1 that’s bad? Or the three in the back? If the intake is coming off anyway all plugs are getting changed. That’s a given. Just not sure about coils.

What other misc. parts would be needed? I’m guessing some sort of gasket(s) related to the intake?
 
Posts: 5325 | Location: Modesto, CA | Registered: January 27, 2005Reply With QuoteReport This Post
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I offer all the above options to clients. Most of them opt for just the bad one. The upper intake manifold (plenum) has a gasket, but it is metal. It can usually be reused, but it doesn't cost that much either.
 
Posts: 21991 | Location: Johnson City/Elizabethton, TN | Registered: April 28, 2012Reply With QuoteReport This Post
Team Apathy
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quote:
Originally posted by egregore:
I offer all the above options to clients. Most of them opt for just the bad one. The upper intake manifold (plenum) has a gasket, but it is metal. It can usually be reused, but it doesn't cost that much either.


How many hours of labor are we talking to get the cowl and intake off for a good mechanic? If it’s only an hour of shop time to do the job then I can see maybe just changing the one. If it is more substantial time than that changing the back three seems to make sense.
 
Posts: 5325 | Location: Modesto, CA | Registered: January 27, 2005Reply With QuoteReport This Post
delicately calloused
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My advice is to replace them all with verified OEM parts. The reason for that is if you don't, you'll be battling reliability issues from now on. Here's how I know: My first coil pack died at 175,000-ish miles. Out of convenience and my inescapable cheapness I bought a new one from O'Reilly. All seemed fine until the second coil pack went out about 10,000 miles later. Back to O'Reilly. All is well and then #3 puked.....O'Reilly. That is when I decided to replace the rest of them proactively since when they went out it was always at the worst possible time. However, O'Reilly was charging me over 100.00 each.......and I'm a cheapskate. So I found an OEM source online for less than half and bought them. Seems if you plan ahead you can save money and time. Whodda thunk it? Thinking I was done and driving in a very remote area IN THE FREEZING WINTER, one of my coil packs puked. Upon replacing I noticed it was one of the O'Reilly parts. Turned it over and there was the fatal flaw......Made in China. Shiiiiiiiii. That coil pack didn't make it 5,000 miles. I wasted 300.00 on O'Reilly Chinese crap. The other two Chinese packs puked on the same day about 3,000 miles later. Fortunately, I had bought those OEM parts and by then was anticipating their failure. Replace them all with OEM so you can have reliability and convenience.

To punctuate my disgust for O'Reilly junk parts I'll mention the tie rod ends I bought from them. Both loose and garbage after 6 months. Never again.



I'm sorry, I'm thinking about the cats again...
 
Posts: 24911 | Location: Highland, Ut. | Registered: May 07, 2008Reply With QuoteReport This Post
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quote:
Originally posted by darthfuster:
My advice is to replace them all with verified OEM parts. The reason for that is if you don't, you'll be battling reliability issues from now on. Here's how I know: My first coil pack died at 175,000-ish miles. Out of convenience and my inescapable cheapness I bought a new one from O'Reilly. All seemed fine until the second coil pack went out about 10,000 miles later. Back to O'Reilly. All is well and then #3 puked.....O'Reilly. That is when I decided to replace the rest of them proactively since when they went out it was always at the worst possible time. However, O'Reilly was charging me over 100.00 each.......and I'm a cheapskate. So I found an OEM source online for less than half and bought them. Seems if you plan ahead you can save money and time. Whodda thunk it? Thinking I was done and driving in a very remote area IN THE FREEZING WINTER, one of my coil packs puked. Upon replacing I noticed it was one of the O'Reilly parts. Turned it over and there was the fatal flaw......Made in China. Shiiiiiiiii. That coil pack didn't make it 5,000 miles. I wasted 300.00 on O'Reilly Chinese crap. The other two Chinese packs puked on the same day about 3,000 miles later. Fortunately, I had bought those OEM parts and by then was anticipating their failure. Replace them all with OEM so you can have reliability and convenience.

To punctuate my disgust for O'Reilly junk parts I'll mention the tie rod ends I bought from them. Both loose and garbage after 6 months. Never again.


