Car runs fine for days then rough. Check engine light comes on, flashes. Days later it’s running okay again. Why?
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1st thing, we need to know is what the codes are (the reason the check engine light is on), without that anyone is just guessing, like a crapshoot…
How many miles are on your 1997 Camry and what engine does it have??
When the Check Engine flashes, it means a major misfire is occurring that can cause damage to either the catalytic converter or the engine,
In the mean time, don’t drive the vehicle while the Check Engine light is flashing until it’s found out what’s causing the misfires.
Tester
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Mechanics handle this kind of thing every day…so I’ve heard.
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We’re talking about one of YOUR favorite cars 
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We sure are…and my ears perked up! I definitely hope we are able to help this person keep this quality vehicle on the road for many more years.
The car is already 28 years old . . .
Almost broken in!
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Different codes at different times. PO300, 301, 303, 304, 130, 133, 150, 153, 330.
267,000 miles. V6, 3.0 liter.
How old are your spark plugs, spark transformers, and ignition wires? Remember that on this engine, there are three spark transformers, which have two outputs–a direct coil-on-plug connection to each front cylinder, and an ignition wire going to the rear cylinder behind it. If any of these components are defective, that can cause an intermittent misfire.
Are there any reasons to suspect fuel delivery problems, such as a worn-out fuel pump which doesn’t maintain the proper pressure, worn-out fuel injectors, etc.
Does the engine make abnormal valvetrain noise? Fortunately, there’s no VVT, so you can rule that out.
@hank40, remove the footer from your response in post #9. You probably shouldn’t broadcast your email and phone number.
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I’m with @bcohen2010 on this one . . .
How long has that timing belt been in there, by the way?
Before you do any more testing or replacing parts, I’d do a compression test on ALL cylinders
Yes, ALL of them, including the ones that are kind of under the cowl
You’ve got adjustable valves on this car . . . bucket and shim style, meaning if anything’s off, you’ll need to replace shims
If your valve lash is too tight, you’ll have lower compression, which can cause misfires
Also, if that timing belt has jumped a tooth, all bets are off
But please answer my question about that timing belt
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Timing belt replaced 09/2013 at 185,140 miles.
I believe your timing belt is due again by time and mileage . . .
But I would consider doing that compression test
What about those coils, plugs and wires?
When were they done last?
I don’t think that we know how many miles were put on that replacement timing belt, but on the basis of elapsed time, it is much overdue for another replacement.
But, as you stated, the first step should be a compression test.
This is weird . . .
Earlier this morning, op posted the year and mileage at which the timing belt was last replaced
But that post has now seemingly disappeared
I’m seeing it.
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WTH?? You are the 1st person I ever remember calling an ignition coil a spark transformer… lol
Anyway, agreed…
By any chance was that a 305 instead of a 304??
Cylinders 1, 3, and 5 are all on the right side (firewall side) and use Ignition wires from the COPs that are on cylinders 2, 4, and 6 on the left side (radiator side) of the engine… If so, I would say the ignition wires are breaking down, but you could still have #4 ignition coil breaking down as well as 1 or 2 of the ignition wires…
As mentioned, I would run a compression test on all 6 cylinders, if it passes, then replace all 6 spark plugs with the correct OEM spark plug, NOT OEM equivalent, all 3 ignition wires and the #4 ignition coil (unless it was a 305 vs 304) and see what happens, the other 2 coils can be replaced later if wanted/needed…
And since the timing belt is 11+ years old and has 82Kish miles on it, I agree it is time to replace it also…
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If I knew the compression was good, I would replace ALL the plugs, wires and coils
Thats the way I do things at work . . . do everything, or don’t even touch it
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I always recommend all coils, but sometimes it’s a budget thing, like I said, the other 2 can be replaced if wanted/needed in a matter of a few minutes, now if they are hid under the plenum, I replace all hard to get to… But yeah, always all plugs and wires…
I have replaced 1 coil on one of mine with no issues with the others failing as long as I owned them… But the Infinity, I had one going bad and replaced all 6 at the same time…