Neil64

Hello All,

I have a 98 GS400 with 61K. I am not the original owner but the car was fairly well taken car of. It had all of its Lexus services up to the 30K service. Since then, the only thing that has been done to my knowledge is the trans fluid has been changed using Dextron 3 or 4, not the Toyota Type and the air filter has been replaced with a NAPA brand filter. Oil is Mobil 1 5W-30 and a regular Purolator Oil filter.

My question is, what can be causing a hesitation, a stumble or a miss when I am cruising 60 or better? It happens for a split second and I am just maintaining speed, not accelerating or decelerating. It only seems to happen when the outside temp is above 70 degrees. It was happening last summer but did not happen over the winter. I thought the problem went away but it has come back in the last week or so even though it has been hot in Maryland for awhile now.

Other than this problem, the car idles smooth as silk, revs to 6000 rpm when floored. I was thinking it could be an ignition problem but that usually shows up at idle on the tach or during high rpm. I also think maybe the fuel filter needs to be replaced but why would the car pull hard to 6000 rpm if it is a fuel problem.

The car is out of warranty and I hate to drop $400.00 or more at the Lexus dealer for something I could have replaced myself or taken to another shop that would charge half.

How hard is it to replace the spark plugs on the car? Any special tools, material or tips?


Ideas?



Thanks..

Neil

Neil64@verizon.net

Neil64

I forgot to mention that I have a delay or hesitation when I floor the car. I hear it is common on all GS'. No other time other than flooring it. Is it because the drive by wire? Maybe I should clean the throttle body?

Thanks..

Neil