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  • Fix your hesitation

    As many of you know I've had some bad leaning out when under full throttle. I have tested everything to try and find the root cause, and finally today I fixed it lol. So I'm going to walk you threw the steps on how to fix your hesitation/wot throttle problems/ leaning out. Basically you can stop fixing when one of these tests work So if one doesn't work, follow next step.
    1) Check your ECU for codes. To do so, follow this link [URL=http://forums.gtrcanada.com/showthread.php?t=13657[/url]
    While you're doing that test your O2 sensor, it should flash between 5-10 times in 10 seconds. If your codes came back 55 then you'll need to go threw all these step by step If it showed you something, chances are that is your problem Try searching through here to see if you can fix it though.

    2.) Check for vacuum leaks- to do this get a propane torch and don't light it, and just run it along all the vacuum lines in your car slowly while the car is running, if the idle jumps, you have a vacuum leak. Replace the vacuum line. Take your car for a ride ( remember to shut off the torch ) and see if this fixes your problem.

    3.) Try resetting your ECU --Always start with the cheapest fixes first, and work from there. To do this simply take your negative battery terminal off and step on the brake for about half a minute.

    4.) Try adjusting your Throttle position sensor(TPS). To do this manually with a multimeter--yess you'll need one for 2 parts of this howto--Locate your TPS. It is a small black box on your throttle body. Once you've found it you'll see two wires coming out of it-DO NOT TEST THESE WIRES. You want to look under that box, you'll see three wires connecting to your TPS. Your going to want to tap into the middle wire. Now, turn your key to the ON position (inside car) and then go back under your hood. Take the positive probe from your multimeter and tap it to that middle wire, and then ground the negative probe anywhere you can ground it. Now if you see your voltage above .5 you're going to want to reduce it to under. I would go .48 to be safe. If it is above this you will have hesitation problems with the throttle as it starts throwing bad codes. To adjust the sensor just unscrew those two bolts holding the TPS to the throttle body a little bit and wiggle it. This is probably the hardest part using all three of your hands. Anyways adjust it under .5. If it is way lower than .5 then adjust it higher. Do this until you're around .48~.49.

    4.)Try cleaning your maf--Hopefully those two things would have solved your problem, but if not continue on to testing your MAF sensor. Your maf sensor is located behind your cone filter (hopefully you have one) or stock airbox. It is a little black cylinder with a box sticking out of it. Once you have removed it be sure that it is cold (haven't driven car for a couple hours) To speed things along put it in the fridge. If you don't do this you will ruin your maf. Now, once it is nice and cool look at your maf, You'll see an ugly sensor behind the mesh screen. Get some Brakeleen or electrical contact cleaner and spray that thing down along with spraying the screen of the sensor (do both sides) and then whipe it down. Let everything cool off and the chemicals to evaporate. Hopefully you will have cleaned the sensor and may fix your problem. Take it for a drive. If not you're going to need to test it more

    5.) Resoldering the connections on your maf-First of all before doing this try someone elses Maf sensor that you know is working well. It will save you some time. Follow procedure three to get your maf off the car and once you have done that look at the top of the black box sticking out the side. The top is sealed by rubber. You're going to have to use a exacto knife or something sharp to cut through this rubber part. Once you have done so pop it out (can be difficult use something as a wedge to help it out . Now you will see a copper plate on the top, and then look to where the wires usually plug into the maf on the outside. Now look how they connect to the internal part of the maf. You're going to be resoldering this today So warm your soldering iron up and destroy these connections. Spray them down with electrical contact cleaner (not necessary but advised). Now get some shiny new solder and redo the connections ( don't be afraid to use a lot ) but don't touch the plastic sides as you will melt it haha. Let everything cool off. To reassemble you're going to want to use some INSTANT GASKET. You can find it at canadian tire for about $5.00. Rub that around the sides of the plastic square top you just took off. And reinsert. Let everything dry/set and take it for a drive. If you tested another MAF sensor and it fixed your problems, and this did nothing you need a new maf. If this fixed your problem, GREAT!!! If not, proceed to step 5.

    6.) CLEANING/Testing COILS / Change PLUGS/ and goodies
    Okay so this is where it gets fun and you'll have to use a strange tool called an Alan key and a spark plug socket. Okay so use the Alan key to take off your spark plug cover. It's that black thing that goes between your valve covers. You'll need to remove some of your intake piping to do this. Once you have it off (see it wasn't hard) You'll see 6 black things, those are your coils, and under them are your sparkplugs Yes I am dumbing this down for the non-technically inclined people. Okay, so first things first if you see any red dust go get your cars timing redone and get new pully's /bearings. If not, proceed! To run a basic test, reconnect your intake piping and start your car. Unplug one coil at a time and see if your car runs like crap. If nothing happens that coil is dead and you need to replace it. If the car runs bad when you unplug them your coils are functioning (okay, maybe good, maybe bad). Now we're going to test for resistance. To do this remove one coil at a time and use the resistance testing function on your multimeter and tap it to the Positive and negative parts of your coils. It should be clear which one is positive and negative as it says right on the coil above where the plug would connect
    This should read between .6-.9 ohms. If not in this range you need a new coil. Repeat this on all coils. If changing the coil didn't help, proceed and follow directions on this link:[URL="http://forums.gtrcanada.com/showthread.php?t=16618"[/url]
    While you're in there you may as well change your spark plugs.
    I recommend BCPR6EIX(iridium) or BCPR6ES(copper). You can also go up to a 7 grade plug as well if you wish, but isn't needed.

