90 LS low idle

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tsirovy

tsirovy

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Hello all. This is my first personal post. I just bought a 1990 LS400 that had been sitting for a year without running. It needed a starter so I replaced it myself and bought a new TrueStart battery--FIRED RIGHT UP!! It idled high at first then came down to normal when starting to warm up. When it was fully warmed up it started to drop below normal idle and idles just enough to stay running(fine line from dying) ~200 rpm. After replacing the starter I attempted to use the old interstate battery that wasnt even the correct size as I came to find out- it was too underpowered and would not start the engine. Here is what I have gathered after reading several threads on this site. I removed and cleaned the throttle body and ISCV (the ISV was in the open position when I removed it and would not manually move from that position-idk if this is normal). I made sure all hoses were connected and sealed. The only thing I can think of other than these are the fuel injectors or the passenger side ingnition coil. I read somewhere that a bad ignition coil will cause low idle and when I first tried starting the engine with the bad battery I saw a rapid poof of smoke come from that general area from inside the car while trying to start the engine. I also read that the injectors will cause low idle- when I removed the fuel rails i cleaned up the injectors and some of plastic on the bottom and top sides of the injector were cracked and frail. Any ideas on something else I could search for to correct this low idle issue? Thanks in advance. :newbie:
 
If it was sitting for a year I would change the plugs, wires, and rotors, then check the ignition coils.... The TPS throttle position sensor could be out of whack but is unlikely...Check the alternator and ground cables too...Cleaning the throttle body and injectors is what I would have done first..Air filter too...

Hard to say but it sounds electrical to me...
 
Oh yes.. In the meantime, while I was waiting over the weekend to pick up my starter, I had every thing disassembled and ready to install it. This gave me good opportunity to replace the spark plugs. The old plugs were really old and it showed. This car was pretty neglected- it didnt even have a lick of oil in the engine. So I replaced all plugs with bosch platinum double tips and cleaned up the engine as much as possible- along with the injectors. The wires seemed very clean and almost could be newer?? I also replaced the air filter before starting the engine as the old one was the dirtiest filter I have ever seen in my entire life- so many dead bugs and filth. Just fyi I do not think the previous owner every cleaned the engine and there is a thick grease covering several parts of the engine especially in the front side... and near/on the alternator. I am curious what it is meant to check the ground cables..which ones?? I would go get a check for the alternator but I dont have plates for the LS yet to drive there (can you test this with a multi-meter?)--- Furthermore if the coil/coils were bad wouldnt the car not start?? Ok now im lost:Eyecrazy:
 
If any of the coils/ignitors were bad, then
A) it would idle rough if a coil or an ignitor was dead
B) it would break down at high rpm/high load if a coil or an ignitor was on its way out
C) it would break down when a coil or an ignitor got hot.

The ISCV will not move without power, unless you pull it apart.
There are 2 small bearings in there (or is it one, I can't remember), try replacing that.
It always should go to the most open position every time you turn the car off (its why it revs high for 2 seconds when you start, and then comes down).


With a clean ISCV (and clean where the ISCV seats), and a clean TB, and the TPS is in IDL with the throttle plate 100% closed, and there are no intake leaks, then it should idle perfectly.

Unless either the TPS, the ISCV, or even the ECU is faulty, then who knows what would happen.


If you can cleanly rev it to say 4000rpm, then I doubt fuel is the problem.

Although with it sitting around for a year, it would be worth replacing the fuel and the fuel filter.


Cracked injector base rubbers are normal, just buy some new ones, but they'd be more likely to cause high/erractic idle than low idle.
 
Oh yeah forgot about the old fuel and fuel filter...Good point Peewee!!!!

What I ment in regards to checking the ground cable, I was talking about the main battery cables positive and ground leads should have good contacts on both ends...Faulty contacts could give you problems...

You also could have bad sensor reads or an ECU problem if the car warms and runs different as you explained... Still sounds electric or possibly a fuel problem..
 
