Truck Dies, unless I keep my foot on gas pedal

I am quite lost on this one, I was driving to the store when suddenly as I was coming to a red light, my truck (2006 DC) died. It started back up but it would died again if I did not give it gas. No CEL. I had to drive it back home with foot one foot on brake pedal and the other on gas to keep it alive.

Next morning, it started just fine, but about 10-15 minutes later it shut off and would not stay running unless I had my foot on gas pedal. The following morning battery was dead...I jumped it and started just fine and ran for about 10 minutes then shut off and would not stay running.

It just dies, does not struggle. No RPM fluctuation

I have cleaned the throttle body, Mass Air flow sensor but did not help any. Absolutely no codes...Any help would be appreciated.

 

Check your alternator.

Check your battery terminals on the wiring.

Check your grounds

 

Is there a check engine light? Any codes pending/stored?

Did you pull the negative battery terminal for at least 10 minutes after cleaning the TB and MAF?

Has any other maintenance been done to the truck recently?

Since it's DC and thus a V8, when was the last time the timing belt was changed, and have you verified the crank position sensor wire wasn't mis-routed during the job, and isn't getting clipped by a belt or pulley?

Have you checked all vacuum hoses?

 

If it runs during warm open when on OL fuel trims then dies once warmed up, maybe O2 sensors.

 

Alternator seems to be charging the battery just fine. Truck starts up immediately after shutting off.

I had the battery tested and came back "Good"

Battery terminals are clean and wiring is snug.

 

Check engine light is not on and No codes pending nor stored.

Is disconnecting the battery after cleaning the TB and MAF really that critical? I had similar issue on my 4runners and Camrys and I cleaned the TB without disconnecting the negative cable and that fixed it. Should I clean it again and disconnect that battery?

No maintenance has been done on it recently. Absolutely no issues with it in the past.

Cannot recall mileage for timing belt of the top of my head but definitely not recent.

I did a quick check in the engine bay to make sure nothing was loose, including hoses around the brake booster, and intake but everything seemed fine. Also, It has been a bit difficult trying to work on it as we have been getting snow recently, which has not allowed me to dive into it more.

 

Sometimes it does this after running about 10 minutes on cold start and other times after 2-3 minutes. Is there anyway to test whether O2 sensors are the culprit?

 

O2 sensors would give a code.

what is the age of the battery. Low voltage does weird things.

 

Not always. We’ve definitely seen cases on here where no code was thrown but sensors were dying. Or they’ll throw a code and it’s for the cat. These trucks are weird with the O2/AFR sensors.

 

Kinda?

Unplug the negative battery cable for 10minutes, forcing the computer to re-learn. It’ll start with known-good values at the next start. Does the truck run normal for the first 30-60 seconds?

I’m sure there are other tests possible but forcing a relearn should be a good evidence piece.

 

So, Long Story...

I disconnected the negative battery cable, started it but died immediately 2 times. On the 3rd times it stayed running for about 1 minutes then died, there was a slight RPM fluctuation and very slight shaking (Maybe from Idle re-learn?) then died.

I started it again, but this time I kept my foot on the gas for about 3 minutes and slowly let off. It ran for 10 minutes then died.

Started it again, foot on gas and slowly let off, by now it was idling fine. I reversed about 3 ft and it died.

Same procedure, 10 minutes in wanted to shut off but held rpms to about 1500 for a minute and stayed running. Ran for 20 minutes straight without me interfering.

Went to take it for a spin and died 3 times in a span of about 1/2 mile. Usually when I let off gas or slowing down.

Came back home Parked it, and it ran for 20 more minutes. Not sure how to proceed...

 

Throw some seafoam in the gas tank.

Next would be spark plugs and coils.

Leave the intake off and have someone watch the throttle body at idle, see how open it is.

Could be fuel pump.

Could be vacuum leak.

 

I think you might be surprised what happens if your truck is warmed up and you pull the intake snorkel off (change air flow reading to zero).

