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  • Hesitation problem

    I've been having a hesitation problem for a while and I'm at wits end now that my Ty is my daily. I have a PLX wideband and when in park if I barely tap the gas like 7.5% TPS, my AFR goes to 10.0. the rpms dip, and then it revs up. It does the same when in drive and hitting the gas from a stop light, and also if i'm slowing down into a turn and accelerating out of it.

    I've checked timing with the tan wire disconnected and that's good, replaced plugs and even messed with the gap, replaced the fuel filter, ran mystery oil in the tank and crankcase, I don't have an easy way to test the plug wires, so I just took one brand new plug wire and swapped it all around all 6 plugs to see if there was a difference, and nothing. Fuel psi is correct. Vac lines are still all good. Ignition is good. I just checked the PCV valves and noticed they're not the 8995910's with the E on the bottom, so I ordered some of those. I read a bunch of threads on the PCV valves, but didn't find any info if using the wrong ones will cause a hesitation like this.

    I did a search on here and read a bunch of threads on hesitation problems and a lot were from the truck going lean, or a bad o2.

    Figured I'd check here to see if anyone had any suggestions before I go wasting money swapping parts out.
    I have
    Turbo Tweak chip
    Walbro
    50# Injectors
    AFPR
    PLX wideband

    The PLX, Walbro, and injectors all have a lil over 3k miles on em... so while it's not impossible, I don't think any of that can be the culprit. I tried pulling the turbo tweak chip and putting my ATR pitbull chip in, but I could barely get it to idle with it. So I don't really have anything to test against to rule out if it's a prob with the chip.

    Thoughts? Opinions? Gas can and matches?
    1991 Syclone #1931 (sold)
    1992 Typhoon #0627

    To truly love these trucks, you must HATE them more.


  • #2
    So is it doing this after the truck is fully warmed up? Does it do it cold? Truck is definitely overfueling if youre going 10.0 on a light tip in. MAP go bad? You have the dip switches set correctly on the chip for closed loop?

    Comment


    • #3
      Yeah, it does it all the time regardless if it's cold or warmed up. I thought it might be the MAP as well... I don't have a spare 3-bar, so I popped the old 2-bar in there today, just to see if there was any change at all, and it still does the exact same thing. Datamaster shows closed loop, so it's not a dip switch. I haven't checked the EGR yet, or the cap/rotor... although the cap/rotor was also replaced about 3k miles ago... Only other thing I can think of would be maybe a valve is burnt or sticking? Once it's warmed up, and in park I do hear a faint a pop err miss about every 10-15 seconds, but it goes away when it's in gear. It still pulls strong under boost with minimal knock for the crappy 91 we have here.

      MPG is pretty bad though... If I go through a whole tank just cruising to work at 70mph without going into boost, I get a lil over 12mpg. I used to get over 16mpg on the highway in my Syclone running 75-80mph.

      I'm out of town this weekend, but I'll try a lil more troubleshooting next weekend, and do a couple more Datamaster runs to see if anything pops up.

      Thanks for the reply!
      1991 Syclone #1931 (sold)
      1992 Typhoon #0627

      To truly love these trucks, you must HATE them more.

      Comment


      • #4
        Take a look at the cap and rotor just to be sure, but sounds to me like it's a little vacuum leak-ish.

        How's your vacuum at idle?




        Justin "RealFastV6"
        1991 GMC Syclone
        1993 GMC Typhoon

        Comment


        • #5
          You have a 3-bar map that you swapped with a 2-bar. If the 3-bar was bad, it and the 2-bar would probably cause the same problem. I'd invest in a new, good 3-bar.
          ...Rob
          All my wife can say about it, is that it's really scary
          Sy #1654 Link to my Photobucket page

          Comment


          • #6
            Whats your IAC counts at?

            Comment


            • #7
              When was the last time plugs ,wires and fuel filter replaced ?
              Last edited by 1blkc4; 02-27-2019, 07:59 PM. Reason: spelling
              1992 typhoon 0384
              1999 c5 frc vette

              Comment


              • #8
                I'll try to answer everyone at once here...

                I was thinking vacuum leak too, but I have all silicone lines and have gone through them so many times... Everything is connected correctly and there are no cracks, or splits in the lines. I'll have to try the innertube on the intercooler trick again and see if I can hear anything... Could one of the check valves in the lines be stuck and cause this?

                I'll swap out the PCV valves and check the cap and rotor tomorrow when it's not raining.

                Vacuum at idle is -18/-19, which is about right, no?
                I thought the 2-bar and 3-bar MAP sensors were essentially the same only the 3-bar could read higher boost levels? Is the calibration of the sensor totally different? If so, I never knew that, and just learned something.
                IAC is at 40 once it's warmed up, it's in the low 50's when it's cold.
                I just swapped the plugs out a few weeks ago some CR42TS's, and gapped them to .032
                Plug wires have about 3k on them, and the fuel filter has maybe 2k on it.