I am going to replace the fuel filter as that is cheap and probably needs replaced anyway. The fuel system seems to function optimally. I checked the grounds and they appear stable. I am going to replace the right ignition coil b/c that is where I think I saw a poof of smoke come from on my first start attempt. Furthermore there is an unusually thicker whitish smoke from the exhaust-could this be linked to my low idle issue? Also I noticed my coolant level continues to drop as the engine runs and is clearly leaking from the underside of the car- I lifted the front end and took a look underneath and I could not pinpoint where the leak originated. Although I thought it was between the junction of the transmission- but this could just be where the fluid was running to.
 
Today I decided to check the distributors and test the resistance of my wires. The wires were good and tested well. On the right distributor the connections of the wires were solid- on the left distributor the connections of the wires would not even stay in place... moreover they had thick grease and even oil in cap plug in and wire plug in. I do not even know what this oil is from as it was not on the other side and the grease too. Needless to say I am going to replace both caps and rotors. The rotors on each side were cracked from each screw holding it in place on both sides. Somehow they were still operating though just waiting to shatter in a million pieces I assume. Hopefully this replacement will solve the idle inconsistency. Guess I now need to solve where I am leaking antifreeze from. :hypnotized:
 
Yeah, typically when a car is sitting for a long time, you need to replace alot of crap to get the car running just right...Even the tires can become warped from standing in one place for so long....
 
I have replaced the rotors and caps with new. After starting up there was no difference with the idle. I drove the car for the first time today and it accelerates and runs just fine when driving. The idle still stands low at a stop though. I dont know what else could be doing it- I will need to replace the fuel filter and see how that works. I had to fill the coolant two times while out driving though so I have a severe leak somewhere coming from the front side of the engine. My engine is burning oil too and I am not sure what causes this. I found out that my steering is loose too and I do not know what causes this either. AHHHHHHH!!:no:
 
Wow, sounds like you need to fix several things...Like I said many things tend to foul when you leave a car sitting

Hopefully your coolant leak is a broken line or hose and not the block or head gasket..... As far as burning oil goes, how much does the engine burn on average? How many miles are on the car? Does your oil show any signs of coolant in it? Worn piston rings causes the oil to burn but is usually not that bad with these lexus 1uz-fe motors unless it has a ton of miles and has been severly neglected...Could be an oil leak instead, look for oil drops on the ground where you leave the car parked after a long period of time, or look for drip indications from under the car like forming droplets coming off metal parts... Low idle still sounds like a faulty sensor read, ECU, or even the Throttle Position Sensor...Hard to say...

You may want to get an engine diagnostic check at a local import repair shop...Computer diagnostic checks sometimes reveal the problem when they throw a code...Does your check engine light flash?
 
""I read the following - White smoke when first started is normal. If white smoke continues you have an internal coolant leak, i.e., cracked head/blown head gasket.""

I think I just got a really good Idea of where my coolant leak is and why I have white smoke coming from my exhaust!! Oh no. Is there a way to test if your head gasket is blown? Does anyone think this can be the very reason a) I am leaking coolant b) I have low idle c) I have white smoke coming from exhaust ?? :boggled: The car has 200k on the engine. Could this also be a reason I might be burning oil?? My oh my.
 
That is why I asked if you found coolant mixed in with your oil...That is a clear sign of a blown head gasket... Yeah, with 200,000 miles it's probably normal that you should use maybe one quart of oil in between regular scheduled oil changes...Anymore then that and you probably have really worn piston rings or an oil leak that should be taken care of...
 
