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2004 Toyota Matrix misfires and injectors keep failing

I have a 2004 Toyota Matrix, 2 WD, 4 cylinder. I’ve had the car since it was new, and starting in March of 2008 the check engine light has come on several times for a misfire on cylinder #2 (code P0302). First the intake gasket was replaced, then the ignition coil and spark plug, then the injector (twice), then all 4 plugs, then the ignition coil again, and now they are saying the injector is bad again. Always on cylinder #2. All of this at the dealer where I got the car.

I’m not sure how they’ve determined the coils have been bad, but they’ve moved the injector to other cylinders and the misfire has moved with the injector. Yet it always initially goes bad on #2.

One bit of frustration: while the notes aren’t clear, the service guys have said that when they replaced injectors, they wouldn’t go into #2. I.e., they would swap the injectors between #2 and #4, and when they found that the misfire moved to #4, they put the new injector in #4, rather than swapping back and putting the new one in #2. So it is unclear how old the injector currently in #2 is.

Initially, the car was under warranty, so I didn’t have to pay anything, but as it stands now they want me to pay for a new injector since it is out of warranty. It seems to me like there’s some issue that was happening while still under warranty that was causing this, but they said they can’t think of anything. It seems odd that any injectors would fail, more odd that 3 would fail, and even more odd that all 3 failures would occur on cylinder #2.

Below are all of the service notes from the dealer. Any ideas?


March 18, 2008


“Cause: Found code P0302 stored testing found faulty intake gasket”

“Correction: Replaced intake gasket and cleared trouble code”

May 14, 2008


“Cause: Inspect for cause, found cylinder #2 ignition coil failed”

“Correction: Replace cylinder #2 ignition coil and spark plug”

May 19, 2008


“Cause: Code P0302 SW #3 & #2 inj now miss on 3”

“Correction: Replaced cylinder #2 fuel injector”

September 5, 2009


“Cause: Code P0302 stored”

“Correction: Perform diagnostic scan test. Miss on cylinder #2. Swap ignition coil and spark plug. Noted plug had ash build up. Perform compression test. Swap injector to cylinder #4 and miss followed. Replace #2 injector.”

--Out of warranty, May 2010–

October 16, 2010


“Cause: Code P0302 misfire #2 cyl. Found bad s plug.”

“Correction: Replaced all 4 plugs”

November 24, 2010


“Cause: Code P0302”

“Correction: Installed a known good #2 coil, and code has not come back. Customer to monitor.”

--Check Engine Light came on twice during this time, went off before going in for service–

January 7, 2011


“Tech verified misfire. Found code P0302 for #2 cylinder misfire. Swap #1 and #2 injectors. Reassemble and test drive now misfire on #1 cylinder. Recommend replacing injector now in #1 cylinder. Customer declined at this time. Estimate to replace fuel injector with Toyota injector $350 and aftermarket injector $258.”

There is absolutely no way at all that you should be paying for anything. It seems clear that you’ve had the same ongoing problem and they have not dealt with it. Don’t hesitate to get Toyota corporate involved.

I have to assume that they have done an exhaustive search for all technical service bulletins?

Do you happen to know what the results of the compression check were (9/5/2009).

If it were me I’d now be suspecting a problem with the PCM (engine computer). It fires both the injectors & plugs and a problem with it may be continually frying the #2 injector. That’s the first thing that comes to my mind anyway - depending on what the compression numbers are.

Whatever it is - don’t let them make this out to be your problem.


I haven’t yet checked out the bulletins. I’ll do that next. The guys at the dealer said they had never heard of anything like this, but…who knows.

No idea about the compression check, other than I’m assuming it was ok, since there were no further notes. I can follow-up next week.

I generally like my dealer, but today I had to point out a few things on the history that they missed. If they won’t budge when I speak to them next I’ll likely escalate to corporate. We’ll see.

My understanding is if the problem was attempted to be repaired under warranty it is covered after the warranty. Going with Cig.

Two things…

  1. I haven’t been able to find any relevant bulletins.

  2. My knowledge of this is quite limited, but my understanding is there’s always power going to the injectors, and then when they are to be fired the computer grounds the circuit. Which would seem to prevent, say, the computer from sending too much voltage to the injector somehow. And if it was somehow firing it too much, I would expect misfires and/or error codes about too rich of a mixture. Perhaps I’m missing something?

The computer idea sounds promising, but I’m just wondering how it could actually ruin the injectors.

Is there a pvc port or vaccume leak at that runner? What makes a bad plug? Was it carbon fouled. Fuel fouled? Oil fouled? Mechanical failure? Worn? Was it replaced with same plug in all four? Same resistance and heat range? Is the factory wires being used? They have a set resistance. The injectore should be replaced in groups or check all resistance in each. A low resistance can cause high curernt to mess with driver circuits. Make it’s not finding ground before plug because of bad wires/tubes. I’m not a tech but I try to think like one. But If a coil has gone bad in a reasonable time the rest are probably soon to follow. Same with plugs wires and coils but sometimes it’s a judgement call.

That is normally the way injectors operate and I can’t explain how a PCM fault damages components that it controls but it does happen.

Of course, I am grasping at straws.

Here’s another “straw” - there is some problem in the head cooling passages around cylinder 2 - this area of the head overheats and eventually fries the injector.

There was one mention of ash buildup on the #2 plug. Do you know whether or not this has regularly been the case? Perhaps there is a bad valve guide seal on that cylinder. That can not only mess with the plug creating firing problems but can also gunk up the injector.

Either way I still think this is Toyota’s problem - you’ve had the same problem since March '08 and about 63K miles. The dealer has continually administered aspirin but hasn’t figured out what is causing the headache.

