Won't start unless you hold foot pedal down just a little

2001 6.0L engine. Suburban? 2500HD
the coolant must be full, no air pockets that cause ETC sensor to lie.
and chev, love to self protect the engine at overfheating
or the ECT telling lies , AIR pocket there = lies.
my scan tool I can watch the ECT full time. even graph it.
all I have are questions, things I see in person fast.
IMMO lamp glowing wrong on dash, IMMOBIlizer? ?????
if yes it cuts the engine is 3 to 10 seconds. by design.
seem spark is good and only fuel wrong is fuel pressure at spec?
or is AIR wrong, all engines must have air to start, or stalls.
air comes 2 ways (old to newer) IAC/ISC or TWB (GM TAC)
TAC IS 3 PARTS (TB/TPS,CONTROL TAC, AND PEDAL TPS.)

6.0L told so the answer. is.
yes this engine is TBW , throttle by wire. see that TB see the huge motor on side of TB well it sticks closed, there is no IDLE air.
scan the PCM yet, see DTC errors, never skip scanning or go broke guessing, the tools is free RIO paid for 1st shop hour labor not paid.
see?
TBW errors, DTC , throttle by wire, errors must not be ignored
and goes to limp home mode or stalls.
or is low fuel pressure;. this too, is a tool for fuel rail pressure at spec, if low can be FPR stuck open or weak pump./
best is scan at the same time as the stall, (real savvy like that)

bad TB motor or bad throttle pedal assembly , the system as up to 4 TPS. (
2 up top, and 2 in the pedal, all cars with TBW , all TPS POT.;s
must agree, or car goes dead or is 20MPY limp home restricted.

so fast right foot fails to save the stall
but if the TB motor is jammed that foot is ignored.
TB = throttle body, all Xyz names here are ASE/SAE standard names./
oops 6.0L has IAC, my tech answer is the IAC is faster than that huge TWB TB motor . so IAC is clogged. lean IAC and TV, throttle valve.
are your cars foot pedals FIXED, (not adjustable option)
who GM has spare TPS sensor for throttle pedal assembly,
nice that, if DTC say any TPS bad it is.
this is the pedal TPS, , TWB TB sensors is there and changed by you, but pedal has one too. I scan first and not go broke throwing parts,
2001 Chevrolet Silverado 2500 HD .USA truck.
reading cars schematics NOW the pedal has 3 POTs. not 2.
APP 1 TO 3, ) AND TO POTS IN THE TB TPS UP TOP FOR 5 TOTAL POTS.
TBW ,MEANS GM TAC MODULES ALL. TB+TPS + APP)
Accelerator Pedal Position (APP) Sensor


https://www.rockauto.com/en/catalog/chevrolet,2001,silverado+2500,6.0l+v8,1371529,interior,accelerator+pedal+position+sensor,5061

Spray some throttle cleaner into the throttle to clean it out. It will also clean the IAC valve. See if that will help you. You may need to have a scanner hooked up to see what is happening to the fuel system.

We have no idea what engine/vehicle, year you're working on.

Do you feel the brake pedal go down when you hold you foot on the pedal while starting the truck ? Maybe the power booster is bad. The power brake booster is vacuum controlled in most cases an if you hold your foot on the brake pedal when starting you should feel the pedal go down if working correctly .

The TPS would be what I would do had that problem once myself solved the problem. as for the ticking noise sounds like a lifter is bleeding down as long as the noise goes away you will be ok. But may I suggest that if you are going to keep the vehicle for awhile longer you might want to have a set of lifters put in it.

Check or test the TPS. Even though it doesn't appear to present any problem, it's initial setting at idle may be off. Just a guess, but I wouldn't rule it out without testing it.

Your clutch is not releasing, check the slave cylinder. Consider bringing it to a professional.

Sounds like a sticky throttle if you can't keep idle. It won't hurt to try.... you can try a quick cheap trick by spraying a little carbon remover (buy at any auto store i.e. autozone, oreiley's) inside the throttle, open the valve, spray just small amount, close it back up and rev it a few times and repeat. It removes the carbon film after long use. fixed my idle issue in my cars. If its really bad you might have to clean it thoroughly but i highly doubt you have to do that.

https://www.youtube.com/watch?v=41yFXjibtLY

tps needs replacing

The switch at the throttle is called a TPS, throttle position sensor. It is fairly easy to change, has 2 screws and 1 electric connector. When you put your foot on the gas pedal a cable running to the Airhorn will move a part which the TPS is connected to.

The TPS is a variable resistor and it is possible to be bad on one end and good further up. Now if replacing the TPS does not solve your problem, something else is slightly off that can be compensated with the footpedal. You may have low fuelpump pressure or a low Vacuum pressure level contributing to the starting problem.

Both Autozone and Oreillys can scan your car and they do it free. You may find another component is bad. The scans will help, but do not cover every system. The TPS is not an expensive part and it is where I would start.

I hope this is helpful to you. Thanks for using Fixya.