Hi,
My car is camry 2007. I got the check engine light on for 1 day then it turned off for 1 week. Sound of knocking at morning appeared. Again, it turned on again. I went to the mechanic (my friend) and he checked the errors and they were as following:
1- P0171: System too lean
2- p0304: Cylinder 4 misfire detected.
I went to the dealer and asked him about these errors. He told me that my injectors need cleaning and they will cost about 100$. My friend advised me to add injectors cleaner additive to the fuel tank and i did (2 days ago). Till now the check engine is still on. Anyone had this problem before? Is it really injection problem? Any advice?

 

P0171: System too lean - could be a lot of things.. could be a vacuum leak, check for hoses that are ruptured or loose. MAF needs cleaning, Air filter clogged. PCV valve clogged. These are easy and cheap fixes. It's possible that they could be the fuel filter or fuel injectors (but not likely most of the time)

p0304: Cylinder 4 misfire detected.could be your spark plug or coil. Swap the coil see if the misfire goes to another cylinder, if still the same error then change the #4 plug, otherwise it's the coil.

fuel injector cleaners that you put in the tank normally don't work.

 

well, if your air filter is clogged, then you do not have enough oxygen coming into the system, and will run rich. unless ECM thinks engine runs rich, and cuts down on gas supply.
gas line cleaners do work. that's good news. Seafoam does miracles. You want to pour it into almost empty tank, BEFORE refill, and flush in with gas. keep in mind, you need funnel to pour it in.
but if it's misfiring, I'd have simply replaced all spark plugs. they are about due anyway, and yes, I know they are 100 000 miles warranted.
solid state ignition coils are very reliable and last forever. unless you have loose or corroded contact, so cleaning them and greasing with dielectric grease won't hurt either.
codes will stay until you clear them. locate fuse box, locate ECM fuse, or computer fuse, and pull it out for at least 15 or so minutes. clears all codes.
if system is running lean, your ECM thinks there's too much fuel supplied into cylinders and cuts it down. your O2 sensor might as well do this.
heck, bad or loose gas tank cap can throw lean code.

good read for you here:
http://www.2carpros.com/articles/rep...-manufacturers

 

Thank you guys. I already replaced the spark plugs, changed the oil and oil filter. Also, i checked for any leak in vacuum. I will wait to finish the fuel tank if this will help. Then will go with other tests and solutions. WIll update you. Thanks.

 

honest to god, Seafoam is strong medicine. if you had new plugs, and it still misfires, something's not right. can you, actually, teel IT'S MISFIRING? ENGINE RUNS HECK ROUGH IF IT DOES. sorry, dain fat fingers and caps..
here's more food for weekend project for you:
http://www.aa1car.com/library/misfire.htm

 

very likely this:

"Lean misfire" can occur when the air/fuel mixture is too lean (not enough gasoline in the mixture) to burn. This can be caused by a dirty, clogged or inoperative fuel injector; air leaks; or low fuel pressure because of a weak pump, restricted filter or leaky pressure regulator. Low fuel pressure would affect all cylinders rather than an individual cylinder, as would most air leaks

clean MAF sensor. it's very easy to do, but make sure you get cleaner all the way into the sensor, onto a little "light bulb" tip. as it tells ECM how much air is put inside, and ECM figures how much gas to put in.

what gas brand are you using?

 

Till now, the check engine light is on BUT the car is stop knocking at morning. so, i guess the injectors are clean now. Here we don't have the seafoam but i used Total cleaner and Wurth cleaner. From the link provided, if p0304 and p0171 are exist, then most likely it is dirty injector. About the MAF, we don't have a cleaner for him here in Jordan but i checked it and it seems very clean. About Gas brand, we don't have brands for Gas where all the gas has the same source but I usually using it from Total gas-station. The truth guys, i am the responsible about this issue where i used to fill the car with 90 octane not 95. Also, last month (before this issue is happened), i added additive to increase the octane number and i am sure this caused the problem.

 

try clearing the MIL(Check Engine Light or CEL) using the scanner (if possible) or disconnect the battery for 5-15mins. If it goes back then the problem is still there. Never drive it for a longer period with MIL on, it could ruin something else (especially your catalytic converter)

------
When the engine misfires, high concentrations of hydrocarbons (HC) enter the exhaust gas. Extremely
high HC concentration levels can cause increases in exhaust emission levels. High concentrations of HC
can also cause increases in the Three-Way Catalytic Converter (TWC) temperature, which may cause
damage to the TWC. To prevent these increases in emissions and to limit the possibility of thermal
damage, the ECM (included in hybrid vehicle control ECU) monitors the misfire rate. When the
temperature of the TWC reaches the point of thermal degradation, the ECM blinks the MIL. To monitor
misfires, the ECM uses both the Camshaft Position (CMP) sensor and the Crankshaft Position (CKP)
sensor. The CMP sensor is used to identify any misfiring cylinders and the CKP sensor is used to
measure variations in the crankshaft rotation speed. Misfires are counted when the crankshaft rotation
speed variations exceed predetermined thresholds.
If the misfire rate exceeds the threshold level, and could cause emission deterioration, the ECM
illuminates the MIL and sets a DTC

 

No doubt if it is a lean cylinder that particular one will run hotter than the others. If it is consistent that could damage the rings on the piston. I would think being lean you would hear lots of clatter from that cylinder when accelerating.

I would suggest adding a bottle of Techron (recommended by top mechanics) on your next fill-up. You can buy Techron at most all auto stores, including Walmart. Techron is a safe Chevron product and they use it in their gasolines.

If you find it is fuel injector related, I would make sure I was using a toptier gasoline. I will include the web site below. Brands that are in the top tier list add extra cleaners too their gas over those recommended by the Government. Toptier gas can keep your injectors running clean, including the valves and piston rings.

All toptier stations include a extra additive similar to Techron, but with a different name.

Here is the website where you can learn why toptier and which auto companies pay for the testing.

http://www.toptiergas.com/

 

folks, he LIVES IN JORDAN.

he does not have Techron or Walmart.

we don't have a cleaner for him here in Jordan

let's try to cater our suggestions to what he CAN use.