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Amedee
Amedee, Lexus Technician
Category: Lexus
Satisfied Customers: 21787
Experience:  ASE Master Technician advanced level specialist. Wisconsin certified emissions state inspector
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98 lexus gs300 no start/ hard starting condition ---- air fuel

Customer Question

98 lexus gs300 no start/ hard starting condition ---- air fuel mixture is very rich -- 32,7 m/s on injectors. Let mw know if you have any ideas many hours investesd and many parts throwmn at the car
Submitted: 4 years ago.
Category: Lexus
Expert:  Amedee replied 4 years ago.
Hello!

Are there any codes in the computer?
Customer: replied 4 years ago.
no codes current or pending
Expert:  Amedee replied 4 years ago.
If you were to unplug the injectors and try starting fluid, does the engine fire up?
Customer: replied 4 years ago.
yes i can run the vehicle on own fuel supply - but injector m/s seems very high fuel is being dumped somehow
Expert:  Amedee replied 4 years ago.
SO if the engine runs with alternative fuel, the valve timing and ignition timing is good, we have spark... and we can rule out a bad crank sensor...

If this is true, then we are just looking at bad input to the computer.

Either bad engine coolant temp sensor or a bad mass air flow sensor.
Customer: replied 4 years ago.
ect and mass air flow both been replaced -- maybe computer? it does run better a higher rpm - defintly has fuel issue cat glows on the exhaust
Expert:  Amedee replied 4 years ago.
How can the cat glow if it does not run?
Customer: replied 4 years ago.
just told you runs on fuel supply such as carb cleaner or hot start -- but once you reconnect fuel pump connector is dump excess fuel
Expert:  Amedee replied 4 years ago.
How long have you had it running alternative fuel supply before the cat starts glowing?

Fuel pump connector? So the engine shuts down when you connect the fuel pump connector?
Customer: replied 4 years ago.

with carb spary had it running with out seeing cat glow but I start the car then connect the pump to monitor reading on scantool after two min. you seem it running rich and see the cat glow- I've even previous diconnected exhaust a manifold think that had somthing to do it

Expert:  Amedee replied 4 years ago.
So the engine shuts down when you connect the fuel pump connector?

Customer: replied 4 years ago.
after engine loads up with fuel it will stall out for sure - seconds if your not racing up rpms - any common problems dumping fuel or idling issues that lead to engine flooding out
Expert:  Amedee replied 4 years ago.
Potential Causes:
Sticking Idle Air Control (IAC) Valve
Likely Causes
Fuel Pressure Regulator - (if equipped)
A fuel pressure regulator that is malfunctioning either by leaking fuel into the intake through a ruptured diaphragm or mechanically sticking causing high fuel pressure can cause an engine to flood during cranking. Verify proper fuel pump pressure while cranking.
Throttle Position Sensor (TPS) -
A malfunctioning TPS can cause an engine to flood during cranking. Verify proper TPS voltage when cranking.
Idle Air Control (IAC) Valve -
An IAC valve that is malfunctioning can cause an engine to flood during cranking. Check for a valve that is sticking or damaged.


Engine Coolant Temperature (ECT) Sensor -
An ECT sensor that is out of calibration or related wiring and connections that are not correct can cause an engine to flood during cranking. Verify the sensor voltage is correct for the temperature of the engine.
Ignition Coil -
Customer: replied 4 years ago.
i wish i could say i haven't tried them - ect new and reads correctly on scantool and throttle assy has iac & tps on it and it has been replaced -
Expert:  Amedee replied 4 years ago.
Ok.. so I guess I am confused. Why are you disconnecting the fuel pump?

DO we know if its the injectors or the fuel pump?

What is fuel pressure at?
Customer: replied 4 years ago.
i disconnect fuel pump cause it dumps fuel and i really trying to avoid killing the cats -- Went down the road of injectors too. I really came to a dead end in many cases with my tech service
Expert:  Amedee replied 4 years ago.
What is the fuel pressure at? Does it leak down when the key is turned off?
Customer: replied 4 years ago.
45 psi- no holds pressure - i really tried alot of things - stupid question just brains stroming spark looks good and it does run on hot start ever see a problem withan ignitor not having good spark quality but it does seem like just to much fuel
Expert:  Amedee replied 4 years ago.
Ok... your fuel pressure is right in specs... there should be no reason to dissconect the fuel pump.

Customer: replied 4 years ago.
it will flood engine drain oil 3 times in past 2 days it foold engine bad -
Expert:  Amedee replied 4 years ago.
If in fact the fuel pressure does not leak down, then it is going to be a signal to the computer causing the injector pulse width to be way too high.

Are we sure the fuel pressure does not leak down with the key on engine off?
Customer: replied 4 years ago.
I guess i double check it see it leaks down but the injector width is defintly too high so want would be the fix
Expert:  Amedee replied 4 years ago.
Is it that high only on start up or when running too?

What about at idle?
Customer: replied 4 years ago.

high start up - high low idle - only goes lower/ normal with rpm are raced up

Expert:  Amedee replied 4 years ago.
What kind of scanner are you using?

What is the o2 sensor signal at idle and at 2500 rpm?

What is the injector pulse width at idle?
Customer: replied 4 years ago.
snap on solus --injector read 32.7 m/s at idle the 02 dont really have a reading to rely to you right now
Expert:  Amedee replied 4 years ago.
Sorry for the delay!

Just getting done with dinner..lol

If you create a vacuum leak, does the injector pulse width go up?
Customer: replied 4 years ago.
no injector pulse not affected by vac leak -- comes down if i disconnect fuel supply and race up rpm
Expert:  Amedee replied 4 years ago.

