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94 hesitats on take off!

Discussion in 'Chevy Trucks' started by starfiresx, Dec 22, 2005.

  1. starfiresx

    starfiresx Member
    Messages: 30

    my 94 Chevy 1500 hesitates on take off and if going from cruz speed to speed up. other wise it is fine idles fine. I have had this truck for under two years now. I gave it a complete tune up minus the fuel filter. I did not change the filter because I could not get the line nuts lose of the line and did not want to twist a line. and then forgot about it. I now have the correct parts to fix the filer problem, just don't want to do it in the cold. cap and rotor have the brass lugs. I hate the aluminum one's! but all this started after we had a big wet snow fall. I put in two bottles of Lucas fuel treatment hoping that I got some bad gas. still the same. got some fresh gas from another station. still the same. so I decided that I will change the fuel filter. I go the coin wash to give the truck a quick bath so I don't have to touch all that salt. and what do I see! a hole lot of snow that has turned to ice covering the fuel filter and line.

    so would ice around the filter make the gas freeze in the line and give me some of my problem?

    any advice is appreciated.

    thanks Joe
     
  2. R Thomas

    R Thomas Junior Member
    Messages: 6

    If it is not the filter then the fuel pump could be going bad. Change the filter and it if still does it you might want to test the fuel pressure (low pressure will cause that problem). If it only acts that way when the tank is low on gas it could be the baffels in the tank are broke and the gas is moving away from the pump on take offs. (all of the above things have happened to me at one time or another)
     
  3. redhenny16

    redhenny16 Senior Member
    Messages: 134

    Remove the vacume line from the EGR valve and see if the hesitation is gone. If the EGR valve opens to soon it could cause a hesitation. This truck uses a positive back pressure EGR valve and if the valve goes bad it will pull open to soon. It could also be a bad vacume control solenoid for the EGR valve.
     
  4. starfiresx

    starfiresx Member
    Messages: 30

    Update!!!

    :confused:

    I have changed the fuel filter still the same.
    I also did what redhenny16 suggested with the EGR vacuum line. still the same.

    funny thing is it is not all the time. it will run flawlessly for a time and then it just starts acting all funny. like it is missing. I am going to check the plugs and cap.

    how do I check, or should I ask where do I check the line pressure on these TBI trucks?

    thanks Joe
     
  5. Plowfast9957

    Plowfast9957 Senior Member
    Messages: 280

    i would make sure that when you did the wires they arent arcing out on something. go outside at night turn off all the lights open the hood and start the truck. if you see sparks jumping from the wires to metal re-route them. same thing happent to my 88. drove me nuts for like a week. good luck
     
  6. starfiresx

    starfiresx Member
    Messages: 30

    Plowfast, thanks for the info. I had thought of that. but not to much. I will try that. I have had this problem with my old 91 GMC, but it always was the cheap aluminum caps. I bought a good one with the brass and never looked back. but this one has me going in circle's.

    thanks Joe
     
  7. R Thomas

    R Thomas Junior Member
    Messages: 6

    on a TBI you have to check it at the fuel line, had mine checked at the fuel filter and it was low pressure. If you don't have a way to check it yourself you will have to take to a repair shop (about 60 to 80 dollars around here to check it). You say it only does it sometimes so if it only does it when it is low on gas it could be broken baffles in the gas tank.(when you take off fuel sloshes away from the pickup tube)
     
  8. starfiresx

    starfiresx Member
    Messages: 30

    well I have the big tank (34 gal I think) and it does not matter if low or full on gas.

    I also forgot to mention that I have a small crack in the passenger side manifold. but it has been there since I bought the truck almost two years now. would this make it do some weird things?

    Joe
     
  9. schnitz

    schnitz Member
    Messages: 98

    For whatever reason, there's a gasket under the TBI that caused my old '93 to run rough. I changed that, problem solved. Maybe it won't work for you, but it's worth a shot.


    In a while, Chet.
     
  10. starfiresx

    starfiresx Member
    Messages: 30

    thanks schnitz. you know I just was playing with the air cleaner assembly before all this started. more like fighting with the plastic air hose from the fender well. in this cold weather it is not as easy like in the summer.

    for the 4 bucks at the local parts store I will give it a shot.

