chippern73

I have a 1994 LS400 with 132,000 miles on it. All stock. It just developed an accleration issue. When traveling up a hill at around 55 to 60 MPH at almost 2000 RPM the car stops accelerating and the check engine light comes on. If I press the gas pedal the car jumps along like its starving for fuel. Once the speed and RPMs drop to 40 MPH and below 1500 RPMs the car drives normally. This only happens on hills. Not on flat ground or If I put the car in neutral and rev the engine. If it was a fuel pump, injector, or fuel issue wouldn't it happen at non-load barring times? Thanks for your help.

chippern73

Anyone had a similar issue?

Superfast1

Based on your symptoms, sounds like you have a clogged fuel filter and/or your fuel pump is on its way out. Hook up the scanner & let us know the error code. If you don't have one, go to Autozone, O'Reilly or Pepboys, they'll scan it for you for free.

dicer

They won't know what to do with OBD1. Technically the plug in the code reader didn't happen on all cars till 1996. And those auto parts joints do not use a scanner, its a code reader, huge difference between the two.

Superfast1

Dicer- My bad. Didn't pay attention it's a 94. I use the term scanner/code reader loosely. One has more functionalities than the other but you can achieve the same answer in this case providing it's the later model w/ OBDII.

Chippern73- In your case, you can put a jumper on the 2-pin connector then count the Check Engine light's blinking (# of flashes) to determine the code. If you're not sure on the location of the connector & how to decipher the code then just Google it.

Legender

I'm assuming here that you've already checked the ECU for possible failure of the capacitor's? Not that a hill has anything to do with that problem though...
That is one strange problem...

chippern73

Thanks for the info. I'll look into a fuel pump.

oldskewel

iTrader: (1)

This is a tough problem to diagnose, so I did not want to chime in with advice, but since you're planning on a new fuel pump I'll say I agree that's a good idea.

This post/thread might help with any circuit debugging you might try to do:
https://www.clublexus.com/forums/ls-...ml#post9777959

I posted that when I was working through a problem on my '91 that ended up being fixed with a new fuel pump. Intermittent / soft failures made the debugging difficult. In my case, I did not notice anything related to hills (mostly pretty flat where I drive), but there was a heat connection. All that circuit analysis and debugging mostly saved me from replacing un-needed parts, but it did not really point to the fuel pump as being bad. So it was helpful mostly by process of elimination.

Fuel pump replacement is pretty easy to do. Far easier to just replace it than careful debugging was. Pump is accessible by removing the rear seat. I put in a Denso pump (not a Genuine Toyota one, but Denso was the OES on the pump, and this one I put in was made in Japan). Cost around $100. China brand ones are $30 and a Toyota one will be about 10x that. I re-used the gasket with no problems. And I had replaced my fuel filter a few years before that.

Good luck.

Superfast1

Replace the fuel filter first then see what happened before you tear down & replace the pump. Process of elimination & it's cheaper that way.