SOS! Please Help, GS400 running VERY ROUGH
08-26-14, 12:26 PM
#31
Driver
Join Date: Jan 2012
Location: Toronto, ON
Posts: 150
Likes: 0
Received 0 Likes
on
0 Posts
08-26-14, 06:01 PM
#32
Driver School Candidate
Thread Starter
Join Date: Jun 2014
Location: Florida
Posts: 49
Likes: 0
Received 0 Likes
on
0 Posts
Last edited by PTYGS400; 08-26-14 at 06:15 PM.
08-26-14, 06:14 PM
#33
Driver School Candidate
Thread Starter
Join Date: Jun 2014
Location: Florida
Posts: 49
Likes: 0
Received 0 Likes
on
0 Posts
Fuel quality test
Hello folks, FYI, the fuel quality theory has been eliminated. This morning I needed gas for my Yamaha WR426 (high output, high 12.5:1 compression motor). A few days ago, when inspecting the fuel tank and filters on the GS400 I took a one gallon gasoline sample.
I thought, what the heck, this is a good chance to test this gasoline (just hoping not to gum up a carburetor that is a pain to remove and clean up). The bikes tank was almost dry. I put half gallon of the GS400 sample gasoline. The bike ran flawesly.
Bottom line: gas in the tank is good enough.
It´s 8 pm, I am going vaccum leak hunting. I´ll keep you guys posted.
I thought, what the heck, this is a good chance to test this gasoline (just hoping not to gum up a carburetor that is a pain to remove and clean up). The bikes tank was almost dry. I put half gallon of the GS400 sample gasoline. The bike ran flawesly.
Bottom line: gas in the tank is good enough. It´s 8 pm, I am going vaccum leak hunting. I´ll keep you guys posted.
08-26-14, 09:56 PM
#34
Driver School Candidate
Thread Starter
Join Date: Jun 2014
Location: Florida
Posts: 49
Likes: 0
Received 0 Likes
on
0 Posts
August 26th Update
Vaccum leaks hunting....
Jeff Tsai suggested that my resonator could be cracked. I plugged all the hose ports and filled the thing with water. There is a tiny crack on the bottom. I can repair it later, however, I don`t think it`s meaningful.
While inspecting the resonator/intake tube I noticed that the gasket that seals the intake tube on the throttle body was out of position. There was hope, not much but some hope....
I installed it nice and tight and gave it a try. Rough, rough running. Nothing has changed. I let it run at around 1000 rpm with about 25% throttle for a couple of minutes. Once every few seconds the intake goes pop pop. And sometimes it stalls even with the throttle open 25+%. When it stalls you can hear the intake backfire. I put a wrench under the throttle cable so I could go to the engine bay with maf cleaner and spray the intake and injectors looking for changes in RPM. Spraying around bank #1 makes no difference, but it does respond to spraying bank #2. One of the times it stalled with a pop/"sneeze" I saw smoke coming from bank #2. (Same bank that leaked smoke last night during the cigarette test).
I wasn`t planning on working too long on the car tonight, but I really wanted to know more about this terrible vacc. leak in bank #2. I decided to take the whole manifold out. Removed all the hoses, wires, fuel rails etc. The lower intake manifold is held by 10 12mm-head bolts/nuts (5 on each bank). Here is the most important finding of the day: while removing them, I found out that most of the #2 bank bolts were loose.
Not so on the #1 bank side. There is hope again.... But I am too tired, and it will take me about one hour or more to put it back together. I´ll leave it for tomorrow, but before, I will smoke the intake manifold again and make sure the thing is really air tight.
Good nite and thank you for following my story...
Jeff Tsai suggested that my resonator could be cracked. I plugged all the hose ports and filled the thing with water. There is a tiny crack on the bottom. I can repair it later, however, I don`t think it`s meaningful.
While inspecting the resonator/intake tube I noticed that the gasket that seals the intake tube on the throttle body was out of position. There was hope, not much but some hope....
I installed it nice and tight and gave it a try. Rough, rough running. Nothing has changed. I let it run at around 1000 rpm with about 25% throttle for a couple of minutes. Once every few seconds the intake goes pop pop. And sometimes it stalls even with the throttle open 25+%. When it stalls you can hear the intake backfire. I put a wrench under the throttle cable so I could go to the engine bay with maf cleaner and spray the intake and injectors looking for changes in RPM. Spraying around bank #1 makes no difference, but it does respond to spraying bank #2. One of the times it stalled with a pop/"sneeze" I saw smoke coming from bank #2. (Same bank that leaked smoke last night during the cigarette test). I wasn`t planning on working too long on the car tonight, but I really wanted to know more about this terrible vacc. leak in bank #2. I decided to take the whole manifold out. Removed all the hoses, wires, fuel rails etc. The lower intake manifold is held by 10 12mm-head bolts/nuts (5 on each bank). Here is the most important finding of the day: while removing them, I found out that most of the #2 bank bolts were loose.
