alien1974

I am curious about why it didnt have a gasket in the first place, what i might do on the weekend is to spray some carb cleaner round the air pass with the cover on with the engine running to see if it is leaking.

PlatinumV8

Remember this is a tough area to spray the complete edge of the mating surface while assembled.

I also doubt at idle you will notice anything unless you are watching the tach at the same time.

It is not a combustion path per se, more of bleed air, like the bypass air on a jet that feeds fresh air to the cabin while under pressurized flight.

PlatinumV8

So, the drive home was splendid, but not long enough to give any meaningful MPG data.

Seat of the pants, reminded me of my 1990, shifting was smooth and purposeful. It was not like it was deciding whether it was choosing the correct gear.

Parking lot behavior was smooth and predictable. I owe that to the properly adjusted throttle cable.

Taking out a half dozen turns of that shaft is no small issue for the drive by wire system to try and compensate for.

Put the car in the garage tonight and after it cooled down a bit I took off the cover to the bleed air port and it slid right off my DIY gasket. No mating or impression in the material. Not that I expected it.

The engine side, the actual port with the rough machined surface was a different story.

It had a secure grab on the ends, like it was glued down. The middle narrow sections were loose though and were easily lifted with a fingernail. That is where the major leaking happens IMO.

Slipped a small screwdriver blade under the gasket and once I found the cleavage plane, it lifted with a little caressing, until I reached the passenger side screw hole. It was so well compressed, it had to be torn one layer deep to remove the gasket.

See one picture shows the slight damage to the gasket from trying to torque the screw down enough to seal the port. The other shows the fiber gasket residue locked into the machining grooves in the port under the screw location. The last ones show the variable clutch drill I used and the array of permatex I had on hand. Doubted myself using the red and after seeing how hot the intake gets, chose it to use on both sides of the gasket for my next test repair, that I believe will solve my concerns about leaking vacuum around that cover.

Edit : The bamboo skewers are for clearing the bolt holes of Permatex before and after the gasket is dropped in place. Roll the shaft of the skewer to pull off the sealant, don't just smear it around.

PlatinumV8

My technique is to dab a good amount on my palm with gloves on, and treat it like you are dredging a fish or chicken filet in beer batter. I work the excess off against the clean part of my gloved fingers and then drop it in one motion onto the port, so it does not need to be adjusted more than a nudge or two.

I reapplied the thread locker to the screws and then tightened them loosely at first and then three finger tight with a small screwdriver. Tomorrow morning, I'll tighten them up completely, once the Permatex has set up nice and firm.

DON'T OVER DO IT WITH THE PERMATEX! YOU DON'T WANT IT TO GET SQUEEZED OUT AND INTO THE INTAKE AND/OR INJECTOR PORTS! I TAKE NO RESPONSIBILITY WITH THIS FIX, IF YOU ARE NOT COMFORTABLE WITH DOING THE JOB, PLEASE TAKE IT TO A CERTIFIED MECHANIC AND ASK THEM TO DO IT!

Also don't do this repair and then go drive the car immediately. We all want to see results, but letting this material set up is critical. Tube says 24 hours, but with a warmed up engine and mild outside temps I'd say 8 hours is more than enough.

Good luck everyone and PM me if you have questions or want to know more about my attack cat.

He has his summer lion cut and lounging in the piano room in the AC right now, it's 85 and Florida humidity outside. Time to change out of my business clothes seen here and into something more comfy!

Sleep well Sophia, you get woken up tomorrow for a day of test driving!

Debbie

Edit: Woken up, because I disconnected the battery. I want a clean slate each time so there is no behavior added from previous driving. It may take some time to test the MPG gains or losses, as the ECU relearns my driving habits.

PlatinumV8

Just woke up and went downstairs to my shop/garage (under my house like Iron Man!) and took a short nubby Phillips screwdriver and used both hands to tighten the screws even more. Moved about an 1/8 of a turn. I know I broke the thread locker free, but I wanted to see how much squish I got out of the set up Permatex. Felt nice, like a hand shake, versus a brick wall with the factory hard gasket.

So, hooked up the battery, started her up and backed outside.

Idle RPM cold (65 F) in Park : 800 RPM

Idle RPM cold with foot on brake and in D : 450

Let her warm up and once the needle pulled two marks off cold the readings were:

450 RPM in Park

400 RPM in Drive with foot on brake.

Also, backing out of my long uphill garage driveway to park in front of the house in the upper circular driveway, there was no drama like before. Smooth, like a giant was moving me along as his personal hot wheels car. Where before it felt like my C5 Vette auto drop top, unpredictable and sudden movements. Like riding a bull versus a show horse.

Now I have not driven to work yet and the computer is saying .3 MPG (only moved 100 feet and spent a long time idling), but I think we may be onto something here. Fingers crossed!

Debbie

PlatinumV8

Smooth as silk! Ohhh, that was a nice drive!

Tonight I'll try some more parking lot testing and try to get her to misbehave.

Yamae

Congratulations on your success to fix your car.
Thanks for the update. I'm glad to know that.

I thank you understanding my explanations and ideas written in my limited English. I think I know the car a bit more than average dealer mechanics regarding ECU related area but I have difficulties explaining things in English. LScowboy has understood me and he has started the ECU capacitor thread. Now it is the biggest thread in the LS400 forum except the sticky.

