O.K. Team ClubLexus I need your help!!!
I have a 98 GS400 with 402,000 miles (not a typo).
When I first start her up she sputters a little, usually stalls. After several attemps and after warming up a bit I can take her out on the road. She accelerates slowly at first, usually get a misfire or two, but once the car reaches 2,500 to 3,000 rpm it kicks in and runs smooth and true. I have been told that I have a vacuum leak and was hoping with the support and expertise of all of you, that I may be able to resolve the issue myself. What I am looking for is, basically, where to start, what to look for, best way to find a vacuum leak, best place to get replacement hoses, etc.

I look forward to your help, thank you in advance !!!!!!!!!!!!

-Steve

 

Wow with that many miles, how much oil do you use?
Your symptoms suggest you might have low compression when cold.
I would try and do a compression test on all cylinders.
Not many vacuum lines in the 400 look at them all...

Good luck and welcome

 

Oil doesn't seem to be much of an issue, I add maybe 1 qt. Every other month, roughly 8 - 10k miles. Thanks for your speedy reply!

 

MAF sensor maybe no good with 400k miles? Check vacuum leaks by listening for an air suck. A stuck opened PCV is the same as having a vacuum leak. Also do a compression test to see if engine still good.

 

Any thoughts/opinions/answers as to why the engine changes how it performs after reaching the 2,500-3,000 rpms? Does the engine change it's air intake at that point? i'm curious why the mechanic I spoke with said definitely a vacuum leak.

 

Is your CEL light on, is that why you say vacuum leak? Having a 98 GS4 as well, it is fairly easy to find a vacuum leak. Just remove the engine cover and follow the hoses, it is usually pretty easy to tell that the line is broken.

 

Did you read mines?

 

400K?

Post pix of your odometer. Thats one hell of a milestone.

 

Spray brake cleaner around your engine and see if there's any change in it. When the engine idles beter, then that is where your leak is.

 

Not sure if this worked, here's a picture of the odometer. . . .