1993 Ls400 Rough Idel

[MrPink]

I'm brad new to the forum so I'd like to start out with a hello to all!!

I work in the car Biz and jsut took a LS400 in trade that I bought. My father has had one for the past 11 years and has had only normal Lex problems. Any how love the car but have a few questions for all.

I bought my LS400 for $4500 with 160,000 on it. The guy I bought it from had 2 repair manuel that appear too be from a Lexus dealer. Big SOB's. Someone said they cost alot of money don't know if they will be much uses to me, but should help who ever I have work on the car. Do any of you know what or where these books came from?

1. Car runs rough when at cold idel. Goes away when warn. Also get a vibration when running on the freeway that kinda feels the same. After I pulled over and put the car in N, rev engine, ha no vibration. I think they are related, maybe needs plugs and wire? Calle the local dealer and will sell plugs to me for $80 and wires for $130 after my industry discount. Should I look else where for a better price or stick with Lexus parts?

2. Car needs front rotors. Where whould you recomend I get these, and how much should I pay?

3. Also very minor but does anyone have problems with thier window switchs? One will roll window down but has a hard time rolling back up. Window works fine from drivers side, 9 times out of 10. Don't know what whould cause this.

Sorry so long. Hope some one can help. Thanks Mr Pink

[Ross W.]

Your idle issue could be a combination of things.

First off, try and find out the service history for that car. You might be lucky in that the plugs and wires have been replaced recently. If not, do the plugs, wires, and caps and rotors.

Second, check the condition of the motor mounts.

Third, clean the intake, throttle body, and fuel injectors. Lexls.com covers that.

Fourth, get a can of plastic safe contact cleaner and a tube of dielectric tuneup grease, and clean ALL of the connectors in the engine bay's wiring harnesses. That made a world of difference in my car.

Fifth, check the grounding system, starting with the chassis ground lead furthest from the battery, and gradually work your way back. These cars are known for having weak grounds, particularly under the battery tray. Clean them with a wire brush and use LPS-3 to protect the connections.

Sixth, although it makes no difference when the car is cold, replace the oxygen sensors. Start with the upstream sensors ahead of the catalysts. Refer to Lexls.com for that as well. There's some debate as to replacing the downstream sensors, which I have not done yet, but my car ran a lot better afterwards.

Seventh, check the condition of the driveshaft couplings. Eventually they crack, but they're an excellent design and should not be a problem.

Eighth, while under the car, check the condition of the transmission mount.

For your brakes, I'd suggest going to iRotors.com. I put a set of their drilled/slotted rotors on my car, and they've been great. With your industry discount, I'd consider factory rotors as well. And make sure you get '93 - up rotors, if your car is newer than a '92, because they're bigger than the earlier cars.

With your power window issue, the tracks may need re-lubing or (Sound familiar?) the chassis grounds may be dirty, limiting current to the drive motors.

Lastly, check the condition of the timing belt and serpentine belt, and leaks at the power steering pump and water pump.

And last but not least, welcome to the forum!

[SKperformance]

You are looking at the books and asking us if we know where they are from or who makes them?

If you posted pics them it might help.

Vibration can be a number of things and rotors have been covered too many times to repeat again.

Read the red link in my sig "new and old members please read"

[MrPink]

Thanks for all the good advise!! I'll get to work tomarrow. By the way WHAT WIRES IN THE ENGINE BAY?

[cardona6569]

Hi: ]

I would hold on the recommendation of changing the oxygen sensors since he is not/ you are not having check engine light problems, and they are expensive items. Doing all the other recommendations will probably cure the problems you have. I had a bad O2 sensor and the idle was perfect and everything else but the check engine light that indicated something was wrong.

C. PR

Thanks for all the good advise!! I'll get to work tomarrow. By the way WHAT WIRES IN THE ENGINE BAY?

[LScott400]

Ross, do you know the specific locations for the engine grounds or know where there are pics? Thanks.

[Ross W.]

Ross, do you know the specific locations for the engine grounds or know where there are pics? Thanks.

I'll have to take a close look, but there will be definitely a braided ground strap off a cylinder head, and there are more than one I believe under the battery tray. I'll look around during lunch. I don't have my camera today otherwise I'd get some pics. I might do that tonight.