Your fixing process should be added to the FAQ. I hope you do something similar. The red nails would be attracting boys. There are many people who suffer the same problem and they will be happy doing the same what you have done.

PlatinumV8

Thank you for your recommendation to the board for consideration of my posts for inclusion on the FAQ pages.

I am sincerely flattered. As far as your English it is better than most Americans these days. We understand you perfectly, right guys? Red nails attract boys? Wait until you see my boating pictures!

Whoops, that would violate the safe for work rules. Darn.

As far as the hesitation issue, this fix appears to have solved:

Here is my take on that cover leaking vacuum. If it leaks, debris can get inside the port. If it leaks moisture can get inside the port. Moisture allows the carbon to build up in layers and finally block the smaller ports. Based on how loose my cover was, I'd say if anyone drives in heavy rain or snow, power washes their engine, etc., they are getting contamination.

Also, if the cover is not sealed, the air flow to the injectors has to be compromised. They are there for a reason. I can see no good reason to have them drawing unfiltered outside air. I wonder that the air path is a dumb system, in that there is no sensor that can detect that outside air is being pulled into the injector system, and not from the intake plenum.

You can tune a car all you want, replace sensors and fluids until you are blue in the face. Until you realize that the engine is a big fancy air pump that cannot leak pressure or vacuum to operate as designed, you will keep hitting a brick wall.

Fuel, spark, compression, vacuum, timing. The big five, we live by in the racing community.

I for one, am looking forward to the first all electric Lexus. The dealerships sure aren't! Lol!

RA40

iTrader: (6)

Congrats on getting this ironed out. One of the areas I have experienced on other older cars as well as the LS400 is vacuum leaks. With as many vacuum assisted switches, those leaks present some subtle and obvious changes.

sha4000

iTrader: (1)

Did I missed something out did you already run the car without the cover to see how it affects the engine? I'm sure it will have some effect but not sure it's responsible for the low idle issue. I did check my throttle cable and it does have some slack which might account for the delayed response when hitting the pedal from a stand still. I've already cleaned the throttle and intake when I had them off during my starter replacement last year.

PlatinumV8

Ra40,

Most definitely, vacuum leaks can be a bugger to track down, especially when you don't realize you have one. I've seen 5.0 Mustang guys tear their hair out trying to track down a tuning issue and end up trading out cams, heads, carbs and it ends up being something like a hairline crack in the intake.

No issues at idle or WOT, but midrange it would give them fits. (At idle the intake was not being flexed and at WOT, the flow rate was high and the engine flexed to the mount limits.)

Sha4000, You might be brave enough to drive yours around without the cover on, but I'm not.
Glad you took out the slack in the cable. One more thing to get back to factory spec. These ECUs want factory spec on every component. That is why racers these days have to reflash chips or run a stand alone engine management system when changing out drivetrain parts and accessories.

Keep the questions coming guys. Out of work for the day, gotta do some errands and see how she likes being driven a little harder.

PlatinumV8

Just got back and the car is awesome now! OMG! No more tossing my butt around on the part throttle shifts. I could say, it is like one expects from a Lexus.

Then I did a few full throttle blasts from a stop and from a rolling start. The car revs quicker and stronger by far. Like a tune up and race gas difference. It feels like an extra 30 HP.

The mpg computer ticked up constantly during the ten miles of stop and go traffic at 78 degree F, with the AC off and windows down. Every 1/4 mile it ticked up a tenth. Ending at 18.1 when I just parked it and started barbecuing a whole chicken I had marinating since this morning.

I'd say seal that port guys, sooner rather than later. Make sure to reset the ECU so it can relearn the system and your driving.

Debbie

PlatinumV8

Oops! Double post! Deleted the text, Mods, please delete it or let me know how I can do it myself.

Yamae

I have a question, Debbie.
Does your engine behave low idle rpm without the gasket?

IMO, when the lid has some air leak, the engine rpm usually rises due to the extra air absorbed. That air is not measured by the MAF but the O2 sensors and the closed loop compensate the A/F ratio and the engine usually runs smoothly and higher.

PlatinumV8

Yamae-san,

My idle was lower without the gasket and especially without the Permatex that finally sealed out the vacuum leak on the long side of the port cover. Now it idles 20% higher and has lightening crisp throttle response.

The air bleed on the injector seems to eject combustion gasses if there is no negative pressure.

If you look on the cover you can see high speed gas impacts on the interior, proximal to the 8 injector ports. IMO, when a seal is lost at the port, the combustion gasses travel up the air tube and impact the cover. This may partially pressurize the intake plenum.

The injector port does not seem to have valving. It relies on negative pressure (vacuum) to oppose the propagated combustion wave profile.

Just a theory, I sure wish Lexus could chime in and say whether that port needs to be sealed or if it can just be left to leak to atmosphere, thus the inadequate twin screws.

Edit: Air entering without registering at the MAF sensor will effect a shift event based on the shift map of the transmission. It will be contradicted when the TPS has a reading that does not relate to the angle of the butterfly valve, based on sensor and engine speed.

This explains why adjusting the throttle cable and eliminating the leak at the bleed air port for the injectors was so effective. It makes perfect sense.

New manual driver wants to shift gears at 1500 RPM, pushes in clutch and starts gear change. Instructor says, no, Rev higher, then shift. Passenger feels like shift takes forever and abrupt when it does occur.

Computer and trans are conflicted based on bad engine speed data versus TPS.

That is my two cents.