I have more questions. If my head gasket was blown on either side wouldnt I visibly see where fluid was leaking from the area?? I have more fluid that seems to be leaking from the front side of the engine.. Can my water pump seal be leaking causing antifreeze to leak in excess?? Today I started the timing belt/water pump removal procedure and stripped the radiatior,drive belt,etc,etc... until I got the the crank pulley as we all know is torqued to 181 ft/lb. I actually bent my "breaker bar" that I slide over my socket wrench. So I am trying to get to my water pump and reseal it. But I am tempted to just go further and check my head gaskets. I have never done this type of mechanical work before but there is a first for everything. I have read other posts about removing cams and the head. Can you guys explain to me what is most important when getting to the camshaft/valve area for removal?? It looks so self explanitory but then again there are detailed ways to remove the bolts, to mark parts, bolt the spring loaded gears?? So I really dont want to replace anything that doesnt need replaced yet but moreover just fix what is wrong. Advice at this point would be greatly appreciated so I dont break something that wasnt already broke. :happysad:
 
The water pump would definetely be a consideration for your coolant leak...They are prone to going foul and leaking with that many miles on the engine... I have changed the water pump a few times on several of SC400's and LS400's that I have owned and sold during my dealership days...It's almost a given...Infact many import mechanics recommend changing out the water pump when doing the timing belts...Whether that is a good recommendation or not I don't know for sure but that is what has been said to me on several occasions coming from a few reputable import mechanics...

Hope this info helps and good luck on your fixes...
 
Now after removing and soon replacing the head gaskets b/c I thought this may be the result of my low idle- I found out that my alternator was bad! This is my certain guess why it is idling low. I still havent gotten to removing and resealing the water pump but I will be doing that soon while replacing the head gaskets that I already ordered. I still have much work ahead as my engine is basically broken down all the way. I hope resealing the water pump will solve my coolant leak. I cant get the left header completely off because the manifold seems to be stuck to it... is there any tips on getting this to seperate? Otherwise I am just going to slip the new head gasket in and call it good. Also when I replace the head gaskets do I use a sealant on them or just use the straight gasket? Same with the water pump.. do I use a water pump gasket in conjunction with the sealant or just the sealant?? Sorry about so many questions.:werd:
 
Yeah, well I get a bouncing idle every six months or so...I simply clean my air filter (Pod) then spray out the throttle body and that fixes the idle every time... I also had my car bog down under full load, I had to re-tune my ECU with the Piggy back, and it all corrected... I have also had a faulty alternator which occured from a power steering leak which sits directly above the alternator...The lights dimmed when running but the idle never changed, then finally the battery died out...Hmmm?? Go figure....

Lastly the strangest thing of all that has ever happened to me, one day I started my 1992 SC400 maybe four years ago and my original big bulky stock Lexus battery completely blew up..Booooommm!!! Sounded like a shot gun blast. Battery acid shot everywhere under the hood and all that was left of the battery was an empty split battery shell casing.. Crazy......That scared the sheeeaaat out of me and my neighbor too....Got a new battery and to this day I still do not know what caused that to happen....Maybe low water levels in the old battery or something....

Sorry a little off topic but I thought I would tell that story anyway...Wish I would have taken a picture of it all at the time....
 
Toyota has an inuput for electrical loads to the ECU. If you have a heavy load, the ECU accomidates it. I doubt that is the problem.

I don't know if you used OEM parts or not. I know they are expensive, but they are the best. I have seen Toyota's not start with new Bosch tune up parts. They work great for VW, but Toyota just does not like them. It seems to be hit or miss.

The idle is controlled by the ECU. But all the other things need to be working right in order of the ISCV command to be the correct one. Things like throttle cable adjustment, dash pot, timing, etc. Assuming your older model has the dashpot. Those things have to be correct.

Have you pulled diagnostic codes? (DTC's)
 
So as of now I am waiting on a timing belt and alternator to be shipped. I reassembled everything after replacing both new head gaskets, exhaust gaskets, valve cover gasket, water by-pass gaskets and damm near every gasket on the engine. I have resealed the water pump with high temp red and replaced all new o-rings on the engine. Also I resealed the oil pan with the high temperature red sealant. In the meantime while waiting for my parts I drained my oil pan before replacing the seal and immediately when pulling the drain plug a massive amount of coolant was draining from the pan. I hope this was the cardinal indication that I in fact had a blown head gasket and that was the prime reason for white smoke out of my exhaust. Well Ill be back when I assemble more next week. :biglaugh:
 
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