Hey all,

I'm pretty new here, more of a lurker / searcher. I have a small problem on my 93' LS that has been driving me crazy trying to track down. It has a stutter / power loss issue when getting on the throttle relatively hard (anything more than half or so). It does it sometimes less than that. Its almost as if it kinda "pops" once or more for a second then struggles along. I've also noticed as the car warms up to temp it gets sluggish - alot more than if its cold, almost as if its not getting enough fuel? Out of all the threads that I have searched, I've only found people that have lost pretty much all power OR a whole bank of cylinders etc .. (fuel pump or ignition coil). The car has 325K - Canadian in kilometers. I've also done quite a bit of maintenance since purchasing the car at 294K. The only things I can think of now are possibly a weak ignition coil or failing fuel pump, or even a sensitive knock sensor?

Anyone have any experience with this on an early LS?


Car in question ..

 

Maybe since its so low hitting bumps causes the oil pan to hit and makes it feel that way.

 

..... Can't tell if serious .. ?

 

Randomly, the ECT sensor, TPS and reading the ECU capacitor thread.

 

could be leads or plugs. I had the same issue on mine. If you dont fix it you could easily melt your cat

 

Get your service records here....

https://drivers.lexus.com/lexusdrivers/history

 

I probably should have mentioned the things i have done since purchasing -

Timing belt, water pump
Alternator, PS pump
Starter - all intakes cleaned, injectors resealed, new gaskets everywhere
All vacuum lines / hoses replaced
Air filter
Fuel filter
Caps, rotors, plugs, wires
ECU Caps as per Cowboy's guide - all high quality from Digikey
TPS, set using FSM
New 4 gauge grounds run + batt terminals
Coolant temp sensor
Tried 2 different AFM's with the same result

And probably more that i can't think of right now - I've done quite a bit hence why I'm a but frustrated in tracking this down, It does cause enough of a drive-ability problem to make me go a little bonkers.

The only things I haven't touched yet are the ignition coils, the fuel pump (or resistor) and the crank / cam sensors. Everything else seems to be new?

 

If you're on the original fuel pump, you are due for a new one. I would bet on that being your problem. Mine failed soft on my '91 at around 190k miles. Really tough to diagnose, as you are finding too. My symptoms would come and go, and tough to even describe, sound similar to yours.

A Denso fuel pump can be found for around $100. Will probably fix your problem. And if not, it will be due soon anyway.

If you're able to do electrical debugging, this post might be helpful:
https://www.clublexus.com/forums/ls-...ml#post9777959

and other stuff in that thread too. Although, like I say there, the conclusion of my circuit analysis and testing basically ruled out problems with all the other components, and still did not definitively point to the fuel pump. So it saved me from chasing relays and the FP resistor, as many do. But I did end up basically taking a guess on the fuel pump. Really tough to diagnose carefully with a soft failure like this. In my case, it was the right choice - problem is completely solved.

One test I did not do, which would be great to do if you have the proper tools for it, is to test fuel rail pressure. At some point, a $100 fuel pump was the easier choice for me.

Also, one thing I replaced (months or a year before finally nailing it with the fuel pump) was both ignition coils. Zero change following that, so I saved the originals as spares. They are known to last a long time.

 

Thank you very much for the input sir! I kinda figured i had it narrowed down to that. Almost ordered a couple of ignition coils last night, but I'll start with the fuel pump first as I'm quite sure it's original.

Also appreciate the link to the post you created regarding testing the fuel pump - will perform those as well. =)