Sorry for the delay!

 

What is the o2 sensor reading when this happens?

Customer: replied 4 years ago.

can't keep engine running into closed loop to get readings- please let me know a few things discovered engine vacuum is fairly low - what could effect that compression is good and inspecs -- on a vaccuum gauge like 8 psi at say 1000 -1500 rpm and gauge flucates 8- 12 at high rpms 4000rpm -

Expert:  Amedee replied 4 years ago.
Wait... your saying that engine vacuum is only at about 10 inches or so at idle?
Customer: replied 4 years ago.
yeah doesn't idle great but at lower rpm 1000 say low vacuum for sure
Expert:  Amedee replied 4 years ago.
Well, heck, there is our problem!

Either you have a major air or vacuum leak, or the ignition or valve timing is way off!
Customer: replied 4 years ago.

dont hear or see any air/vacuum leak never mind major one so how do i narrow down to check ignition and valve timing

Expert:  Amedee replied 4 years ago.
Well, your scanner should give you ignition timing data.

To check valve timing you may need ot pull off the front cover to have a look at the timing marks.
Customer: replied 4 years ago.
checked the 3 timing marks on the timing belt and line up --- ignition timing on scan tool advanced 5 deg and racing it up i seen it go up to 16 deg at one point does that help any
Expert:  Amedee replied 4 years ago.
Did you just check the timing marks now?
Customer: replied 4 years ago.
all marks from the timing belt line up -- checked them more than once - whats your suggestion to check next? valve timing??
Expert:  Amedee replied 4 years ago.
Did you just check the timing marks now?

What is engine compression at?
Customer: replied 4 years ago.

i didn't check the timing marks right now i did yesterday afternoon - but they did line up and also yesterday compression was avg 160 psi (Do you suggest I double check each of them today)

Expert:  Amedee replied 4 years ago.
Well, no.. I think that it is a possibility that maybe one of your cams is off a few degrees. Even if the timing marks line up, if the dowel pin behind the sprocket breaks (that goes into the cam), it will cause the camshaft to be out of time and the timing marks will look like they are dead one... but in fact the valve timing is off.
Customer: replied 4 years ago.
if i pull valve cover how can i verify the valve timing is off
Expert:  Amedee replied 4 years ago.
I can explain... but first, this thing also has a variable valve timing solenoid or actuator...correct? Maybe its stuck?

With the engine running actuate the oil control valve, the engine should go from running smooth at idle to running rough at idle
Customer: replied 4 years ago.

is it possible that the soleniod could be the whole problem cause it never idles properly at idle, so it wouldn't really be possible to activate the soleniod and determine engine roughness -- do they have a high failure rate is it worth trying -- or another way to test it

Expert:  Amedee replied 4 years ago.
YES! THis is a very likely possibility YES! This is in fact very common!

Apply power and ground to the oil control valve to open and close it verifying the operation.
Check for oil leakage out of the variable valve timing actuator on the camshaft. If leaking replace the actuator.
Customer: replied 4 years ago.
if i take out the actuator - i believe it unbolts right out can i apply power and ground and be able to visually see if it is bad
Expert:  Amedee replied 4 years ago.
Sure.. you could try that.. I have never done it that way...
Customer: replied 4 years ago.

if i take it out - is thier anything that can slip or get screwed up by removing it cause it does work with timing. And can i tell by activating it what does it do, I honestly never tested one in the past

Expert:  Amedee replied 4 years ago.
Before doing that,I would ohm it out.

Using an ohmmeter, measure the resistance between the terminals.

Resistance: 5.5- 12 Ohms at 20°C (68°F)


Customer: replied 4 years ago.
7.8 ohms seems in spec
Expert:  Amedee replied 4 years ago.
Well, try to activate it with the engine running before pulling it out
Customer: replied 4 years ago.
but wont really tell me much cause it runs rough all the time (possible stuck closed)-- so it cant say it will go from smooth to rough --- what does it do anyways advance or retard timing? Another thing You do feel the problem is with valve timing is there a way to test the timing if i remove the valve covers
Expert:  Amedee replied 4 years ago.
You could pull off the valve covers and look at the valves on number one cylinder when the number one piston is at top dead center coming from the compression stoke going on the power stroke both valves should be close closed.

Also, the should definitely run different when you active the solenoid. Just check to see if it runs any better or worse. If not, then I would suspect a bad solenoid.

You can accept any one of my answers and we can still continue our conversation. I think w got it pretty well nailed down.
Customer: replied 4 years ago.
i did pull off the solienod and activate with power and ground- it moves not to sure what it is suppose to do but i believe it to be good- next it did pull off the valve covers previously if i roll the engine by hand serval times would i see a problem or should the cam shaft have slack -What can verify that the valve timing is off?
Expert:  Amedee replied 4 years ago.
NO... the camshaft should not have slack.

Valve overlap needs to occur when the piston is at TDC.

When turning the motor over by hand, as the piston comes up to TDC the exhaust valve should close and the intake valve should open.
Customer: replied 4 years ago.
ok the intake cam is not a straight bolt on camgear like the exhaust- little bit of a special gear on intake side if i remove the the front cover and remove large nut- I have slack in shaft with out t-belt moving is that my problem or is that normal? does that mean the key is broken
Expert:  Amedee replied 4 years ago.

Well, its hard to say. It depends on how much slack there is. I would have to see it.

 

I am going to be off line for a few hours. I will check back with you shortly.

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