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Need Help with TBI on 88 Pickup! Updated - 4 Jan

Discussion in 'The Garage' started by Russ, Jan 2, 2004.

  1. Russ

    Russ 1/2 ton status

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    I am looking for some help with my 88 Chevy Dually V30 (350 TBI). I bought it a few weeks ago and it was running OK. It appeared to have not been maintained much, so I ran a compression check and averaged 170 on all the cylinders. I went ahead and ran some top end cleaner through it, and changed the plugs/wires/distributor cap and rotor. It was running pretty good at first, idling a little high I thought, and then I noticed some noise aroungd the EGR. I pulled everything out of the way and saw that the EGR valve gasket had been leaking. I replaced the gasket and now it will not run at all. It would barely start and pump out black smoke as it is running extremely rich. I could pull one of the injector wires and actually get it to run better. I pulled the IAC and it appeared to be pretty clogged up, so went ahead and replaced it. That made it worse. Now the only way I can get it to start is by holding the throttle wide open as it appears to be getting way too much fuel. I have rechecked everything I took off, plug wires, vacuum connections etc.., and even replaced the Ignition Control Module with a spare I had. Nothing makes any difference. Does anyone out there have any suggestions that I might try? I am running out of ideas. Thanks for any help.

    Russ
     
  2. Confedneck

    Confedneck 3/4 ton status

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    Re: Need Help with TBI on 88 Pickup!

    why not replace the egr valve? if its stuck open or closed and not allowing the exhaust gas to recirculate.. then the truck wont run right..
     
  3. Russ

    Russ 1/2 ton status

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    Re: Need Help with TBI on 88 Pickup!

    I checked it out when I had it off and it opens and closes very easily by applying vacuum to it. I believe it is fine. Thanks,

    Russ
     
  4. Confedneck

    Confedneck 3/4 ton status

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    Re: Need Help with TBI on 88 Pickup!

    valve is good, maybe some debris within the egr tube?just changing that gasket shouldnt make the truck have problems running..maybe check your tps voltage?... should be .4-.6 at idle (closed) and 4.6-5v at wot..
     
  5. Confedneck

    Confedneck 3/4 ton status

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    Re: Need Help with TBI on 88 Pickup!

    btw, where's crestview?
     
  6. Russ

    Russ 1/2 ton status

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    Re: Need Help with TBI on 88 Pickup!

    I was kind of thinking that possibly there was a problem previously and the extra air from the gasket leak may have been leaning out the engine and making it run OK. Then again, I could have absolutely no clue what I am talking about. I do have a spare TPs that I thought about putting on, but it seems too bizarre that the problem started just by putting a gasket under the EGR. I am pretty well stumped by this and don't have the kind of equipment to test anything.

    Crestview is about 25 miles north of Ft Walton, 50 miles east of Pensacola.

    Russ
     
  7. Confedneck

    Confedneck 3/4 ton status

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    Re: Need Help with TBI on 88 Pickup!

    you dont have a voltmeter? thing is, a tps can go bad out of the blue.. getting ready to put the 2nd replacement on my moms 99 s-blazer on monday..
    ever been to fort myers?
     
  8. Russ

    Russ 1/2 ton status

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    Re: Need Help with TBI on 88 Pickup!

    I have an old Simpson 260 multimeter that I bought about 25 years ago, but it doesn't really measure very accurately anymore. I will probably try and swap the spare TPS tomorrow and see if that makes any difference.

    I have never been to Fort Meyers that I know of.

    Thanks,
    Russ
     
  9. sandawgk5

    sandawgk5 3/4 ton status

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    Re: Need Help with TBI on 88 Pickup!

