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  • Idle issues

    So it was finally time to start the car up yesterday and this is what happened: it fired right up but the idle jumps from 1500 to 2000 and just bounces up and down up and down. My boost gauge shows about 10-15 on the vacuum side. A little background on my car: I have an hx 35 and because of this I needed larger injectors so I put some dsm 450cc injectors in along with the necessary rewiring and resistors. I also have a z32 afm and have done the necessary changes for that. I am currently running the L28et-z32-450cc bin with a romulator as a base for tuning, but since my wideband has not arrived yet, I cannot do too much tuning. I also have the pathfinder intake manifold with no idle devices; my idle will be set via the TB. I talked to a friend (turbobluestreak) and he said that it might smooth out after it reaches operating temperature so I let it run for a little bit. The temp gauge on the dash, which always worked before, was going crazy. It was shaking and jumping all over from hot to cold for a few minutes and then finally settled in the middle (but I don’t think the motor was up to temp yet). I currently have no o2 sensor because I have no exhaust after the turbo (probably going to fab this up tomorrow). I did not expect the car to run anywhere near perfectly, but it would be nice to know what might be causing this. If anyone has any ideas, I would appreciate the input.

    440whp on pump fuel and the STOCK MAF

  • #2
    im assuming you have stock cams.. if so, it sounds like you have a vacuum leak.. the gauge should read much closer to 20 provided it is the same scale as mine which is inches of mercury or something like that.. a vacuum leak after the tb would also explain the high idle..

    also, PM me and i will send you a BIN that should make the car run much nicer.. i used the bin you are using as a base for my setup and i found it to be off the chart rich. if i recall correctly, i think the guy who made that bin left it very rich because he didnt have a wideband.. i ended up making a whole new one.. i havent gotten into the timing at all, which is significantly backed off.. as far as afrs, its consistant mid 11s under boost.. cruizing is very lean, like 16-1 at about 48 degrees. no O2 sensor.. i get close to 30mpg on the highway, my plugs dont have a hint of detonation, they look perfect.. with a 54 trim compressor on a stage 3 wheel at 18psi i made 329 horse and 411 torque.. that was with like 13 degrees advance at the top end.

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    • #3
      Thanks for the BIN Chris! It did make the oscillation stop, but now the car will not continue to idle for some reason. It starts right up, goes up to 2000 or so, stays there for a few seconds, then just dies out. The boost gauge now reads about 20 in. Hg on the vacuum side while it is running. I do not have any idle devices at all, so I just keep adjusting the TB for idle control, but it doesn’t seem to help much. The funny things is, when it was oscillating, it would continue to run and I had some major intake leaks on the manifold that I overlooked. After fixing them and fixing the RPM oscillation, it won't stay running. Any new ideas?

      440whp on pump fuel and the STOCK MAF

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      • #4
        i would definetly hook the idle control back up. without idle control my car will not stay running in the winter until it is warmed up. its a pain in the ass.. do you even have an air regulator? its strange how it shoots up to 2000 and dies if you have no idle controls hooked up. also, make sure the throttle switch is adjusted correctly.. i would still be thinking about vacuum leaks as well. go over everything again, you may still have a leak. good luck

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        • #5
          I have nothing on the manilfod at all. No air regulator, no idle control. I checked everywhere for vacuum leaks, and am sure there are none. When I start the car up, it shoots up to 2000 and if i give it throttle, it just dies. I cannot keep the car running with the throttle to the floor, so my guess is that it might be fuel related? I switched to the k value from the other bin (l28 z32maf 450cc), and that didnt help at all either. Any ideas?

          440whp on pump fuel and the STOCK MAF

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          • #6
            can you keep the car running by holding the gas? to be honest with you i bet the reason the car wont stay idling is because of the lack of idle control.. why did you remove that stuff?

