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Billydpowell, How would you know the universal cats are no good? I suspect they would be good but planning to try. I'm not sure if it's worth it to replace with those who have the flanges. At twice as expensive as the universals. Thanks in advance.

I'm sure there is no misfire now. I put my hand at the tail-pipe and I can feel very steady and constant puff-out. A few years ago, before I replaced the Bosch plugs with NGK, I could feel some random misfire. Not any more after the plug replacement and some of the cables. The mileage is about 166k. I'll keep you guys posted after I checked the sensors. Btw, in case I want to replace the cats, do you think the universal ones are OK (those without the flange)? It's about $70 each on Ebay. Thanks again.

Sorry but I missed SRK's comments. Yea, I agree with you. Check the O2 sensors first, following the specs from the repair manual. I still doubt the bad exhaust would be gone with the replacement of the sensors. SRK is right. It was CO, not CO2. My mistake again. Thank you all again.

Thanks guys. I haven't checked it yet but the air filter should be around a year old. Do you think it's bad enough to fail the inspection? But I'll certainly check: thanks for the reminder. I cannot check the code since the CEL is not on. I used to check it by reading the number of the flashes of the CEL as the CEL was on. I think the code was 28 (not quite sure; flash twice then stop for 3 seconds; then flash 8 times; then the same cycle again until turn it off), which meant the oxy sensor on bank 2 before the cat was faulty. I replaced it but did not help much: CEL came back on after a couple of months... Do you guys think that faulty oxy sensors can cause the bad smell in exhaust in stead of the cats, and the failure in inspection? I think the cats are more likely to be the culprit. If they can, I did not know they were that powerful. OK, I'll check the air filters and the code again, even the CEL is not on (it's possible it's already burnt out). Btw, I got a typo in my first email: it was CO too high, not CO2. If it was CO2, it should be good news. Sorry. Thanks again.

Hi, My 91 LS400 failed inspection today: HC and CO2 are too high. I used to use Bosch plugs but I replaced them a couple of years ago with NGK; newly changed timing belt and water pump (in fact, timing belt was OK; but the bearing on the water pump was gone). After the replacement, the car runs great and there was no misfire, not stalling, no hesitation as accelerating... The only problems that I have are the exhaust smells pretty bad (but not like rotten eggs); the valve clearance needs adjusting because you can hear the clicks as the engine idling. According to the inspection report, as the engines idles at around 650 rpm, the HC is over 360 (standard is 220); as idling at 2500 rpm, HC is back to normal; but in both situations, CO2 is high. I suspect the valve clearance has something to do with the HC emission. Because at around 2500 rpm, you won't be able to hear the clicks as the engine idles at 650. Not sure if I make sense. I poured a bottle of 'CRC Guraranty pass' into the gas tank but it did not help. Maybe I did not use up the whole tank of gas before the inspection, as the instruction says, then it did not help. Thanks in advance.

Hi landar, There is no valve like that in my thermostat. It's not a original thermostat. I replaced it a few years ago. Anyway, I'll take your advice and don't do anything and keep an eye on the dashboard. The next project is to replace my 95 LS400's lower EGR pipe, which is definitely a PITA job. I think I can say that I'm almost half way there but so reluctant to proceed. The right converter has been off; 2 out of 4 bolts are out (the lower ones); but the upper ones are still there. I am planning to remove part of the intake manifold to get access to those bolts since it's too far to reach from under the car. I'll keep you posted. Thanks again for your help. I like Paul's story too. Take care folks.

Thanks again for all you guys' help. Now the car is running smoothly. It looks everything OK to me. I've put about 300 miles on it since the replacement and there is no leaking around the water pump so far. Hopefully it will last. One more question. Not sure about the thermostat position is right or not. Is it going to be horizontal by the little bracket that holds the center valve, or vertical? It doesn't look like it makes any difference. Thanks in advance.

Sorry I did not make myself fully understood. For testing, I turned the crank timing sprocket (without crank pulley installed) to see if the other 2 timing marks on the cam pulleys matching the marks on the engine (about 11 o'clock on the left and 1 o'clock on the right); as they matched, I noticed the "u" mark was at 12 o'clock and the "0" mark on the timing cover pointing to the mark (the little "v" shape slot) on the crank pulley installed, which means TDC. Hope I'm right. Let's see how the engine runs. I agree with you that it doesn't make much sense if I do partial installation, just for save some sweat if start over again. Thanks again for the tips, and have a good one.

Thanks landar for the tip. I think I did it right this time. After mounted the TB, I installed the TB guide and cover, and the crank pulley as well. Make a few turns. The 3 marks matching correctly (2 for the cam pulleys and 1 at the TDC). Btw, I heard someone said about the "u" mark on the timing sprocket means almost nothing. But I used it as my reference of TDC position since it's at exactly 12:00 at TDC, without the crank pulley installed. Let me ask you something. What's the minimum installation that I have for testing if the pump holds water and timing too? I am just trying to take a short cut, if any, to test my work, instead of completing the installation, then spot something wrong, so have to dismantle almost everything and start over again. What about just having fan bracket and distributor installed; leaving the rest out for some 10 mins, after start the engine? Is that doable? Thanks again.

