good day all

I recently purchased a 2007 RX350 WITH 78K Miles and recently the 0304 code came up, the previous owner seems like he tried to tackle this because i checked the plug and it was a champion ?? i replaced all front three with denso 3426 if i remember correctly the code is still there

also noticed that all three coils where different ???? only the far right one towards the front of the car cylinder 6? was a denso the other 2 different brands?? i am waiting on a set of new denso coils to change the other 2 but how would that trigger the VSC light ? guessing it automatic for all fault codes ??
odd that at low speed at a stop sign the car feels like the ABS in engaging/activating

 

Automatic VSC for any engine fault codes, so you're on track there. If one of those coils is misfiring you'll get surging and chugging in gear. I'd focus on those replacement coils and go from there.
Good luck!

 

Again so damn odd i brought 3 new oem injectors and change cylinder 4 and even moved them to cylinder 2 and 6 and eventually change all front 3 cylinders coils plugs abd injector and with 5 to 19 mins check engine apoears ???? Back to a misfire at cylinder 4 ???
did not find any cracked vacuum lines sprayed the intake manifold down while idling and yet still a missfire ??

ps che ked compression perfect with specs something after the vehicle leaves the closed loop state is getting some type of input tocause a missfire at 78k should not be happening

 

Yah, after closed loop the A/F sensor is noticing that the mixture is lean or rich, and making an adjustment on the whole bank. Since compression ok on #4. and other swaps you have done, may be time to look for electrical problem on injector or coils on #4.

Can you post fuel trims for bank 2? I.e., lean or rich on that bank may be a clue as to fuel or ignition. Old fashioned, since this is the front bank, does plug spark if pulled, and does disconnecting it and/or injector change the idle?

There are some very good posts here about scoping electrical issues on coils and fuel injectors.

 

Something I noticed on our cars is the front bank seems to cook the plugs on the coils and make them brittle and weak due to the exhaust manifold heat and they can get to a point where they don't make a good connection, happened to me.

Rear coil plugs don't seem to get as hot but they fail to keep good connection sometimes too when they get wore out.
A loose plug will also cause a random misfire.

What I mean by a "generic misfire" P0304 is a misfire that is not related to feedback ignition reporting so it can be anything generic(versus specific) on that cylinder such as compression, fuel delivery, etc.
I agree with Mesquite77, plz post up your Long Term & Short Term fuel trims, car must be fully warmed up and at idle, AC off.

 

Thanks you guys for the response this is now kicking my *** and my neighbor but and he is an old school mechanic (45 years) and also stumped but he does state hes not too familiar with toyotas VVTI engine models

so far still have the generic 0304 code even after changing plug coil, AND new injector oem densos

compression on cyclinder 4 (middle front is about 18-24 psi ) less than the other 2

my neighbor attempted to pressurize the cylinder (4) with regular air to hear if there's a leak and hes confused since at TDC all valves should be off but he hears air leaking onto the other cylinders?? but cylinder 2 and 4 have compression ??? he wanted to hear if air escaped thru the exhaust side out the tail pipe but was stumped so he would try with a similar engine at his shop






so i am left at the last step the harness going to that cylinder either the last several inches exiting ontop of the engine or should i change the entire harness since if its that the issue it may pop up at other cylinders?? who has an entire harness (not from junk yard)

this damn car is in near immaculate condition that i would hate to junk her due to a weird misfire with only 78k miles

i dont think i captured the correct live readings from my scanner but these readings look crazy also lol

 

So, -14 perc bank 2 LTFT is consistent with the problem, the sensors are seeing too much fuel and are trying to lean it due to poor combustion on the bank. May have a burned valve, explains leak on air compression test? Removing head is big job, I would scope the electrical connections next. BTW, it is not terrible hard, but tedious, job to drop subframe with engine and trany to pull the head. My 2008 was perfect except it broke a valve spring, did the job in my garage, during covid.

