Intermittent Starting Problem

[GKLCPA]

I have a 1996 LS with about 200K miles on it. Over the last three months, it has developed an intermittent starting problem. When this occurs, the car turns but the fuel will not fire. If I let it sit awhile and come back, it will start up normally. It's almost like the fuel is bad. Lexus and Toyota can tell me nothing unless the car arrives in the non-starting condition. The first couple of times it did this, I was on my last quarter tank. The last couple of times it did this, I had a half tank of gas. Also, my fuel mileage has declined about 2 mpg, but I have one of the front cats to replace and that may be affecting that.

Here's what I've done in an attempt to solve the problem:

1) Changed all plugs, wires and rotors.

2) Installed a new fuel filter.

3) Changed front 02 sensors.

On one occasion while driving, the car seemed to be having an issue firing the fuel as it seemed to be skipping, but that was before I did the stuff listed above, Before I changed the front O2 sensors I was getting a code indicating that the fuel burning was too lean.

Please help me out here. What is it that I should focus on in trying to solve this problem? It's been suggested that the fuel pump might be bad. Thanks in advance.

[curiousB]

Intermittent problems can be tricky to sort out. You could get a fuel pressure gauge and tap into the fuel rail. Try turning the car on (but not cranking) and see pressure reading. Maybe the fuel pump has a dead spot on the commutator such that it gets stuck every once in a while. If you see a low pressure reading followed by failure to start then you can bet a new fuel pump is in your future.

Another possibility is a leaky injector such that fuel drips into cylinder while shut off and then when you go to start it is flooded. I am less likely to think this though as with 8 cylinders even if you flooded one the rest would be enough to start. Again the fuel pressure gauge would help. Pressure should stay up for several minutes after shutting off engine. If it drops to zero quickly then there is a leak somewhere.

[GKLCPA]

Intermittent problems can be tricky to sort out. You could get a fuel pressure gauge and tap into the fuel rail. Try turning the car on (but not cranking) and see pressure reading. Maybe the fuel pump has a dead spot on the commutator such that it gets stuck every once in a while. If you see a low pressure reading followed by failure to start then you can bet a new fuel pump is in your future.

Another possibility is a leaky injector such that fuel drips into cylinder while shut off and then when you go to start it is flooded. I am less likely to think this though as with 8 cylinders even if you flooded one the rest would be enough to start. Again the fuel pressure gauge would help. Pressure should stay up for several minutes after shutting off engine. If it drops to zero quickly then there is a leak somewhere.

Thanks for the response. I'm nearly certain that the fuel pump is the problem.

[landar]

Another rather simple test is to spray some starter fluid into the intake snout when it will not start. If it fires up, you know that it is fuel starvation. If not, then most likely an ignition issue.

[GKLCPA]

Another rather simple test is to spray some starter fluid into the intake snout when it will not start. If it fires up, you know that it is fuel starvation. If not, then most likely an ignition issue.

Thanks for that tip Landar! Until I get this thing fixed, I think I'll keep some starter fluid around just in case in addition to being able to isolate the problem.

[skymasteres]

Well, I will definitely need to try the starter fluid bit.

I am having the exact same issue on my 93 LS400...

[DEATH_AWAITS_YOU]

What DTC code did you get, exactly? There is no "lean" code for an oxygen sensor. If you did, however, get a lean code, it indicates that the engine is running out of fuel. How does the engine operate under wide open throttle? Your problem is most likely that the injector driver's are failing in the engine ECU. The reason you may not be getting as many MIL's as you think you should, is because the ECU doesn't think anything is wrong. Replacing the ECU should take care of your problem. I would advise against buying a cheap aftermarket 'rebuilt' unit as they are not very reliable. Good Luck.

[SRK]

GKLCPA- take a step back for a moment. The problem isn't an O2 sensor, and it it most certainly not the ECU. It's failure of ignition, or fuel. And you'll need to determine which. So the starting fluid idea is good, just be careful with that stuff.

Whatever it is, it appears not to pop a code, so it may be something that doesn't pop a code eh? That could be the fuel pump. So check the pressure, don't replace it. In fact don't replace ANYTHING without first diagnosing the problem.

And unlike others I'm not advising you to spend $2000.00 on parts on a "guess". Diagnosis is the key, and yes, if it fails to start completely at some point, the diagnosis gets easier.

SRK

[curiousB]

ditto..

Parts are fairly expensive for these cars so swap until its fixed can get expensive. If you're comfortable doing a few things on your own go pick up a fuel pressure guage for $10-20. A useful tool to have around. See what fuel pressure is on warm starts and cold starts. Could confirm/debunk a fuel pump, or fuel pump relay, or fuel pump resistor problem ( I doubt the resistor though as that wouldn't tend to be intermittent).

[pj8708]

This is the beauty of the LOC. You just got probably $2,000 worth of advice that would have other wise had to come from a dealer. These guys are great!

Paul

[DEATH_AWAITS_YOU]

This is the beauty of the LOC. You just got probably $2,000 worth of advice that would have other wise had to come from a dealer. These guys are great!

Paul

My advice IS from a dealer!

[pj8708]

This is the beauty of the LOC. You just got probably $2,000 worth of advice that would have other wise had to come from a dealer. These guys are great!

Paul

My advice IS from a dealer!

Good for you. That is what I mean. The forum has the ability to bring together a critical mass of resources from an almost infinite number of people. (yeah, infinite might be a stretch). And it's given gratis.

p.s. What address is death waiting at? It will save me some time.

[LEXIRX330]

p.s. What address is death waiting at? It will save me some time.

Yea I want to know too. I might need to get another million or so of Life insurance!

[SRK]

My advice IS from a dealer!

I don't think so.....

[landar]

Now boys..... be nice!

Considering the original post is from Feb., the OP probably has resolved the issue by now and we just await the results... and death, of course.

And to skymasteres, the others are right about attacking this problem by isolating between spark and fuel. Try spraying the starter fluid first but easy does it and be careful. Highly flammable you know. If the engine seems to gain life, even for a brief moment, then you know you have a fuel delivery issue. Else, start looking at the ignition system.

[GKLCPA]

Not sure what happened to this thread since February, but it appears to have been very heavily edited with a few exchanges now missing and altered. Not sure what's up with that.

In any event, the problem was the fuel pump. This is something very difficult to diagnose in advance until the thing is ready to give up the ghost, which in my case it nearly did. So after trying the recommended fuel induction service, the problem persisted and I told them to change out the fuel pump. Upon doing so, the problem resolved itself and my fuel mpg returned to normal. Had I done this all over again, I would have went with my original hunch and just switched out the pump at the outset as it would have been cheaper. A fuel gauge didn't really help as the problem was too intermittent to test. So sometimes, you just have to guess rather than test. Of course, if you can, testing and knowing what the deal is with certainty is preferable.

The experience has been helpful though. I recently put my 1987 BMW 535i back on the road after 10 years of sitting in my garage and have decided to park the Lexus so as to preserve it. Lo and behold, I've encountered a sputtering problem with this car. This car happens to have two fuel pumps and the main one supplying the fuel injection is failing. This time, I've picked up enough knowledge such that I'll swap out the pump myself.