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  1. #1

    Exclamation Electrical Problem-eng surges, tach needle freaks out, shift up light blinks randomly

    I have a 1994 chevy k1500 4x4 ext cab with the original factory 5 speed manual and a TBI 350 from a 1991 chevy caprice(apparently).
    What is the usual cause for the problems described below?:

    The starter works nicely, but the engine just doesnt want to start easily. It will turn over eventually, but it takes a couple cranks and my foot almost to the floor on the accelerator for it to work. It had a low idle before and sometimes it stalls out before this problem occurred, but now it literally wants to die. When you give it throttle, it feels as if I'm not getting combustion on every stroke as if some strokes werent firing. The aftermarket Tach's needle is going all over the place and the "shift up" light is blinking on and off in a random fashion as if there were an electrical problem(ie bad connection). If I dont try to keep it running, it clunks out.

    Someone told me ignition control module, but that doesnt sound right at all cuz how would that affect the tach and shift light. I think its an ECU problem or something along those lines. Or it could be a combo of a bad ground and bad ignition control module.

    Edit: Actually the ignition control module might make sense because when i took the air cleaner assembly off and looked at the injectors spray as my dad was trying to keep the truck alive, it wasnt cutting the spray ever...so yea.

    Edit:
    So I replaced the ECM with the correct one and it came with a new PROM that was also the correct one for the truck.....didnt fix the problem totally. However, you can tell that it runs a lil bit better and it doesnt always just die by itself anymore. Also found out when replacing ECM that there was an animal nest in my dash right on top of the blow motor, bunch of the wires were nibbled on. Fixed those and they didnt change anything.

    So it leads me to believe its something to do with a sensor. What kind of sensor would cause too much fuel to be added and to make the tach/shift up light freak out? I took off the ignition control module and it turns out its after market, it is an Accel 35370 performance control module. Since it is a performance part, I'm not really sure it would fail. Along with that, this car has an external MSD coil/wires and a stock distributor cap.

    What about grounds? What grounds would affect the amount of fuel being injected, the shift up light, and the tach? Right now I know the ground that attaches to the passenger fender and the one that attaches from the negative of the battery to the engine are good. I have to check the one that attaches to the front of the intake manifold. The tether ground that went from the engine to the frame is severed(due to it being chassis lifted), but that wouldnt cause the engine and tach/shift light problems because this has been severed since it was owned and it didnt have this problem initially. Any grounds in that section of power and ground points on the passenger side on the firewall that is "usually" supposed to be covered by some sort of plastic box?

    Also, I determined that somewhere in the chassis electrical, the parking light circuit is tied into the brake light circuit. When I have the key off and hit the brake pedal, the dash lights, the parking lights, and brake lights turn on, and the annoying bell goes off in unison with whenever i hit the brake pedal. When I have the key on, the buzzer doesnt go off like that, but the lights still act the same. Also, when i just turn on the parking lights, the brakes will come on too. So where would be the most likely place that would happen? The hitch mount area?



  2. #2

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    Replaced the ignition control module, didn't fix it. I'm going to test map and tps tonight.

  3. #3

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    TPS tested bad, threw a new one in, idled a little rough in the beginning. Replaced semi-kinked vacuum hard line, truck cold started rough but drove great and idled great when it warmed up.......Tried driving it the next day, barely got it started, ran like super crap, sounded like misfiring.

    After I test compression on the engine, the test will determine if I keep putting more money into getting it running, or just looking for a 350 tbi in better condition/rebuild the one i have(whichever is cheaper) and part out the 350 I have. My best guess right now is that either the IAC valve or EGR is super clogged but not throwing any more money until i test compression.

    It would be wonderful to get some thoughts from some people that know their **** on here.

  4. #4

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    Make sure that your ECM isn't dead. You can check it by seeing if it displays the code 12, flash code which means the ecm is functioning normaly. You can do this by crossing pins A and B with the key on engine off and the service engine light should blink like this... blink........blink.. blink.........then it would repeat it another 4 times and if there are any other codes it will flash them after.

    Could also be a crank sensor too. That would be giving incorrect stroke information to the ecm so it would cause the timing to be thrown off for the fuel and spark timing. Also take the air filter assembly off so you can see the two injectors clearly and have someone turn the key on so it turns the fuel pump on but dont start it and see if the injectors drip or leak. If they do they are bad, the start it and watch them and see if one or both isn't atomizing(spraying) fully.


    You can take your igntion control modual to autozone and they can test it for free and let you know if its bad or not.
    Make sure that your fuel pressure isn't low.
    And make sure your intake manifold isn't leaking because of a bad gasket. You can spray starter fluid around where it seals when its running and if it speeds up in RPM its sucking in the fluid so it would be leaking.




    Remember when troubleshotting check...... Fuel-----> Ignition-----> Compression

    That means make 100% sure that everything is working correctly in the fuel system, fuel pressure, injection, intake, ect.
    Then ignition which is timing, spark, ect..
    Then lastly check compression to make sure it isn't low.


    Good luck hope it helps a little!
    1995 C1500 4.3L 2WD. JET TBI Spacer, JET stage 1 chip, 10mm Taylor custom wires, Pulstar Iridium Pulse Plugs.
    260k miles and still going strong...

