Question about 1998 Lexus LX470

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1998 Lexus lx470 intermittent fuel pressure problems

Occasional starting problems, car wants to turn over but appears not to be getting enough fuel. Took to a mechanic and could not do a diagnostic scan because no fuel pressure. After battery is unplugged and computer resets it starts right up. Check engine light non existent untill it want start. Mechanic states it checks out good after computer resets. Seems to happen more often in high humidity, may be just a coincidence. Happens multiple times on the SC coast, happens occasionaly when it rains inland. Please help with any suggestions, much appreciated!

Posted by mdlindley on


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  • Lexus Master
  • 918 Answers

Maybe the engine coolant temperature sensor dont work properly , sometimes do not the check light come on

Posted on May 08, 2017


5 Related Answers


Ronald Mueller

  • 1263 Answers

SOURCE: 95 Lexus ES 300 check engine light is on and the overdrive off light is flashing

chances are you don't have to replace the computer. the reason i tell you this is because you did not mention that the car is running lousy. no complaints of rough idle or missfire or hard starting. chances are that your engine speed sensor which sends the signal to the computer which then controls the transmission is most likely the culprit.. and it could just bhe that there is a loose connection between the two. if that is ok then your transmission control module is faulty. this is not the main computer, but the gobetween the trans and the ecm.. hope this helps please rate this...thanks(btw....the knock sensors control timing not the trans mission)

Posted on Sep 03, 2008



  • 60 Answers

SOURCE: engine shuts off while driving

check one of your coolant sensor's

Posted on Dec 07, 2008


  • 2 Answers

SOURCE: Car won't start

k is there power to fuel pump? yes,,, check grounds..... NO check relay only get kia relays for main and fuelpump since o2s run on the same relay,..... if relay is good suspect comp.... mine has same problem with no power to fuel pump i have now traced problem to ecu sux but at least it has a new fuel pump and relay lol.....

Posted on Mar 02, 2009

Richard Scordino

  • 6982 Answers

SOURCE: turn the key and nothing happens,no crank,no sound,no start

It seems that you have a loose wire, bad connector or perhaps the main computer itself that is causing a problem If the shop is not seeing any codes, or codes come and go, likely I'm right...but someone is going to have to actually do some intensive testing to find the real cause. You can likely get another computer from a local scrapyard far cheaper than what the dealer will charge far as wiring, you need a good accurate schematic a good volt/ohmeter and lots of time to trace wiring. When checking connectors test the pin, then probe the wire going into the pin...often the problem is where a wire meets the backside of the pin, either corroding or breaking..This also applies to any modules such as the security system...what you see on the dash does not always tell you that connection to components is good. This is not a "fix, but rather, a direction to go in. (exactly what I"d need to do if I was there)
Right now, everything is suspect including fuel system, till you rule it out!!!

Posted on Jun 05, 2009

Nicolo Carlo Parazo

  • 2187 Answers

SOURCE: 1998 Saturn SW2, 180,000+ miles. Recent starting problem.

It does sound like an electrical issue.  Double check if the ground connections are all OK.  You may have to check out the wirings, even the wiring loom if all wires are still OK.

Posted on Jun 06, 2009

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2001 chevy tahoe code po440, po171

DTC P0171 or P0174
Circuit Description
The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during open and closed loop. During open loop, the PCM determines fuel delivery based on sensor signals without oxygen sensor input. During closed loop, the oxygen sensor inputs are added and used by the PCM to calculate short and long term fuel trim fuel delivery adjustments. If the oxygen sensors indicate a lean condition, fuel trim values will be above 0 percent. If the oxygen sensors indicate a rich condition, fuel trim values will be below 0 percent. Short term fuel trim values change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. If the PCM detects an excessively lean condition, this DTC will set.

Diagnostic Aids
• The system will go lean if an injector is not supplying enough fuel.
• A lean condition could be present during high fuel demand due to a fuel pump that does not pump enough fuel.
• Use a scan tool in order to review the Failure Records . If an intermittent condition is suspected, refer to Intermittent Conditions .
With every DTC a diagnostic flow chart is given for a diagnostic direction .(thing's to test ) For these test's you need a professional or factory scanner ! Plus knowledge of how these system's work would be nice .