Not so on the #1 bank side. There is hope again.... But I am too tired, and it will take me about one hour or more to put it back together. I´ll leave it for tomorrow, but before, I will smoke the intake manifold again and make sure the thing is really air tight. Good nite and thank you for following my story...
Last edited by PTYGS400; 08-26-14 at 10:00 PM.
08-27-14, 05:39 AM
#35
Pole Position
Wow man you've have a busy weekend! Nice to see some real troubleshooting going down and not just whining because we haven't fixed it for you yet. 
All those bolts loose is a good lead and if the entire bank is not air tight, then yes that's a big issue.
Let us know how that goes and hopefully we can put this thing to bed!
Good luck!
All those bolts loose is a good lead and if the entire bank is not air tight, then yes that's a big issue.
Let us know how that goes and hopefully we can put this thing to bed!
Good luck!
08-27-14, 01:39 PM
#38
Driver School Candidate
Thread Starter
Join Date: Jun 2014
Location: Florida
Posts: 49
Likes: 0
Received 0 Likes
on
0 Posts
On the positive side, this intense troubleshooting adventure has been a Lexus GS400 technical crash course. First time I ever worked on a GS, and in less than a month, I have left almost no stone unturned.
After I get all the ghosts out, she´ll be fully mine.... Life is funny, when I was shopping for the 1UZ motor, I almost bought a 2JZ-GTE (I am a long time turbo fan, experience with rotaries, road racing, stand alone programming, etc) but didn`t because I didn`t want to thinker with the swap. I confess feeling some remorse now and then, but this is the path I chose and will go through all the way.
Thank you, thank you once again.
08-27-14, 01:48 PM
#39
Pole Position
Don't have any regrets. The 1UZ is legend and everyone should experience it at least in one car they own in their lifetime. 2JZ's are all fine and dandy. I have one in my SC (love it too) but had a 1UZ in my former GS400 with a full complement of mods. I love my 2JZ but that 1UZ... I will miss it. There's plenty to be said for a nice simple NA V8 with intake and exhaust. Gave me goosebumps every time I started it up.
Enjoy it. It will be worth it in the end.
08-27-14, 10:06 PM
#40
Driver School Candidate
Thread Starter
Join Date: Jun 2014
Location: Florida
Posts: 49
Likes: 0
Received 0 Likes
on
0 Posts
Victory!
From last night´s episode of this saga...
Trying to find the vaccum leak, I found loose bolts on the lower intake manifold. I tightened them up but it was too late to finish the reassembly. Today...
Got more cigarettes and smoked the intake again. Still lots of smoke coming out from bank #2.
Got the whole intake manifold out. And found a bolt nut sitting between the head and the intake.
What a nice "spacer"!!!, the perfect size to keep the intake manifold from seating on the head. 
On the plus side, I am glad it didn´t fall into the intake port.... Removed the nut, put the whole thing back together and....
I am so happy, it`s been lots of work, many hours, many late nights, a lots of hard thinking.
Thank you guys for all the support, It really makes a difference to me having knowledgeable people giving me ideas and valuable information.
I still have issues to solve.... the gauges, the hard wired fans, alignment, shifter rod adjustment, low oil light going on and off. But thats all minor stuff. My engine purrs like a kitten!
Thank you all.
Last edited by PTYGS400; 08-28-14 at 06:59 PM.
08-28-14, 05:15 AM
#42
Pole Position
As they say, if you want it done right, you have to do it yourself.
Angel, congrats. Finally, the payoff! At least is was a free fix without having to shell out cash for anything expensive or even worse having to pull the motor or something. That is an ENORMOUS vacuum leak. Obviously that is pretty gross negligence by your starter guy. It's a shame, but in this business I see stuff like that a lot and I am paid to find and fix mistakes made by others.
You lost a lot of time but you learned a lot and confirmed all the right things with your car so not all is lost.
Congrats again! Even tho you're not done with all the other stuff, you're well prepared for it.
08-28-14, 09:19 AM
#44
Driver School Candidate
Thread Starter
Join Date: Jun 2014
Location: Florida
Posts: 49
Likes: 0
Received 0 Likes
on
0 Posts
08-28-14, 09:20 AM
#45
Driver School Candidate
Thread Starter
Join Date: Jun 2014
Location: Florida
Posts: 49
Likes: 0
Received 0 Likes
on
0 Posts