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  • Hesitation and flooding...

    I have another thread going on over at .net, but figured I'd try here too...

    I've been having this hesitation issue for a while. But it's a hesitation from what I think is flooding. When the truck is parked and idling, if i barely tap the gas the AFR goes to 10.0, the rpms dip, and then the engine revs up. It does this whether it's hot or cold, in park, reverse, or drive. From a stop light, I'll hit the gas, and it's the same thing, rpms dip, then it picks up and goes. It does this when I slow down and accelerate out of a turn. If I get on the gas it'll get up to about 5-7psi before the rpms start bouncing around and the truck bogs out. Idle smells rich, and MPG is not good either. I also get random pops/misses at idle. Fuel psi is good and solid, and climbs # for # with boost.

    I have 50# injectors, a turbo tweak chip, AFPR, PLX WB02.

    I did the bike inner tube trick on the upper IC, and there's no vacuum leaks other than a slight hiss coming from the bottom of the throttle body...

    So far I've replaced the cap/rotor, plugs, coil, ICM, and MAP sensor. I don't have anything to test the plug wires, but I took a spare good plug wire and swapped it out on every cylinder with no change. I don't think it's a bad or clogged injector, because it's going rich instead of lean.

    I also get this buzzy/ticking/grinding sound every time I tap the gas...I can hear it in the cab and under the hood... I made a video of it with a link below... In the cab it kinda sounds like pushing a plastic bucket upside down on concrete... under the hood it sounds like taking a comb and dragging it down the edge of a table real quick... and it sounds like it's coming from the distributor.

    https://youtu.be/FBt9aRIH_6A


    Just curious if anyone here has any ideas... or heard these noises before.

    Thanks in advance and have a good weekend!

  • #2
    Does it make the bucket sound or the comb sound when the engine's not running and you hit the throttle? Possibly linkage noises?

    Hesitation and stumbles are typically ignition related. The tach bouncing is ignition related. Are there any loose grounds anywhere?

    What kinda of fuel pump is on your truck? How long has it been in there?
    -Brandon

    I'm trying to win the internet.

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    • #3
      Originally posted by Aeroking View Post
      Does it make the bucket sound or the comb sound when the engine's not running and you hit the throttle? Possibly linkage noises?

      Hesitation and stumbles are typically ignition related. The tach bouncing is ignition related. Are there any loose grounds anywhere?

      What kinda of fuel pump is on your truck? How long has it been in there?
      It only does it when it's running, and it doesn't matter if it's hot or cold. If I advance the throttle while under the hood with the engine off it doesn't make any noise, so it's not the linkage.

      I have a Walbro 255 in there with about 3k on it, and fuel psi is always solid. I checked the grounds too, and there's nothing loose or suspect there... I'm with you thinking it's ignition related, although usually when there's an issue with the distributor it makes a noise all the time, not just when you rev the engine...

      I ordered a new distributor anyway, since that's where the noise is coming from. The water pump is squeakin and leakin too, so I gotta do that next. The perils of daily driving a 28 year old truck haha.



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      • #4
        Sounds like spark arcing to me. You could have spark leaking to ground possibly a damaged plug wire, cracked cap/plug, coil etc.

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        • #5
          Well, I put a new set of wires in, and!!! Nope. Still having the same problem. I caved and bought a multimeter just cause it's probably a good thing to have around the house and to test my old wires. As it turns out #6 and #4 were indeed arcing, which is why I couldn't find the problem when I was swapping out 1 wire at a time. The idle has smoothed out a bit and hesitation isn't as bad as it was, but the AFR still goes to 10 when I tap the gas, and it still bogs out at 5psi with AFR going to 10. I also still have the noise when I tap the gas.

          I'm gonna have to get the stethoscope out and see if I can pinpoint exactly where the noise is coming from. Initially I thought it was coming from the distributor, but now I don't think it is. Is it possible for an injector to arc? I'll post what I find or don't find with the stethoscope.

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          • #6
            If its arcing you should be able to see it at night. Park in a real dark area and pop the hood and see if you can see anything jumping around the coil area. I dont think its possible for an injector to arc.

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            • #7
              Originally posted by Static View Post
              If its arcing you should be able to see it at night. Park in a real dark area and pop the hood and see if you can see anything jumping around the coil area. I dont think its possible for an injector to arc.
              Correct, Injectors are 12V pulsed GND, arcing is impossible.

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              • #8
                Originally posted by Typhoon0627 View Post
                the AFR still goes to 10 when I tap the gas, and it still bogs out at 5psi with AFR going to 10.
                What calibration ("PROM") is in it? I'm guessing it is not a stock calibration, because I don't see how a proper calibration could do this. An aftermarket calibration with a mistake or overlooked calculation could.

                I will never, never, NEVER forget trying to help a guy on .net chase a code 21 TPS high. We went around and around for two weeks, and nothing made sense. He had data logs, and he was NOT meeting the parameters to set Code 21. It was impossible. After two weeks, the author of the PROM came in and said he changes the parameters for Code 21, and that it was likely that he WAS setting 21. What the F? Why change the parameters of a DTC and not tell anyone? Makes diagnostics impossible for anyone. The author of this PROM has the word "weak" in its name.

                I tell this story to illustrate that one has to be cognizant of "mistakes" or "issues" with other than stock calibrations. There can be anomalies that haven't been uncovered by exhaustive validation like only the OEM can perform.

                EDIT: I see you have a xxxxxxweak chip. I've seen peeps with these chips have so many weird problems that I don't even try to figure issues with trucks with these chips out.

                Having said that, the loss of power, break-up, and "bog" at 7 psi is EXACTLY what my red/gry did when it had a plugged cat. Took me 3 weeks to figure it out.
                Last edited by DaveP; 04-13-2019, 12:27 PM.

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                • #9
                  The noise is too perfect to be arcing. Sounds more like maybe a noisy IAC, I don't think it's related to the rich \ hesitation issue.

                  What is the full mod list?

                  Was this truck running fine at some point and then this all started?

                  Have you tried putting the stock chip and (2) bar map back in it?

                  Is the TT chip installed correctly?

                  Have you datalogged all this?

                  Have you sent Datalogs to Eric?

                  Can you post the datalogs?

                  I'm with Dave - this sounds like a TT gremlin, and we're all blind to knowing what's really going on.


                  There are 7 adjustable settings built into the TurboTweak Velosyty chip for the GMC Syclone and Typhoon. This article will cover all the software and hardware settings in the chip. This article is based on content of the Velosyty Version 2.0 chip documentation. Their docs are available on their site in pdf format. You'll need a scan tool that can display INT and BLM (or LTerm) to make adjustments outlined in this article.

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