Hey everyone,

I have a 2000 4Runner, 3.4, V6, SR5. Automatic, 185,XXX kilometres on it.

I noticed it struggles to start when it sits for a short period of time (5 - 20 minutes for example). Takes a few extra cranks, and doesn’t start as “strong” as it normally does compared to when it’s been sitting overnight. I even had one case where it took about 6 attempts to get it started (started, sputtered, and died within seconds) after driving it up a rough dirt road, parking it, hiking around, and attempting to start it again roughly 20 minutes later. It eventually went, but it was reluctant to. I don’t notice anything while driving it. Sounds good, powerful, guzzles more gas than my 1995 3.0L T4R, but I think that’s normal with the 3rd gen..? Or could also be a symptom of this problem perhaps.

I live on Vancouver Island, west coast of British Columbia, Canada. It’s between 0 and 10 degrees Celsius lately. I’ve only owned the truck about one month.

I thought I’d start with the fuel filter, then run some SeaFoam through the fuel system. After that if no improvement, spark plugs. I heard someone mention it sounds like a “fuel regulator” issue perhaps, haven’t done any maintenance on those before. Also heard whisperings about an air mass flow sensor?

Any input helps, and please be descriptive. It’s a new vehicle to me so I’m not very familiar with locations of things, etc.

Cheers,

Frazer.

 

I have a similar sounding problem..
Really kind of random, but mine seems to depend on two things: temperature and time.

Question for you, when its struggling to start, does cracking the throttle (giving it a little "gas") make it start sooner? is so i would suspect the IACV is not opening properly during cranking and id start there. Engine needs very little air lots of fuel to cold start, but warm start it needs lots of air. Normally the iacv dials super open during start. Google 5vz iacv clean. stands for idle air control valve. You will need to remove the throttle body, probably wont need a gasket but if you need truck asap better buy a throttle body gasket and a IACV gasket. IACV is on the bottom of the TB with two coolant lines running through it. 4 screws pop it off clean with sensorkleen until it looks brand new.
good how to here:
When it struggles to start, are the RPMs lower than you think they should be after startup?

The way I describe mine is by number of cranks or "err"s when starting. Most 5vzs ive driven start after 4 or 5 errs (like er-er-er-er- ROAR).

My list of possible culprits:
-leaking injector
-bad FPR
-bad signal from MAF
-Vacuum leak or leak of air into intake manifold
-IACV not closing or opening properly
-Bad coolant temperature sensor
-Bad ambient pressure sensor.

Try plugging in a OBD2 reader and watching your coolant temp (ECT). It should rise steadily as car warms up to about 200F then kind of hover between 200 and 160 ish. If youre seeing huge spikes or drops or an intermittent signal, replace it. Check it after a short hike. If your ECU thinks its back to COLD it probably isnt and so its feeding it the wrong A/F mixture. Can also watch your MAF signal to make sure it makes sense. And while youre at it may as well watch intake air temp signal (which also comes from maf). Should be relatively accurate to outdoor air temps, then heat up slightly as engine bay heats up. After letting it sit off for 20 minutes or whatever it should be at its highest (heat soaked), then drop when you start it. ambient pressure sensor should be relatively accurate, check local weather station for pressure. Keep in mind it varies with elevation. Drive down or up a large hill. Should read less with more elevation.
Uhh dont know how to test the fpr...
Can just take the IACV off and follow the manual to see test procedures, give it a clean. Check resistances.
You could also try driving it, parking it for a bit, then pull the spark plugs and legit smell all the holes haha and see if any smell like raw fuel.
You could also try and mount a fuel pressure gauge, although this is somewhat more involved. Pressure should not bleed off after shutdown.

Subscribed for interest. Off to make my own post.

 

Thanks for the info. I posted on a few Facebook pages too, and basically have the same answers. I hooked it up to a code reader at my buddy’s place. Nothing stood out regarding coolant temp or air sensors.. it’s an annoying issue because I don’t know where the best/easiest place to start would be. The valve covers are leaking, so maybe new injectors, cleaning the MAF sensor, throttle body, fuel regulator valve.. seems like stuff to do “along the way”..? We pulled a few plugs to confirm they were the twin ones, they were. They were fairly loose, but not sure what they should be torqued to. Hand snug plus an eighth to quarter is typically what I’ve done in the past.

I’ll try and follow your thread as well, not a lot of chatter on this one, maybe posted in the wrong spot? Perhaps yours will be more popular.

