toyota corolla 2003 check engine light P0301

[Jeroen]

Hey Guys,

I’m looking into a check engine light P0301 (misfire cylinder 1) on my toyota corolla (2003). (it’s a 1600cc VVTi engine with only 27000 kilometers on it (about 17000 of 18000 miles))

****short version*****
already replaced plugs and air filter
cleaned maf sensor and throttle body
****end of short version*****

*****long version***** 🙂

I started using this car about a year ago at which point it had been sitting for 2 years. (it belonged to the deceased father of my girlfriend) When i took it into use i brought it to a toyota dealer and explained that it has been sitting for 2 years and asked for advice what service was needed. They suggested to do a oil change and take it to the mandatory inspection. It passed the inspection. I also inquired about the old fuel still left in the tank (2/3 full). They said that i could just use this fuel without a problem. (i was more inclined to remove it and fill her up with new fuel but since i couldn’t get it out in a simple way i stuck with the dealers advice and used up the old fuel.

So from that point on i used the car from time to time. (i only did 1700 miles with it this last year) I always seemed to have a bit af a rough idle where it sometimes dipped a bit low and appeared to be on the brink of stalling. I first thought i might be the old degraded fuel. But after 1 or 2 fill-ups it still remained. Since i didn’t use it alot and it never actually stalled i got used to it a bit. Then after 4 months of using it i noticed a performance issue (loss of torque and rough running of the engine) After a short while i got a check engine light. I took it to the dealer to have it checked (unfortunately i didn’t read the code myself) and they replaced the sparkplugs and reset the check engine light. This solved the performance issue but the rough idle still was there (although it seemed to be a bit better then before). Since it was not completely solved it took a look myself and saw that the air filter was a bit dirty (looked quite grey/black and contained some debris of fallen tree-leaves) so i decided to replace it since it wasn’t expensive and a clean air-filter is always a good idea 🙂 At that time i also checked the maf-sensor (sprayed it with some compressed air to clean it (the parts store here didn’t have any maf-sensor-cleaner at that time) and some contact-spray on the electrical connections for good conductivity. Lastly I cleaned the throttle-body with some throttle-cleaner. That seemed to improve the situation with the idle (or it could be just in my mind 😉 but it still wasn’t gone completely. But since I thought it was better i decided to give it some time. Last week i got a check engine light again. I usually only do short trips with this car but that time i had done a 30 minutes highway drive (so the engine was well warmed up). When coming from the highway i was waiting on a slight uphill and there it hiccuped again very noticeably but without stalling only to flash the check engine light a bit further down the road for a few seconds and then having it constantly lit. Strangely enough the light went off on the next ride. But a few days later it was back. (flashing a few seconds and staying on and this time also on the next rides) Yesterday i got out a laptop and odbII-cable and it was a P0301 (cylinder 1 misfire detected).

******end of long version*****

After reviewing lots of information on this and other websites i decided that this weekend i will check for vacuum-leaks as a next step(already watched the videos by eric). (and also maybe check the ignition: plugs, cables (but i suspect they would have already looked into that at the dealer when they changed the plugs some months ago)

What do you guys think? Good idea? Or should i look into other things first? Or does anyone have some pointers/experience on this type of engine?

Thanks in advance

Greetings

Jeroen

ps: i’ll hopefully get back with more findings after the weekend. (just wanted to see if i can check other stuff as well while i’m in there;)

Topic

[Daniel]

I would not assume they looked at the wires. I would pull one wire at a time (so they don’t get mixed up) and visually inspect each one. Look for abrasions, cuts, burns, and any rigid parts in the wire. You should also look at all the wires while the car is running to see if there are any electrical arcs (this works best when in total darkness.) If that thing has a “points” distributor you may want to go ahead and replace the cap and rotor. If it has coil packs you may want to get them tested.

[Jeroen]

Super i’ll check those things as well. (maybe i’ll already fire her up tonight when its dark to check for arcs) If i’m not mistaken Eric used a spray bottle with water in one of his video’s to search for such a problem (but he found a vacuum leak instead in the end). I’ll try that as well.

