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I am looking for a vacuum diagram for 1996 Lexus LS400 or even just a picture somebody can take of their engine bay on a 1996 Lexus LS400. When looking at the front of the intake manifold on my 96 one of the vacuum lines is capped. The right one is capped the little nipple has a plug on the end of it it looks like a vacuum line used to go there.
it would be greatly appreciated if somebody with a 1996 LS400 to take a picture of their stock engine bay. So I can figure out what the previous owner did at these vacuum lines.
That'd be great if you could take a picture of the engine bay or provide the vacuum diagram because on the left hand side of the engine bay near the intake tube there is some jerry-rigged vacuum lines....
here is the car in question. Left nipple is plugged..
On the left you can see a makeshift adapter with clamps on either side from two different sized vacuum lines I believe.. that line ends up running somewhere on the driver's side of the engine to a hard metal vac line... Which runs down the ?frame rail?
As I said, the cap on that port on the upper plenum is factory. Here is a parts diagram of the vacuum system. That hose that has the repair is an EVAP emissions hose coming from the charcoal canister. The repair is because someone removed the hose from the, what Lexus calls, the intake connector (the large black thing that the connects to the throttle body) and it split. It's very common. The hose get's hard from the heat over the years and it splits right down the side from getting brittle. That repair is sufficient and is meant to replace the split without replacing the entire hose. That hose new from a good Lexus parts source is $32 if I remember correctly. I just replaced that one actually. It's remolded and has the foam protector in the right spot to protect from chafing from the appearance cover. You vacuum system, from those photos, looks complete from what I can see.
The two that group together going down past the passenger side valve cover goto the power steering air control valve. They are common to leak internally allowing power steering fluid (ATF) into your vacuum system causing your engine to smoke. You can usually look right down at the small hoses connecting to the ACV and see if they are wet at the ends. They are usually wet on neglected cars from power steering leaks but if it's pretty dry down there and the ends are wet that's a good sign that the ACV is leaking if your car starts smoking.
Bottom line is, those hoses look fine to me. Are you having any drivability concerns?
Thank you for the informative response. In terms of drivability. Not so much. Only thing I noticed is my idle is around ~1500 when starting the car. Once it warms up it idles around 800 rpm. is this normal?
If my power steering isn't capped off... Should I do so? Just to be safe? My exhaust does smoke a bit...
That is a normal idle for a cold engine in park. Most engines do this. The reason is because internal combustion engines emit more pollutants when they are cold. Internal engine components also wear much much greater when they are cold. Engines hardly wear AT ALL when they are running at operating temp. Most an engines wear over it's life occurs when the engine is cold. That is in normal operating conditions of course, racing and the like wears on internal engine components regardless of temp. To aid in the engine warming up faster most ECM's are programmed to idle higher when cold. The idle will come down to normal as the temp increases. Lexus say's the idle should be between 600-700 in park/neutral, operating temp, AC off and all accessories off. It will go a little lower in gear but the computer and IACV should keep the idle at least near 600 with the AC off. With the AC on it will run a little higher in gear, like 700ish. There is no way to adjust the idle on these engines. The computer takes care of it through the idle air control valve (IACV.) If your idle is way high or way low you either have a vacuum leak, bad ECM, or a bad or misadjusted throttle position sensor. Bad ECM's will give you crazy idle RPM's because the engine coolant temperature circuit goes nuts and the car will think it's cold and pour tons of fuel in choking it out and causing all sorts of issues.
I have noticed the cold engine idle strategy is different with different ECM's. In 1996 there were two different ECM part numbers. The early cars got one ECM that ended up having some problems with the car shutting off when exiting the highway from an extended drive. Somewhere in 1996 Lexus superseded the ECM 1 number to fix this issue as well as some others that we don't really know about. I think the cold idle speed is one of those changes I have noticed a difference on the same car running each of the two ECM strategies.
I'm a purist and like to replace the ACV on the power steering pump if/when they go to leaking. They're not insanely expensive. I would say most people stuff a bolt in there or weld the hole in the valve shut after busting all the plastic off. Dicer has had success replacing the o-rings in side the valve but I can't speak on the source for those or what's required to get it apart. Your engine shouldn't smoke oil smoke at all and the 1UZ generally doesn't have this issue. Keep any eye on your power steering fluid and see if the level drops. If you want, you can reach down the pinch the hose clamps on the 2 vacuum hoses on the ACV and pull one off at a time. If fluid runs out of the nipple there is the smoke source. If they are dry just hook them back up. Your smoke COULD be fuel vapor from the cooler climate we're starting to get. These older cars run pretty rich when cold as you can smell I'm sure.
the most wear/damage is done to a engine/car/structure by 3 things... FAST: starting, stopping and turning.. it is programmed to perform all other movements the key is SPEED.. if you get angry, walk around the block.. save your LS.. my father told me this when I started driving...1948 in my 1939 chrysler
Just had my motor mounts and tranny mount replaced on my 1996 ls400. After the repair, the car seemed to idle higher than normal when cold ( 1200) and was I concerned that a vacuum line was displaced. The car does idle as normal when warmed up. Banshee,s explanation regarding idle makes sense and the car behaves as he describes. I guess my question are there vaccum lines going to the tranny and could they affect the idle?
Just had my motor mounts and tranny mount replaced on my 1996 ls400. After the repair, the car seemed to idle higher than normal when cold ( 1200) and was I concerned that a vacuum line was displaced. The car does idle as normal when warmed up. Banshee,s explanation regarding idle makes sense and the car behaves as he describes. I guess my question are there vaccum lines going to the tranny and could they affect the idle?
There are no vacuum lines going to the trans. What is the idle when warm?
It idles around 650-700 when warm. The car seems to be running fine. I just never noticed the higher idle when cold / or just did not pay attention to it. I do tend get a bit hyper observant after I get my car back from the shop, listening to sounds and the like!
Thanks for your response!
11-17-16, 04:18 PM
Vacuum line diagram for 1996 ls400
