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1994 chevy K1500, 350. low idle stall

This is a discussion on 1994 chevy K1500, 350. low idle stall within the Technical / Maintenance forums, part of the General Discussion category; Ok guys, i have a 1994 chevy w/ 350 tbi. after it reaches operating temp. it will dip down on ...

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    1994 chevy K1500, 350. low idle stall


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    Ok guys, i have a 1994 chevy w/ 350 tbi. after it reaches operating temp. it will dip down on idle a couple times,then die. unplug the ECT sensor & goes to open loop & runs at a higher idle but doesn't stall out.

    heres what has been done- intake was removed & cleaned due to blocked egr ports,throttle body cleaned,IAC changed,ECT changed,ignition module checked & changed,swapped PCM with known good pcm.alternator tested for grounding out & spiking the pcm. new EGR valve,wires traced from pcm to ECT,IAC,TPS & egr control solenoid.

    ANY IDEAS?

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    Re: 1994 chevy K1500, 350. low idle stall

    bump...... need a couple ideas

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    Registered User tazman171's Avatar
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    Re: 1994 chevy K1500, 350. low idle stall

    Have you looked at the injectors with the air cleaner off to see if they are spraying gas when it try's to die? You can hook up a timing light and shine it at the injectors to see the pulses. Your injector(s) could be partially clogged and that sounds like the only thing you haven't changed. Also, the PCM (or ECM maybee) should be the last thing you ever change, they almost never screw up and they are usually very specific to the year, model and emissions setup. The module will also tell you when it's bad, it goes into limp mode to get you home.
    94' Silverado Z71 King-cab 4x4
    Flo-Pro 3" Exhaust, K&N Aircharger,
    Rebuilt 350 with P&F heads, bigger cam, Rebuilt 4L60E (again) 12 vane pump, etc.
    Prestige Auto-Start Security, Pioneer DEH-8400BP, GM-5500T Amp,12" subs
    All Blue LED Interior lighting, Custom Grill by T.C.W.


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    You won't like my tastes Swims350's Avatar
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    Re: 1994 chevy K1500, 350. low idle stall

    my 88 tbi does this. It's all new rebuilt motor, resued the tbi and all the sensors, so they aint new, all new ign. though, coil, dist., cap, rotor, wires, plugs, air cleaner, only thing not new is injectors and sensors, and when it gets up to temps it idles very low and when going from one gear to another or turning the wheel sometimes it'll die out.

    It usually doesn't do it on it's own, you usually have to be turned at the low idle from a dead stop, or switching from drive to reverse and bam it'll die out. Also when mine does it, it smells funny, like it ran out of gas or has old bad gas in it that's been sitting in it forever. it's also hard to get it started back, usually have to let it sit for a minute or so then it'll start up pretty easy.

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    Re: 1994 chevy K1500, 350. low idle stall

    Check IAC counts with a scanner it need 15-30 counts with engine at operating temp 195F in gear.
    04 K1500 Silverado EXT 3:73 gears, 5.3L 265/75-16,Pace Edwards tonneau,

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    Re: 1994 chevy K1500, 350. low idle stall

    well, here is what i have found, it'll run great at 14 psi fuel for a good while & then all of a sudden psi will drop to 8-9. not enough fuel to really run it. especially if you try & give it gas.

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    Registered User tazman171's Avatar
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    Re: 1994 chevy K1500, 350. low idle stall

    Does the PSI come back up if increase the engine speed? When it dies, do have to hold the pedal to the floor to get it to start again?
    94' Silverado Z71 King-cab 4x4
    Flo-Pro 3" Exhaust, K&N Aircharger,
    Rebuilt 350 with P&F heads, bigger cam, Rebuilt 4L60E (again) 12 vane pump, etc.
    Prestige Auto-Start Security, Pioneer DEH-8400BP, GM-5500T Amp,12" subs
    All Blue LED Interior lighting, Custom Grill by T.C.W.


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    Re: 1994 chevy K1500, 350. low idle stall

    barely, had an old,good fuel pump & swapped it. drove fine & then started this morning after driving into work & it died out again.