Test Description
The numbers below refer to the step numbers on the diagnostic table.
If conditions were not corrected, refer to Fuel System Diagnosis for a possible fuel problem.
If conditions were not corrected, a worn cam, worn intake or exhaust valves, or other engine mechanical failure may be the problem.

Did you perform the Diagnostic System Check-Engine Controls?
YES - Go to Step 2
NO - Go to Diagnostic System Check - Engine Controls
Important: If any DTCs other than P0171 or P0174 are set, refer to those DTCs before continuing
Install a scan tool.
Start and idle the engine at the normal operating temperature in closed loop.
Record the Long Term Fuel Trim.
Turn OFF the engine.
Turn ON the ignition, with the engine OFF.
Review the Freeze Frame/Failure Records and record the displayed data for this DTC.
Does the scan tool indicate that the Long Term Fuel Trim is greater than the specified value?
YES - Go to Step 3
NO - Go to Diagnostic Aids
Operate the engine at idle.
Observe the HO2S parameter with a scan tool.
Does the scan tool indicate that the parameter is within the specified range and fluctuating?
200-800 mv
YES - Go to Step 4
NO - Go to Step 5

DTC P0440
The EVAP LARGE LEAK TEST is based on applying vacuum to the EVAP system and monitoring the rate of vacuum decay. The powertrain control module (PCM) uses the input from the fuel tank pressure (FTP) sensor in order to determine the rate of vacuum decay. At an appropriate time, the PCM turns the EVAP canister purge valve ON (open) and the EVAP canister vent valve ON (closed). This allows the engine to draw a vacuum on the system. At a calibrated time or vacuum level, the PCM turns the purge valve OFF (closed), and tests the system vacuum. If the system is unable to achieve the calibrated vacuum level, the PCM will set DTC P0440.
This could be caused by a leaking purge valve . Do you know what that is ? Mounted on the engine ,under the plastic engine cover . Disconnect the hose that goes to the vapor canister under the back of the vehicle . With the engine running see if you can feel vacuumn . If you do replace it .

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I would think the crankshaft position sensor or ignition control module could be the problem , but without testing ,that's just a guess .

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Running lean , not enough fuel . Have fuel pump pressure an flow tesing done . Have a scan tool hooked up to look at engine sensor data . Any number of thing's can cause this type problem . an looking for a magical fix on here is going to fix it . Newer vehicles have complex electronic's , PCM/ECM engine computer an sensors ! Diagnostic equipment an someone who knows what to look for is what fixes the modern automobile . Training as well !!!! Coolant temp sensor could cause this .
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I have a 1998 626 Mazda and it's been having some occasional jerking.

have the fuel pressure tested to be sure its at the correct psi and does not loose pressure even after turning off engine. is the check engine light on? if yes have it scanned and that will help to pinpoint the problem...

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My car (2002 mercury sable v6 DOHC)is acting like it is possessed!!! Yesterday when I got in it acted like the battery was dead, but after a couple of time turning the ignition switch it turned over. I...

It may be a bad ignition switch.

Also, It could be a fuel pump, remote chance. A fuel pressure test would prove if bad. Should have 40 psi of pressure.

Any warning lights on, on the instrument panel? Check engine light? Or, they come on after the stall?

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This exact same thing happened to me, it can be a number of problems. You might not have enough battery charge to get the car going since the fuel pump in this car is electronic, my car did not start but when i took it to a mechanic thinking the battery was perfect because lights and all were on they jump started it and it started then immediately died, i also had a choke pull off failure, leaks in my carburetor, and the float was to heavy causing flooding. 185 dollars later and a rebuilt carburetor my car had a smooth idle and turned on immediately after turning ignition. but then to find out my alternator was bad hence the battery only having enough power for the radio and in short try jumping the car even though the battery seems good, check your carb or get it checked by a mechanic, then check if your alternator is ok. if i waited for two days without attempting to start car then trying it would start if i held the ignition and pushed the gas pedal down until it started. (see if thats the case for you) my guess is you carb, battery, and alternator.

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If that is your only transportation you need to call other repair shops. Find out about towing fees and what diagnostic fees they have.

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For instance, you are told you have fuel pressure. You are told they installed new spark-plugs. You were not told if the spark-plugs are getting electricity to fire. You were not told if the fuel injectors are getting electricity to allow gas to reach the cylinders. You can have fuel pressure but the fuel injectors must open to put gas into the engine.

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