This. Electrical parts should always be OEM. You’re asking for trouble if you go cheap.


———————————————-
Those who can, do. Those who can’t, manage.
 
Posts: 806 | Location: North And East Of The Big Chicken | Registered: November 18, 2017Reply With QuoteReport This Post
Team Apathy
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quote:
Originally posted by darthfuster:
My advice is to replace them all with verified OEM parts. The reason for that is if you don't, you'll be battling reliability issues from now on. Here's how I know: My first coil pack died at 175,000-ish miles. Out of convenience and my inescapable cheapness I bought a new one from O'Reilly. All seemed fine until the second coil pack went out about 10,000 miles later. Back to O'Reilly. All is well and then #3 puked.....O'Reilly. That is when I decided to replace the rest of them proactively since when they went out it was always at the worst possible time. However, O'Reilly was charging me over 100.00 each.......and I'm a cheapskate. So I found an OEM source online for less than half and bought them. Seems if you plan ahead you can save money and time. Whodda thunk it? Thinking I was done and driving in a very remote area IN THE FREEZING WINTER, one of my coil packs puked. Upon replacing I noticed it was one of the O'Reilly parts. Turned it over and there was the fatal flaw......Made in China. Shiiiiiiiii. That coil pack didn't make it 5,000 miles. I wasted 300.00 on O'Reilly Chinese crap. The other two Chinese packs puked on the same day about 3,000 miles later. Fortunately, I had bought those OEM parts and by then was anticipating their failure. Replace them all with OEM so you can have reliability and convenience.

To punctuate my disgust for O'Reilly junk parts I'll mention the tie rod ends I bought from them. Both loose and garbage after 6 months. Never again.


So, the Denso, which I think is OEM for Toyota, are $53. United Motor Products replacement, which is marked as made in the USA, is $33. Do you think those are probably ok as they are domestic?

This message has been edited. Last edited by: thumperfbc,
 
Posts: 5325 | Location: Modesto, CA | Registered: January 27, 2005Reply With QuoteReport This Post
delicately calloused
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Yes, the Denso part is OEM. $53 each is about what I found mine for. You can see why when O'Reilly charge me over $100 each and they only lasted a few thousand miles, I was fairly upset. I will never go back to O'Reilly for anything ever again. The other thing I would do if I were you and access to the coil pack and spark plugs is difficult, is I would change the spark plugs while I'm in there and be sure to change all of the coil packs at the same time so you can go trouble free for another hundred and thirty to 140,000 miles.



I'm sorry, I'm thinking about the cats again...
 
Posts: 24911 | Location: Highland, Ut. | Registered: May 07, 2008Reply With QuoteReport This Post
Team Apathy
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quote:
Originally posted by darthfuster:
Yes, the Denso part is OEM. $53 each is about what I found mine for. You can see why when O'Reilly charge me over $100 each and they only lasted a few thousand miles, I was fairly upset. I will never go back to O'Reilly for anything ever again. The other thing I would do if I were you and access to the coil pack and spark plugs is difficult, is I would change the spark plugs while I'm in there and be sure to change all of the coil packs at the same time so you can go trouble free for another hundred and thirty to 140,000 miles.


A coworker is going to help me out with the labor. He used to work at a Chevy dealer and says he has done the job before on similar set-ups, though not the Sienna specifically.

I'm going to pick up the Denso oem plugs (all 6) and probably 3 of the coils from Amazon. The other 3 coils are easy enough to get to that I'll do them later in order to save money now. I'd rather just do the one bank with quality parts while access is available than do all 6 with cheaper parts.
 
Posts: 5325 | Location: Modesto, CA | Registered: January 27, 2005Reply With QuoteReport This Post
Just for the
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Picture of comet24
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My parents have the same generation Sienna and about a month ago my dad was talking about changing the plugs. He wanted some help so sometime this summer I will be helping him but after looking at the engine I am not looking forward to it.

I would definitely change out the plugs at that mileage. I would bet the original owner never had them changed. I don't normally suggest changing working coil packs but those back ones are such a PIA to get to. I would use factory parts for those coil packs. Changing factory working coil packs with cheap ones will sometimes do more harm than good.

