throttle hesitation

[skyway]

Good afternoon guys

 

My ls430 has some throttle hesitation, I have changed the plugs and coil packs also found an air leak and dealt with that but its still there at low rpm if I am gentle with the pedal as I normally am there is no lag but if you poke it a little more the rpm goes up then drops below tick-over  then at some point goes back up hopefully before getting hit by a oncoming truck.

Any ideas?

thanks again

john 

[ColinBarber]

If you rev it out of gear is it still the same?

Try cleaning the MAF sensor and the throttle body. Where was the air leak?

[skyway]

hi... Colin the maf sensor is clean, it revs the same out of gear the air leak was the airbox

[Spacewagon52]

Have you cleaned the throttle body - common problem on the LS400?

[ColinBarber]

Definitely check the throttle body. If you had an air leak after the MAF sensor then the long term fuel trims are probably way out which will take a while to come back in line. Might be worth resetting the ECU to clear everything - just disconnect the Battery for 30 seconds.

Was there some other issue for you to change all the coil packs? You would normally just replace one that is failing, they don't all fail at once.

I assume there is no engine check light / error codes being generated? Ideally you want it connected to some diagnostic equipment to test and see if all the sensors are working as expected, otherwise we are just speculating and going through a trial and error process. It could be temp. sensor, air/fuel ratio sensors, MAF sensor, fuel pressure etc. etc.

[skyway]

I have tried resetting the ecu I changed the coil packs and plugs as a service its gone a long way 240k thought it was about time and i had them so no foul no harm.

I had some error codes which were to do with the air leak which I think I have sorted and cleared, I am beginning to think that its the injectors .... (its rare) when I switch to LPG i don't get the hesitation and the last links in the chains are the injectors I better clean them tomorrow and see what happens.

[skyway]

so.... I hang my head in shame.

I found a small quiet exhaust leak at the front y section which was the cause of the throttle hesitation.

Problem solved can't believe that such a small leak could cause such a thing 

Thanks again for everyones help and sorry for wasting your time

[Spacewagon52]

2 minutes ago, skyway said:

so.... I hang my head in shame.

I found a small quiet exhaust leak at the front y section which was the cause of the throttle hesitation.

Problem solved can't believe that such a small leak could cause such a thing 

Thanks again for everyones help and sorry for wasting your time

Never a waste of time, a problem shared helps everyone learn. Great result!

[Herbie]

Glad you got it sorted mate and like David said above, it's never a waste of time to help others  

[ML EXUS]

Thanks to all.

 

I have a similar problem and will print this page and hand it to my service engineer. 😉