93 Sc400 Hesitation On Acceleration

[deuterij]

Looking for help:

Problem is that the car hesitates to the point of no power during acceleration. Happens mostly in mid-throttle position with RPM between 1200 and 2000. Seems to clear up above 2500 RPM. Worst when cruising in top gear at about 40 MPH and you try to accelerate. Engine sputters around 1500 RPM and won't surge ahead until a few seconds later or I floor it.

I've seen many posts about stalling and acceleration problems with this car. I've tried jumpering the E1 and TE1 leads in the diagnostic connector but that only made the OVD and check engine lights blink on the dash (no fault codes read out on the clock) Then I tried jumpering the B+ and FP leads and that made no difference in performance, so does that mean the fuel pump ECU is NOT the problem? Just before this problem creeped up, I had accidentally tried to start the car with the fuel pump and gauge sending unit disconnected at the tank. I reconnected and the car started but has had this acceleration problem ever since. Is there anything about trying to start the car with the fuel pump and sending unit disconnected that could mess something up?

Appreciate any insights.

-Eric

[UCF3]

I'm guessing the fuel pump(Bad) or the Fuel Filter(Dirty) might be the problem. Otherwise I'm out.

[JDOwen2]

Your current problem may be coincidental to the disconnection of the fuel pump. Verify timing and plug condition. What is your vehicle mileage?

[SCdriver]

Sounds like it could be a problem in either the fuel deliverysystem or electronic management. The simple things to do would be to change the fuel filter if it has not been changed for some time and to add 1-2 bottles of techron fuel additive to the gas tank to clean the intake,valves and injectors. The next thing would be to check the plugs,distributor and wires and change them if they are due for replacement. Review your service history and if the problem persists see if lexus can have a technician test drive the car and run diagnostics to see if anything has shorted out etc .

[jimbostar]

Have you done a tune up lately?

Also, as a quick fix (maybe), try a GOOD fuel additive like Chevron Techron, it's cleared up problems like this for me in the past. It's a little more expensive then some others, but it's well worth it.

[deuterij]

Thank you all for the posts. I will try these suggestions. I have also heard the fuel pump changing from low to high mode when I jammed the accelerator pedal. If I listen close to the gas tank, I can hear the fuel pump whine shift from low to high pitch coinciding with hitting the gas pedal. So that confirms that the fuel pump ECU is doing its job. Now whether the pump is actually putting out the required pressure is another story. A defective pump might make the appropriate noises yet still fail to put out enough pressure. I might hook up a gauge to monitor system pressure. I saw the spec pressure in another post somewhere.

But thanks again for the help. A new filter and gas additive, then a tune up are in the works.

BTW vehicle mileage is 125000.

[pargolf]

Thank you all for the posts. I will try these suggestions. I have also heard the fuel pump changing from low to high mode when I jammed the accelerator pedal. If I listen close to the gas tank, I can hear the fuel pump whine shift from low to high pitch coinciding with hitting the gas pedal. So that confirms that the fuel pump ECU is doing its job. Now whether the pump is actually putting out the required pressure is another story. A defective pump might make the appropriate noises yet still fail to put out enough pressure. I might hook up a gauge to monitor system pressure. I saw the spec pressure in another post somewhere.

But thanks again for the help. A new filter and gas additive, then a tune up are in the works.

BTW vehicle mileage is 125000.

Just curious, do you still have the problem>??

What fixed it?

[turbo6]

check tps or afm, most likly its the afm.

[Air Force Rascal]

check tps or afm, most likly its the afm.

When was the last time you cleaned the Throttle Body..?

[92Lex]

Dude, the post was like 3 years ago.