Hello all,

Looking for some help.
Car info:
2005 Toyota Camry 4 CYL auto.

I was getting a flashing CEL and read the codes. They were P0304 and P0420. My scan tool is an Innova 3100e.

I have replaced the coils and plugs on all cylinders. I removed the negative terminal from the battery before staring the repair. Hooked everything back up and started it up.

Seemed ok. Maybe still running rough. Took it for a test drive. Got about 2 blocks and CEL started flashing again. If it idles the CEL goes off / wont flash. Got it back to the house and checked for codes. Scan tool is reading no codes.

HELP. What now?

 

Any issues with needing to add coolant on an ongoing basis or the engine coolant temp varying/getting too hot? The engine is known for having issues with head bolt block threads pulling out. The result is a failed head gasket.

Unless the code clears itself, need a scanner to reset codes.

The check light blinks when emissions converter temp reaches a level where it starts to become damaged. The cause of this is extreme misfire and resulting high exhaust gas temps due to extreme rich mixture. If blinking check light stop the engine or risk damaging converter.

P0420 is the first converter system efficiency below threshold. Could be the misfire damaged it leaking exhaust system a bad A/F or O2 sensor.

P0304 is misfire No 4 cylinder. Was there a code P0300 which means multiple cylinder misfires?

You replaced all coils/plugs and still have a problem?

Try swapping coils and determine if the P30X code changes to another cylinder, but first assuming its just one cylinder problem check the following:

Wiring issues to coil and injector
Vacuum leaks
Injector problem
Cylinder valve issues/low compression
Intake manifold leak

If suspect more then one cylinder is misfiring check:
Fuel pressure
MAF meter
ECT sensor
Fuel pressure
PCV system
Intake air leaks

Can disconnect the No 4 coil and determine if the engine runs just a bad indicating it is that cylinder. Just don't run the engine with the check light blinking.

 

Thank you for the information.

Here is what I have tried so far.

Disconnected battery again,
Pulled new coils and new plugs checking each one.
As I understand it cylinder numbers from front of car facing the back of the car. Cylinder 1 (all the way to the passenger side) Cylinder 4 (all the way to the drivers side. Please correct me if I am wrong.

C1 is not black like other plugs but has a gas smell. Looked down plug opening top of piston seems to be wet. Plug 4 smelled of gas but other wise looked black like cylinder 2 and 3.

Put that all back together. Pulled the EFI relay as suggested by some one on another form. Put that back and reconnected the battery.

Started the car again and ran it. Revved it up and CEL light started flashing again. Does not flash at idle and light is NOT on all the time.

NO codes that I my scan tool (Innova 3100e) can read are being set. MIL/CEL is NOT on solid only flashes.

car is not running hot, coolant is good.
I have checked wiring and grounds. all seem good. Injectors connections are all good also.

I am a DIYer I don't have all the equipment to check everything listed.

I am baffeled by it not setting a perm code to the computer and leaving the CEL light on.

 

Plug electrodes should be white or gray, not black. Perhaps the engine is overall running too rich.

Maybe changing the coils fixed that code and there has been no code again.

As to the check light and trouble codes. The computer is programmed to have the check light flash when the exhaust temps reach a point they can damage the converter. The check light flashing doesn't mean a trouble code has yet been set. To set a trouble code, the computer must run through a prescribed test procedure. This typically involves driving the car and a test check failing typically at least twice to set a trouble code. There may be no codes to read as no codes are stored.

What were the sequence of events leading up to the engine misfire? Was the engine running OK. Then the engine misfire, then the check light came on or did it just start to blink? How long did you operate the engine with the check light blinking?

There were two codes, P0304 (coil) and P0420 (bad converter), plus a blinking check light. You changed the coils. It's possible the bad coil caused the mixture to overheat causing the blinking light. This overheat damaged the converter which is now melted inside plugging up the exhaust. The exhaust now plugged up causes a rich mixture and poor operation.

Otherwise would look for other things that can cause a gross rich mixture. Check the engine air intake and air filter for plugging from say rodents (has happened). A bad A/F, ECT (sends coolant temp to computer) or MAF sensor. EVAP system failure causing an EVAP purge line to send raw fuel into the engine (would be strange, but), fuel pump pressure regulator failure (rare).

Your best bet is to get a Haynes service manual for the car or download service info from Toyota Tech center ($20/two days). Then with an VOM meter start checking items. See private message.

With the right ODBII scanner one can read out real time data via graphs to see what is really happening. Meaning is the mixture OK but a plugged exhaust. The A/F sensor operation is within range, etc.

 

Some added info and I will try to answer all questions.

CEl was on for an ABS code before. Light started flashing about 3 miles to home. This is my SO's car and she was driving. Came home parked car so flashing light was not on long. Flashing occured before I replaced the coils and plugs.

Last night I swapped coils between two cylinders, Exhaust manifold on cylinder all the way to passenger side was cool to the touch compared to others. So, I don't think that the coil is the issue. Others have suggested a bad injector. I am thinking that is it and going to replace injector today.

Flashing light and P0420 makes me think that the below value means that it was not getting the exhaust it is looking for. So I doubt CAT damage especially with low about of time driven with CEL flashing.

I will check air filter. Never hurts to check and replace easy and good maintenance.

I will update after I replace injector and check air filter.

Please feel free to let me know any more info. I appreciate the help.

 

Update.

Replaced the injector for the cylinder all the way to the passenger side. Feeling the exhaust manifold this is the one that is "cold" compared to others. So my thinking is that this is the one not firing.
Air cleaner is good, only a few months old. No rodent nests.
Plugs and coils replaced.

Ran the engine with the new injector cylinder still cold.

When I started it up this time, there was some smoke from just behind and below the engine. Checked underneath the car. The smoke was coming from the back of the flexible woven connector just before it transition to hard pipe is leaking. Maybe that is where the P0420 code is coming from? It is before the O2 sensor under the car. this still does not explain the cold cylinder.

I am officially out of ideas and talent to fix it.

 

Changing the injector changed nothing in terms of engine missing?

Take out the coils and plugs to ease engine turn over. Install a plug in one coil at a time and crank the engine to determine if it makes a hot spark.

 

Swapped two coils and made no difference. At this point I am taking it to a local mechanic for work. I am beyond my knowledge and tools available.

Thank you to all who helped. It gave me good advice and a direction on what to look for.

 

Please post back with whatever fix is found.

 

So,

It was a defective new coil. I was afraid to drive it to get the code to set in the computer. I did not want to damage the Catalytic converter. Driving it to the mechanic that is a few blocks away was enough to set the code.

There was also an exhaust leak at the flexible portion of the intermediate pipe before the O2 sensor. I had that replaced also.

Thank you all for your help in trying to get it fixed. I hope that in the future this helps someone else.