Long crank when warm - Issue after valley pan repair

[jmanscotch]

I have an issue that’s reared it’s head after my valley pan repair and cooling system replacement and I could use some ideals on things to double check this weekend when I dive into it. I’ll note this has never been something that’s happened until right after I did the valley pan repair, water pump, thermostat and radiator replacement.

Here’s what I know: occasionally, the GX will crank over for several seconds before it actually fires up. It always fires up (except maybe once). It also exhibits a sort of rough idle type condition when stopped in traffic. It doesn't seem to be a low RPM type stumble as it stays around 650-700 RPM while it happens (verified numbers on scan gauge), but more it feels like what a ~400 RPM rough idle would, a bit of engine stumbling shake.

Here’s a clip of it exhibiting the starting problem.




If it sat overnight or at work for 8 hours, it starts right up.

When I’ve driven it somewhere and the engine is warm, then I park it for about a hour and go to start it again, that’s primarily when it acts up. Twice it’s done this after sitting for 8 hours and those were on the warmest days we’ve had recently (50+ degrees). If I restart it immediately or soon after using it, it starts fine. Sitting for a hour or so after warm is the primary occurrence sequence.

I’ve checked all the electrical connections I touched and they’re connected, but I didn’t verify continuity completely. All air hoses are connected and a smoke test didn’t reveal any cracks/leaks on the intake system, secondary air pump piping nor various other sections of systems I could plug into.

Theres no codes pending or thrown, passes my scanners evap system test. I see no evidence that I cracked an injector or anything (while probably leaning on the fuel rail a time or two during the repair). There is a cracked cover on the injector rail that I can’t identify, but doesn’t seem to be a likely issue:

My next moves are to check power and signal voltages from the basic sensors that make sense to me (as I handled them during repairs):

- MAF
- Throttle body
- MAP

Then I'll plan to:

- Clean throttle body thoroughly on a bench (had done a half ass job cleaning it while the intake manifold was off)
- Check each connection I took off and ensure electrical continuity across each side to make sure a pin isn’t making intermittent contact

Anything I’m overlooking that make's sense or might be worth looking at?

 

[Acrad]

I wonder if you have a failing injector that is sticking open? Have you run a fuel pressure test?

Diagnostic grid out of FSM

 

[jmanscotch]

I haven’t, I’ll have to figure out where to get a tester locally that has the right connections for the wonky GX setup.

Best search I found seems to suggest I’m looking for 46.5-47.4 PSI. Looking at the repair manual, the symptoms suggest it's possible the fuel pressure regulator is stuck open, so I can check to see if the fuel system is maintaining pressure a hour after shutdown.

Seems like a good first step on the fuel system (since fuel pump is clearly working even when the problem exists).

 

[carlos33018]

I haven’t, I’ll have to figure out where to get a tester locally that has the right connections for the wonky GX setup.

Best search I found seems to suggest I’m looking for 46.5-47.4 PSI. Looking at the repair manual, the symptoms suggest it's possible the fuel pressure regulator is stuck open, so I can check to see if the fuel system is maintaining pressure a hour after shutdown.

Seems like a good first step on the fuel system (since fuel pump is clearly working even when the problem exists).

This is one of my biggest fears when it comes to doing large repairs, which involve removing multiple sensor connections etc.

Things to try:
Look for vacuum leaks and take a close look at the throttle body and fuel delivery. Rough idle can be a number of things, all of which could be caused by incorrect data from a sensor going to the computer.

if everything checks out, you might have to get a scan tool that’s able to see live data, so you can check out what’s going on when the condition occurs. Check out bluedriver or perhaps techstream.

 

[jmanscotch]

This is one of my biggest fears when it comes to doing large repairs, which involve removing multiple sensor connections etc.

Things to try:
Look for vacuum leaks and take a close look at the throttle body and fuel delivery. Rough idle can be a number of things, all of which could be caused by incorrect data from a sensor going to the computer.

if everything checks out, you might have to get a scan tool that’s able to see live data, so you can check out what’s going on when the condition occurs. Check out bluedriver or perhaps techstream.

I get it, but it’s how it goes sometimes. Even shops have these issues during repairs.

I ran my smoke machine on it, on several different parts of the system under the hood, no leaks found.

I have an high end diagnosis scanner that I ran diag with, has live data, taps into all sensors, etc. This thing is the best gift my buddy ever gave me, years ago when he left his dealership job abruptly, but the software is getting a little out of date.

All sensors are talking, didn’t see any issues with the data stream. That’s what has me leaning towards the fuel pressure regulator. The GX has no sensor to measure fuel pressure and it’s one of the few things that I have left to check.

I checked a few autopart stores and none had the right fuel presser tester (or rather none had the right connections).

Amazon has the right one, for $70 or so. Me being lazy, confident in that answer and thinking I’d rather throw $$ at the part than a test, I went ahead and ordered a new regulator from the local dealership. $122 and will be here Wednesday.

I’ll follow up once that’s been replaced later in the week.

 

[jmanscotch]

The repair manual has some great fuel system troubleshooting tips and here's what I'm focusing on:

Mine acts up primarily 1 hour plus after stopping the engine, so it's in that fuel injector seal to pressure regulator range. If the new regulator doesn't fix it, then I'll look at the fuel rails, but I see no external leaking, which means I'd have to pull the fuel rails and install new seals, an annoying job.