I had it “stall” after start yesterday for the second time in two months. It was once again, after a short amount of time for the engine being off (20 minutes, so it was still warm). I gave it some gas on my next start attempt as I was cranking it over, it reluctantly started, and ran normally after that.

Not sure if that adds to ones theory or not, but worth mentioning that giving it gas “does help” but it feels “forced”. Good to know if I’m in the bush though. Regardless, when it’s warm, it’s not starting properly. Sometimes it’s worse than other times, but I feel like every time, it’s in the verge of stalling shortly after it starts (within a second or two).

 

Id pull the TB off and give the IACV a good cleaning. Pretty easy/cheap to do. Worse case you wind up with a clean IACV. Next thing I'd do is pull off all the vac lines and plug one end and blow into it and see if they leak. With the OBD2 tool, check your fuel trims (long and short term). If they're super +, it could be vac leak.

Also maybe next time you start it after it struggles, get someone to watch your tailpipe and see if it smells like gas or sweet like coolant or what, and also report if it is black smoke, white smoke, blue smoke, or no smoke when it does catch. I was also thinking, maybe pull some vac lines that lead to your intake off and literally smell it, see if it smells like raw fuel.

So far zero replies on mine. Sometimes I think I give too much info and then people dont want to read it haha. Problem I'm having is that 6 injectors is big $$$ and even the fuel pressure regulator is ridiculously expensive. I dont wanna just be blindly throwing money into the ol toyota hole.

 

The other thing maybe worth checking out is the fuel pump. If your diagnostic port on the 5vz works, you might be able to jumper it to run.

If you are having the trouble starting, maybe try jumpering the FP on and see if it fires right up. If it does, maybe you dont know why the fuel pump isnt running properly but at least youve narrowed down the issue.

 

If the fuel pump doesn't run unless you jumper the diagnostic connector, you've isolated the problem to one of two items. The COR, or the MAF. Testing the MAF's switch that controls the COR will then isolate the problem to the failed item. If the switch in the MAF is working correctly, it's the COR gone bad. If the switch in the MAF fails the test, ie: does the switch close when the vane is moved, even very slightly, the MAF is bad. You still need to verify the COR in that case, just to be safe.

Does that help at all?
Pat☺

 

I am experiencing a very similar issue that I have found only surfaces in the colder months as last winter I would have the same symptoms daily with no luck on diagnosis and not being able to afford just throwing parts at it. I then noticed in the hot summer months the problem completely disappeared on its own and it has now returned since the cold is setting back in. I have the lean code P0171 and misfire code P0300 that I believe relate to the issue as well as P0446 and P0440 that are common evaporator codes but may be related also. Was wondering if since it is a year later if you ever solved this issue as I believe your solution may be the answer to my troubles.

 

Cleaned the MAF sensor when a code finally came up, other than that, I didn’t do anything and it seems to have corrected itself? Still doesn’t start as strong as I’d like, but no official resolve. Starting to get colder here on the coast, so we’ll see what happens..

 

I replaced the starter contactor (I had a 3.4L) and replaced the fuel pump and got the injectors cleaned.
It's unclear which of these solved the problem but it solved.
I think it was a bit of each. The injectors would leak through the o rings into the cylinder, which also emptied the fuel line. The fuel pump has a check valve in it but I suspect it was dirty, draining the fuel back into the tank. The starter also clicked but didn't fire. The contacts were missing their seats as I had rebuilt it when I put the engine in and the throw wasn't enough it was somehow out of spec. I just got a whole new one.
Anyways did all this, and replaced the upstream O2 and it was super reliable and got pretty dang good on gas.
I wound up selling the 4runner as a really nice 04 quad cab taco came up and I bought it.
I will likely do an injector clean and fuel filter replacement and a front o2 on the new 3.4 to try and save on gas as it's getting significantly worse mileage than the '90 4runner with the t100 3.4.

 

The COR, or the MAF. Testing the MAF's switch that controls the COR will then isolate the problem to the failed item. If the switch in the MAF is working correctly, it's the COR gone bad.

 

I know this is late entry, but after changing my engine, I had a hard time starting my 2000 4Runner. I replaced the fuel regulator and the problem still existed. It was worse when it was cooler. I noticed somebody mentioned Coolant Temp Sensor, and remembered I had a code for that. Didn't think it was related and said I'd get to that later since my coolant gauge worked. Turns out, the temp sensor connector wasn't fully seated and was the problem. Plugged it in and it now starts like is should. Hope this helps anybody else having troubles getting started.