DMPesso

What's up CL! Haven't been on here in a while since I barely drive anymore (commute by train) and the car was running good up until now. So, long story short, the car was running fine until I went and got some gas at shell. I started it up, and it started misfiring. I THOUGHT it was bad gas so I ran the tank down, even put some injector cleaner but it was still misfiring. It finally threw a code for Cylinder 8 so I replaced the coil for 8 and that spark plug. I had already put some octane booster in the tank because it was the only thing that would stop the misfiring and made the car actually drivable. After changing the plugs and with some booster still in the tank, the car was driving like never before, a total speed demon and super responsive. Almost too fast. NOW, last week the car was still misfiring but it won't throw a code, it only blinked the CEL when the misfiring was very bad, and I noticed it would go away after the car has warmed up. I changed ALL the spark plugs since maybe the plugs got fouled out by bad gas or the octane booster. The mechanic said whatever I put in the tank can't be good because it made my plugs red, so I got excited thinking that was the issue and the problem would stop. Car drove BEAUTIFUL when I left the mechanic and even felt smoother at idle. Next day, start the car and it started jerking and misfiring until it warmed up for 5-10 minutes. I was so mad, but the mechanic said he THINKS it could be the OCV (Oil Control Valve). The car is definitely more responsive now after changing the plugs so maybe whatever the original issue was destroyed my plugs which were fairly new anyway. At lower RPMS the car feels much more responsive as before the car sometimes wouldn't recognize I am even pressing the gas at such a low RPM and it would stutter. I am getting the misfire at cold starts now but its much less noticeable and goes away pretty much right away after the car warms up. The CEL isn't blinking anymore either. I don't want to waste money on an OCV if that is 100% the problem, I just find it weird the car threw codes before but now it isn't but the problem is still there just not nearly as bad. Any insight you guys can provide would be greatly appreciated. I am not new to Lexus I know a lot about the GS' and this one has me stumped! On a side note, I am considering getting another car that is safer for the winter since I have my first baby coming and I am a little paranoid about driving this car in the snow everyday with him in it. I would still probably keep the car in the garage, as I can never see myself selling it for under 4k since it drives so amazing (besides this), it is more worth it just to keep it. I will make a separate thread about that, as I need some opinions.

DMPesso

come on guys, someone has to know something. Now I am getting a cylinder 6 misfire, P0306. I already had a cylinder 8 misfire, changed that coil, was driving great for a while now its misfiring again but only until the car warms up, then it drives normal. Is it really the other coil now? I am starting to think it is something else like an injector or oil control valve.

kevin3344

Do you have a 2GS3 or 2GS4?

DMPesso

sorry it's a 2001 GS430 with 165k

kevin3344

Check the vacuum hoses under the engine cover, they get cracked over time. I have a '99 GS4 and fought with misfires and random stalls at stop lights for a while. Finally got some codes took it to the dealer. The paperwork said "replaced rubber sections of line at purge valve". It was a simple rubber hose. The car drove fine after that! Something else to consider.

DMPesso

ok I will have my mechanic check this later, I am praying as I can't keep throwing money at this car, this is one of those problems where its hard to pinpoint what is actually causing it.

Thanks bro!

DMPesso

what I do find weird is that directly after changing the plugs the car was idling SO smooth and driving amazing and was very responsive at the pedal. Then the next day after sitting it started acting up again. So the brand new plugs temporarily fixed the problem, which I find weird.

badblackgs

iTrader: (1)

I suspect that whatever wound up in your fuel tank damaged your fuel injectors. maybe not all of them but it is possible the misfiring is coming from an injector. you said that cylinder six is misfiring now, so lift up your fuel rail and swap injector six with one on the other side of the engine. clear the codes and go drive it. also, just cause you ran the tank down doesn't mean that crap is all gone from the tank. the fuel pump sits in a little tub so that its always in fuel. you should remove your back seat, remove the fuel pump sending unit and suck that tank dry. you cant do anything about the other side unless you drop the tank from the car but suck as much fuel out as possible. than wipe the tank out with lint free cloths. no towels or anything that will leave fibers. than fresh fuel and re check your spark plugs. that gas station should pay for these repairs. drop it off at the dealership and demand that shell pay for it. Good luck.

DMPesso

yea I'm actually starting to think it's the oil control valve because I just found out the old mechanic who I don't use anymore changed cylinder 7 instead of 8 when the code came up for 8 last time and after clearing it it never came back. Now all the sudden it's showing cylinder 6 and my favorite mechanic says if it's all throwing codes for the same side since all the even numbers are on one side then it's something on that side and he's seen the oil control valve go bad and there happens to be one from each side. We just switched the coil 6 with the new one that was put in 7 by accident. I have a strong feeling it's not that coil, but we'll see.

DMPesso

so we switched the coils, and I noticed it still misfiring but once it gets warmed up it virtually goes away. Now I am waiting for the code to come back. I am leaning towards the oil control valve since it only threw codes for 6 and 8 which are on the same side, and the problem gets worse when the car sites and goes away after its been running so it seems like the valve might be getting clogged.

Cbb129

I have a 99 GS300 and experiencing similar symptoms. Did you ever get it figured out ?

DMPesso

yes it was one coil I replaced it drove fine for a few months then just a few weeks ago all the lights came on and it started driving real ****ty and all the cylinders gave misfiring codes on the same side (1/3/5/7) so that confirmed it was the oil control valve on that side (bank 1). Changed the oil control valve and its driving amazing ever since. Much more responsive. It was probably the OCV the entire time.