P0301 Error Code

I have a v4 and over 200K on a 2007 toyota camry. Few days back check engine light came on and got the codes diagnosed at Autozone. Replaced Battery and all 4 spark plugs. This seems to have fixed it temporarily and after a few days, the check engine light came back on. Now, the same error code P03 (cylinder 1 Misfire Detected) showed up again. Looking to replace the cylinder 1 engine coil and see if this fixes it. Anything else, I need to be looking at ? Thanks in advance for your suggestion.

Don’t replace the coil.

Instead swap it with a coil form another cylinder.

Erase the P0301 code, and then drive the vehicle to see if a misfire code moves to the cylinder you installed the coil from cylinder 1.

If not, it’s not the coil.



When you removed the plugs from your inline 4 (not V4) was #1 oily? Oilier than the other 3?


I would check for an Intake air leak

Read more: P0301 2007 TOYOTA CAMRY Code Cylinder 1 Misfire Detected


Thank you…will do.

don’t remember seeing any oil. Will open it up again and check it out. thank you.

I doubt replacing the spark plugs and battery actually fixed the problem. The CEL is automatically reset when the battery is replaced, and it takes a few miles of driving before the computer will turn it back on again for the same misfire problem. Single cylinder misfires typically caused by one of these

  • spark plug
  • engine compression
  • fuel injector
  • coil
  • wiring to coil

Other possibilities as well (e.g. injector ok, but not getting its electrical pulse), but those above are where to start; have to eliminate them one by one. Start w/a compression test, followed by swapping components cylinder to cylinder. That is usually the best method, as posted above by Tester.

I’m always of the opinion that whenever a spark plug comes out the compression should be checked; even on a low miles engine much less a high miles one.

If the compression is down then nothing is going to cure the problem except an expensive fix. Lowered compression can also kill a new spark plug so that is something to keep in mind. If bad news exists it’s best to figure it out now so plans for the future can begin.

As an example of miles not meaning anything, a near new Subaru was towed in once with a trashed top end and that car had 7k miles on it. Yes, single digit 7. Compression was 60, 60, 0, and 90 when all should have been 190. Owner would not 'fess up but it was self inflicted.

1 Like

In my experience this is how an engine like yours tells you it’s time to have the valves adjusted. I would do all the steps suggested by @George_San_Jose1 and, if that fails, get the valves done. With 200,000 miles on the engine it’s surprising that it hasn’t happened already.

These engines don’t require a valve adjustment unless there’s an indication (valve noise) detected.

The valves are adjusted by measuring and replacing shims between the lifters and the cams.

This engine utilizes shims to set proper clearances, you will need a micrometer, valve clearance adjustment tool set for shimmed lifters,small magnetic arm, appropriate shim selecting charts (manufacturer will have this if you can get the nec. measurements).
Measure thickness of shims removed (using micrometer) and use this formula where T=Thickness of old shim; A=Valve clearance measured; N=Thickness of new shim required.
Intake valves: N = T + (A - 0.02 mm (0.008 in.)) Exh. valves: N = T + (A - 0.25 mm (0.010 in.))
Then you need to find shims as close as possible to the calculated values.
Valve clearances (cold) are as follows: Intake 0.15 - 0.25 mm (0.006 - 0.010 in.) Exhaust 0.20 - 0.30 mm (0.008 - 0.012 in.)
Note, if you are not familiar with precision measuring using a micrometer, this may be better left to a trained tech. These are high revving little power plants and you don’t want a problem at 8K rpm.

I drove my Camry well over 200,000 miles, and serviced other peoples Camry’s that had well over 200,00 miles.

None ever had the valves adjusted.


So if the compression is OK, and there’s no valve noise, leave them as is?

Valves too tight can cause the exhaust valves to burn worst case scenario or lower compression on the intakes. Valves too loose can cause valve train damage. Beats the cam lobes, valve adjusters up along with mushrooming the valve stems.

