WMurphy

I have a 93 Lexus Ls400, that is surging and losing power on acceleration. I have changed the Fuel filter, Fuel pump, and Throttle position sensor and still having the issue. I have disconnected the battery, re the ECU resetting, but still having this surge problem, It also is surging in park, even at times when idling. I just bought this car as a project car, had thought about using it just for a parts car, Could anyone shed any light on what else might I need to check. The previous owner advised it just had a new tune up, premium spark plugs and premius gas had only best used in it. He thought it might be the ECU . or Throttle Postion sensor, but I changed that out.

willhickey

iTrader: (1)

did you check timing?, any check engine light, does it have new roter and caps?, plug wires?, how many miles on it, did you adjust the tps when you put it on or just put it on?? you have to give as much info as possible to get a response... new coils? cats plugged up???

WMurphy

It has 321,000 was a daily driver, up until a month or so ago, It is not missing, just has that hard surging, and you can ease into and it will go, but if you try to give too much gas, for acceleration, it will stall, and then start surging, until you let off the gas and slow back down. Cat is not plugged up, Plug wires, I have not checked, as the previous owner said he just had it tuned up. and he had also just replaced one of the coils. Do you think it might be the ECU? I did put a throttle position sensor on it, pulled it to maximum rpms. The car runs runs smooth, when idling for the most part, until you accelerate, W Murphy

willhickey

iTrader: (1)

fuel pressure my sc was doing that before the pump went out..

neostar43

clean throttle body; check reisistance on old ignition coil

Piston1047

It could possible be your mass air flow sensor (MAF) after your air filter. It could be the sensor itself or the wires going to the sensor. Sometimes you can check the connector by moving it a little and seeing if the engine idle is affected. If the MAF is reading the wrong resistance then it could be metering the air coming into your motor incorrectly causing a limp mode or stalling. I have had this happen on my Q45 and your symptoms seem similar. Sometimes you can clean them using electrical cleaners, especially if you use a oil based K&N type filter this is a good idea. But sometimes cleaning them can mess them up so be careful. Your best option is maybe to get one form a junkyard and test it out. Only other thing I can think is a ignition issue, maybe your ignition coil or igniter unit. Hope this helps, let me know if you have any questions.

Here is a pic with the MAF sensor in green.

WMurphy

Thanks for everyone's replies, I have changed the MAF from another Lexus I had that was running good, and it did not help it. I don't think it is the coil, as I had a friend, who had coil issues, and his just would quit when it got hot. Mine starts right up, and you can drive a few minutes, until you accelerate and then it starts the stalling, then surging, and I hve kept it from totally dying, by just letting off on the gas and easing back down slowly on it.Also something else I have noticed, is that my dash lights started going on and off, when this surging problem started, not sure if they have any connection to it, but they might stay on a few seconds when you first crank car, and then not sure if it connected to the surging issue, but seems to occur about the same time it starts, the dash lights go on and off and now are off

Piston1047

Crazy idea but what about the alternator, maybe it is overcharging and causing a voltage spike under acceleration. I guess you could check this with a voltmeter. Or you could disconnect the alternator and run it on the battery for a wile. Most likely this probably would have damaged the battery by now. Maybe a bad ground also. I hate electrical problems. good luck.

PureDrifter

iTrader: (10)

did you check the iscv? i forget if the 1LS even has one, though im pretty sure it does.

StevieA

Agree, eeewww sounds electrical now that you mention the dash lights but before reading that I would say confirm you have good fuel pressure.

Or an even easier fix - my '93 had similar symptoms it was the hood insulation sagging and choking off the breather intake extension above the radiator - certainly worth having a lok at - just remove the extension over the rad and go for a spin when I did that mine turned back into a v-8

deanshark

It sounds like fuel pressure problem. The pump might be on it's way out. Also, even though the previous owner said it was just tuned up, he could be BSing you. I thought that it might have been the AFM also. Try unplugging it, drive a bit and see if you get your power back. Any codes?

bagyo

I have the exact same problem going on with my 92 LS! It accelerates just fine with about 50%-70% throttle; anymore throttle than that and the annoying surging rears its ugly head. I've used the search button for the answer and read that it was the fuel pump needing to be changed out, but your thread said you've already swapped that out. Let me know if you find the answer Bro It gets dangerous in the freeway when you think you can change lanes with faster flowing traffic and the surge happens

etex

Could the trunk hinge wiring be a factor in this?

WMurphy

Someone mentioned about the trunk hinge, That is a new line of thought, why would you say that? I also am goinjg to try to clean the MAF sensor, and clean the throttle body, I got some Synthetic Fuel injector cleaner, and put that in. Talked to a mechanic friend, and he seems to think it might be the MAF sensor, possibly being dirty, as he has seen other makes of car, doing this surging, and they have cleaned the MAF sensor, and it worked.

PureDrifter

iTrader: (10)

because electrical shorts do very weird thing to the LS' engine management systems...

http://www.lexls.com/tutorials/lighting/bulbout.htm