    Joe
     
  11. schnitz

    schnitz Member
    Messages: 98

    Hopefully it works for you. Just please do us all a favor and let us know if it does. Someone else down the road may have the same problem.


    In a while, Chet.
     
  12. Caleb55

    Caleb55 Member
    Messages: 44

    You might want to check the injectors one the TBI too. Make sure they are shooting fuel out evenly.
     
  13. starfiresx

    starfiresx Member
    Messages: 30

    Yes I did check the injectors. all looking good.
    when I got the truck one was dripping. not shooting. put some Lucas in it and all has been good since.

    thanks Joe
     
  14. starfiresx

    starfiresx Member
    Messages: 30

    well today, I checked the plugs,wires, and also all the vacuum lines. also changed the TBI lower gasket. still the same.

    the truck only does this after the engine has heat soak. note when it is cold.
    would a Ox censer cause this? maybe another censor on the TBI? I am at wits end with this.

    thanks Joe
     
  15. douglasl330

    douglasl330 Senior Member
    Messages: 356

    Any type of vacuum leak will cause a problem similar---I would double check those lines(also anything on the intake)--TPS could be bad?-- Egr could be sticking like previously stated! Have you got a check engine light on? If so this could be helpful--Had an 88 and the ECM went bad and did some goofy things--wouldn't give me a code! Started as lots of black smoke out of tailpipes on take off and got progressively worse! Truck when warm would buck and fart if on the accelerator, but idle was fine ran without a skipp. Hope this helps! Best of luck!
     
  16. PlowingHD

    PlowingHD Junior Member
    Messages: 26

    I would check fuel pressure and check the fuel pressure regulator. To check fuel pressure, you can basically only check it at the filter with an adapter that goes in place of the fuel filter, that has a schrader valve on the side to attach a pressure gauge. Fuel pressure should be 9-13 psi. anything less than 9 lbs, it will not run. To check the regulator, you need to block off the return line with a pair of hose pinch off pliars (on the rubber portion of the hose in front of the filter). When you do this you should see a spike in fuel pressure, which is max pump output, (truck runnning in both tests) If you don't see this happen, especially when you blip the throttle, you have a bad regulator and the engine is running out of fuel. this condition would be more prevelant when the engine is cold and requires more fuel. Other things that I have seen working on these TBI engines are as follows-

    -plugged fuel filters
    -low output fuel pumps
    -bad egr solenoids
    -stuck egr valves
    -TBI base gaskets blown out
    -loose,dirty,broken grounds at the t-stat housing (for PCM)
    -coolant temp sensor harness wires broken or CTS out of range
    -cracked pickup coil magnet in dist. and or bad ign modules, worn out dist shaft bushings
    -broken up cat, causing plugged exhaust

    - one other thing I might try would be finding a junkyard distributor to install.

    Good luck- HD
     
  17. starfiresx

    starfiresx Member
    Messages: 30

    no engine light. no dark smoke out the exhaust.
    the exhaust is fine. flows good.

    is there a way to check the egr valve? can I use a vacuum pump to do so?

    I actually have a new distributor in a box. I will try it out. I also will look into the others you pointed out.

    thanks for all the good advice guys. I will go pick some parts off my old 91 that my Aunt bought from me. it just sites there any way.

    Joe
     
    Last edited: Dec 27, 2005
  18. starfiresx

    starfiresx Member
    Messages: 30

    Well, nothing new today still the same.

    I bought a new engine temp sensor.
    also swapped out the distributor.
    still runs bad.

    I pinched off the return line to the tank. it set off the light. code 45. rich condition.

    Now onto the IAC and the TPS. I hope one of these will help out.

    Joe
     
  19. starfiresx

    starfiresx Member
    Messages: 30

    Well, nothing new. still runs the same. I did swap the TPS sensor with another one from. still the same.

    today I made up a T fitting with an AED fuel pressure gage. pump puts out right at the upper limit. 13 psi. I even gave it part throttle and the pump kept right up with 13 psi.

    I also looked at the ox sensor. I have a three wire sensor. I will get a new one and try that out.

    thanks Joe
     
  20. PlowingHD

    PlowingHD Junior Member
    Messages: 26

    I keep thinking about the fact that the ECM is throwing a code 45. Do you have a scan tool? would be nice to see what the O2 sensor is doing. That is probably the problem, unless the fuel pressure regulator is leaking.