Okay, 1993 Chevy C3500 that is sitting on a 1994 GMC K3500 frame/running gear. Also has the 94 454 TBI under the hood.

Trucks been doing well in this cold weather up until recently. Yesterday it was a few digits above zero. I went out and started Christine and came back in. She warmed up and kicked off high idle. I went out and the temp was between 100 and 210 on the gauge. I put her in gear and she died. (It did this last year to but would do it when it would get into the 20's already, but since I did my TBI rebuild and put a new computer in it, I haven't had this problem up until now) This is a little irritating, but no big deal to put it back in park and start her up. Which takes nothing to do. She's running before the starter has a chance to start spinning! After that she was fine.

Now this morning I went out and started her. 6 below the donut this morning. I went in and let her warm up. She idled for about 3 or 4 minutes and then I couldn't hear her anymore. I go to the door and there she sat. Marker lights all on but she just died. WTF? :confused: So I finish getting dressed and go out there. Again, it took nothing to get her started again and it ran fine since then. The temp gauge this time was just getting off the 100 mark.

Any ideas on what this could be? She has been using a lot more fuel since it got cold to. I have dropped down to around high 6's to low 7's running all city miles and a little snow driving. I just don't get it. About the only thing that I could come up with right off the bat is that I should get some Heet in the tank. I just filled up yesterday and come to think of it, I filled at the same station as the last tank where she died when I would put her in gear.

I get no SES light until she dies (of course!). I suppose I could bring her in and have it scanned just to see if something comes up. Just wondering if this sounds like something common or if anyone has any ideas.

seeing as how no one has posted yet, ill give it my best shot, but know little about that motor. could it be a bad O2 sensor?

or a clogged fuel filter

the newer models when cold started don't rely on sensors (maf or O2) untill they get to a certain temp. if it's running long enough to get to temp then it probably is an O2 sensor. if it's dying when it's still cold it's somthing else..I don't know if 94's are programmed the same. but thats how the ls motors are...

I won't rule out the fuel filter, but that was changed early this summer and hasn't been driven much since then. But, like I said, I will not rule that out.

Outside of the cold start, it runs strong. I was curious about the O2 sensor and considered it until the dang thing died this morning and it was JUST starting to warm up. The O2 sensor should have nothing to do with the equation at that temp.

Granted I was inside and it all I can hear is the rumble of the exhaust, but I didn't even here a stutter or anything. It was just the rumble and then nothing. Just like you walked out and turned the key off.

There is a reason why she is named Christine. (For those Steven King fans out there! :D)

How about fuel pump?

If you changed your filter, then its likely not it as you said. (i dont know what type of filter you have, but be sure its not in backwards if its even possible, this happened to our race car, it ran fine for a week then had problems, we found it was backwards and then it was fine... just a thought.)

I ALMOST made that mistake when I installed the filter. I was just getting ready to tighten the lines when I noticed that the arrow was pointing the wrong way.

I have thought about fuel pump to, but from what I know about them, it seems like trucks get hard to start when they start going out. This one pops right off. Even at 6 below this morning, my 454 cranked and fired within just a couple seconds.

I jumped the A B terminals on my OBD 1 connector and the SES light just flashes a 12. So, whatever it is, the computer doesn't seem to think anything is wrong.

Another thing I thought of at lunch is that I do have an adjustable fuel regulator also. I am running around 26 PSI right now. I had it at 30 when I first installed it. That was too high because it would stumble a bit if I took off before it was warmed up. (this was about 2 months ago.) So I turned it down and it seemed to run very well so I kept it that way. I'm wondering if it is possible that the pressure is still too high? And with the colder temps, the computer is richening up the mixture and if my pressures are too high, then the truck might be getting too much fuel?

Can you tell I am grasping for straws? :)

You may want to check that fuel pressure. The max that I have seen suggested for TBI is 15 psi. May want to check this out http://www.cfm-tech.com/gm_tbi_fuel_pressure.htm .

The 454 runs a higher fuel pressure than the other TBI gassers.

10-4 Rttoys

The stumble you had when still cold was from running open loop (not reading the sensors till warmed up) I think thats a different issue than your cutting out problem. although it's not really an issue. once warmed up it should run smooth.

