08 4.0 Tacoma Starts and Dies unless revved.

2008 Tacoma 4.0 Prerunner 2wd
Starts immediately, idles up then dies. There are zero DTC or CEL. If I continuously rev it it will stay running but as soon as I hold at a steady rpm it just turns off. I can’t count the number of forum posts, YouTube videos and articles I’ve read and tried.
What I’ve done so far:
Dropped fuel tank, cleaned with tank cleaner replaced entire fuel pump assembly and filed with fresh quality fuel. Same issue
Replaced fuel pump relay (even though the old one tested fine)
Replaced throttle body (programmed throttle pedal according to SM)
Replaced MAF about 2 years ago and then replaced it again under lifetime warranty just in case.
Replaced all vacuum lines on the intake.
Replaced air filter
All fluids were replaced
Tried all 3 different keys I have. All the lights on dash come on like they are supposed to if the transponder is working.
The truck sat intermittently except being moved around the property for long periods cause I had a company truck and traveled a lot. All the fluids, belt, plugs and what not were replaced and I refreshed the suspension and brakes. Truck drove perfect on multiple trips (about 25miles) testing the suspension and alignment. Then driving down the road it just starting slowly losing power no matter how much I pressed the pedal before dying and that’s how I got to where I am now.

 

Sounds like it might be a fuel pump resistor problem.

 

If I unplug the resistor it won’t start at all. Could the resistor still be the issue.

 

Any chance you could post a video of what it's doing?
All I can think of is maybe the exhaust or air intake is plugged up or a fuel pressure problem, pretty much anything else that would make it run that poorly should set a code.

 

https://youtube.com/shorts/JdVWDxafxeQ?feature=share

It doesn’t sputter, miss or run rough. I’d hate to pay a fortune getting it towed to a shop and it be something simple I’m missing. I already spent $3500 getting it back into shape to start driving it regularly.
I’m pressing the gas making it rev.

 

Unplug the MAF sensor and see if it will stay running, it will be in limp mode but I just wana see.

 

I’m not home…but it doesn’t.
I’ve had the battery out of it for the last 3 or 4 days. When I get home in the AM I’ll hook it up and try again and then unplug the maf again and try it.

 

Let us know, beyond that I'm thinking we need to check actual fuel pressure and see if there's a problem there.

@Bishop84 any thoughts?

 

Needs a pressure gauge. Without it, it's just guessing.

I've seen wire corrosion at random places that can cause this. I've had to test pumps while they are hanging from the harness dry to test the circuit under load to find resistance.

It seems like a fuel supply issue for sure.

 

$35 BETOOLL Fuel Pressure Test Kit 0-100PSI with 9.497.896.30 Fuel Line Fittings

https://www.amazon.com/BETOOLL-Fuel-Pressure-0-100PSI-Fittings/dp/B07LF26ZTJ?

 

OP, I just today am having a very similar issue, what did you learn??

My truck starts and idles for 30 seconds then stalls, or sometimes it will almost stall and regain idle for just a fee more seconds then stall. Sometimes pressing the gas to the floor will rev it up, but as soon as try to maintain any RPS off the rev limiter, it dies. I drove it home this way, holding low gear and revving hard, it would cut out and re fire constantly as long as I stayed about about 3K on the tach.

Sure could use some help on this one!!

 

Unfortunately OP hasn't returned since this was posted in Aug of 23. So chances of an update are unlikely.

 

I'd guess ignition coils being funky as they sometimes are. Start it, let it die, pull plugs and check for that wetness. unless there's reason to assume a severe vacuum leak (like recent servicing). that's on top of the previously listed potential causes.

 

Solved! (for my truck anyhow).

To be more clear, i understand this is only on the 4.0, my truck died while cruising the highway, just died. started right back up but would die in seconds, over and over again. I figured out that sometimes I could pump the gas pedal, and get it to rev up, and keep it running at high RPM, as long as I keep moving the pedal, hold the pedal still at any RPM and it died. I managed to smoke the tires and limp home in low gear, but no way I could get into the garage this way.

Found a youtube video where they guy figured out that the 4.0 Toyota uses a Resistor unit, for the fuel pump circuit. This resistor, reduces power to the fuel pump, for any cruising; but for starting, accelerating, and WOT; this resistor is bypassed by the ECU. Is described as a measure to extend the life of the fuel pump.

Anyhow, my resistor is rust damaged, and out of spec with very high resistance, such that the fuel pressure drops tremendously. Basically my fuel pump turns off any time the ECU utilizes this resistor.

To verify this is the problem, simply unplug the resistor unit and jumper the two wires of the harness with a paperclip (isolate to not touch metal!), and the truck runs great.

I will order a new resistor, but run it with the paperclip, till part arrives.

This resistor unit is an aluminum finned block, about 2in x 4in and mounted in front of the battery, on a bolt with 10mm head, and has a 2 wire connector. Mine is corroded badly, from salt damage.

Hope this helps others!!

 

Mine does exactly what 08NardoTaco's truck did...exactly....mine snapped back to life after all the things described above were done, and then found the fuel pump relay was suspect. May but contacts, fuel pump may be drawing too much...next thing I have to check.

 

Best advise yet, if you suspect a fuel issue first thing to do is put a pressure gauge on it. Easter egging just leads to frustration down the road. A fuel pressure test would have eliminated the first 2 steps in the OPs first post and pretty much rule out the fuel system or confirm it. Work smart not hard.

 

I have the exact same issue after swapping the engine. I replaced the fuel pump with a URD upgraded pump (wanted the external fuel filter). I've tried all the other TS'ing, MAF, throttle body. When it does die, there is a loud sucking sound coming from the brake booster hose.
https://youtube.com/shorts/7T__gHg8TMI?feature=share

 

Some Ideas:

The brake booster noise after it dies, seems to me that the check valve at the booster is dirty and leaking, the vacuum in the booster should hold steady Negative-pressure after engine dies, but it sounds like it is bleeding off, leaky gasket or dirty leaking check valve. This is worth checking into, in case engine dies while driving, so you still have brake assist.

The stalling, seems alot like a faulty resistor that I describe above. But in your case, it may be that the resistor is fine, but that the aftermarket pump does not like running on the reduced voltage of the resistor? I am speculating, but can tell you that if your truck has the FP resistor (location on post above), then is it fact that the ECU sends full power to the FP on start, and then switches to sending sending power to the FP through the resistor; and then when there is heavy acceleration, the ECM will go back to feeding the FP full voltage. You could test this by holding the pedal to the floor when it and see it it stays running!!!!! ;0 or simple test, is to locate the resistor, unplug it, and jumper the two wires instead of connecting the resistor. A Paperclip worked good for me. If that keeps the truck running, then make a permanent jumper, your new FP does not tolerate the reduced voltage mode. I am not sure what years included the resistor, and suggest you look for the resistor on your truck, Dealers too often are unaware and cannot find a pert number for this resistor, so asking if your truck has one is a gamble.

Hope this helps, let us know how you make out!!

 

Thank you, I really appreciate your ideas! I did test the resistor before I replaced the fuel pump. But, your theory makes sense. I will jump the resistor next week when I get back in town. Again, thank you for all the ideas.

 

I tried jumping the resistor and still have the exact issue. It starts and dies unless I throttle it.