'91 LS400, 95K
Was a couple minutes away from home when I noticed the RPMs fluttering, and it felt like the engine was stumbling a little. Then I noticed the RPMs fluttering while waiting at the next light. When the light turned green, I wasn't able to accelerate. Step on the peddle, and the RPMs remained fluttering at a low RPM. After pressing the pedal 4-5 times, engine finally kicks in and the RPMs fly up. Turn onto my street and the engine shuts off! I restarted the engine and was able to cruise the last stretch home.

A friend (not a car person) who was driving behind me last week did mention he thought there was excessive fluid leaking from my exhaust pipes. But it was a cold morning and I hadn't been driving for long, so I figured it was just condensation. Don't know if it's related to what happened today, as I've never had any powertrain-related issues with this car. Any idea what's wrong?

 

Welcome to CL. Is there any check engine come on? It could be either your coil pack goes bad or the spark plug wire, TPS.. I recommend take it to the shop and get proper diagnosic.

 

It could also be something as simple as having a dirty MAF. Open up your intake and try to clean up around your MAF as much as possible. But please be careful, a busted MAF sensor is a very expensive thing to replace and those babies are fragile as hell.

A dirty MAF sensor will have trouble reading the amount of air being sucked in by your intake and this will cause it to give erratic codes to your injectors and thus the "rpm fluttering" you are experiencing.

I am just saying this might be the cause, but it's always better to bring it in for a checkup.

 

Is the connector to the MAF hooked up? This is the wire that connects just behind the airfilter intake assembly.

Random thoughts: Dirty MAF or loose connector, ignition wire/s, injector problem or a vacuum hose is disconnected somewhere. If a visual inspection does not show anything obvious have it towed in for a diagnostic. Don't drive it, you would not want to risk further damage.

 

Thanks for the suggestions. The check engine light didn't come on when this happened. I'll check the MAF connector and look around for anything obvious.

Was going to take it up and down the street to see whether it acts up like before, but that now sounds like a bad idea.

 

any ideas on how to clean the MAF?

 

I had mine diagnosed at the dealer, and it turned out to be the fuel pump - a rather $$$ repair.

 

To clean a MAF you can use either brake dust cleaner or carburator cleaner. Personally, I was told specifically by Lexus to use brake dust cleaner. Carefully spray this on to the thin wire that is usually covered in gunk on one side. Normally, it is entirely red when clean. Afterwards, wipe it off gently.

If your check engine light came on, you want to (with the key OUT OF THE IGNITION) pull out the EFI, #13 fuse in an RX300, for 30 seconds, and then put it back in. That should reset the light.

If you do have a bad MAF, the car will not accelerate very well and could overheat slightly.

 

That's weird about the electronic fuel pump. These don't tend to be intermittent issues as they either work or not. Hope you car is driving nicely now.

 

LS4Lexus, I see your in CA, Check your air filter first , do to the fires and winds there is an excess amount of dirt in the air can plug the filter......................And then mas...........and throttle body..

 

My cousin thought the same thing as you. And I wasn't able to reproduce the engine stumbling after that one incident. Dealer couldn't either, and requested that I leave it overnight so they could check it out the next day more closely - they called the next day and said it was the fuel pump. Cost almost $800 after it was all said and done.

 

$800

What was also included in that service? line fuel filter, in-tank filter...