Thanks for the extra pointers 🙂

[Jeroen]

Ok i got round to checking some stuff:)

I removed the engine-cover and unplugged the cables/harness that goes to the sparkplugs. I then pulled the ignition coils that connect to the sparkplugs and found something interesting right away. The left most coil had a large rupture in the lower rubber boot which fits over the sparkplug. The sparkplug-hole was also showing some rust while the other 3 holes were looking as new. I got some pictures but the uploading feature of the forum seems to be out for a few days… (i’ll post them asap) But the main question now is will replacing the rubber boot/whole ignition coil be sufficient? (because i would presume this problem wasn’t there when they changed the sparkplugs at the dealership… they didn’t mentioned anything about this anyway) So i would think there might be another problem that is really the root cause of all this…

Any idea’s on this? (sparkplug not properly tightened? gasket-failure around that cylinder? something else…)

Thanks in advance

Perre

[Jeroen]

first pictures

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[college man]

Looks like oil in the spark plug tubes.I would
suggest doing the valve cover gasket.looks pretty
easy.After the install.Replace the cop.
here is a link of what you would be looking at.;)

http://www.justanswer.com/car/10sv8-1999-toyota-corolla-liquid-leak-spark-plugs-one-two.html

[Jeroen]

Hi,

I also pulled the sparkplugs and took a picture. The one in the socket is from the second cylinder from the left (the good one so to say) the other one is from the problem-cylinder. Looking at the plugs and checking some pictures of spark-plug-problems on the web there doesn’t seem to be oil on the sparkplugs… Or am i mistaken? (both plugs where dry) The problem-ons just looked a bit more used.

I also felt into the spark plug well and it was not oily. It was dry and had some black dusty powder on the sides. Would it be safe to say that the gasket would be fine? (i could remove the cover and check the state of the gasket. I have a haynes manual which describes the procedure. It seems doable.)

Also i went to the parts store and to a toyota dealer. A new ignition coil from denso would be 230 euro excluding taxes and a aftermarket one from the parts store would be 100 euro excluding taxes. Does anybody have any experience with aftermarket vs brand-parts for these parts? I hardly do any miles with this car. (i’ll probably end up doing 3000km this year with it) So i’m not sure if the denso one would be worth the money. Although i am convinced you should stick to brand-parts for the best results in most cases.

@college man: just to be clear: by “Replace the cop” you mean the ignition coil?

Thanks in advance

Greetz

Perre

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[college man]

The cop is (coil on plug)If it were me I would buy
the OE Toyota cop.due to the other the are factory.
In my opinion I would not pull the valve cover to check
the gasket.I would just replace it.If the oil in that spark
plug hole is not fresh.The leak may have happened when the car
sat.the gasket shrank.then when you stated driving it again it leaked
until the gasket reswelled.Not worth buying an expensive coil to have
a leak blow it again.Fix it once and be done with it.clean all that residue
out with brake clean.install new plugs or plug.;)

[Charles]

I think what you are seeing is corona caused by high voltage leaking. When TV’s were servicable used to see it around high voltage leaks all the time. You get the same thing inside the old distributor caps. You can prove it by swapping the coil pack between 1 and 2 and see if the code moves to the number 2 cylinder. You might be able to find a good OEM replacement at a salvage yard.

[Jeroen]

Current status:
ordered a new gasket at the toyota dealership
ordered 2 coils second hand from the same model corolla (with roughly the same mileage)

Once they come in i’ll get back with you guys with hopefully teh final result 🙂

[college man]

keep us posted.;)

[Jeroen]

Just stopped at the toyota dealership and picked up the gasket. The second hand coils are also on their way. Tomorrow i will install the gasket. That way i will only have to put in the replacement coil when it arrives and test-drive it 🙂

Just a question still about putting the spark-plugs back in. I have a 16mm socket which i used to get them out but it seems the spark-plug sits quite tight into the rubber inside the socket so when i want to reinstall them the socket is releasing from my wrench-extension rather then from the spark-plug. At that point the socket is to deep into the tight spark-plughole to get it out with for example some pliers. Any tips on this? I already saw there are some longer pipe-wrenches which could be used but they don’t allow to use a torgue-wrench with them. I’ll check at my local auto-parts-store tomorrow if they have anything useful. But if someone has a good tip… that’s always appreciated.

[college man]

see if this helps

[dreamer2355]

You can buy an extension that will lock your socket in place to stop it from falling off.

Perfect for tune up jobs 🙂

[Jeroen]

Hey Guys,

Due to the holidays i’m a bit late with my response. I got all the parts and went ahead with the repair. I cleaned the sparkplughole and replaced the gasket. Torqued evreything down to speck and replaced the coilpack on cylinder nr 1. Took the car for a testdrive and it felt smoother then before. So i guess this is a succesfull job. I will do some more driving to see if anything comes up but i’m feeling confident that it will be fine now 🙂

Thanks for all the advice

A good 2013 for everybody here 🙂

Greetz

Jeroen

[college man]

Thanks for the update.Happy New Year. 🙂

[Author]

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