Michael88

So as many of you know, I have been chasing down this issue for about 6 months. After having a great day of 100 miles and 7 starts without issue on Wednesday, I had a no start situation on Saturday. It was new brake pad day (which I found new challenges but that is another thread.) After completing the first axle's brake pads, I had a no start situation. The car was cold and 75 degrees outside, dry. Popped the hold and heard the all so familiar sound to me of "buzzing" from the throttle body with the key in the ignition and on, not started. I have learned to disconnect the battery and unplug the accelerator position sensor (APS). Wait a few minutes, plug in the APS, reconnect the battery. Turn the key on. let reset somethings inside the console and dash, starts right up, and idles at about 1400 in Park until it calibrates to about 900-1000 in park. On Sunday, I changed the negative battery terminal connector to a new brass connector. I pulled the drivers headlight out, and replaced two electric fan relays that were not working. The electric fan runs now. I have ordered a new throttle body gasket (which is more metal than gasket material), because the old one seemed damaged and there is a little bit of engine vibration (shudder). It is three sheets of metal with a rubber gasket in the middle. On one corner, my three pieces of sheet metal could be shuffled like a deck of cards. Not horribly detached, but enough for me to think I might a big vacuum leak. I am soaking screws that mount the APS with PnB Blaster because they are being difficult. I will mostly have to look into the "4 pin bad soldering" issue I have read about on the forums. I used to have a frequent hesitating gas pedal, that is now infrequent but the pedal still feels like I am having to "coax" it. As far as predictability, Let's just say I am learning a bit of a pattern during summer weather. The idle RPMs while in drive will gradually decrease on each and every new trip. When all is good it idles at 650 rpms. This will maintain for about 5-6 trips. It will gradually decrease to 550-500 rpms for a couple of trips, and then to about 450 rpms when I start thinking it's not going to start next trip. So I think I might have to just disconnect the battery every time I get home just to not get stranded. Anyone experienced this? What is the cause. I have no codes, but will get a bluetooth code reader, soon.

dicer

Code readers are kind of worthless. What is needed is a quality scan tool bi directional, even a cheapy one is better than just a code reader, something that shows live data, it would report the throttle position and that sort of thing, but a costly scan tool would show more and also allow to switch stuff on and off to test its functionality. On CAM system cars its the only way to fix some things and alter some settings if needed.

Yamae

When was the last time you clean the air mix passages as well as the throttle body?

Michael88

You are correct I used the wrong terminology. Scanner all the way. I am thinking of buying the Bluedriver. Which scanner do you recommend?

Michael88

Is the air mix passages the little rectangular cover atop the throttle body? I cleaned that and the throttle body about 1000 miles ago.

Yamae

Yes, those passages are under that cover. There are 8 or 9 small holes connected to the throttle body to get air and 2 bigger holes at side are connected to injectors to supply air coming from small holes. These 2 holes are often badly clogged and it is not easy to clean without using a compressor with a can of carbon cleaner or more. The clogging causes a longer cranking time as well as poor and rough engine runnings especially at lower speed. How did you clean those 2 bigger holes, if I may ask?

Michael88

Thanks soooo Much! I thought about how I cleaned this Air Mix Path (little rectangular atop the throttle body), and believe I could do a better job. In fact, I didn't even notice the two large holes or put much effort into cleaning those. I did it with the engine off, and only used about a 1/4 can of carb cleaner on the 8 little holes. I believe there is a gasket for the rectangular cover, too. Correct? I think that gasket may be getting thin. Change the gasket if lubricating it with oil does not restore the appearance. I do not have any idle revving when I spray starting fluid around that area.. Bad place for air leakage I would bet. So, the plan is to put a can of carb cleaner in each big hole with the car running and push it with compressed air. Let it set about an hour with the battery disconnected and then repeat if necessary.

dicer

I've read that for the $ the Autel is pretty good, it is under $1000. anything else will be more.
$779. on amazon Autel Maxidas DS808
Its supposed to even beat some of the snap on units on some things. It will not do OBD1 only for OBD2 stuff. But is suppose to do all the various imports. Snap on stuff requires special packages to up grade to do import stuff. It is bidirectional.

