Warm Start Issue(5-20 min after stopping) 1997 3.4L V6

[rorikk]

Hello all,

I have been browsing around the forum for a ton of info the last few years and it's been so helpful! Lately though, the other posts haven't quite had my specific problem. I am working through the fixes they used to try and isolate the issue.

I have been chasing an issue on my Runner for the past week or two, but the problem has been around for the past several months. The truck will not hold idle(it cranks, fires up and then dies) when it has been running for about 30 minutes and then tried to start up again 5-10 minutes later, say stopping for gas or grabbing groceries on the way home from work. If it's fired up right after turning off, it will work fine, the longer you wait, the lower the idle sits at when fired up, or it dies because it can't hold it. If the idle starts low but doesn't shut off, but holds, driving around will bring it back up to normal. If you wait about 45 minutes or so it will work just fine or from a cold start. If the truck turns on and holds idle, it will drive no issues at all until I stop and turn it off again.

I'm thinking it has to do with the computer thinking it still has fuel in the system, so it shuts it off, or that being warm, it doesn't pump anymore fuel in thinking there should be residual fuel and it dies. Seems to be less efficient recently

No CEL has come on for this issue at all. I thought it had culminated and finally gone to crap when I got a misfire code. I limped home and started troubleshooting that. New plugs, no fix, and then new wires, no more misfire, no more CEL. Warm start problem still there.

I've been poking around and cleaning things as I have time. It gets me to work and back, but multi-stop trips make me not want to use it haha.

What I've done:
- new TPS (swapped spur of the moment when I couldn't get it to start for an hour and we were stranded. Started up, but we'd sat long enough to cool down)
- new spark plugs
- new spark plug wires
- bottle of Techron injector cleaner in a tank of gas
- measured correct resistance on all 3 coils
- measured correct resistance on passenger side injectors(other 3 injectors inaccessible without removing both plenums)
- cleaned TB
- cleaned MAF


Yesterday:
- measured correct resistance IAC contacts
- cleaned IAC (idle moves around a tad more, was solid at 700/750, but will lower down to 600 occasionally. Too soon to tell, but I don't think it solved it)
- measured EFI relay for continuity (got 93ohms)
--may be a red flag, will measure it cold to see if different. It works fine all other times.


I'm going to be measuring COR and other relays or hopefully while warm and cold the next several days to get readings that might tell something. Probably check the coolant temp sensor readings in the ECU terminals.

Does anyone have any other simple suggestions to check that don't require throwing parts at it or ripping too much apart?? It's my daily driver, so major time apart would have to be the weekend.

(Sorry for the long description, but it's a pretty specific thing and wanted to share the most info I had available)

Thanks!

 

[Kanoe]

A good cleaning of the TB and particularly IAC has always fixed this issue for me. Have done it on several toyotas. By cleaning I mean IAC off, cleaned well on the bench.

Maybe your issue too??

 

[rorikk]

A good cleaning of the TB and particularly IAC has always fixed this issue for me. Have done it on several toyotas. By cleaning I mean IAC off, cleaned well on the bench.



Maybe your issue too??

Thanks so much for throwing that out there. I had cleaned the throttle body a few weeks back without really removing it. I went for the IAC last night, unbolted it from the throttle body, sprayed and cleaned it up(although it looked really clean having replaced it two years back) and put it all back together. Haven’t extensively tested it, but going to check again when I drive back from work tonight to see if it’s still an issue. I would love if that fixed it since that’s an easy one, but I’m not confident that’s it.

Will keep you updated on that, but looking for other things to check in the meantime.


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[norcalassassin]

When was the fuel filter last replaced?

Had the exact same issue and the fuel filter fixed this!

 

[gamefreakgc]

If it's not the fuel filter, then replace the entire throttle body assembly. For the 96-98 years they are cheap enough to find on Ebay or at a junkyard. Or at least the IAC, but normally it's not that much from a junk yard to snag the whole thing and then you've got a spare.

 

[rorikk]

When was the fuel filter last replaced?



Had the exact same issue and the fuel filter fixed this!

Ok! That’s on my list.
I’ve got a fuel filter on hand that I should get to by this weekend. Curious how that stops things up when warm, maybe it just settles and then won’t go?

If it's not the fuel filter, then replace the entire throttle body assembly. For the 96-98 years they are cheap enough to find on Ebay or at a junkyard. Or at least the IAC, but normally it's not that much from a junk yard to snag the whole thing and then you've got a spare.

The IAC checks out electrically and I replaced it with a brand new one two years back. That looked much better than the throttle body. If it keeps coming up, I may look into that.

Some people have mentioned coolant sensors? Fuel pump relay?



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[LittleCaesar]

Maybe a fuel pump? Also check grounds and for vacuum leaks.

The EFI fuse, if it has continuity, will just give you a beep from your DVM, stating that there is no break. Just pop off the top cover for a close inspection.

 

[rorikk]

Maybe a fuel pump? Also check grounds and for vacuum leaks.

The EFI fuse, if it has continuity, will just give you a beep from your DVM, stating that there is no break. Just pop off the top cover for a close inspection.

Thanks for the input.

