15 June 2012

My 2004 SC 430 with 85,000 miles has a slight hesitation when I push the throttle lightly in gear. I have replaced the spark plugs and changed the very dirty air cleaner. I now have great power again but still have the hesitation. It's kinda like the fuel cuts off for a 10th of a second at high speed or low. If I put the shifter in 4th at 60 mph, no hesitation.

I will love some advice an what to do next.

Thanks,

Dennis

 

That just sounds like a normal hesitation from our cars. You can buy a Blitz throttle controller to help a bit. Also, maybe reset the ECU because it learns driving habits to achieve better gas mileage. One more thing, switch the ECT power button to the on position.

 

My first action would to be to clean the MAF and throttle body and then reset the ECU. Lots of posts in this forum how to do it. It's an easy do it yourself.

 

There are have been several threads about this in the past. The ECU that controls the responsiveness has a learning feature (disability in some of our minds) that learns how you drive and tames it down a bit to try to match the engine response to your driving habits and perhaps to help improve mpgs. More than likely, the ECU settings are the culprit. You can reset the ECU settings by following this procedure.

If you want to reset the ECU without losing your seat and stereo settings,
perform the following procedure:
1. Get in your car and insert key. (It doesn't matter if you close the door or not.)
2. Turn the key to the on (not start) position.
3. Press the gas pedal to the floor.
4. Hold the pedal to the floor for five seconds, then turn the key back to the "off" position
(don't remove the key), then release the gas pedal.
5. Wait 2 minutes.
6. Remove key.
7. Done

You can also do it by disconnecting the battery but then you also lose other settings (seat/mirror/steering wheel positions, radio settings, etc.).

 

If you did not clean the MAF sensor when you changed out the air filter, I'd do that first. Next, I would give the throttle body a thorough cleaning too. Both are easy DIYer tasks with the proper cleaners. Also, while not related to your performance issue, I betcha the cabin filter is filthy too. From your description of the air cleaner in the OP it sounds like the previous owner was pretty lax about maintenance items, i.e. all fluids. Do you know the maintenance history of the car?

 

This morning I reset the ECU as per the posted instructions. I no longer have a hesitation.
Thanks to everyone for your help.

Dennis Logan