Hello everyone.
I recently purchased a 2001 ls430 CL, 153K.
I had the timing belt/water pump done bout a week ago. (First time ever for the car)
Changed air filter and cleaned the MAF sensor as well.

The issue Ive been having is the RPM dropping to 600 (same amount as when the car is at a red light) every time I take my foot off the gas. Not sure what is causing the problem but the car hasnt been accelerating as well as it should either.
Any help would be greatly appreciated.

 

Did the RPM drop after the timing belt/water pump service? Or did it happen after the air filter change and MAF cleaned? What was the RPM before? The LS430's ECU is very sophisticated, and will make necessary adjustments to optimize performance. The new filter and clean MAF may have thrown it off temporarily. Given enough time, the ECU will readjust for optimal performance, but you can speed this process up by disconnecting your battery for 30 minutes and allow the ECU to reset to default settings. This is a good starting point.

 

No, actually this was going on the whole time. The reason why i did the timing belt was because I thought it was causing it. Then I cleaned the maf and changed filter but that didnt help either. It just wasnt as noticeable before since the acceleration was pretty good. Now it seems like i lost 30-40 percent power acceleration wise.

 

Sounds like dirty fuel injectors to me. Do you know if the 153K miles are stop-and-go city driving? If you started with injectors that have poor fuel spray pattern giving you the low RPM, then the clean air filter/MAF will worsen the fuel/air mix in the cylinders. Your dealership will charge hundreds of dollars to clean your injectors.
I would suggest to reset the ECU, then add fuel injector cleaner in your gas tank, and take the car out for some highway driving. There are many such cleaners available: Chevron Techron Concentrate, Gumout Regane, Amsoil Performance Improver, etc. After the drive, if you notice improvement in acceleration, then you're on the right track to decide if you want to pursue a professional injector cleaning service, or to repeat the gas treatment several times.

 

Will do, appreciate the insight man.

 

Its almost as if the car drops out of gear into neutral every time i let go of the gas.

 

did you clean the throttle body?if not i would do that then disconnect the battery for 5 min and then take it for a drive.

 

Might be time for a new MAF sensor

 

Can you elaborate? Did you mean RPM raised abruptly as if you threw the transmission shifter into neutral? or did you mean the engine acted as if it's disengaged and no longer thrusting the car forward? I want to make sure that you're not describing a transmission problem.
Sudden loss of power can be caused by a failing fuel delivery system, such as a weak fuel pump or a plugged fuel filter. I'd keep this on the back of your mind. For now, let's start with cleaning the throttle body, put some injector cleaner in your tank, disconnect the battery to reset the ECU, take the car out for an extended highway driving, and see if we couldn't regain some of the power.

 

I mean the engine acting as if it's disengaged when I let go of the gas (instead of gradually decreasing rpm they just drop down). Its like when I had a car on manual and I would throw the car into neutral so it just rolls

 

Ive used techron a few days ago with no results. I did disconnect the battery a couple hours ago and connected it. The car seems like its back at full power but the rpm are still dropping like the engine is disengaging when i let go of the gas pedal.

 

That's a good sign...
One other benefit for disconnecting the battery is that it will clear all your old error codes stored in the vehicle's memory. Do you have a OBD-II code reader? If not, your local AutoZone has one and can retrieve error codes for you. Here's what you can do - drive your car for a few days to allow the ECU's to diagnose any potential problems. If problems are identified, the associated ECU will store an error code in memory for you to take corrective actions. This may take several days if the problem is intermittent.
Please let us know which error codes you're getting, if any, in a few days.

 

could frequent use of cleaning detergent like techron hurt any part of the car?

 

As long as you stay within the recommended dosage (1 oz per gallon), and not "overdosing" your fuel, you should be OK to repeat the treatment 2-3 times. The important thing to remember is the cleaner works best with higher flow rate (e.g. highway driving), so plan your treatment accordingly.

 

Hi,
Don't know if this has been said yet, but you are describing transmission slipping issues to me.
Have you had your tranny serviced lately?

Goodluck,