I’ve checked for vacuum leaks, but I’ll keep an eye out. Where would be the grounds I’m looking for?

The EFI fuse I got 93ohms, not beeping and showing continuity. I’m going to check when it’s cold/sitting all day to see if there’s any difference. But I may swap one from the auto parts store just to check as that would be a real easy solution.


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[gamefreakgc]

Ok! That’s on my list.
I’ve got a fuel filter on hand that I should get to by this weekend. Curious how that stops things up when warm, maybe it just settles and then won’t go?




The IAC checks out electrically and I replaced it with a brand new one two years back. That looked much better than the throttle body. If it keeps coming up, I may look into that.

Some people have mentioned coolant sensors? Fuel pump relay?



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Brand new Toyota IAC valve? I tried a reman'd unit a few years ago and it was garbage, made it idle super high since it was put together wrong. What you are describing is a classic IAC valve issue. However, idling between 600-700 is completely within spec. It should idle around 700-800 when warm and in park, and 600 when in drive (turning transmission lowers engine RPM) so that part checks out.

Coolant sensors do affect fueling but cannot pull fuel completely though. They do add more fuel to startup when cold but they don't take away much when warm. Mine on startup when real nice and hot will run in the 16's for Air/fuel ratio (stoich is 14.7) but has no affect on idle speed. The sensor that can pull fuel completely so it dies at idle is the MAF sensor. If the wiring is damaged internally (it has super thin exposed wires) or the harness itself is damaged that might cause it.

It still sounds exactly like a bad IAC valve though... The fact that the hotter the engine bay gets the worse the idle gets just screams IAC to me.

 

[MaineRunna]

Does it start and stay running if you hold the gas pedal down? I've had many Toyota's do this and if I held the gas part or all the way down it would start like an old flooded carbureted car, but stall when I let off. After keeping them running with the gas pedal for a bit they would idle on their own. It always turned out to be a dirty or faulty IAC.

 

[rorikk]

It still sounds exactly like a bad IAC valve though... The fact that the hotter the engine bay gets the worse the idle gets just screams IAC to me.

The car runs fine no problem on a cold start and as long as you want to drive it. It only has issues on the warm start.

It’s not that it’s hotter and hotter that makes the issue. If I start up a minute after shutting off it’ll stay, but maybe at 500rpm, but waiting 2 or 3 minutes after shutting off it’ll hover at 3-400rpm. If you drive it then this will even back out to normal rpm. May be it’s gummed up when it’s been hot and then sat for a few minutes.

Does it start and stay running if you hold the gas pedal down? I've had many Toyota's do this and if I held the gas part or all the way down it would start like an old flooded carbureted car, but stall when I let off. After keeping them running with the gas pedal for a bit they would idle on their own. It always turned out to be a dirty or faulty IAC.

And yep, it’ll drive fine if I stay on the gas, eventually the idle will even back out to normal. Going to test drive it tonight and see if cleaning the IAC valve cleaning last night solved the issue. The resistance on the contacts was perfect, but I guess it could’ve been getting gummed up. Seemed pretty clean to me when I removed it, but I took throttle body cleaner and went at it anyways.

Thanks for the input! I will update if that cleaning helped anything.



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[onemanarmy]

I know you have the V6, but 3rz (4 cylinder Tacomas and 4 runners of the same era) have this issue. With the 3rz, there is a coolant/engine temp sensor near the back of the engine that feeds the computer (not the gauge)....and when it's hot and parked with the engine off, that sensor heat soaks and malfunctions and won't let the engine start. Either a complete no start or it tries to fire but stutters and backfires and shuts off. Only thing to do is to wait it out, it will eventually start.

Maybe something similar is happening with yours?

 

[AntleredRuin]

I just went through the EXACT same thing a few weeks ago. Turned out to be my fuel pump.
There's a check valve in it that is supposed to keep the fuel in the fuel lines when the truck is shut off, to avoid slow starts.
When warm (like after driving for a bit) and then shut off for 10-20 minutes, this check valve slowly fails and completely closes (not just one-way like a check valve should), which lowers fuel pressure. This makes it hard to start, and keeps the idle real low and sketchy for a minute or so, until the valve opens again (due to actual fuel flow, I'm guessing).
Let it cool down for 45 minutes and the check valve fully releases and you get easy starts again.

FYI keep a can of starter fluid on you. If it stalls and dies after a quick errand, you might not be able to restart it without waiting the 45 minutes. Ask me how I know.
I successfully recreated this 'no start' issue in my driveway, and a spritz of starter fluid got it going again.

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[wcjeep]

What is your fuel pressure when cold? Hot? Age of fuel filter? You could have water in the fuel filter from bad fuel. When you turn the vehicle off the water settles in the filter, blocking it. This can also ruin the fuel pump pushing against water blocked filter.

Carry a gasoline approved pressure gauge, rubber gloves and some towels.

 

[huski]

Glad i found this. I'm experiencing something similar, though mine is very intermittent. New fuel filter, TB was cleaned maybe a year ago, IAC hasn't been changed or cleaned, i know i possibly have some vacuum leaks.

I have a jumping off point now. I'll report back with findings.