I just dumped some heet in the tank when I got home. We'll see if that makes a difference. I'm going to freeze my butt off this weekend and look at the fuel pressure, change oil, and rotate tires. I'll look around and make sure I don't maybe have a vacuum leak somewhere. Hopefully I'll find something.

fuel pressure '94

454 = 26-32
350 = 9-13

Worked on her this weekend. Changed oil, rotated tires, new blower motor, fixed the cigarette lighter, permanently fixed my fuel return line, and gave her a good look over.

I could find nothing on the engine. I couldn't find anything vacuum wise. Everything looks great.

So for now I am at a loss on my cold issue. This morning wasn't too cold. Maybe in the high single digits to low double digits. I started it, like before it took nothing to start, and it idled away. I got in it about 5 minutes later and the temp was just getting off the 100* mark. I put it in drive and it stumbled pretty good for about a second or two and then it kicked back up to a normal idle and was fine.

This is such an odd thing. It seems like once it dies once, it is just fine after that.

I did find a new job for me this summer though. My upper control arm bushings are getting worn. With the front tire off the ground and pressure on the suspension, I can wiggle the control arm there. So it looks like I might be replacing them this summer. Seems like it never ends!

I can't remember if your year has one or not, check the TPS ( throttle position sensor) it has 3 stages and you idle stage may be gone.;)

It does have a TPS. I remember taking it off when I had the baseplate trued up and new bushings pressed in. How can I test that?

It does have a TPS. I remember taking it off when I had the baseplate trued up and new bushings pressed in. How can I test that?
You'll have to use an ohm meter and get a repair book for your year. It will tell you the ohms for testing.Did the problem start after you took it off...if so it just may be out of adjustment. The manual will help you there also. Good luck.
;)

No, it did this to me last fall/winter to. It was this summer that I had the injectors cleaned and flow tested, base plate trued, new bushings in the base plate, rebuilt the TBI, installed adjustable regulator, and put a new computer in it also. (Had transmission heat problems and odd codes. Computer was shot)

I forgot all about these issues because it hasn't happened until recently. I am going to dig the net to see if I can find some specs. I could test my resistance/voltage tonight. I have a new throttle cable to install also. Mine is getting sticky and will become jerky when you are trying to apply slight pressure.

No, it did this to me last fall/winter to. It was this summer that I had the injectors cleaned and flow tested, base plate trued, new bushings in the base plate, rebuilt the TBI, installed adjustable regulator, and put a new computer in it also. (Had transmission heat problems and odd codes. Computer was shot)

I forgot all about these issues because it hasn't happened until recently. I am going to dig the net to see if I can find some specs. I could test my resistance/voltage tonight. I have a new throttle cable to install also. Mine is getting sticky and will become jerky when you are trying to apply slight pressure.

That would cause problems with the TPS.;)

New cable installed last night. It's a dream to drive again! It's like fluid when you push on the gas now!

However, it was around 12 above this morning. Went out and started her. Couple cranks and she was running. Went in and finished getting dressed. Was talking to my g/f when I heard the truck kick off high idle. It stumbled a bit. Sounded like it was going to die, and then picked back up and idled fine.

Got in it and the temp was between the 100 and 210 mark again. I push on the brake, change from P to D and when it engaged, it stumbled slightly, picked back up, and then all was well.

I didn't get a chance to test the TPS though for 2 reasons. 1) I couldn't find specific settings for my 94 7.4 Liter, but I did find some general readings. 2) The battery in my mulitmeter is dead. I will get that replaced tonight after work and maybe run some tests.

One more question since I am learning more about all these sensors. I found out what that odd looking sensor was towards the back of my engine. It's the MAP sensor. On my truck this has a single vacuum line that leaves the sensor. Then it goes into a plastic pipe for a bit and then it tees off and then one line goes into the manifold on one of the upper plenums and the other one goes into the manifold down in one of the lower plenums. Is this right?

TPS wires
Gray 5v
Black -
Blue ~ .5v at closed throttle

Gray and black can be tested with the connector off, blue can only be tested by backprobeing with the connector connected to TPS.

MAP vacume lines sound correct.

New cable installed last night. It's a dream to drive again! It's like fluid when you push on the gas now!

