Vehicle stalls only when cold

I have a 93 k1500 tbi suburban. Vehicle has brand new Factory spark plugs, fuel pump, cap, rotor and 02 sensor. After vehicle has been started (after sitting overnight..engine cold) when I try to accelerate engine feels as if it wants to die (rpm on tach actually drops, usually to an idle, have gotten it to die one time)If I hold accelerator down, after about 3 secs rpm picks back up and accelerates normally. Fuel pressure is normal when this occurs (13psi). Throttle position sensor readings are normal as well. After engine warms up, problem goes away and vehicle runs normally. Takes about 4 miles of driving to get it to warm
up enough so problem stops. Any ideas? Thinking possibly Coil, Ignition Module, Electronic Spark module or ecm? Anyone else ever had same problem?

If it only does this when the engines cold and otherwise runs good, I wouldn't think it to be any of the things you mentioned. Check to make sure the flap in the air cleaners horn isn't stuck in the open position. Other than that, I would tend to lean more towards a possible bad ECT (electronic coolant temperture) sensor. You didn't mention what engine you have, but the ECT should be located at the front of the intake right next to themostat housing. Does it idle smooth when cold? The ECM uses the ECT signal to know the engine temperture and regulates the idle air valve motor, timing advance and injector pulses accordingly.

I had the same symptoms as you do on my 92 with 350 TBI. After doing a LOT of reading/searching/googling I finally decided that maybe I had a vacuum leak somewhere that closed up when the engine got warm. Had read a lot of posts saying the TBI base gasket tends to go bad, so I bought a TBI rebuild kit. While I was cleaning the TBI, I found the PCV port was totally clogged up. Cleaned it out with some 8 gauge wire I had laying around and carb cleaner. The kit also came with a new diaphragm for the fuel pressure regulator. When I took the regulator apart, I discovered that the spring inside had corroded and was in several pieces. Needless to say, you won't find this spring by itself ANYWHERE, not even a dealer (at least I couldn't). Ended up installing a new fuel pressure regulator and my truck runs GREAT now. That irritating hesitation is now an irritating memory.

I had the same symptoms as you do on my 92 with 350 TBI. After doing a LOT of reading/searching/googling I finally decided that maybe I had a vacuum leak somewhere that closed up when the engine got warm. Had read a lot of posts saying the TBI base gasket tends to go bad, so I bought a TBI rebuild kit. While I was cleaning the TBI, I found the PCV port was totally clogged up. Cleaned it out with some 8 gauge wire I had laying around and carb cleaner. The kit also came with a new diaphragm for the fuel pressure regulator. When I took the regulator apart, I discovered that the spring inside had corroded and was in several pieces. Needless to say, you won't find this spring by itself ANYWHERE, not even a dealer (at least I couldn't). Ended up installing a new fuel pressure regulator and my truck runs GREAT now. That irritating hesitation is now an irritating memory.
I appreciate it. When I checked the fuel pressure it was at 13psi, I did notice that the fuel pressure starts to drop as soon as ignition switch is turned off...which would indicate a bad fuel pump, which was just replaced, or a leaking fuel pressure regulator. So I'm gonna try the regulator, i will let you know if that helps..thanks.

I removed the regulator and checked the spring and diaphragm, both are ok. I was going to install an adjustable regulator I had bought earlier
but the spring seams to be the wrong diameter. (could not get pressure to go below 15 psi with adjustable reg...spring would not seat on adjuster...oh well) I put the factory regulator back on and I have 13.5 psi which is what most people are reccomending for a stock 350. I haven't done any mods yet...want to get stall problem fixed first. Looks as if I'm back to square one. I think I'm going to try and hook a timing
light to vehicle and see if spark goes out when problem occurs. Will keep you posted.

Alrighty, I'm getting a little closer. Found when throttle swung open rapidly and problem occurs, injectors are firing but seam to be not staying on long enough limiting the fuel to engine and causing engine to want to stall. . If throttle is opened slowly , more and more fuel is delivered normally. So something is causing the injectors to not spray enough fuel. If I disconnect the Coolant temp sensor, I can open the throttle rapidly and fuel is delivered properly and engine won't stall. as soon as its plugged in, problem comes back. Of course after a few minutes, once engine is warmed up. problem goes away. I ohm'd the Coolant temp sensor, read approx 3000 ohms when engine was cold. When problem was occuring was at about 225 ohms. Once it got to about 240 ohms problem was gone. ECT sensor seams to be working normally.
Any suggestions what to check next?

That doesn't make sense. 3K ohms cold, 240 ohms up to temp. The problem occurs at 225 ohms, which would mean it's telling the computer the engine is hotter than when it is colder.

I'd say you found the problem. If you can't find the specs for the ECT sensor resistance, just replace it. It's a $13 part, so you may as well replace it. I'd say there's a good chance that is the problem.

I agree with J-Ri. I think the ECT is bad. Nothing else makes sense if when you disconnect the ECT while the engine is cold, it runs right. You said you can physically see, by watching the injectors, that its running too lean with the ECT hooked up, which it what it would do if the ECM thought the engine was up to normal operating temp. If the ECM "sees" cold, it richens the fuel mixture, which is what the ECM "sees" when you disconnect the ECT. (the higher the resistance reading, the lower the voltage level. Disconnected means no voltage to the ECM) How were you measuring the resistance on the ECT? It has to out of the circuit to get an accurate reading. Meters test resistance the same way the ECM is doing it, by applying a known volage level and monitoring what is returned. You can't do that while its in the circuit. I'd change the ECT out.

check and ajust your choke

Vehicle does not have choke, Its TBI. Anyways, I put a new ECT sensor in it, $8.99. That did NOT fix the problem, but good news, I did manage to find the problem. I noticed my heater was not working (don't use it much anyways in arizona so I didn't really care at the time.) I noticed the lines were not getting hot as they should be so I disconnected from radiator and the engine at the quick connect fitting. I hooked a garden hose up to it to see if it flowed well and it was flowing fine. I then removed the quick connect fitting at the intake manifold and found it was plugged up, apparently a piece of the old one fell off when I changed the fitting last year and plugged it up. I unblocked it and reinstalled it and hooked up the heater core. Truck runs great now!! I guess the lack of coolant flow at the back of the block was keeping the intake manifold too cold when warming up so the fuel wasn't atomizing well and vehicle would stall. Now if I could only find someone who can reinstall all the hair I pulled out of my head trying to figure out the problem...lol.