Hello everyone,

Several days ago I got the CEL, Trac Off Light, and VSC light on my 2001 RX300. The code that came up was P0304 - Misfire in cylinder 4.

I've replaced the spark plug, ignition coil, and bank 2 air/fuel sensor.

After all that the car is still idling rough, fuel mileage has dropped to roughly 11 mpg and I'm still getting the P0304 code. What else can I possibly examine/replace? Any help would be greatly appreciated! I'm stuck here!

 

Based on some research I'm thinking I have a stuck #4 fuel injector. The fact that my MPG dropped, I'm getting P0304 code, and my oil dipstick smells heavily of gas I'm assuming that cylinder is being flooded with fuel and misfiring. Going to swap the fuel injector tomorrow. Anyone have a link to a write up for this?

 

One clear way to find an offending plug or coil is to swap them around and if the problem travels then you know which is the failing part.

Salim

 

I swapped coils and plugs and still get the P0304 error. I've narrowed it down the the injector. Is there a DIY on replacing the front 3 injectors?

 

Not to make you doubt your diagnosis but the debug has not eliminated the things that were not moved ... like the wiring harness ... [so I would say it is likely that you can have injector problem but we cant say that the injector is 100% at fault]. Experts use stethoscope to tell if it is bad ,, but you have to know the good-vs-bad sound pattern.

My hands on knowledge is kind of low on injectors, so if you would like to share, it would certainly enlighten me.

I dont recall seeing a DIY on injectors. There are quite a few on how to remove the top portion (which I think are mostly intuitive too). Once you get there it is a matter of removing the fuel rails.

If you can please write up a DIY.

Salim

 

Here is a good video on injector test if you can get past the accent.








And a DIY guide if you decide to get dirty.






http://hubpages.com/hub/DIY-Toyota-M...or-Replacement

 

**UPDATE**

I replaced the #4 injector and the car runs great with no CEL or codes. It took me longer to remove the back seat to unplug the fuel pump (depressurize fuel) than it did to replace the injector. I'm assuming #1,3,5 are more difficult.

On a side note local dealer (Scottsdale Lexus) wanted $220 per injector! Called Parts Authority (formally BAP) and they have refurb Denso injectors for $40.

If anyone needs help with replacing the 2,4,6 injectors please shoot me a PM.

 

You can undo the quick connector [way below the brake booster].

Great it worked out.

So are you going to post the DIY?

Salim

 

Hello,

I would love the instructions!

Best,

Lea

 

Well, here's what we did to change a fuel injector.
This worked the same on a cool and a hot engine.

After removing the plastic engine cover, locate the fuel injectors for cylinders 2, 4 and 6 - the side of the engine in front of the engine bay.
These have wired connectors running to a harness. The fuel injectors are sandwiched between the top of the valve cover and the fuel rail.
The fuel rail has a 14mm banjo bolt on the right end.
Above the fuel rail is a series of metal tubes with brown and blue wiring connectors that also run into the same wiring harness as the fuel injector connectors.
Remove those connectors and locate the two 10mm nuts that hold that tube assembly above the fuel rail. Remove nuts and place below front windshield so they don't get lost.
Once the assembly is loose, you'll have to remove one of the small rubber vacuum tubes on the left side so you can place the assembly on top of the intake plenum.

Now, you can disconnect the three fuel injector connector plugs and move them aside. I'd recommend wearing safety glasses for the next step.
Take some paper towel and place under the right side of the fuel rail under the banjo bolt. It may be a good idea to also place a rag on top to keep the gasoline spray down.
Using a 14mm socket and ratchet, loosen the banjo bolt fully and remove. Careful, the fuel system is pressurized and will leak/spray at this point.
It only lasts for a short time if you continue to loosen the bolt. Only a small amount of gasoline will emerge.

One the banjo bolt is out, you can unfasten the fuel rail by removing two 10mm long bolts. Gently, apply lifting pressure and wiggle until the rail and the three injectors pop out of the valve cover.
You can remove the injectors by twisting and pulling them out of the fuel rail.

Installation is the reverse of above. The banjo bolt will need to be tightened the most - not sure of the torque, I go by "feel".
Don't tighten the fuel rail bolts too much. Just snug and a bit more. Same with the tube assembly.
Don't forget to reconnect all plugs and re-insert the vacuum hose.

 

A little late to the party, but an easy way to depressurize the fuel system is to remove the fuel pump relay and start/run the engine until it dies. Also, remember to replace the relay when you complete repairs.