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            • #7
              Chris86NA2T wrote: can you keep the car running by holding the gas? to be honest with you i bet the reason the car wont stay idling is because of the lack of idle control.. why did you remove that stuff?
              I cannot keep the car running by holding the gas pedal down. I thought I had seen many other people run intake manifolds with everything deleted without a problem, so I figured it would clean up the engine bay quite a bit. I am just lost as to why it will not stay running now, when it would before with the oscillation....

              440whp on pump fuel and the STOCK MAF

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              • #8
                did you try your bin file and mine? below 40degrees ambient my car will NOT stay running with the bin file i sent you, i have to hold the cas for 2-3 minutes.. it does not have a stock idle control but it has an air regulator. i never rewired mine when i converted to turrbo. if i were you i would definetly hook up the idle controls. they do clean things up, but they work very nicely hen they are functioning correctly if it isnt too much trouble i would throw them back on and see what happens.. if this makes no sense, ignore me, im drunk.

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                • #9
                  I did try both BIN files. Neither one helped the situation. If I hold the gas on mine, it will first want to stall and the RPMs will drop suddenly. If i continue to hold the gas, sometimes it will stall, and sometimes it will rev way up, rough in the lower RPMs and smooth out in the upper RPMs. So you think putting the air regulator back on would be my best bet? The only devices I have on the pathfinder manifold are the AAC valve and an air regulator. I rechecked everything for vacuum leaks and still found nothing.

                  440whp on pump fuel and the STOCK MAF

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                  • #10
                    i removed all the idle control devices from my motor. mine starts up fine and runs in -30* weather. i don't think thats his problem.

                    99% of the time there is fuel, spark or air problems.

                    i would say there is a small vacuum leak. have you checked your AFM?

                    i would take a propane torch, unlite, and run it over all your hoses, and gasket areas, if your idle goes up, that is where your leak is.

                    Chris86NA2T wrote: i would definetly hook the idle control back up. without idle control my car will not stay running in the winter until it is warmed up. its a pain in the ass.. do you even have an air regulator? its strange how it shoots up to 2000 and dies if you have no idle controls hooked up. also, make sure the throttle switch is adjusted correctly.. i would still be thinking about vacuum leaks as well. go over everything again, you may still have a leak. good luck

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                    • #11
                      84z31 wrote: i removed all the idle control devices from my motor. mine starts up fine and runs in -30* weather. i don't think thats his problem.

                      99% of the time there is fuel, spark or air problems.

                      i would say there is a small vacuum leak. have you checked your AFM?

                      i would take a propane torch, unlite, and run it over all your hoses, and gasket areas, if your idle goes up, that is where your leak is.
                      I read posts about yours before, and figured it was colder where you live than where I live, so I didn't think it would be a problem either. There is definitely spark, and there has to be fuel because sometimes it will rev up so some combustion must be going on. Changing the amount of fuel it gets, via k-value changes, doesnt seem to alter things either. I was thinking about checking my MAF and TPS next. You must remember that my car will not idle, so the propane method will not work.

                      440whp on pump fuel and the STOCK MAF

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                      • #12
                        IMO, something is wrong with your AFM. At the AFM plug, did you splice the two ground wires together when you converted to the Z32 AFM?
                        [strike:ff0tp92h]1984 300ZXT[/strike:ff0tp92h]
                        [strike:ff0tp92h]1986 300ZX 2x2 NA2T[/strike:ff0tp92h]
                        2000 Porsche Boxster
                        2007 Toyota Yaris

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                        • #13
                          bemis wrote: IMO, something is wrong with your AFM. At the AFM plug, did you splice the two ground wires together when you converted to the Z32 AFM?
                          please explain this. i have a perfectly working setup with a z32 afm and i made no wiring changes.

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                          • #14
                            bemis wrote: IMO, something is wrong with your AFM. At the AFM plug, did you splice the two ground wires together when you converted to the Z32 AFM?
                            No, i did not. I did not know that I needed to do so.

                            440whp on pump fuel and the STOCK MAF

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                            • #15
                              First check to make sure all the injectors are firing. Are they known good/clean?

                              Then i would suspect the K value. If it's way off it can cause an erratic idle and looping...

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