 

I had a similar, but not exact issue with my 00. No codes, stalling at idle/in drive/@ stoplights. I could also keep it running by double pedaling it and keeping the rpms up. But when it would die it was like flipping a switch, no stumbling or anything, just instantly off.
I fired a rather large parts cannon at the thing over a 7-8 month period (before becoming a member here and getting solid advice). I can tell you I went through the entire fuel system, coils, plugs, cam and crank sensors, MAF, O2s... I mean there wasn't much I didn't have my hands on (which complicated things). Some of those items did need attention but not many. Keep in mind most aftermarket parts are absolute shit now days so replacing parts can make it worse/add problems. I even pulled my ECM out, went through all connections with a fine tooth comb, even opened it up and examined the board with a magnifying glass and saw nothing bad. After all that the problem persisted.
In a nearly last hail Mary effort I bought a junkyard ECM and I'll be dammed if that wasn't it.
Not saying that's your issue, just telling you my story.
A good OBD2 reader and a decent multimeter will be your best friends. Check all your sensors resistance specs. Watch your fuel trims... and O2s in live data. And watch all your readings in live data and look for any that are weird, out of line, or popping in and out.
Good luck, I'm cheering for you. And btw, you landed in the best possible place here with a bunch of guys who are not only smart AF , but actually help.

 

I disagree with coils. That is not a good idea on 1st gen Tundras, the coil packs at least. And it’s expensive as fuck because, for whatever reason, a great number of name brand coils work poorly in the 1st gen V8 specifically.

 

Bruh, I have the same issue in my 1UZ, OBD1... some days it idles perfectly, but others it just dies, no bogs, no stutter, just off. I watch the tach at 40mph, if it doesn't hold at 1k rpm while slowing down, I get comfortable and use the 2 foot method as well. I let off the gas at stop lights and see if it idles, when it stalls I've done it so many times I'm quick to drop it to the neutral turn it back on, hold the gas and back to drive, before the front driver selects their new tiktok video before going on green.
I got the ECU rebuilt and its still doing it. I'm leaning to the O2 sensors, assuming it loses signal from a sensor and cuts the fuel. My old MR2 had a fuel cut defender mod sincenit would stall out per the previous owner, but never went into detail.

 

When idling, something has to control air intake to match fuel flow. Many vehicles use an idle air control valve. The FGT does not to my understanding, it is all computer controlled and uses the TB butterfly to meter the air. So keeping the butterfly clean, and all associated sensors operating properly is key. MAF and O2 sensors are the main ones. If those are functioning well and the TB is clean and operating properly, then computer as another member already mentioned is the next level along with a malfunctioning TB, but that will usually throw a code. The wild card that mess up the operation is a vacuum leak. These trucks are old and the hoses are getting brittle and they will split on the ends and leak air.

 

Yeah ide check if a sensor is dropping out. As mentioned above (at least for me) if you unplug the MAF the engine instantly dies. So watching the OBD2 live data is a good start.
If only we all just had an "Eric O" next door (South Main Auto yt channel)... dudes a wizard at this kind of stuff.

 

I experienced this issue with my 97 LX450 (1fzfe) and, like @BroHon I threw the kitchen sink at it, parts wise. For me, it was the MAF sensor plug coming loose, the clips that keep it attached had broken off or worn out, and it would lose connection with the sensor. Replacing the plug fixed my issue. I'm sure you checked this when you cleaned the MAF, but maybe just triple check that connection is super tight.

 

I'd definitely go get an ECM from a junkyard if they were not So scarce around here. I think I've only seen about 2 or 3 in the last year!

I was leaning towards replacing coils and spark plugs, if there was a really bad coil causing this, then even a cheap coil may fix it, assuming that is the problem. Right...? If it fixes it then I might consider getting OEM later..

Can O2 sensors really cause something like this? Maybe these trucks are weird like that but my other cars bad O2 sensors have only affected gas mileage and maybe acceleration slightly but not shutting off while driving.