                Couple of things I just realized while looking at my DM files and writing this post...

                I looked at an OLD file from 2013 and noticed by voltage is consistently up in the 14's. My latest DM file the voltage is never steady bouncing around from 12.9-13.8 never getting into the 14's. That could be THE problem err at least part of it.

                Also, what kind of EGR numbers should I be seeing on Datamaster? The DC is constantly bouncing back n forth between 0.0 and 95+. I had an Ultimate Chip in my Syclone, which IIRC bypassed or disabled the EGR... So I don't know what's "normal" to tell if that's bad too.
                1991 Syclone #1931 (sold)
                1992 Typhoon #0627

                To truly love these trucks, you must HATE them more.

                Comment


                • #9
                  Really nothing out of whack. IAC is close, TurboTweak uses 30 for setting up their chip. You could always temp block off the EGR and see if thats it. Is the battery hosed or the alternator not charging? I had low voltages in DM but all my charging system was good. I ran a 10 gauge wire to the ecm power and voltage went 12.x to 14.1. Truck was better under load and boost.

                  Comment


                  • #10
                    The 3 bar map has a completely different calibration than a 2 bar, and the map has to be matched to the chip.
                    The EGR is not used in that chip, so that byte of memory is used for something else, so just ignore what you see on DM.
                    If you can email me a datalog from DM showing the problem, I'll be happy to take a look.

                    Eric
                    Eric Marshall
                    TurboTweak Webstore -Click Here
                    2 GN's and Syclone 610

                    Comment


                    • #11
                      Well I pulled the cap and rotor and the rotor is a lil toasty around the edge, and some of the terminals under the cap are a lil burnt, but I wouldn't say they're bad enough to cause this much of an issue. Swapped the PCV's with the correct ones, and it almost seems like it's gotten worse... and now I can hear kind of a weird buzzy type sound behind the dash when I tap the gas.

                      I also did the innertube on the upper IC, and there's a slight hiss coming from under the throttle body, but if I recall that's "normal"?

                      I made a lil video of the problem, but you can't really hear the sound it makes when I tap the gas.

                      https://youtu.be/P-AY6pGyGfw

                      I'm gonna order up a new cap/rotor/wires just to rule those out completely... and I might as well get another 3-bar while I'm at it.
                      Last edited by Mephisto; 03-08-2019, 05:04 PM.
                      1991 Syclone #1931 (sold)
                      1992 Typhoon #0627

                      To truly love these trucks, you must HATE them more.

                      Comment


                      • #12
                        Originally posted by Eric Sy GN View Post
                        The 3 bar map has a completely different calibration than a 2 bar, and the map has to be matched to the chip.
                        The EGR is not used in that chip, so that byte of memory is used for something else, so just ignore what you see on DM.
                        If you can email me a datalog from DM showing the problem, I'll be happy to take a look.

                        Eric
                        Thanks Eric. I'll do a quick run on DM tomorrow, and then I'll drop a link here for download.
                        1991 Syclone #1931 (sold)
                        1992 Typhoon #0627

                        To truly love these trucks, you must HATE them more.

                        Comment


                        • #13
                          Hey guys, sorry for the delay... had to order a new laptop battery for my ancient XP laptop, it wouldn't hold a charge long enough for me to do a DM run.

                          Anyway here's a file of just cruising around for a bit, and getting on the gas a few times... I didn't do any WOT bursts just cause I want to get things sorted out before I create an even bigger problem. But one thing I did notice... At the end of the file, I'm in Park barely tapping the gas to show the problem I'm having, and I noticed that every time I tap the gas, it goes to open loop and then back to closed loop. Hmm... is that right?

                          https://files.mycloud.com/home.php?b...name=3-7-19a_2

                          Let me know if this link doesn't work and I'll try to upload it on syty.net.
                          Last edited by Mephisto; 03-10-2019, 12:43 AM.
                          1991 Syclone #1931 (sold)
                          1992 Typhoon #0627

                          To truly love these trucks, you must HATE them more.

                          Comment


                          • #14
                            Link doesn't work for me. You can email me the log, eric@turbotweak.com The closed loop/open loop operation is normal for the TT chip.
                            Eric Marshall
                            TurboTweak Webstore -Click Here
                            2 GN's and Syclone 610

                            Comment


                            • #15
                              I would rule out crankshaft position sensor(ignition module). Do you have access to known-good distributor? Module isn't Syclone specific. Also, rule out wiring to it.
                              IGottaSy so IWannaTy no longer.

                              Taking the streets by STORM!

                              My smart phone makes me look dumb when I T-Type

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