Definitely look at the plugs when you pull them out. The plug can tell you if there are any issues with seals and oil is getting into the combustion chamber.

I look forward to your report on how this goes since I may be helping/doing this for my parents down the road.


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Because in the end, you won’t remember the time you spent working in the office or mowing your lawn. Climb that goddamn mountain. Jack Kerouac
 
Posts: 15090 | Registered: March 27, 2004Reply With QuoteReport This Post
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I am afraid of Amazon auto parts. I bought name brand and received Chinese knockoff.


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Posts: 3155 | Location: Commonwealth of Virginia | Registered: January 15, 2007Reply With QuoteReport This Post
Team Apathy
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Well, I discovered a coworker was a tech at the local Chevy dealer and he said he was more than happy to do the repair labor for me and he did just that. He was able to relive the intake without taking the wiper and cowl assembly off. He’s got skinny little arms.

Cylinders 1, 3, and 5 all have new OEM plugs and coils.

In the pursuit of curiosity we decided to put the plug from 3 into cylinder 2 and the coil from 3 on to cylinder 6 (old plug). #4 has a new plug. I have new plugs for #2 and #6, but going to run it like it is and see if a misfire happens on 2, 3, or 6 again.

I’m going to get the guy a gift card to a restaurant or something as a thank you... it would have been a $350 labor charge at my mechanic, so I’m thinking $100 is a good thank you?
 
Posts: 5325 | Location: Modesto, CA | Registered: January 27, 2005Reply With QuoteReport This Post
Team Apathy
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A bad update and request for my experience...

The original code, P0303, came back despite new plugs and coils. Not good, I’m guessing.

What’s the next thing we should look at? My buddy says other causes could be oil leaking past the valve seals, but that should have produced a distinctive looking plug. He says the plug was a little dark but that it didn’t appear to be oil fouled. His feeling was unburnt fuel from the insufficient spark likely from a failing coil.

Confused
 
Posts: 5325 | Location: Modesto, CA | Registered: January 27, 2005Reply With QuoteReport This Post
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Could you have a bad injector and are not getting the proper air/fuel ratio, thus causing a weak spark?
 
Posts: 621 | Location: Virginia, MN | Registered: October 01, 2012Reply With QuoteReport This Post
Team Apathy
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quote:
Originally posted by giz55792:
Could you have a bad injector and are not getting the proper air/fuel ratio, thus causing a weak spark?


Was just reading about injectors. I’ve never dealt with them before. I did notice it smelled rich after we had swapped the plugs and coils.
 
Posts: 5325 | Location: Modesto, CA | Registered: January 27, 2005Reply With QuoteReport This Post
Technically Adaptive
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Your getting into scan tool diag. now, need to look at fuel trims (long and short term), see if it's adding or subtracting fuel on that bank.
Find a reputable shop to do some diagnostics on it.
 
Posts: 696 | Location: Willcox, AZ | Registered: September 24, 2006Reply With QuoteReport This Post
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Toyota will also show misfires in real time on a scan tool, so you can see exactly when and on which cylinder(s) it occurs.
 
Posts: 21991 | Location: Johnson City/Elizabethton, TN | Registered: April 28, 2012Reply With QuoteReport This Post
Team Apathy
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So, I had hoped to take the suspect injector off cylinder 3 and switch it with cylinder 4... but I didn’t realize the injector was underneath the intake as well.

If the intake had to come back off, I’m considering just replacing it without doing any trouble shooting...

An injector from the dealer is $180. From Oreilly it is $130. From on online source, for a factory injector that’s been rebuilt here in the U.S. it’s only $20, with a couple day delay.

So if my buddy is going to pull the intake off AGAIN, why not just put the rebuilt one in? Anybody wat to confirm or deny the value of that thought?

If I’m doing cylinder 3, should I also do 1 and 5 since they are only $20?

Finally, is there anything else under there that might just consider switching out?
 
Posts: 5325 | Location: Modesto, CA | Registered: January 27, 2005Reply With QuoteReport This Post
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