I agree with the others that since this was initially reported while under warranty it still should be covered under warranty. Your Owners’ Manual came with a booklet providing contact information necessary to move the decision up to the next level.

You have a good basic understanding of the injector circuits, but there are a few details missing. Because the circuit to the injector is always enabled does not menat that there’s current moving through it. That only happens when the circuit is completed vis “grounding” by the ECU. If there were an “open” in the circuit between the injector and the ground, you could even be misleed by testing for voltage by checking from the injector’s “hot lead” to ground if you were making the ground connection with the meter. Voltage is checked by connecting the meter in parallel with a component, so this is an easy error to make.

It’s impossible for the computer to send too much voltage to an injector. Full 12VDC is applied whenever the injector is activated. The amount of fuel is regulated not by how much voltage is paplied to the injector coil, but rather by how long the voltage is applied. The injector “pulses”, open - closed - open - closed. How much of that time is spent “open” is what regulates the amount of gas. Your comment about expecting codes if it were being kept open too long are correct.

Normally, I’d suspect the #2 injector connector or wiring, but since the problem is moving with the injector, that sort of rules that out. Under these circumstances I’d suspect that something in cylinder #2 is inducing an injector malfunction.

At this point I’d want to inspect and test the failed injector on the bench. Some other problem, like perhaps a minor headgasket leak or some oil getting into that cylinder and burning, and somehow getting back past the intake valve and depositing on the injector, may be causing the injector to gum up and fail to close properly. The comment on the ash buildup would support the theory of oil getting into that cylinder. Unfortunately, a compression test checks the overall integrity of the cylinder walls and the compression rings, but not of the oil rings. You cold have gummed up oil rings in that cylinder and still have it check good for compression.

That would be my guess. Oil getting into the cylinder, burning, and depositing ask on the injector tip, causing a malfunction. Considering the intake valve, the theory is a stretch, but an examination and bench test of a failed injector should be done.

It might even be wise to run some Gumout (or similar) from the parts store through the engine. Just be sure to follow the directions to the letter.

Thanks for this and cigroller’s additional reply above.

At this point, I don’t have much more to offer, but Monday or Tuesday I’ll call the dealer and discuss it more with them.

It seems obvious to me that there’s some overreaching issue that’s been in place since '08, but trying to convince the service guys of that is apparently easier said than done.

I’ll keep folks posted.

Thanks for the reply. Hope you’ve been keeping your copies of the shop orders.

Yeah, I have everything, plus they printed out the history yesterday. I went back and checked, and what they printed matched what I already had (above). Unfortunately, as you can see, the notes entered are sometimes less than amazing.

Other than the plugs in October, I haven’t been charged for anything yet. Good, but of course they want me to pay now for something that’s likely a band aid.

For some reason I think that some one is missing something here. Can you perform some troubleshooting ?
Please read the attached file and let us know how it goes…

Depending on how things go, I’ll try some of that, but at the moment I’m waiting for a call back. On the way home yesterday I was smelling gasoline, and a check this morning reveals gas squirting out near the #2 injector. Apparently they didn’t put things back together correctly. So I need that dealt with first…

well, it is recommended that when removing the Fuel Injector to replace the O rings or seals…

Um. It is not a matter of voltage to the injector unless there is other voltage drops or resistance in circuit then you will NOT get the 12v. It is regulated by the pulse width. Current can be an issue. if the resistance is low more current is produced at the same voltage.This can shut down driver for that or all circuits.

It went back to the dealer (towed) yesterday…they’ll look at it on Monday. I printed out this thread and highlighted a number of things for them to look into. We’ll see what they say on Monday.

I wonder if these injectors are failing electrically or mechanically.

Were any kept for further testing?

I never got any in the past. If they were tested, there were apparently no notes to that effect.

I’ll insist they test the current bad one tomorrow if they aren’t already going to try.

Have them run a compression test of the engine, on all the cylinders.
The 1.8 4 cylinder engine had some problems with the oil control rings on the pistons getting carboned up from 1997 through 2004, due to improper drain holes drilled into the oil control ring channels.

If bad on the #2 cylinder, that would explain the constant misfire for so long.
Then, Toyota will have to replace your engine.


First off, as an FYI, this:

October 16, 2010
"Cause: Code P0302 misfire #2 cyl. Found bad s plug."
“Correction: Replaced all 4 plugs”

Should read:

November 19, 2010
"Cause: Code P0302 misfire #2 cyl. Found bad s plug."
“Correction: Replaced all 4 plugs”

Next…got my car back after the leaking fuel problem. They replaced all 4 injector o-rings and insulators.

Finally, spoke some more with the service manager again. I mentioned the oil rings, but he wasn’t really buying in on it. He seemed to think that if there were problems, they wouldn’t just be on the #2 cylinder, and that I’d be burning oil (which I don’t seem to be). He mentioned using a scope to look inside the cylinder, but when I asked if they had or would do it, he kind of brushed that off. Can’t recall exactly why.

I did get his attention with the spark plugs, though. While the service adviser in November 2010 thought the plugs had never been changed, the #2 plug had been changed in May 2008 at 64,560. So the #2 plug only had ~28,000 miles on it. To my untrained eyes, the #3&#4 plugs don’t look too bad, while #1 and #2 have quite a bit of white buildup on the outside of the side electrode. Keeping in mind that the #2 plug had 64,560 fewer miles on it than the #1 plug. That said, he didn’t seem to know what to make of it. Note that “ash build up” was noted on the #2 plug at 79,974, which was only ~12,000 miles into the life of the plug.

I’ll try and get some photos of the plugs later.

The service manager is going to e-mail his Toyota field tech somebody or another to see if they have any ideas. Hopefully I’ll hear back in the next few days.