Thanks folks, you guys are great! Yes, 91's engine is sort of non-interference but 95 is not. Btw, I have both. The 95 broke down too: the EGR pipe that goes to the exhaust got a crack. Someone says you have to drop the tranny to have access to the pipe. I'm still working on it. Almost took me a week to remove the RHS converter because it was very hard to break the bolts. If I knew it was that hard, I'd use oxy-acetylene to burn it off. Anyway, it's a diff. story. In fact, I like the 91 better because it gives me fewer problems than the 95 does. At least the EGR pipe on my 91 is still OK, maybe a different design (about 165k miles); the 95 has about 110k miles on it. Almost all the lights inside the 95 are gone: the reading lights, the courtesy lights; the strong-arms that supports the trunk lid are broken too. I bought the parts from Amazon but not easy to replace since you have to take off quite some felt before you can access the strong-arms... I mounted the TB a couple of days ago. But after a couple of spins of the crank-pulley, the TDC was kind of off. That's why I took it off. Last night I tried it again. It was better this time. Since it was so hard to mount the belt on the right cam timing pulley, I mounted the TB on the pulley first (matching the marks on the TB and pulley) leaving the TB off the 1st idler pulley; then used a flat screwdriver to pry it up onto the pulley. I found it much easier than mount it on the right cam pulley. Also, I had some slack on the idler side so that's for the tensioner to set in. It might not be a decent way of doing it. But I can't just mount it on the cam pulley. The TB is on but it feels quite tight. I will have to lubricate the water pump bearing with some coolant before turning the crank pulley. Or it might ruin the water pump. Thanks again for replying and talk to you guys later.

Hi, Long time no talk. Hope all you guys are doing well. I'm almost half-way replacing my water pump and timing belt (might not be necessary) on my 91 LS400 (with about 160k miles). The water pump is the major culprit. The problem that I have is I have difficulty of mounting the replaced timing belt. I started from the crank pulley, matching the mark (CR) on the belt with the dot on the pulley; then proceeded all the way up. It looks like it's too tight to mount the belt over the right (passenger side) cam pulley. I turned the pulley clockwise slightly but afraid it might ruin the match between the mark on the pulley and that on the engine. As you tried to take the belt off, fine. Because you could turn it counter-clock to make it match again. But as you mount the belt, you cannot turn it back because the belt will turn too; so will be the crank pulley... I followed what's at http://www.lexls.com/tutorials/engine/timingbelt.html. It sounds quite easy but not for me. Any recommendations? Thanks in advance. Btw, as I took off the fan bracket, it wasn't so easy as what lexls says either. There are 2 bolt that hold the AC compressor to the bracket. They must be turned loose too before you could remove the bracket; another problem was with the water inlet housing. A few taps will not help much. The part on my car was as stable as a rock. I used vinegar to spray over the neck and it helped.

OK. But replacing starter is really really a PITA. I did it on my 1991 400. I did not replace the whole motor, just the points, which cost me about $35 bought from web. Usually the motor can last very long time so it's better to keep it. The starter is located in the engine bay. You will have to remove intake manifold and lots of something else to reach it. You probably need 14 mm flexible head wrench, don't even think about ratchet. The Japanese probably try to make it last forever to place it at the location like that but it's not good enough to last forever. Some guys took pics how they did it and posted them on the web. Good to check them out. They will certainly be helpful.

I think this is the one of the best illustrations for replacing water pump and t. belt: http://www.lexls.com/tutorials/engine/timingbelt.html Hope this helps.

Could you make sure your water pump running OK? It sounds quite unusual for a start to behave like that.

Hi, I got a 95 LS400. The similar problem with lower EGR pipe. I heard some guys did it for 30 minutes. They must be extremely handy because I spent over 6 hours to take off the CAT. The bolts are like being welded to the nuts. I believe I have all the tools that I need: a few air chisels, wrenches, baby ratchets and air/eletric impact guns and more. The PB Blust doesn't work well, or no help at all. I have no choice but use a grinder with cutting wheels to cut the bolts. One of the 3 bolts of the CAT is hidden inside and the grinder cannot reach. I use one of the chisels of long shank to break the nut, so the stud is not broken but I need to tap the thread. My problem now is, after the CAT off and the 2 nuts at the lower end, hard to reach the upper 2 bolts holding the pipe to the water bridge. They might get frozen too since using an impact wrench not helping. I know why some people have to drop the tranny. If tranny is gone, that shouldn't be a problem. What about do it from under the hood? But removing the engine wire on the firewall should be a pain in the neck too. Please help me out there. Btw, I replaced the starter a couple of years ago, which wasn't any fun at all; now the pipe. I'd never buy LS400 again: it's extremely hard to maintain. Really miss old American cars: you could sit inside the engine compartment doing whatever you wanted. Not any more because of the emission stuff. Thanks in advance.