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Tbi Problem!!

Discussion in 'The Injection Section' started by tonto, Feb 2, 2007.

  1. tonto

    tonto Registered Member

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    It is a 91K-5 blazer, stock with the exception of headers and tbi spacer.Over the last cople of years was not driven much. Recent work done. Had the same problem before did this work. I repleced the plugs, wires,cap,rotor,tps,gaskets for the tbi and spacer, vacuum lines, new k&n air filter,complete new exhaust cat and muffler, fuel filter. I think that is all,as far as I can remeber. Does not throw a code, have a scanner. When you lightly press the gas, such as backing up, it tries to flood out. Had the wife do it while I sat over the motor and watched the injectors. Can see them dump a load of fuel in. Stumbles and then clear up. Will cause it to die unless you press the pedal more. Oh yeah forgot that I have ran 4 tanks of super with injector cleaner. Thanks for any help.
     
  2. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    Have you checked the fuel pressure? It would be worth fitting an accurate gauge and seeing what the pressure is doing at that moment. Perhaps with the slight rise in revs the resulting rise in current to the fuel pump is just enough to overload the injectors at that point,
    Is it definately rich? Black smoke from exhaust? Lean can 'sound' like a rich bogging.
     
  3. HarryH3

    HarryH3 1 ton status Author

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    Also check for ANY exhaust leaks ahead of the O2 sensor. It takes only an amazingly small amount of fresh air to make the sensor think that the engine is running lean. The ECM responds by adding more fuel. :(
     
  4. ivie29

    ivie29 1/2 ton status

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    Worked on a van that did the same thing.It would stumble at half throttle but clean up at full throttle and gas would drip from the injectors.I pulled the top of the injector housing of to look at things and it turned out that the lower o ring for each injector was dry and falling apart.I guess that at part throttle the fuel pump was making enough pressure to ovecome the bad o rings and cause the drip but at wot the injectors let enough fuel through to stop the drip. Since you said that it has sat for a while it wouldn't hurt to check for dried out o rings

    Anyways that solved my problem, hope this helps.
     
  5. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    I've had problems with those O rings too. Good advice there to check them.
     
  6. tonto

    tonto Registered Member

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    hve wondered about possible fuel pressure problem, have not had a way to check the pressure. Did not think about the exhaust leak, will have to check for that one. Have had the throttle completely apart cleaned and new gaskets, but no o-rings. How or where on the injectors. I mean I know where you undo the electrical connections and where they mount to the pod but where are the o-rings? Thanks for the tips and advice!!!!!
     
  7. HarryH3

    HarryH3 1 ton status Author

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    The O-rings are down near the tip of the injectors. They're typically included in a throttle body rebuild kit. You have to remove the injectors from the pod to replace the O-rings.
     
  8. Thunder

    Thunder 3/4 ton status

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    Aside from what others have said..... Hook up your scanner and check the TPS voltage. It should go up smoothly as you press in the accelerator. If it varies or jumps around the TPS is bad. If the ECM sees the voltage change suddenly it interprets it as acceleration and dumps more fuel.
     
  9. tonto

    tonto Registered Member

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    Already replaced the TPS. Did nothing. Of course I have got new parts that were bad before. Will try the scanner to see if it reads a spike. Again thank for the help, much appreciated.
     

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