Have 1998 Lexus GS300, I have been chasing Cylinder 1 misfire for months maybe a year. I have had code p0301, and have unrelated code p0446, evap canister.

I was having bad stuttering when accelerating, or coming off a stop. Car would stutter and sometimes I get flashing check engine. Sometime, I have random code as well, but that has been off for a while. now just P0301. After I get going the car runs and drives fine, it all seems to be whenever it wants, sometimes ill drive for hour or so and no symptoms. Then ill take off from red light and it will do it again.

Here is what Ive done. It got really bad a while back so I parked the car and changed,
Spark Plugs, Wires, all coils ( not factory coils but new and changed back and forth with cylinders and still have cylinder 1 misfire )
Timing belt on time, good cylinder compression, changed vvti siloniod.
Rebuilt all fuel injectors, they test fine, and just in case one was bad, swapped back and forth btw cylinders and still cylinder 1 misfire.
New MAF,

I do get pending codes in my scanner, p0770, shift silinoid E I think, I dont know if these are related, but guys totally lost on this misfire.

I even took to lexus shop for $200, they spent 2 hr and couldnt really find anything, just took everything off looked, made sure everything was seated correctly. It ran great for a day or so after they looked at it, but issues came right back, but is there anything I am missing ? Please lead me in some direction.

Thanks

 

Bump, come on someone knows something.

 

Take it to another mechanic.

 

It looks like you and I own the same GS. Years ago I had the same issue with the same symptoms and replaced the same parts except for the fuel injectors. I even had a code for a shift solenoid but mine was for C not E. Normally I wouldn't have put this much time and money into it but my smog inspection was coming up and I had to smog clean. Luckily it was one number way from failing all across the board. After the smog inspection, I really began to try and figure what the cause of the misfire was. Occasionally, the engine operating temps would rise slightly and randomly. After a long time of being in denial, I then came to my senses and realized that my head gasket was the cause. Although the compression test came out good and there were no leaks found during the pressurizing of the cooling system, I still suspected the head gasket. Maybe its me but after 3 2JZGEs and 2 2JZGTEs, all the NA motors had head gasket leaks.

If you plan on keeping the car for a while and its been treating you good, try replacing the head gasket.

 

 

Wow! I had the same hole in my intake resonator too. It makes sense as to why you'd run lean. I probably ran my motor lean too. That would explain why the temps would rise at idle after running it at higher RPMs. Report back on how the motor runs after you've replaced that resonator. I'm very curious to know. Like I said, I've had multiple 2JZGEs die this way. I'm wondering if the intake was the culprit.

 

Just wanted to throw ideas out there...sometimes these things can be hard to find. A while ago I had a strange issue where my GS400 would stutter or shut off at a light when warmed up. It didn't do it all the time so I couldn't duplicate it. After much searching (and many months) it ended up being a cracked vacuum hose under the engine cover.

A couple inexpensive things you can try is your gas cap or OCV. You didn't mention how many miles but if you've never changed your OCV that's a relatively easy part to replace. Lots of people have had good results replacing it. You can find them on Amazon for $25-30.

Of course if all else fails let the dealer do a diagnosis. Keep us posted.

 

Since you replaced the spark plug, the biggest overlooked item is the coil pack harness in the 2JZ VVTI motors. It gets really hot in the plug valley, and when the harnesses gets moved they become brittle from heat treatment over the years. The shielding breaks off and will short itself out. I would strongly start from behind the cam gear and cut open the 3 coil pack harness and inspect them carefully.

 

What made you come to the conclusion that it is the head gasket ? I don't have any coolant mixed into the oil, which I know that would be an extreme case. But yes I plan to keep it, forgot to mention, car has over 247,xxx miles on it.

 

I have already replaced the coil connectors, I did this about a year ago, put new connectors, did them pretty good and put heat shrink on them as well.

 

I already replaced the OCV, I called it the vvti solenoid, which seems to be the same as the oil control valve, I first cleaned old one, didnt work. then replaced with brand new one, to no avail.

 

That's like saying, say f*** it and go to dealer, I tried to go to dealer to get free diagnosis, but they wanted min $400 to have their best techs check on it. I said F it and thats why we have this great community called Club Lexus to help each other not get rapped and ripped off by dealer.

Not saying, I might have to come to that if I cant get a handle on it, But rather ask questions to smart ppl on CL then take to dealer.

 

Car has over 247xxx on it, I have takin very good care with everything, so thats why im trying to wonder why this s*** is happening.

 

 

Seems like you have a hard time accepting advice.
Changing the connector vs checking the wire loom is 2 different things.
These are pics of why this check is recommended.
Very common failure that people overlook,