1988 Chevy 5.7 tbi runs rough cold and....

Discussion in 'Chevy Trucks' started by russ130, Dec 16, 2008.

  1. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,114

    It may be your Throttle Body gasket. I did some searching here
    http://www.automotiveforums.com/vbulletin/index.php
    and came up with this. My 95 Tahoe surges a little at idle. They said to spray carb cleaner around the base of the TBI and see if the engine speeds up. You could be in a situation where the gasket seals a little better when warm. I doubt you have a fuel delivery problem. My experience with pumps is they are fine or dead. And you seem to have plenty of power when warmed up. You might need slightly more fuel when cold, but nothing compared to high speeds under load.
     
  2. OP
    OP
    russ130

    russ130 Senior Member
    Messages: 202

    Spitz - Two things wrong with that idea first is that its not going to tell me what its doing at cruising speed and second is that it also is not gonna tell me about the volume of fuel only that there is enough pressure and that there is enough volume at idle. I'm going to try the filter first and hopefully the fuel line will hold.
     
  3. Spitz

    Spitz Senior Member
    Messages: 192

    You said it runs rough all the time and lacks power, its just a quick little test that i've used a number of times before i try to remove the fuel filter and install our inline pressure gauge. SImply put if the fuel pump cant make any fuel return its junk as even at idle if it cant produce the pressure to bypass the regulator its surely not going to make enough pressure when it really needs it.

    ps- This is why im telling you this, so you can try it before you wreck the fuel line completely. That and you will see fuel volume if you pull the line back, its quite a time saver, but what do i know its not like im employed as a technician.. :)
     
  4. brad96z28

    brad96z28 PlowSite.com Addict
    Messages: 1,527

    Very easy to buy a 20 dollar gauge and filter adaptor and do it the right way it could save some real time.
     
  5. OP
    OP
    russ130

    russ130 Senior Member
    Messages: 202

    I'm pretty sure I said it runs rough when cold and lacks power all the time. Of course the lacking power is really my opinion and it may very well be fine who knows. Look I'm not trying to insult you, not in the least and in fact I will try your method first. I'm just thinking what is this really gonna tell me? It runs fine at or around idle its when you are going down the road and it is not at operating temp that it spits and sputters if you try and give it the least amount of gas. I have all but let off the throttle and it smooths right out until it upshifts then it starts all over again. This symptom disappears as soon as it reaches full operating temp. Everyone here says its the fuel but to me it really feels more like a vacumn leak. I don't think it has a vacumn leak big enough to cause all these problems so that is why I started with replacing a sensor and now I'm thinking the eprom or the cpu. But at the same time it could be fuel. Truth is its cold and I'm in no hurry to lay on the cold ground to find out that the pump is ok. I can return the pump but not the filter since I had the filter for quite a while. As far as the line goes I saw it and I'm the type that has to fix it now. I'll let you know tomorrow during the day how things are going and what I find but I do appreciate all the ideas of things to check for whether right or wrong it does help.
     
  6. Spitz

    Spitz Senior Member
    Messages: 192

    I know, im just suggesting. Anyone can take it for what its worth.. If its running rough when cold it may be because of open loop its running in, the computer will use presets for fuel delievery, any vacuum leak or fuel delivery issue, the computer will not compensate for untill it gets into closed loop, probably a few minutes of running on that old of a vehicle.
     
  7. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,114

    It won't take long to check that TBI gasket. Start her up and spray a little carb cleaner around the base of the throttle body. Needless to say, do this when it's cold.
     
  8. bassfishn1

    bassfishn1 Member
    from ct.
    Messages: 30

    might help you, or might not, i have the same problem also, have not fixed it yet, but i believe it is my air cleaner assembly
    the reason i say this is, there is an flap inside the snorkel, that is suppose to close at cold engine temps, so that the tbi gets warm air from your exhaust manifold, and as your engine warms up, the flap opens also
    not sure if you have this on this truck, but worth checking
     
  9. archeryhead4412

    archeryhead4412 Junior Member
    Messages: 1

    give this a try

    just had the same prob on my truck found the intake sucking air...about 3 1/2 hrs later and a case of beer it was fine...i replaced the intake set.
     
  10. Hall's Lawncare

    Hall's Lawncare Junior Member
    Messages: 3

    I have the same problem with my 5.7 tbi. It doesn't lack that much power (that I know of) but when idling it rev's surge. It will stop once RPM's get over 1k. Ive also noticed if im sitting at a stop light and I put it in Neutral than it evens out alittle. I also haven't looked into it because the truck isn't that bad but first chance I get i'll be working on it. - By the way... new to the site and love it already. You guys have answered so many questions and I just browsed for acouple minutes.
     
  11. OP
    OP
    russ130

    russ130 Senior Member
    Messages: 202

    Well I fixed mine the easy way. I sold it lol
     
  12. lmiller

    lmiller Junior Member
    Messages: 2

    My 88 5.7 V8 wouldn't start when cold unless I pumped the throttle up and down for at least 4 minutes until the engine heated up, and the "service engine soon" light stayed on all the time. I changed the temperature sensor unit ($15) on the intake manifold and now it starts right up and the service engine light is off.
     
  13. Sawboy

    Sawboy PlowSite.com Addict
    Messages: 1,876

    10 year old thread.....
     
  14. lmiller

    lmiller Junior Member
    Messages: 2

    31 year old truck, this 10 year old thread gave me the information I needed to keep it running.
     
    Avalanche 2500 and Mr.Markus like this.