Sluggish on acceleration

Keith Bolton · June 22

Hi ,I have a 1993 lexus sc400 , the problem I have is after running for approx 4 miles the car is slow to pick up speed and is like a misfiring , I have replaced all 4 oxygen sensors and the mass air flow sensor ,these are the parts recommended by Lexus after their diagnostics ,but I still have the same issues ,any suggestions would be greatly appreciated

Keith Bolton

Malc1 · June 22

Keith hi ,

Normal servicing items ?? …… air filter , oil& filter , plugs and all else too

My 91 Ls400 had a misfire when I bought her last August at 97k miles and it worried me a little …… normal servicing ( plugs had recently been changed I was advised ) and the usual Italian Tuneup seems to have cleared the hiccup and now on almost 101k miles she drives very very well in all situations ……. very fast and kwik off the mark …… E5 petrol tho’

for the V8. 4 ltr needs eh!

Good luck

Malc

steve2006 · June 23

If the spark plug leads, distributor caps and rotor arms are original replace them.

Common problem on the LS400 (same engine) is the passenger side coil pack failing when it gets warm due to its location above the exhaust manifold.

Any problems with the above will not flag codes or turn on the Engine Management Light, you do not need a code reader either, just a paperclip to check for any fault codes.

I’m impressed that you managed to find a MAF with it being a Karman Vortex type ( don’t ever use cleaner on it as it is optical and not a hot wire type)

John N · June 26

I recently had a small problem with hit & miss acceleration on the LS430 that turned out to be a Variable Valve Timing Solenoid.

It eventually flagged a fault code saying it was faulty so it was replaced. (An easy 20 min do-it-yourself job.)

That cured the acceleration issue. But it made me realise it had been causing problems for some time before it flagged a fault code. The car had been hesitant to go when you put your foot down, but then would suddenly pick up.