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    Re: 1994 chevy K1500, 350. low idle stall

    Well you know its not the pump, lot of work to find that out. Do you have to floor it to get it started when it dies? Just curious.
    94' Silverado Z71 King-cab 4x4
    Flo-Pro 3" Exhaust, K&N Aircharger,
    Rebuilt 350 with P&F heads, bigger cam, Rebuilt 4L60E (again) 12 vane pump, etc.
    Prestige Auto-Start Security, Pioneer DEH-8400BP, GM-5500T Amp,12" subs
    All Blue LED Interior lighting, Custom Grill by T.C.W.


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    Re: 1994 chevy K1500, 350. low idle stall

    Dropping pressure almost sounds like it's time to buy a TBI rebuild kit. It only takes a few minutes and it is a cinch.

    FYI, I think many people suffer from this same exact problem with different results. Mine too did this as well. I actually went ahead and over the course of two months replaced every single sensor on the engine, rebuilt the TBI, new plugs, cap, rotor and wires. Then I finally found my problem.
    Dist bolt came loose and my timing was way, way off. I set it to 4 bftd and it's been fine. BUT, I'm not confident this is the issue.
    Normally the truck will idle at 700 RPM, but intermittently it will idle at 400 rpm, It is so low my wife even commented on it last night sitting in the drive through at Taco Bell. So if she noticed it, it's bad :) . Anyhow, the only thing I'm down to is the ECM, Bad Wiring/Ground or the Thermostate is screwing up the IAC counts because the engine is running to cool. In my case my buddy owned the truck before I did and he put in a stat that is a 140 or 160, he's not sure. But looking at my gauge it reads just about there so I think it is too low for the ECM to properly manage. I'm going to change it and hope my issue goes away. If not I'm taking it to the dealer and having them look into it.
    The Wife says I need to stop being a cheap ass and buy a new truck. But I like my truck and I'm going to start saving my pennies to buy a truck next year. Unless my kids need new cloths or something then it'll never happen.

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    Re: 1994 chevy K1500, 350. low idle stall

    never does when your kids need something, i know :) timing has been reset & double checked just to be safe. you know, disconnect the IC control wire & set the timing to 0 degrees. here is what i think has happened. the starter solenoid would not engage all the time.sometimes it would just start to kick over. then the a/c diode was bad. both could allow a voltage spike to hit the pcm (with both doing at the same time, i am thinking likely).
    had the aftermarket alternator tested for bad field windings & it tested good. personally i think the pcm has been hit.


    PLEASE TELL ME IF YOU THINK IM WRONG!!!!
    This truck is kickn my ASS!!!!!!

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    Registered User tazman171's Avatar
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    Re: 1994 chevy K1500, 350. low idle stall

    The reason I've been asking him if it need to be floored restart it is the computer controls the start if its flooded. If you put pedal down all the way and start cranking, the comp recognizes this and stops any gas until the comp sense a certain rpm. This was built in to the system to recover from a flooded motor (bad values from the CTS). My truck had the CTS caused flooding prob. I rebuilt the whole TBI for what turned out to be a bad $5 connector.

    My truck has also just recently started trying to die off of idle when it's between 90deg and the first opening of the t-stat 185 deg. I just put a new motor in it and this isn't a flooding issue, just scanned it at my friends shop and had no codes. What it did have was a lack of timing advance from the Electronic Spark Control Module, especially when luke warm, which also told the comp that he TBI didn't need more fuel. This module is a different part than the ignition control module in the distributor. It went just bad enough to never throw a code but it caused low power on steep grades and the almost stalling out prob. If I hadn't had a friends with a true OBD1 scanner in shop I would have pulling my hair out.

    So get a true scan, not just a code check
    Last edited by tazman171; 04-20-2010 at 02:36 PM.
    94' Silverado Z71 King-cab 4x4
    Flo-Pro 3" Exhaust, K&N Aircharger,
    Rebuilt 350 with P&F heads, bigger cam, Rebuilt 4L60E (again) 12 vane pump, etc.
    Prestige Auto-Start Security, Pioneer DEH-8400BP, GM-5500T Amp,12" subs
    All Blue LED Interior lighting, Custom Grill by T.C.W.


