[FIXED] Lexus 2007 RX 350 . Will not run at idle

2007 Lexus RX 350 3.6 Liter

THIS vehicle was towed in because it will not stay running at idle. The vehicle runs fine when you step on the gas (high load). The fuel pump was replaced with no help.I have looked at several videos , but none of them address this condition for a 2006 Lexus.
I have read a few articles on the Lexus forum and I have also done a visual on the engine bay harnesses for loose connection and frayed wires. the article also talked about unplugging the map sensor to see if the vehicle will idle. I have not tried that yet.
Also the article talked about finding a chewed wire on the fuel pump resistor.

is there a web site on line that would show me home to check the resistor values of all five fuel relays?

I'm looking for a step by step troubleshooting guide as to what to check next.

Peterpaul wrote:
is there a web site on line that would show me home to check the resistor values of all five fuel relays?

I'm looking for a step by step troubleshooting guide as to what to check next.

Eautorepair.net
Mitchell DIY for around $30 will give you access to service info and diagrams like Paul uses in the Scanner Danner videos.

Found a couple pages that show conflicting wiring diagrams of how the fuel pump relay controls speed. Shouldn't take too much poking around with a DMM to figure out which is correct. Or that they're both wrong :silly:

I wouldn't worry about any of the other relays in the EFI/IGN chain. If any of those had a problem the fuel pump wouldn't run at all.

www.clublexus.com/forums/rx-2nd-gen-2004...n-2008-rx-350-a.html

www.clublexus.com/forums/rx-2nd-gen-2004...fuel-pump-prime.html

When you put the fuel pump in did you put the oring on the fuel pump motor?

yes, the o-ring is in the fuel pump.

Thanks for your help

Does iac motor adjust for idle? Desired idle to actual idle within 25 rpm?
Or is the difference greater than 100 rpm?

Fuel pressure regulator is it leaking from vac port?

Does tps sensor read .5 volts closed and incrementally increase while slowly pressing pedal to 4.5 volts wide open (gas pedal to floor) with no drop outs or glitches?

I will need to look at the scanner again when I get to work in the morning to answer your questions.

thanks again for all the inputs and help.

there was no change in the idle when we installed the new fuel pump. the vehicle is still doing the same thing. No idle, and no problem when accelerating.

cheers and thanks again

Iac = idle air controller motor not fuel pump motor would be mounted to throttle body

Does the vehicle have a newly installed battery? If so, I have seen a pattern (random Lexus vehicles) after installing a new battery, the car will not stay idling. The repair for this condition is to clean out the throttle body.

thanks , but the battery was not replaced. I did need to charge it back up. I am how getting 12.2 volts to the fuel pump with the ignition key turned on, engine not running thanks again for the help . I also checked and cleaned the PCV valve and this did not help. I'm trying to locate the fuel pump resistor relay as well. It's not in the engine bay. I believe it right behind the fuel pump in the wiring harness. is there a wiring schematic that would show the location of these relays?

So you've found C/OPN but can't find the fuel pump relay? Guess based on other 'yota products is it may be somewhere on the interior fusebox. Probably on one of the edges, or maybe the back, hidden by the trim panel.

Worst case the OEM SI should show where it's located and is only $20 for 48 hour access.

techinfo.lexus.com/

I think CurrentDraw's suggestion of cleaning the throttle body is worth while.
I don't see how an issue with a fuel pump relay would cause the engine to run at part throttle and not closed throttle. I'm not terribly familiar Toyota fuel pump circuits so maybe someone can correct me if I'm wrong.

Noah, the "fuel pump relay" would be better described as a pump speed relay. It's the C/OPN relay which actually powers the fuel pump circuit. The "fuel pump relay" just switches in a resistor for low speed. Sounds like there's a problem with either the "fuel pump relay" itself, or the resistor loop, which is killing the pump when the PCM commands low pump speed.

Try running it off of alternative fuel at idle. If it runs continue with fuel pump diagnosing. If not move on. It have an egr sticking open?

Matt T wrote: Noah, the "fuel pump relay" would be better described as a pump speed relay. It's the C/OPN relay which actually powers the fuel pump circuit. The "fuel pump relay" just switches in a resistor for low speed. Sounds like there's a problem with either the "fuel pump relay" itself, or the resistor loop, which is killing the pump when the PCM commands low pump speed.

Thank you for the education, that makes much more sense!

Got some follow up for this one. Could use a second or third set of eyes from the big brains around here.

Talked with Paul last night, and made the suggestion to jumper across the fuel pump resistor connector. With the jumper installed, the vehicle idled for an hour, no problems.

I Painted the OE diagram because it's (strangely) easier to understand than Mitchell :silly::



Any reason not to replace the resistor?

Tyler wrote: Got some follow up for this one. Could use a second or third set of eyes from the big brains around here.

Talked with Paul last night, and made the suggestion to jumper across the fuel pump resistor connector. With the jumper installed, the vehicle idled for an hour, no problems.

I Painted the OE diagram because it's (strangely) easier to understand than Mitchell :silly::

Any reason not to replace the resistor?

And who would’ve thought all that coloring as a kid would’ve paid off... :silly: :silly:

Tyler wrote: Any reason not to replace the resistor?

Was the resistor ohmed out? Found a listing on ebay which shows 0.32 ohms printed on it. If the resistor doesn't show high resistance I'd dig a little deeper.

Search ebay for 274241968193. forum software

Whether it's worth the cost and delay to replace it depends on vehicle condition and use. If the idle fuel trims look good with it bypassed, and it hasn't set any codes, maybe making a bypass with the resistor pigtail is good enough? Think I've been watching too much PHAD :lol: :silly:

Dtnel wrote: And who would’ve thought all that coloring as a kid would’ve paid off... :silly: :silly:

Marketable job skills! :silly:

Was the resistor ohmed out? Found a listing on ebay which shows 0.32 ohms printed on it. If the resistor doesn't show high resistance I'd dig a little deeper.

Search ebay for 274241968193. forum software

Whether it's worth the cost and delay to replace it depends on vehicle condition and use. If the idle fuel trims look good with it bypassed, and it hasn't set any codes, maybe making a bypass with the resistor pigtail is good enough? Think I've been watching too much PHAD :lol: :silly:

No ohm testing, we were just pumped that the stupid thing ran. :lol: If it were my Lexus, I'd permajump it and call 'er done.

Paul let me know that they actually found some wiring damage near the resistor. Don't know if it's on the resistor side of the connector, or the harness side. If it's on the resistor side, the test was valid. If it was on the harness side, then... I'm confused. He's going to send me a picture.