Thanks!

 

[rorikk]

UPDATE: Might have been solved by IAC cleaning!

UPDATE: After testing my way home last night and way back into work this morning trying to recreate the warm starts after half hour of driving, I haven’t seemed to have an issue whether 5, 10, or 15 minutes after shutting off.

Soooo...looks like it was the IAC valve gummed up. Even though it looked pretty darn clean, cleaning it and the TB a tad more seems to have done it. Not celebrating yet, but I think it may be solved! (Bummer it took me that long to get to it. Kept thinking it couldn’t be since it’s newer and I’d already cleaned the TB). Glad I asked for all the help when I had just cleaned the IAC and that may have solved it...

If it’s not solved, I still have the fuel filter on hand to replace in the next few days regardless.

When warm (like after driving for a bit) and then shut off for 10-20 minutes, this check valve slowly fails and completely closes (not just one-way like a check valve should), which lowers fuel pressure. This makes it hard to start, and keeps the idle real low and sketchy for a minute or so, until the valve opens again (due to actual fuel flow, I'm guessing).

Let it cool down for 45 minutes and the check valve fully releases and you get easy starts again.

FYI keep a can of starter fluid on you. If it stalls and dies after a quick errand, you might not be able to restart it without waiting the 45 minutes. Ask me how I know.

The check valve sounds like exactly what it might be if the IAC cleaning proves to not have been the solution. Fuel filter will be my first go to as that’s a simple swap i'm planning on anyways.

And yep, I know how you know! I got stranded like that trying to pump the gas pedal several times before starting and still having no avail, leading me to replace the TPS as I thought was the fix.

I have a jumping off point now. I'll report back with findings.
Thanks!

I hope it helps! I was finding threads similar to this all suggesting different things but they all had different solutions haha so I was a bit confused as to what to tackle next. Hopefully this helps you out!


You all have given some great suggestions on other things to check as well! I’ve mostly just read threads for info as it seems all things from 3rd gens have been discussed and researched extensively, but it’s so useful to have quick responses for questions that are still a little fuzzy! Thank you all!
:tea:

 

[Spktyr]

And yep, I know how you know! I got stranded like that trying to pump the gas pedal several times before starting and still having no avail, leading me to replace the TPS as I thought was the fix.

Pumping the gas pedal prior to a start attempt does absolutely nothing good on any port fuel injection vehicle. At best, you just wasted your time and calories. I don't know why people still do this as there hasn't been a new design car or truck sold in America for more than 20 years that pumping the pedal would do anything on, once GM's TBI system was taken out back and shot. At worst, on some systems, doing that tells the computer the TPS is broken and that it should go into limp home mode - making it even harder to start.

The only pedal work that does do something prior to start is flooring the pedal and holding it while attempting to start. This is the universal "clear flood" method and tells the computer to turn the fuel injectors off entirely while cranking to clear a flooded engine. This has been the case on all port fuel systems since at least 1980 and I'm sure even further back.

 

[JohnOfTheJungle]

Did this issue ever get solved? I had something similar happen to me today after wheeling all weekend and then driving 150 miles on the highway home.

Was running fine, stopped a gas station to fill up, restarted it to move it to a parking spot and went inside. Came out 5 minutes later and it didn’t want to start. Giving it gas with low idle kept the engine barely going for 5 seconds then it ran like normal and I drove home another 100 miles fine.

 

[jzarech]

What year is your 4Runner?

I just went through the EXACT same thing a few weeks ago. Turned out to be my fuel pump.
There's a check valve in it that is supposed to keep the fuel in the fuel lines when the truck is shut off, to avoid slow starts.
When warm (like after driving for a bit) and then shut off for 10-20 minutes, this check valve slowly fails and completely closes (not just one-way like a check valve should), which lowers fuel pressure. This makes it hard to start, and keeps the idle real low and sketchy for a minute or so, until the valve opens again (due to actual fuel flow, I'm guessing).
Let it cool down for 45 minutes and the check valve fully releases and you get easy starts again.

FYI keep a can of starter fluid on you. If it stalls and dies after a quick errand, you might not be able to restart it without waiting the 45 minutes. Ask me how I know.
I successfully recreated this 'no start' issue in my driveway, and a spritz of starter fluid got it going again.

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I have a 1997 4Runner that dies upon start after it's hot --
I looked online and didn't see a check valve for a 97 3.4 Liter -- only a fuel pump. If I buy a fuel pump will it have the check valve built in?
Thanks.
ja

 

[gamefreakgc]

I have a 1997 4Runner that dies upon start after it's hot --
I looked online and didn't see a check valve for a 97 3.4 Liter -- only a fuel pump. If I buy a fuel pump will it have the check valve built in?
Thanks.
ja

Look into or search cleaning your Idle Air Control valve that's under the throttle body. There's some videos and write ups on here to help. When hot the valve will stick and not open which kills the engine at a stop or idle.

Also look into cleaning the Mass Air Flow sensor, also lots of good photos and writeups on here.

Both of those solutions are basically free (except for a new gasket for the IAC) and waaay less work than replacing a fuel pump. Our DENSO units are known to last 300K easy.