    I had a problem similar to this with my 87 K5. I unplugged each injector one at a time. The first one stopped as expected, however the second one aparently had something in it causing it to stick open and keep flowing full flow even when unplugged. I got it to crank like you did by holding the peddle down to allow more air in and i drove it to get it home. Had to put in neutral and keep rpm up to keep from flooding out. Some how on the way home it started running right I got it home unplugged the faulty injector and it stopped flowing. PFM!!!!!!. Any way a lot of words to say maybe one of your injectors is sticking open. Hope this helps.
     
  10. Confedneck

    Confedneck 3/4 ton status

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    Re: Need Help with TBI on 88 Pickup!

    in other words, try a fuel induction service.. run a tank cleaner, some top end cleaner.. and spray out the throttle body with some "spray carburetor cleaner"..the foaming kind..
     
  11. Russ

    Russ 1/2 ton status

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    Re: Need Help with TBI on 88 Pickup!

    Thanks. I had not thought of that. It just so happens that the same time I changed the EGR gasket, I also changed the fuel filter. I tried to ensure that I did not get any dirt in the lines, but the lines and frame were extremely greasy and dirty. So there is always a possibility that some dirt got in the line.

    Russ
     
  12. Thunder

    Thunder 3/4 ton status

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    Re: Need Help with TBI on 88 Pickup!

    Have you bothered to check trouble Codes??
    It should be the first thing you do when you have engine issues.
    Check for trouble codes before you do anything. The computer may be able tell you exactly what is wrong.
    It may save you from needlessly throwing money at it.
    Better yet, buy a scanner.
     
  13. Russ

    Russ 1/2 ton status

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    Re: Need Help with TBI on 88 Pickup!

    I did bother to check trouble codes before I started replacing parts and the only code that shows up is 12. Thanks,

    Russ
     
  14. Thunder

    Thunder 3/4 ton status

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    Re: Need Help with TBI on 88 Pickup!

    Does it run rich when cold starting or is it rich and hard to start after it wrms up?
     
  15. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Need Help with TBI on 88 Pickup!

    Did you reset the ECM (pull fuse or disconnect battery) after replacing the IAC? Whether wrong or right, the IAC would use the same setting with the new one. Disconnecting power the ECM forces the IAC to "relearn" what is correct. At least this is the way TPI IAC works, I'd bet TBI is the same.

    It doesn't sound like it's really your cause, but if you need to reset the ECM and haven't, that may hinder any future attempts to troubleshoot.
     
  16. Blazer1970

    Blazer1970 1/2 ton status

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    Re: Need Help with TBI on 88 Pickup!

    I would check very close for a bad injector. You need to run a volume/time test to check them properly.
     
  17. Russ

    Russ 1/2 ton status

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    Re: Need Help with TBI on 88 Pickup!

    It is definitely running rich on startup. I can't even keep it running long enough for it to warm up. It sounds like it is running on 3 cylinders and pumps out the black smoke.

    Russ
     
  18. Russ

    Russ 1/2 ton status

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    Re: Need Help with TBI on 88 Pickup!

    I did try resetting the ECM after swapping the IAC. Did not make any difference. Disconnected the battery for 30 seconds. I know when I am looking at the TBI running on my 90 Blazer it does not put out nearly the spray of fuel when idling as this truck is. It seems to be getting an awful lot of fuel.

    Russ
     
  19. Russ

    Russ 1/2 ton status

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    Re: Need Help with TBI on 88 Pickup!

    I will take a close look at the injectors today. I don't know what I will be able to tell just by looking at them, but will see. I am not sure how to accomplish the volume time test.
    Thanks,

    Russ
     
  20. HarryH3

    HarryH3 1 ton status Author

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    Re: Need Help with TBI on 88 Pickup!

    This is when a data scanner would be handy, so you could check to see what the ECM thinks the engine temp is. It sounds like the ECM might be seeing a temp that is much colder than it really is. This will cause the ECM to inject too much fuel, as it thinks it needs extra fuel to compensate for the cold. (Think of it as an eletronic replacement for a choke. Instead of closing a plate over the throttle body, TBI just injects extra fuel.)
     

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