Just Picked This Up. I'm Impressed Despite Issue.

[KJG]

I was looking for a third vehicle for when I want something easier to drive than the Excursion. I also plan on passing this car down to my son next year when he gets his license. I like the solid feel it has and all the gadgets are pretty cool too as long as they stay working. What I liked about these cars is the durability of them. And I liked the fact that the 1st gen cars are non interference motors. This car has had all the normal timing belts stuff done along with the power steering pump, rack and all that jazz. It has had plugs and wires along with a egr and the ports cleaned. The whole a/c system has been replaced at one time as well. The emissions report that was done last week is impressive for a 1992 with 150k on it. Passed with flying colors. The H&R springs are a nice touch as I know my son will have wanted it lowered and will probably put a set of wheels and tires on it. He has been looking at them already. I really don't have to do a thing to it as the interior is perfect, good tires and brakes and everything on the car works. But it is not without a issue.

It has the low idle issue and the transmission when at 55 mph want to surge. I don't know if it is the trans or not but it is time for a service at least. I've cleaned the IAC, removed and cleaned the throttle body (that thing was horrible), bypassed the power steering pump valve, did the fuel pump relay resistor bypass and even adjusted the throttle cable (doing this only made the car surge going into gear so I put it back). After the throttle body cleaning the rpms went up from the first line (200 rpms) to the second line (400 rpms) while in gear warm. No fluctuation at all when the a/c is on. Now in park it will idle at the third line (600 rpms) with the a/c on and then jump up to the fourth line (800 rpms) with the a/c off. I didn't check the TPS but with all the reading I've done I doubt that is the issue. Next weekend I'll fool with the TPS but I think I know where this is heading and that is the ECU. I've looked at having it rebuilt but I also have read about certain caps to use to do it right. Here are a few pictures of it.

[landar]

Welcome Damon! Sweet looking LS. And it sounds like you are already pretty knowledgable about it and the normal issues. Are you getting your son involved in working on it? Good father/son 'projects' ahead!

[KJG]

Yes he was out with me today taking stuff apart, cleaning and showing him what everything was. I went into this purchase blind, never owned a Lexus let alone a Toyota before. Should be interesting. One thing also is the head of the connector that plugs into the IAC crumbled in my hand as I removed it. Lovely. I taped it up the best I could but who knows if it will hold.

[Exhaustgases]

If its perfect body and paint, take care of it. All the other stuff is the easy fix. It will never have a good factory paint job again.

[KJG]

It's not perfect but nice. Once it cools down I'm going to clay bar it, compound, polish and wax it bit has a good shine now but it's not smooth. It was owned by a old guy in Daytona Beach and garaged its whole life so that really preserved it and the interior.

[VBdenny]

That is a beauty and in my opinion perhaps the best Lexus car ever made. I still miss my LS400 and will probably end up getting another one at some point. Car should idle at 600 rpm's when at temperature. I do know the 400 does take quite awhile to reach operating temperature. It is the perfect family project, something I highly endorse. Enjoy it before your son gets it because he won't want to give it up.

Welcome, nice to have you here at the LOC. Best auto group on the net, hands down.

Denny

[Exhaustgases]

There was a 90 that was in Ca that a dealer had with 3000 or so miles on it, I think its sold now. They had a top price on it at first but then price went down. I don't remember the color but it was very base with no options.

[KJG]

Have been back at it. Yesterday the computer came back and the used IAC that I bought came in. I repaired the pigtail for the IAC and put everything back together. Sadly the two problems still were present. I poked around and found that the rubber intake tube from the air meter to the intake was junk. I sealed it up and the idle got better but not the 600 or so idle in gear that it should be. The off the line hesitation was gone though. The other thing was the surge/shutter or miss that it has at 55 to 60 mph. The rpm's jump up and down in that range. I think the tach on the car is off because at 60 mph it is saying I'm only turning 1k and that cannot be right. If I rev the motor in park to 800 rpms the car is revving to much. I bought a rpm tester so I will try that. People have said that the trans mount can be a issue and others have said it could be the TPS. I'm going to hunt for more vacuum leaks but I think I'm going to measure the true rpm's and then swap out the TPS and adjust and see what happens. The CEL is not on, but I've only put on 12 miles since putting the computer back in. My wife and son have it out today and will put on a bunch of miles so I'll check for codes then when they get back. The car idles so smooth and runs great for me to think that their is a major problem. I may resort to taking it to a customer of mine that is a independent Lexus service shop.

[landar]

With the symptoms that you describe, I would be looking at the cam and crank sensors. Also, if the distributor caps and rotors have not been changed recently, do that first thing.

[KJG]

The caps and rotors have been changed. I'm sure the coils have been changed out too. The car does not run rough. It does not idle rough, just in that 55-60 mph range does it shudder. I'm almost sure that the cluster is bad so the rpm's it shows are irrelevant. I'm going to try out the tps first, those are cheap.

[Exhaustgases]

Check the operation of the original, resistance .