TB and MAF cleaned, I checked vacuum hoses around intake and brake booster and all good. Unless I missed something?

Wait yours dies if you unplug the MAF...? I unplugged mine and it ran for about 10 minutes slightly rough then died.

I checked the plug and its tight, Truck runs with it unplugged but dies a few minutes after.

 

If you indeed are not recording pending nor active codes, don't see how it could be a coil.

On my 04 DC LTD, it still runs if I start with MAF unplugged. There are other sensors I have made note of that will not prevent my O4 from running. Of course, I knew what the affects would be with MAF unplugged....air-fuel ratio goes bonkers, among other things.

• FUEL DELIVERY....pump, filter, regulator, fuel pressure, pump resistor, pump relay
• AIR....filter, MAF, no cracks in air intake tube accordion ?

Do you have a friend with a scan tool that reads live data ?

 

Maybe, running 1 side open loop and the other side close loop may send the ECU down the path of self perservation.... I was going to say a small part of what @BubbaW said. More than likely an air tube problem. I went to harbor freight to get some zip ties and seal the intake and resonator below the intake tube. Probably leans out chamber, snuffing out combustion. I do get a strong smell of fuel after a stall, but this is more than likely apples to oranges, since my techbis so old.

 

I would be smoke testing. I still suspect air is the problem. Could be fuel, or if OP did something stupid like spraying cleaners directly into the throttle body, but I suspect air is the issue.

 

That was one of the things I went through with the throttle body. You can turn the key on (don't start it) and watch how the motor moves the throttle plate. Not sure what year they stopped using the throttle actuator motors but mine has it. In my head I thought maybe the issue was the throttle plate being sucked shut at idle and starving the engine of air.
With the key "on" that motor sometimes makes quite a loud buzzing noise.

 

While an 00 is different than his 06, knowing the throttle position is indeed important given that it should be approx 15% whether it's with IGN ON or even once we've reached normal operating temperatures with no load.

That's why in cases such as this issue, a scan tool able to read live data is very important. We can theorize all day about air and fuel culprits on problems such as this but sometimes we have to see what the ECU is seeing or take a whack a mole approach. One can find a decent scan tool that reads live data for < $100 which will pay for itself quickly.

 

I think that's 15% reading in live data, and that is taking for granted the TPS is giving the correct data. I think it 4deg physically open is what I read in the FSM, or maybe 5deg?

 

I have 3 cents to offer...I suspect fuel pressure dropping intermittently, either due to fuel pump, resistor, or regulator. You can monitor fuel pressure via OBDII. Run live data and see if you can catch it it failing.

 

Not 100% sure but I believe that would be true for 00-02 given they have an actual IAC(idle air control) valve that performs idle speed control such as fast idle during cold operating conditions and idle-up. Where as starting with the 03, idle speed control is now performed by the throttle control motor, which controls the throttle valve opening.

 

***********************************UPDATE************************************

Ok so, New Mystery/problem. It started when my battery was dead and I tried jumping it with a portable jump starter, it started but died immediately. Tried again but it was a no crank, no start. Next day I checked the fuses and EFI NO.1 had popped. The following morning I remote started it and it ran for 15 minutes straight then died. A few minutes later I noticed the parking lights would not turn off, so I went to take a look. I tried to start with the key but it gave that dead battery sound for like half a second and then absolutely nothing when turning the key. EFI NO.1 had popped again. I replaced it with a 15A since that was the only spare that was available in the fuse box but when I turned the key it blew immediately.

EFI NO.1 is Multiport fuel injection system/sequential multiport fuel injection system.

Not sure if it is a coincidence or if its related but I read that on other Toyotas this fuse is also for fuel injectors, Fuel pump, O2 sensors, MAF and Throttle body. I hope to have some time over the weekend to get it running again so I can get live data.

 

Pretty sure my 00 doesn't have an IAC. I would have had my hands on it testing it cleaning it in that 7-8 month period I was searching for answers. I'm going to have to look now,