Michael88

I ran a total of two cans through the two big holes in the Air Mix Path. I started with the first can and noticed the engine was going to die. S,o I throttled it up while spraying more, and about half way through the first can I noticed the driver's side began to take more spray without dying than the passenger side. I continued until the can was empty, using compressed air to "push" through the holes. I noticed the gasket seemed quite thin, but not broken. I replaced the square cap and went for a test drive. The acceleration improved, the shifts seemed better, and the brake pedal seemed more firm. All good things. I did a few 5 sec full throttles on the road, which was fun. I stopped and got another can of CRC carb cleaner. I thought the car would not start when I came out, but it actually started fine. The idle in Drive was 650 rpms with the AC on, and 500 with the AC off (which still concerned me.) I drove it on the interstate to evaluate the shuddering and found it improved considerably. It used to shudder at all speeds, and now it shuddered only between 45 - 65 mph and with less force. When I got home, I sprayed the second can into the two big holes and began to notice that spraying either side the car would not die. I could unload into a hole and not get it to die. I assume this is a good thing. I continued and used compressed air to push it through. The gasket broke clean off when I took the cover cap off, so I had to prep and clean and put a permatex "gray" liquid bead on. Disconnected the battery while during this. Cleaned and reinstalled the cap. Observations upon cleaning where "brown" discolorations under the gasket on the throttle body square in the back. I believe this was an air leak, small, but with the amount of suction at this cover, I am betting it was a huge amount of unexpected air. Now I wait 24 hrs. for the liquid gasket to harden.

I am starting to second guess my choice of permatex in this location, because of the amount of suction. I think I might order an replacement gasket and cleaning it off before trying to start the car again. Don't know what damage could be done by sucking pieces of permatex into the fuel mix path.

Yamae

I think you now understand how important to clean those 2 bigger holes thoroughly. But I wonder how much of damage could be caused by the sucked Permatex. If it were blocking the passage badly, you'd have a similar problem in the past. In the worst scenario, you have to remove it removing injectors. I hope it's not that bad.

Anyway, your car is getting better and better but you still have some minor problem(s) and you need to fix those remaining. Don't you think it's a kind of fun to find the root cause of problems and to fix those one by one. At first, you have to fight against invisible enemies but don't give up. Our cars are very well built and there are many useful tips on the Forum. Search the forum and most of problems can be fixed. If you can't find any tips, then ask people here for a help. People here are kind and nice. Sometimes some people try to help others without knowing much though.

Michael88

No permatex has been sucked in. Applied it with engine off, and waiting 24hr to dry and not starting it. Going to remove the permatex and buy some gasket material to trace out a new gasket just in case. Read that I can't order a replacement gasket.

Michael88

So, I cleaned the permatex off, and cut my own gasket from 1/32" fiber/rubber composite gasket material. I rubbed it with oil on both sides and along the edges until it was saturated. I reinstalled the gasket and cover plate. Turned the key on and let the computer calibrate. Started the engine with no problems. It idled at about 1500 rpms for about 3 minutes with vibrations and slowly settled to about 800 rpms in Park. Let idle more and in another 5 mins it settled to about 700 rpms and the vibrations went away. Went for a test drive and it improved considerably. Acceleration, pedal feel, brake feel, and engine sound were all better. Most importantly, the shudders that were present from 45 - 60 mph had reduced to 41 - 45 mph. I stopped and tested the rpms with AC on and off, and it would settle to about 650rpms for both. This is an improvement. It used to drop to 500 rpms with AC off. I turned it off and started three more times with no problems. The final start it would idle at 650 rpms in Park and in Drive. I think this is a good thing. Only time will tell. I believe there might be more small ait leaks that I will be searching for.

Yamae

Congratulations on you success, Michael. You now can suggest and help others who have the same problem. The clogging at the air mix passages is a rather common problem among 98-00 LS400s and Celsiors. People say, " I cleaned the throttle body as well as the air mix path" but it is the often case that the cleaning is not enough. The ECU is confused by the clogging and it causes the poor engine running and the strange AT shift.

Michael88

You are a big help Yamae, thank you.