However, it was around 12 above this morning. Went out and started her. Couple cranks and she was running. Went in and finished getting dressed. Was talking to my g/f when I heard the truck kick off high idle. It stumbled a bit. Sounded like it was going to die, and then picked back up and idled fine.

Got in it and the temp was between the 100 and 210 mark again. I push on the brake, change from P to D and when it engaged, it stumbled slightly, picked back up, and then all was well.

I didn't get a chance to test the TPS though for 2 reasons. 1) I couldn't find specific settings for my 94 7.4 Liter, but I did find some general readings. 2) The battery in my mulitmeter is dead. I will get that replaced tonight after work and maybe run some tests.

Glad to hear it is getting better for ya.;)

Just for giggles it wouldnt hurt to check the coolant temp. sensor too. This will make it run to rich or to lean if it is reading the wrong ambient air temp. Sounds like you are on the right track though. Check all your grounds too, make sure they are clean and tight.

Come to think of it didnt these trucks have intermitten PCM problems? Doing a tap test on it wouldnt hurt either. "tap it with the handle of a screw driver and see if the engine changes idle or even quits", sounds stupid but i have seen it.

My 95 7.4 stumbles a good bit when its cold out. It doesn't get too cold here in NC so I can imagine it'd be worse in colder areas.

But to point out, there is NO heat pipe on my truck (no provisions for it) so it will stumble to the point where it will almost stall out. Also upon idling every so often it will attempt to idle down and if not warmed it will again almost stall..

Since the TB is so large the IAC (Idle Air Control) can't always operate fast enough to prevent a stall. So these 94/95 (maybe newer too) use a vacuume operated kicker to bump the throttle open. (similer to the an AC high idle thing) If this is broken the PCM will attempt to do its best to keep the truck running with only the IAC.

The plastic control gizmo was busted on mine when I got it and the truck would do like you've indicated until warmed up then not have any issues.

This gizmo is dumb in that the PCM can't see it, only turn it on or off. So when mine was broken it also didn't present any codes just stalled out..

Good Luck -mike

Is that the vacuum diaphram that sits right by the throttle linkage? I have not tested that.

I created a whole new problem for myself now though. :rolleyes: My starter developed a dead spot in it around the time it got cold. It is way too easy for me to just tap the starter with the handle of my snow brush so I haven't replaced the starter. (Was hoping for warmer weather.....like SPRING!)

This morning it wouldn't engage. I get out and tap the starter. But, it was dark and I didn't get my flashlight out of the truck. I ended up snapping the damn connector on the knock sensor off. *sigh*

So, to pay for my laziness, I get to lay on cold concrete tonight and fix the snapped off end.

Thanks for the TPS Voltage readings. I will check those tonight to if I get time. And thanks to everyone for all of the suggestions! I will keep you all posted on my findings!

Also, any readings for the coolant sensor?

And I know that my grounds are good. When I was having transmission heat issues (which turned out to be a toasted computer) I went through the stock grounds and cleaned them up. I also ran 3 more of my own ground straps. One from the battery to the frame. One from that connection to the bellhousing bolt and then another one on the other side of the bellhousing back to the frame.

Okay, here is what I found. Warm idle, that little vacuum thing is pulled all the way away from the linkage. I'll try to remember to see if it pulls it away right away on cold startup to.

Knock sensor is fixed and SES light is off.

TPS Readings:

Blue wire: .62 Volts with the key in the run position but engine off. (That little vacuum thingy is pushing on the linkage)

Blue wire: .44 Volts with the truck running.

Blue wire: 4.45 Volts at WOT key on but engine off. (Voltage slowly increases with the entire range of throttle movement with no dead spots or fluctuations)

Gray wire: 5.01 Volts with the key in the run position but engine off.

Gray wire: 5.03 Volts with the truck running.

i think u are getting too much fuel. are u running stock tune?

u need a a/f meter a good one to see what is going on and make fuel pressure adj with that.

I've been wondering the same thing. When I first had my fuel pressure set, it was somewhere like 32. It ran well and had great power, but when it started to get cold, if I didn't let it warm up, she hesitated some. I dropped the pressure a little and that went away. I'm wondering if I dropped the pressure some more, if this issue would go away also.

I don't suppose there is a decent A/F meter for cheap is there? I don't suppose I could tap off from the O2 sensor on the truck and watch the readings on my multimeter?