Truck stalls out on cold start, starts just fine the second time. What do?

What’s up everyone, long time lurker and first time poster here. I’m driving a 2000 Tacoma 4x4 with the 3rz engine and 5spd manual trans.

Problem: After a big trip recently the truck’s been stalling out right after I start it in the morning. it’ll catch and fire up for just a second before dying. Then when I try a second time, it starts up no problemo. No CEL after stalling.

What I’ve done so far: tested battery and alternator, all good. Tested for gremlins/ electrical parasites, all good. It’s getting fuel and spark.

Any ideas on where I should go from here? The only system left in the trio is air intake, which I haven’t inspected though the air filter’s clean and there’s no cracks in the intake. IAC valve maybe?

 

Bumping for desperation it’s gonna get real cold and real wet, real soon

 

I know the worst case scenario is your fuel pump.

 

Thanks for replying, I replaced the fuel pump recently since there was a whine coming out of the fuel tank. The stall’s been happening before and after the fuel pump

 

FF changed recently?

 

Try cracking the throttle just a bit on the first cold attempt... I am thinking IAC might be sticky.

 

I changed the fuel filter 10k miles ago.. what a pain in the ass that was. I’ll try giving the throttle the feisty feather in the morning and report back.

 

Any difference if you use the clutch/start/cancel button in neutral to start rather than the clutch?

 

Same problem with the clutch start cancel. It started incredibly rough this morning but got going the first time with a little gas.. I’m getting a new throttle body and IAC gasket from Toyota today so I can start pulling things apart and getting a good look. Ill report back later.

 

Lord have mercy it was dirty in there. After cleaning the throttle body, IAC, and replacing the gaskets the truck idled at 1500 before the computer re-learned. Back at 750 now. I guess the real test is the cold start tomorrow.

 

Well, no dice. Not sure where to go from here. I guess I can’t completely rule out fuel pressure being an issue, although turning the key on before starting didn’t solve things.

 

Fuel pump won’t prime until key is in start position and the engine’s cranking unlike similar year vehicles from other manufacturers.

Have you tried spraying a little starting fluid into the intake prior to starting the first time? That could rule out fuel delivery at first crank.

You said it won’t cold start in the mornings, what about later in the day after it’s sat long enough to be cold again?

There’s a chance one of the sensors that controls ignition is getting finicky.

2000’s aren’t distributor trucks are they?

@Speedytech7 might know another thing to add to your diagnosis.

 

Well, crap. This is one of those issues that you can spend $ and lots of time trying to perfect it. Sorry to say this but if it starts the second time every time I would live with it unless you like puzzles. If you have a scan tool that can show live data using OBDII rather than manufacturer specific mode start to eliminate the good, i.e. what does the scan tool show as engine coolant temp before you start it, same for intake air temp etc, etc. If you know what "good" is then you can focus on the bad.

 

True - if you can even get an inexpensive Bluetooth / wifi ODB 2 dongle you can read engine temp and a few other live data parameters with an app on your phone like Torque for Android or InCarDoc for Apple.

Coolant temp sensor was something I was thinking of too, but no sense in replacing it if you don’t have any data supporting that it’s not reading correctly the first time.

 

I had a similar issue with my 2002 gmc sierra 1500. I took it to a mechanic and they said it was a dirty TB. They smoke tested for leaks all around the intake.

The truck was also consuming between a quarter quart to about half a quart of oil between fuel ups. It would weep out of the rear main seal even after that was replaced.

I drove it for another year until the cold start/stalls basically made the truck unreliable in the winter so the truck sat until it warmed up in the spring.

In the spring, it finally threw a CEL, PO420, bad catalytic converter.

I replaced both cats, and the truck now cold starts just fine and also no more consuming oil.

TL;DR - Excessive back pressure from clogged cats may be a cause of stalls during cold starts.

 

No distributor cap, and the truck will start later in the day when its cold again. It's only that first start in the morning. It'll fire up every time after that... for now. I can't risk the chance that It'll poop out on me in my current circumstance, so into the puzzle I go. I have a BlueDriver scanner that I’m quite fond of using.

I've looked and have no reason to believe that the intake air temp or ECT sensors are unreliable. I'll pick up some starting fluid and give that a shot! What other parts could cause the lack of fuel delivery at first crank? Pressure regulator maybe? Denso fuel pump's brand spankin' new, no fuel leaks anywhere.

On the topic of clogged cats, I have heard a rattling coming from the exhaust since i bought the truck. Dumb question, but is there any way to test or inspect the cat or rest of the exhaust for clogs and the like?

Thanks for the input everyone. I am constantly impressed by the robust community surrounding these trucks.

 

You can test the temp of the exhaust pipe before, after, and at the cats to test for a clogged one. Rattling is often material entering the muffler from the cat(s).

If you have a leaky injector or oil leaking into the cylinders it could also make for a hard start in the morning after enough has accumulated throughout the evening. The same thing could be replicated if you don't drive it on a day off and wait until the afternoon to start it to rule out cold morning temps vs time it's sat being the primary measurable variable.

Have you done a compression check at all lately?

IDK if FPS will potentially be the cause of it. IDK how expensive they are though and whether it's something worth replacing without a verifiable reason. I've heard of people adding a shrader valve in line with their fuel supply to verify their fuel pressure.

 

I think that the ECU knows the truck didn't start so it defaults to a different fuel-air open loop situation.


you can check this with an oscope. hook it up to the fuel injector and another probe to the crank position sensor. watch the duration of the injection and see if it changes between the failed start and the second good restart. comparing the timing will take a little work, counting pulses etc.

you should be able to smell gas out of the exhaust pretty quickly when it doesn't start.

 

good info. I have not done a compression check. I've got some starting fluid to try tomorrow morning so i can see about ruling out fuel delivery. if it starts, i know i've got a fuel delivery problem. if not, well.. back to square one. since my working season is over for the moment ill try the mid-day start next, and I'll see about borrowing a temp gun. I am not sure if i've got the intestinal fortitude for using an oscope. i may bite the bullet and have a professional do that if it comes down to it. I'll report back with more information.

 

you can wire up a 1 watt 12v lightbulb and probably could catch the difference by eye if there is a difference in injection duration.