 

Lord I am dreading to think that may be the head gasket issue and having someone else perform the job, it may be faster and cheaper probably with replacing the engine? but only one cylinder is about 20 psi less but not leaking, my neighbor found it odd that it has compression but when blowing air in it can be heard seeping onto the other 2? which in theory it shouldnt?

how would i scope out the connectors (praying thats the issue and possible repair) so odd upon code being cleared it runns perfectly till the cod epops up and then it idles a little rough but after idle it drives perfectly until i need to stop like at low speed and the misfire is not evident just a slight rumble/vibration

i am extremely handy and mechanically inclined and ventured into alot of repairs, but not a 24 valve high tolerance engine and if i am already there might as well do both banks??

 

By scope, I mean check wire signals, and Margate330 (his post above) is the man: https://www.clublexus.com/forums/rx-...agnostics.html.

If you have time, and it comes to engine rebuild (I don't think you'd find a good used engine with fewer, gentler, miles than yours), see this to make you shiver, lol: https://www.clublexus.com/forums/rx-...ve-spring.html

Running until open loop seems to be an indication of poor combustion in a cylinder, as ECU tries to compensate, and messes up the other 2 good ones instead, meaning you are left with one bank not firing properly.

 

Thank you so much for the very informative links damn that's alot to absorb there wish i had the space in m y garage I definitely would tackle this !!! its that time is running short, I purchased this low mileage car for my daughter and its a shame I can't get it running even with the misfire on one cylinder its insanely smooth and quiet after idle speeds but i don't want to further damage is its a not completely closing valve on cylinder 4

But i will scope and pray i cant track a possible electrical issue to either the coil or injector harness to cylinder$ 4 by using the device in the above link (all three front bank have new injectors coils and plug all oem denso products) that eliminates components

I will also purchase an exhaust gas reader (chemical changing device) hopefully it remains blue!!!!!

AND YES THE PRICE for used engines and their mystery history is incredible, 3k for an undocumented mileage especially when they claim it came from a low mileage vehicle but when asked for the vin they dont have one????

 

Yeah i agree with Mesquite, these fuel trims are way off and what's worse is they are running way positive on one bank and way negative on the other bank which is unusual.
My apoligies friend as I see you are a DIY guy but you tried the easy stuff and if the head gasket check doesn't work you will need someone at dealer level diagnostic experience to figure it out. Might cost a couple hundred to figure it out and worth it- don't let anyone tear your engine down without a dealer level diagnosis first.

Are you consuming lots of oil?

PS- You need a Scanner Danner lol.

Just for fun I'll drop this one, it's one of my fav's.



Thank you for the High 5.
For the record, mesquite77 is the only one on here I ever seen who pulled the engine DIY at home without a lift to drop the engine cradle so I know where I'll be coming for help if I ever need.

 

Good day all

Well after making some time to take my truck to my neighbor's garage (his place of business lol not where he lives)

I help him take the engine out which is not a simple task without a lift, we removed the heads and did several internal tests and clearly cylinder number 4 valve not holding pressure and with shop air it is blowing out but not down thru the exhaust seems like the intake valve is either not fully closing, spring broke or worse.

we (mostly he ) removed the heads and we sent them out to an engine shop who is about 2 weeks behind but upon removal of the lines to the oil cooler we noticed small metallic bring shavings pieces of something???

now we shipped the engine to the same shop to tear the engine down hopefully no damage further inwards

while waiting since the engine is out might as well replace things that i do not want to go back again there for a long long time

any suggestions on where to get real replacements parts ??? rear engine seal, radiator with all hoses, rear egr sensor? (already have coils plugs and injectors) water pump and thermostat real coolant not generic ?? and maybe new engine mounts? iIkeep searching and cant find one place that has all the parts

 

I used a victor-reinz (sp) engine rebuild gasket set from rock auto, and it had every gasket and seal you could imagine, plus some, high quality as far as I can tell, no problems. Surge tank (aka plastic intake, plenum) and exhaust pipe flange seals are separate IIRC. I think engine mounts should be fine, don't see a lot of failures of these. Of course make sure you have metal VVTi lines for the rear bank and oil cooler (if installed).

 

thanks i would definetly be viewing rockauto since i would need most of all those gaskets if and if its only a head rebuilt if its further than that then the machine shop mostly likely take care of most of those items i just want tobe preventive with 78k mikes might as well change items that may be ready to fail thats why i prefer a whole new cooling system to avoid future issues a prefer as much as near oem parts or better grade if possible