richaroo

Basically the whole bank 1 side of cylinders are misfiring and I can't figure out why.

Codes 300, 301, 303, 305 (bank misfiring) and 0171 (system too lean bank 1).

My first guess would be a vacuum leak. A mechanic (told him i dont have much money, asked to do quick diagnostic, he did this) did the quick and dirty spray down with carb cleaner to see if rpms changed. He said he sprayed it down good and yet there was no change at all. Secondly, using torque pro i found the fuel trim doesn't change when at higher rpms, where vacuum leaks typically get better at higher rpms. Also, wouldn't vacuum leaks cause both banks to misfire (or would intake manifold leaks be cylinder specific)? I recently changed the intake manifold gaskets so perhaps i did it wrong?

Anyone have any ideas? Anyone with with insight into a leaking intake manifold gasket?

Other info/questions:
I used a mechanic stethoscope to listen to my fuel injectors and they all sound exactly the same. Would a clogged one still sound good (and thus misfire bad enough to mess up the timing and throw all 3 on that side off)?
The coil packs are relatively recently replaced.
Had spark plugs replaced last year.

Car was running poorly suddenly, threw codes for both ocv's, replaced both and car drove much better. However, I distinctly remember I used a non oem ocv on bank 1. Could this be faulty and not throw a code? (Bank 1 and 2 are different orientations so I can't swap them to see if the problem moves).

I don't know which direction to pursue now. Should i just order another ocv only this time get an oem one? Should I order the fuel injector pulser and do an easy balance test (or just skip it and replace the injectors)?

Sorry for so many questions, I'm just stuck it seems and so frustrated.

Thanks for any info at all.

u054662

Hello Richardoo,,

I had a lexus es300 98 Mode and I had a similar problem with same codes.

I read a lot about this problem and I read about the vacuum leaks, changing the MAF sensor, changing the spark plugs, and all such things.
I changed all of the above and more but the problem continued. I reached a stage where I purchased a diagnostic tool and I was monitoring the problem and the codes closely.
I guess you will suffer from engine hesitation and less fuel economy and maybe some other symptoms.
Your problem might be one or more of the following

1) Vacuum leak in Bank No.1 hoses which is rare because if there is a vacuum leak then probably it will affect both banks 1 & 2 but you have to start from here if you want to avoid unnecessary repair cost.

2) oxygen sensor malfunction either Sesnor1 Bank1 OR Sensor2 Bank1 and this is was the source of my car problem so either you need to replace both bank1 O2 Sensor or just one, so you need to check that all bank1 O2 sensor are working good. For me I made this check using Torque Pro app on my android smartphone and it turns that bank1 Sensor2 is not working so I had to replace it, so probably you can do the same


3) Catalytic converter need to be replaced, because if one sensor is telling the ECU that the system is lean in one bank then this will lead to increase in the fuel flow to that bank and the excess fuel that is unburnt will go to the first catalytic converter and there it will burn and lead to the burning of the catalytic converter honeycomb filter which will clog your catalytic converter and that is the reason for your car running poorly.

Advice: Do not change any coil, any spark plug, or any injector

u054662

Sorry I mean Richaroo,,,

NotADood

Lexus master tech here,

From what my personal experience, the VVT gear on bank one has failed resulting in the misfire on all 3 cylinders on bank 1. It's a pretty involved job as the camshaft on bank 1 (firewall side) has to be removed to change it, and there are some special procedures involved in the replacement. Don't just take the job to anyone, or your engine will sound like it's coming apart after the repair.

ES300NZ

^ wow. damn good advice.

Hayk

iTrader: (1)

I noticed nobody mentioned the timing belt. I would check/replace it to make sure your timing is not affected by it.

richaroo

@notadood, would you happen to know how long a job that is/how much it would typically cost?

Would it be worth it to change the vvt solenoid again first in case it happened to be defective and is a cheap part anyway?

Side note, it was leaking oil from a lot of places randomly, including the valve covers. Regasketed them and changed the clogged pcv but maybe it's leaking somewhere else too? Ie into the timing belt?
Would that at all be related to bad vvt gear?

Also, thanks all for your help!