  5. #5

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    Ok, so thank you for responding, its awesome to finally get a response from someone that can speak tech wise (no offense to those who responded)

    So first off I can tell you ignition control module isn't bad. The injectors are atomizing correctly(at least visually) ill check that drip though during priming. This style engine apparently doesnt have individual crank or cam sensors at least according to the documentation ive seen. Ive done the check for intake leakwith carb spray (which should work the same as start spray) and it didnt effect anything....then again the engine was running like crap regardless soi probably wouldnt notice much of a difference anyways. Unfortunately idont have a fuel pressure tester or gauge so im out of luck on that. But it seems like its running rich anyways. I do still needto do acompression check, just havent had time. Also, I dont know if my style ecu has that ALDL function because I dont have tpi or MAF system so I dont know if that diagram is saying thats only available to tpi/maf systems or its standard but just an option on tpi/maf, buuuut I will try the jump across A &B.

    One thing someone mentioned on another site is it could be the pickup coil since that affects the tach signal and can mess up the timing therefore causing missfire conditions like im experiencing. Also, thatcould be it because I noticed the dizzy cap was missing a chunk (wasnt at a contact location so it isnt the core problem) so I bought new cap,rotor,and pickup coil.

  6. #6

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    So took the distributor apart and found out the pickup coil was toast, there were shards of copper EVERYWHERE in the distributor. and the cap was actually broken. So I just replaced the distributor, got an accel cap and rotor, and reused the accel performance ignition control module. But, my dumbass forgot to take a picture of where the distributor and wires were going and since this motor is a plethora of parts from different cars, i have no idea what model I'm supposed to follow so I just basically put the spark plugs in the firing order that is pressed into the intake manifold and then i just move them all one by one in one direction until i get it to work. I found one position that wanted to start but wouldnt, but by that time I think the engine might have been flooded haha So i'm going to let it sit for a while and then we'll try again.

    If anybody has the numbering for wires on the distributor for non hei i would appreciate if you posted it, mine has the coil mounted next to it and there is no vacuum advance and has the opening for the little control module. I've found references online, but they always reference the one that has the coil sitting in the actual distributor cap(which i think is whats known as HEI) so that doesnt apply to me.

    The distributor that matched the one that I had was from a 1990 Caprice that had the high power 350 or the code that was with the engine was HP so i assumed high power

    Last edited by DeathByNissan55; 10-08-2012 at 01:55 PM.

  7. #7

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    Quote Originally Posted by DeathByNissan55 View Post
    So took the distributor apart and found out the pickup coil was toast, there were shards of copper EVERYWHERE in the distributor. and the cap was actually broken. So I just replaced the distributor, got an accel cap and rotor, and reused the accel performance ignition control module. But, my dumbass forgot to take a picture of where the distributor and wires were going and since this motor is a plethora of parts from different cars, i have no idea what model I'm supposed to follow so I just basically put the spark plugs in the firing order that is pressed into the intake manifold and then i just move them all one by one in one direction until i get it to work. I found one position that wanted to start but wouldnt, but by that time I think the engine might have been flooded haha So i'm going to let it sit for a while and then we'll try again.

    If anybody has the numbering for wires on the distributor for non hei i would appreciate if you posted it, mine has the coil mounted next to it and there is no vacuum advance and has the opening for the little control module. I've found references online, but they always reference the one that has the coil sitting in the actual distributor cap(which i think is whats known as HEI) so that doesnt apply to me.

    The distributor that matched the one that I had was from a 1990 Caprice that had the high power 350 or the code that was with the engine was HP so i assumed high power

    Fixed font color so post is readable.

    1995 Silverado 4x4
    6" BDS Suspension Lift-3" Body Lift-Add A Leaf in rear -Trailmaster SSV Shocks-Duel Steering Stabilizer Kit -AirAid Cold air intake-
    4.56 Gears with Detroit Auburn Locker-Pro-Comp Traction Bars with duel shocks-Aluminum Skid Plate Kit-38.5" x 16.5" Mickey Thompson Baja Claws-Constant Dropping fuel gauge

    2005 Yukon XL Jet Power Programmer, Bilstein Shocks, Bilstein rear springs, Helwig Anti-sway bars, EGR Window Visors, EGR Hood Shield, Denali Headlights, Headlight harness upgrade, GE NightHawk Bulbs, White Night Rear lighting system, Russell Braided SS brake lines, PowerStop Brake pads, PowerStop cross drilled and Slotted Rotors, http://www.gmtruckclub.com/forum/sho...5-GMC-Yukon-XL
    2002 Silverado ext cab 2wd (Sold)
    2003 Yukon XL (Totaled)

  8. #8

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    Fixed it. I was wondering why it was so hard to read, i dont even remember clicking on anything related to font color

  9. #9

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    This is the firing order and setup for the engine you mentioned...


    1995 C1500 4.3L 2WD. JET TBI Spacer, JET stage 1 chip, 10mm Taylor custom wires, Pulstar Iridium Pulse Plugs.
    260k miles and still going strong...

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