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    Re: 1994 chevy K1500, 350. low idle stall

    unplugging the cts tells the ecm that the engine is cold thereby the ecm adds fuel and raises idle. check fuel pressure to rule out a fueling problem.(9-13 psi)
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
    Matching Ninja 500r


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    You won't like my tastes Swims350's Avatar
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    Re: 1994 chevy K1500, 350. low idle stall

    ok this might sound dumb but what is the cts and where is it at?

    Also I found out something about mine today...

    when I built the motor and put all the new ign. stuff in it, complete dist., new cap, rotor, wires, plugs, and removed the AIR pump, it would not run at zero degrees base timing, wouldn't run past 40mph, it idleing and everything good but wouldn't pull out of it's own way. I set the timing up and fixed this, but ever since it's had a lil puff or miss to it sometimes on idle, and was told it's a lean pop. Well the truck stalled out today after it was up to temp. and didn't want to restart, mine will crank fine then start to slowly crank like it wants to drag, sometimes my dad tries to hit the gas to get it going and I tell him not to. it doesn't help of course.

    Anyways, I get home, advance my timing with the connector unplugged, shut it down, plug it in, try it, and with it more advanced it was missing worse and then it would die instantly in gear. So I had to pull some timing out of mine, I just hope I don't loose the power I had.

    I was thinking if I did maybe I should try the CTS, oh wait lol coolant temp, sensor LOL. D"OH but was thinking maybe unplug it, but would it work driving like that? I gotta drive back and forth to work and it's about a 15-20 minute highway drive, then some city before and after, 15-20 minutes total one way.

    If not then should I change the cts? or should I make sure I got a 195 t-stat I think mine may not be that high, may be a 180 or 160 not sure.

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    Registered User tazman171's Avatar
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    Re: 1994 chevy K1500, 350. low idle stall

    When it got to temp it would start flooding out every time you tried come off of idle unless you really feathered it.
    94' Silverado Z71 King-cab 4x4
    Flo-Pro 3" Exhaust, K&N Aircharger,
    Rebuilt 350 with P&F heads, bigger cam, Rebuilt 4L60E (again) 12 vane pump, etc.
    Prestige Auto-Start Security, Pioneer DEH-8400BP, GM-5500T Amp,12" subs
    All Blue LED Interior lighting, Custom Grill by T.C.W.


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    Re: 1994 chevy K1500, 350. low idle stall

    Quote Originally Posted by slikrnsnot View Post
    Ok guys, i have a 1994 chevy w/ 350 tbi. after it reaches operating temp. it will dip down on idle a couple times,then die. unplug the ECT sensor & goes to open loop & runs at a higher idle but doesn't stall out.

    heres what has been done- intake was removed & cleaned due to blocked egr ports,throttle body cleaned,IAC changed,ECT changed,ignition module checked & changed,swapped PCM with known good pcm.alternator tested for grounding out & spiking the pcm. new EGR valve,wires traced from pcm to ECT,IAC,TPS & egr control solenoid.

    ANY IDEAS?
    that sounds like the temp sensor the one thats on the manfoild next to thermostat if unpluged or bad sensor or wiring thats what thay do

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    Re: 1994 chevy K1500, 350. low idle stall

    if a new cts(ect) sensor doesnt fix it check fuel pressure.
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
    Matching Ninja 500r


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    You won't like my tastes Swims350's Avatar
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    Re: 1994 chevy K1500, 350. low idle stall

    I tried unhooking my cts and the truck wouldn't start, then after plugging it back in was very hard to start and had to feather the gas, once it started it smoked out the tailpipes. Does that mean mines bad or is it normal?

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    Re: 1994 chevy K1500, 350. low idle stall

    might just be a fueling problem.
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
    Matching Ninja 500r


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    Re: 1994 chevy K1500, 350. low idle stall

    i have the same problem as slikrnsnot(first post) and i was hoping to get a little help. Did yall ever figure it out

 

 
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