Troublesome dashboard check engine light

[Redneck]

I have a 2004 Toyota Tacoma with a 2.4L 4-cylinder engine. I have a check engine light that keeps coming on when the engine is started. The engine appears to idle rough at 800rpm. For the first 5-8 minutes the light will flash and then will stay on constantly after that. I have taken the truck to my neighborhood auto repair and parts store to have the error code analyzed. It was an error reported as "a miss on cylinder three". I have replaced the spark plugs as the truck has 78,000 original miles. The spark plugs did not correct the situation. Next I changed the coil pack on the #3 cylinder and at first the truck ran smoothly and the check engine was off. After driving about 40 miles the light came back on again. I figured this was a faulty coil pack so I replaced the coil pack again with the same results as above.

Currently, after replacing the spark plugs and after replacing the coil pack twice, I am back tom where I started with the engine running rough at low idle of approx. 800 rpm. I'm getting approx. 23-24 mpg which I feel is pretty low mpg for the 2.4L engine.

[The Phoenix]

Flashing CE light means misfire or engine knock. I'd check all the coil packs. I remember reading that the order in which the cylinders fire might throw you off in diagnosing the correct coil pack.

[Redneck]

What do you mean by engine knock?

[The Phoenix]

Originally Posted by Redneck

What do you mean by engine knock?

Engine knocking - Wikipedia, the free encyclopedia

[Redneck]

I had purchased a repair manual while at the auto parts store and the manual confirms that the third cylinder back from the front of the engine id the #3 cylinder. I think I will test each coil pack connection with a test light to make sure that it is actually getting fire. What else could i check?

[mustang67408]

You can also check the injectors and I would also perform a VALVE CLEARANCE CHECK. These engine seem to get tight exhaust valves. Have seen this a few times over the past few years.
I hope you used NGK or DENSO spark plugs, they seem to work the best.
3 cylinders back is cylinder #3, you are correct.

[Redneck]

Master of Disaster

Wow, what a great looking 67 Mustang. I had an old 69 mustang in 1978 and wish I still had it?!

I'm an old Toyota guy and have been driving Toyotas since i sold the mustang in 1978. All together I have owned eight toyota's consisting of the following, 1978 Corolla 2-door hatchback, 1984 Toyota Camry, 1989 Corolla sedan, 1984 Toyota 4x4 pickup with a straight axle in front (my old hunting truck), 1994 4Runner, 1997 4Runner, 1997 camry (Which my wife still drives) and my current 2004 Tacoma. They have all been great vehicles except for the 1994 4Runner which was a bad year for the engine that came with that model. I had to have the head gasket replaced twice.

I hadn't thought about getting the valves checked as you recommended, but i think I will have to let somebody else more qualified at a shop to do this check. I think I have done just about everything i can do from my driveway/garage and will consider taking to a shop to have them check the valves and injectors.

Would a bad injector on #3 cylinder cause me to get a check engine light?

Thanks for your input

[mustang67408]

Originally Posted by Redneck

Would a bad injector on #3 cylinder cause me to get a check engine light?

Thanks for your input

Yes a bad injector or partially plugged injector will cause an engine light.
If the injector is not letting enough fuel into the cylinder, then that cylinder will misfire, if it is stuck it will flood that engine causing a misfire.
When the engine light flashes, it means that cylinder is misfiring over 50%, this can cause catalytic conveter damage. Injectors are not usually intermitant, they are either bad or good (usually).Definatly have the valve adjust checked by someone who knows Toyotas, here is a PDF if you want to try it yourself, but adjusting them can be a pain if you dont have the correct tools.

[Redneck]

I agree with you about the injector being good or bad. Generally the CEL will flash for the first 5-8 minutes after first starting the engine to go to work in the morning or coming home from work in the evening and after the first 5-8 minutes the CEL stops flashing and just stays on. Does this sound like a valve situation to you? Would this also result in a decrease in my gas mileage?

I really appreciate your input. How much can I expect to pay for someone to check my valves?

[mustang67408]

Originally Posted by Redneck

I agree with you about the injector being good or bad. Generally the CEL will flash for the first 5-8 minutes after first starting the engine to go to work in the morning or coming home from work in the evening and after the first 5-8 minutes the CEL stops flashing and just stays on. Does this sound like a valve situation to you? Would this also result in a decrease in my gas mileage?

I really appreciate your input. How much can I expect to pay for someone to check my valves?

ALLDATA pays 2.9 hrs X (labor rate) to check and adjust valves.

Actually if it only does it cold, it sounds like excessive carbon build up on the back of the intake valves, but that is a hard one to prove cause it usually sets MULTIPLE misfire or random misfire codes.
Yours said Misfire #3, so it should be related to that cylinder. So I am back to the tight valve scenario again.
Without being there, this is my best GUESTIMATION.


What plugs are in it?
Fuel Pressure?

A compression test MIGHT show a tight valve or a CYLINDER LEAK TEST.

[Redneck]

Master of Disaster,

I just purchased and installed new plugs before replacing the coil pack. I told the guy at the parts store to give me the best because I would be keeping the Tacoma for a llong time. I bought some iridium plugs and have installed them no problem. Assuming that the valve needs to be adjusted, will this cause fouling of the spark plug.

I will plan on having somebody check the valves on each cylinder while checking #3.

Thanks for your great advice.

[The Phoenix]

I hope you aren't using Bosch or something else. NGK or Denso only!

[mustang67408]

Originally Posted by The Phoenix

I hope you aren't using Bosch or something else. NGK or Denso only!

Exactly where I was going with this.
MOST of those autoparts guys dont know anything about anything. They sell you what you want to hear or what they make the most money on. I can match or beat just about any price on spark plugs at my dealership vs the junk they sell so price usually isn't an issue. If they are not NGK or Denso, I would return them and get the good stuff. Just my opinion.
Then have the valve adjustment checked.

[Redneck]

Originally Posted by mustang67408

Exactly where I was going with this.
MOST of those autoparts guys dont know anything about anything. They sell you what you want to hear or what they make the most money on. I can match or beat just about any price on spark plugs at my dealership vs the junk they sell so price usually isn't an issue. If they are not NGK or Denso, I would return them and get the good stuff. Just my opinion.
Then have the valve adjustment checked.

Wow, I did not know that the sparks were that important. I think you have a good point. I'll install the correct sparks (NGK or Denso) first then do the valve check. I'll be keeping the truck for a long time. Is there any type of NGK or Denso spark plug that would be recommended?

[mustang67408]

Originally Posted by Redneck

Wow, I did not know that the sparks were that important. I think you have a good point. I'll install the correct sparks (NGK or Denso) first then do the valve check. I'll be keeping the truck for a long time. Is there any type of NGK or Denso spark plug that would be recommended?

Toyota does not show an option for Platinum.
DENSO # 90919-01164 is trhe (STOCK) plug

Denso #90080-91184 is an IRIDIUM substitute. This should work just fine.