An exhaust valve too tight can burn in very few miles and the damage may be microscopic. However, adjusting that valve does not cure the problem. It may raise the compression temporarily but the damage is done. At some point that valve (or plural) is going to be an expensive problem. May be a month, 6 months, or a year or so but it’s going to happen.

Just because an engine appears to run fine does not mean the problem does not exist. I’ve only run into a “not needed” valve lash adjustment situation a very few times and that could be counted on a pair fingers. And that is from countless valve lash checks which were SOP.
Twice in my life while on motorcycle trips I’ve stopped to help a couple of people. One a guy with a new engine on an antique Harley. Lash was not rechecked after the rebuild and he was stuck in CO with near zero compression and the nearest city with any size 200 miles away.
The other was a pair of young ladies in a 4-banger Accord with a dead miss due to tight lash. I adjusted that valve by feel, got rid of the miss, but warned them when they traveled that last 300 miles home they MUST get that cylinder head repair done or they are going to be afoot. Hopefully they made it.

1 Like

My point was that, in my experience, the valves needed adjustment. And the reason was that the exhausts were too tight. A too tight valve does not make noise at all, and also does not close fully and/or for long enough, and the engine runs poorly and reports an intermittent miss in one or all cylinders.

While it may not be common, it does happen and if nothing else works it could well be happening here. We know nothing about the maintenance of the engine. While @Tester has not seen a need for adjustments in the Camrys he has worked on, the fact that owners have called upon a skilled mechanic like @Tester to maintain their engines tells me the engines themselves may be generally in better than average condition.

My Corolla has 200 K miles, uses the shim method for valve adjustment per Tester’s post above. I’ve never needed to change the shims. I always measured the valve clearance when I change the spark plugs every 24 months. Valve clearance is approaching the “too much clearance” end of the scale spec on several of the valves, but so far they all remain within Toyota’s spec. OP might want to have their shop measure the valve clearance, easy enough to do, and an opportunity to replace the valve cover gaskets, but I wouldn’t expect to find any sort of serious valve clearance problem at 200k. If there’s a problem under the valve cover, oil sludge is the most likely.

My point as always is this. If someone is not checking the valve lash then how do they know exactly what is going on in that top end?
I’ve messed with mechanical lifters my entire life and I cannot even begin to tell what the clearance on a single one of them is unless it’s godawful loose and tapping away madly.

My sister in TX has a 2017 Accord with 70k miles on it and the dealer where she bought the car told her they are to be inspected “audibly”; which is the most asinine recommendation ever made. I told her a year ago the next time she took the car in for service to ask the service writer what is going to happen if the valves are quiet and tightening up on the exhaust valves. All she got in response was “Well…uh…uh… I don’t think it’s a problem…uh…don’t worry about it”.

She will run the risk of ending up with a miss like the 2 young ladies I ran into on the way back from Sturgis due to a tight and burned exhaust valve. And sis says that she intends for that Honda to last her the rest of her life and she is only 61. And no transmission services either as the service writer told her the “fluid lasts forever”.
I’ve told her several times the “rest of her life” ain’t gonna happen at this rate.


…so it seems bad advice to do valve adjustments only if there is noise from the valve train. And yet that is often the advice we hear or read in owners manuals.

I wonder if the carmakers want to 1) avoid an expensive maintenance procedure that usually does no good and that 2) if not done well can produce a valve problem that would not have happened if the valves had just been left as is.

Do valve clearances tend to get bigger or smaller just through normal engine operation over time?

Yes… Both. Seat recession reduces clearances and wear increases clearances. Both can happen.

1 Like

Every few years I have adjusted the valves on my 1999 Honda Civic. There are always several that have gone away from spec. Some had excess clearance; I am not sure but possibly some had gone too tight.

I adjusted the valves only once on my Honda S2000 at around 90K miles. Some were a little out of spec, tight and loose. I adjusted all to the same clearance in the middle of the spec. The engine idled more smoothly after as I expected. Nothing else changed.

1 Like

I think it’s amazing that in the year 2022 we still have engines that employ mechanical valve lifters that need periodic adjustment. We’ve had hydraulic valve lifters since at least the late 1940’s.

1 Like