 

[carlos33018]

What scan tool are you using ? And how do you like it ?

 

[jmanscotch]

What scan tool are you using ? And how do you like it ?

It’s an OTC/SPX Genisys diagnostic scanner, they’re several thousand dollars new, so while I like it, I don’t recommend it. I just came into it as my buddy took it as a parting gift from a job as an automotive tech.

 

[jmanscotch]

Well, we’re back to this point today.

Theres a 12MM bolt on the back of the passenger side fuel rail that’s near impossible to get off without taking the intake off.

Fuel rail off and inspected and no signs of external leaks, no signs of internal leaks, no signs of tweaked o-rings or cracked injectors.

Fuel pressure regulator won’t be in for a bit, backordered. I’m still leaning towards this as the problem. The FSM has many notes about a bad fuel pressure regulator and the symptoms align darn near perfectly and more than anything else I can research (even matches slightly better than a leaky injector symptom).

- no initial combustion but not no combustion
- problem occurs 1+ hour after shutdown on warm engine only
- slightly hesitant idle

In the meantime, I can bench test the injectors but not sure that’d show a slow leak down, will research that a bit more.

Trying to figure out how to bench test the fuel pressure regulator.

Here’s the passenger side fuel rail, fuel pressure regulator is the black hat looking piece on the top right side of the rail. Has a small air tube that goes to the air intake box resonator, a main fuel inlet pipe and then feeds the passenger fuel rail (passenger fuel rail feeds driver side fuel rail via a crossover line that routes behind the air intake manifold).

 

[carlos33018]

At this point might as well get new injectors:

8x OEM Denso fuel injectors For 10-13 Lexus GX460 4.6L V8 #23250-0S020 | eBay

Genuine Denso fuel injectors 10-13 Lexus GX460 4.6L V8. These injectors have been fully tested to ensure a better optimization of fuel for better gas mileage and throttle response compared to worn injectors.

www.ebay.com

 

[jmanscotch]

I considered that route, but meant to wait to try the fuel pressure regulator first before pulling the injectors, but got a hair up my butt and now find myself here and underprepared with no parts.

Would just carpool with the wife for the week, but she goes to work a hour and a half after me and doesn’t enjoy waking up so early, so 4+ days of that while waiting on parts wouldn’t make a happy wife.

It only takes ~30 minutes to get the fuel rails off, once familiar with the intake removal, so not a hard job in the future if need be. Beside a little intake gunk buildup around the nozzles, the injectors look pretty clean for 110K miles. Will run some cleaner through them while on the bench hooked to a 12V battery.

 

[jmanscotch]

@carlos33018 how’s your coolant level issue been since the WP/Thermostat replacement?

 

[carlos33018]

@carlos33018 how’s your coolant level issue been since the WP/Thermostat replacement?

I have purposely not talked about it don’t want to jinx it lol BUT it hasn’t dropped any more !!. I live in Austin TX and we had that snowpocolypse last week which means I have not driven much. Let’s see !! The water pump was done on feb 9th and the coolant level has not moved. I think I be put a solid 200 miles or so on it so far. The water pump was the original one, which had 153k along with the original thermostat . I also replaced the thermostat cap with an oem one.

 

[jmanscotch]

Good to hear!

Y’all thawing out nicely? My sister, in Pflugerville, had a hell of a time and is still waiting for clean water.

 

[carlos33018]

Good to hear!

Y’all thawing out nicely? My sister, in Pflugerville, had a hell of a time and is still waiting for clean water.

Oh thats right down the street from us!! we live in North East Austin , near 130 and 290. Electricity and water did come back, but I did hear that a lot of the city still has a lack of running water . Hopefully thing are improving for your sister, weather wise the last couple of days have been perfect, in the 70's so thats a positive. How are things with the GX, any new news ?

 

[jmanscotch]

Oh thats right down the street from us!! we live in North East Austin , near 130 and 290. Electricity and water did come back, but I did hear that a lot of the city still has a lack of running water . Hopefully thing are improving for your sister, weather wise the last couple of days have been perfect, in the 70's so thats a positive. How are things with the GX, any new news ?

Buttoned it back up this morning, went for a drive and got it warm. Parked it, waited a hour, went to start it and same problem.

Fuel pressure regulator should be in this week, will replace that then see what’s next if that doesn’t fix it. Maybe injectors, maybe drive it off a tall mountain, endless possibilities.

 

[r2m]

Maybe leave it unlocked in a bad neighborhood??

 

[jmanscotch]

Seriously. This weekend my wife went to get something out of the backseat and the exterior door handle cracked in half, so add that to my list of frustrations with my GX so far this year.

 

[r2m]

Seriously. This weekend my wife went to get something out of the backseat and the exterior door handle cracked in half, so add that to my list of frustrations with my GX so far this year.

Seriously asking, was it really cold? I know in sub-freezing temperatures plastics and other materials with become brittle, especially if the material is old.
What year is your GX?

 

[carlos33018]

Seriously. This weekend my wife went to get something out of the backseat and the exterior door handle cracked in half, so add that to my list of frustrations with my GX so far this year.

Uff sorry to hear that . It will all be ok soon . Right after got my 2010 GX, I went ahead and pulled the plugs, and they were full of oil 800 bucks down the drain to replace the valve cover gasket / spark plug tube gaskets , then the drop in coolant I was pretty upset, these trucks are super reliable but things do happen.