    7.) Test your Igniter pack -- I hope the above solved your problems, if not your car is sounding like mine and the problem is hidden somewhere . To test your igniter pack you're going to need to get another one (borrow one from another GTRCR) and take it for a ride. If there is a noticeable difference get a new igniter pack. If not, continue

    8.) Checking PCV valve and lines - To do this locate your PCV valve. It will be a weird looking bolt thing connecting to the front most part of your intake manifold. It will have lines going across the engine as well. To remove this, just untwist the bolt.. duh. Be careful with the lines while removing this as they are old and have oil in them (oil eats rubber) and will crack easily. Before removing it pinch all your lines first, if they are hard then buy new lines and replace them as you're doing this step. If they are leaking it will cause issues as well so replace as needed . You can find the rubber hoses at Canadian tire for about 5bucks per 6 feet. Now once you have the PCV valve off and you've changed your broken hoses take some new hose and attach it to the front of the valve and blow. Did any of the air get through (and do you feel light headed from fuems?) If the air came out the other side then good! your PCV valve is fine. If not, replace it.

    9.) Changing fuel filter-I sincerely hope your not on this step, but if you are. We're going to talk about fuel systems . This is the nissan part number:16400-53J10 so you can pick that part up at your local parts store. now to locate this look at your engine from the front of your car, look to the left and down. You'll see a metal tin with a line going to it. That is your fuel filter. Now remove these lines. (you might get fuel everywhere!) But if you want to avoid this simply open the fuse box, and pop out the fuel pump fuse and try and start the car. It should drain the lines. Now remove the lines after shutting off your car and replace with new fuel filter (This is probably the hardest part of this howto... Do your hands hurt yet? Now take your car for a drive, see if this solved your problem. Hurray it did? GOOD! If not, try next step .

    10.) Test your fuel pressure regulator - To do this locate your fuel pressure regulator. It is located underneith your PCV valve. It's a black looking thing that has a hose going into the intake manifold. Now to test, be careful and remove the hose connecting to the intake manifold. Now you need to plug that hole, to do this simply get something rubber or plasic that will slip over it and plug it. I used a marker cap. Then take something to plug the rubber hose as well ( i used a screw and some tape). Take it for a small drive, but a SMALL one. See if this solves your issue. If not, reconnect. If it did buy a new one.

  • #2
    11.) Test your fuel pump, well actually there is no real way to test it if it works and your having issues, but anyways REPLACE YOUR FUEL PUMP. I went with a 255 litre per hour pump off ebay that resembled a walboro design. I'd recommend a walboro pump. A '98 240sx pump will work (thanks Cory). To change this, open your trunk, now you'll see 4 bolts on the right hand side of your trunk, and another two to the right of it. Start by removing the two bolts to that metallic cover thing where the electrical lines are connected. Now once you've done that disconnect it, go start the car. This is going to drain the lines. OTherwise you'll do what I did and spray 94 octane all over yourself! . Once you've done that proceed to this link to follow a very good DIYhttp://forums.gtrcanada.com/showthread.php?t=23083
    Now this fixed my problem and holy **** is my car fast now lol.

    If your car is having idling issues adjusting the TPS might solve it, if not try following this tutorial: http://forums.gtrcanada.com/showthread.php?t=24404

    Hope this helps you all, the only thing I didn't cover in this tutorial is testing your carbon cannister, but rarely it is the problem. If you've done all this and want to test the carbon canister you can pm me and I'll tell you. Be sure to check the lines connecting to it.

    Also while I was doing this I also picked up a can of (SEA FOAM) You can find it at NAPA for about $11.00. It cleans out EVERYTHING!!! To use I put about 1/3 in my gas tank, 1/3 in my oil, and then the third part is tricky. I disconnected the Fuel pressure regulator and connected some clear tube from the intake manifold and then the other part back into the seafoam can and then let it suck it all in slowly, your car will start to die while doing this so you'll have to blip on the throttle body a bit (use a friend) your car will also shoot out some white stuff. Once you've got the whole can in there, shut your car off for 5 minutes and then start it up and you'll have to blip the throttle a bit and your block will fill up with Gross white clouds...My car shot out smoke rings haha. This will help your hesitation and all and all run your car better. Definitely recommended.

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    • #3
      Glad to hear you finally got it fixed
      1989 Gumetal GT-R - Nismo Turbo etc
      ivoac.ca Join the fight for the right! If you're not part of the solution, you're part of the problem......

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      • #4
        Well thanks to your help as well buddy! And the permagrin just won't fall down. It's like all the mods I did to the car finally caught up with the fuel flow and I gained like 80 horsepower haha! It feels that way anyways. Scary fast now haha.

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        • #5
          Sticky material for sure!

          Nice job writing up a logical how-to. This will answer about 50% of all tech questions!!!

          Cheers,
          Dan
          sigpic
          The Beaumont Connection

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          • #6
            Thank you, I hope I can spare some people some time,money, and frustration LOL! This at least gives people a reference point for problems they are having. As well as combines everything into one document!

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            • #7
              one note to your seafoam idea.

              If you have the spark plugs off anyway a cap full of ANY Automatic transmission fluid into EACH spark plug hole (while it is out) will work the same as sucking the sea foam through the vacuum line. ATF has some cleaning detergent properties and it works to the same affect. Most people should have it lying around anyway, so you can try that to clean the inside.

              Also, it would be GREAT if you snap a picture that shows what you are talking about in most of your diy. Even if you just take an engine picture and put arrows with number beside it so everyone can see what part you refer to.

              One last thing. The parts you recomend replacing could use part numbers, or equivalant parts from other cars. ie: Fuel filter from a maxima (I think thats what it was), spark plugs are the same as what is listed for a 91 honda civic, PCV valve was the same as the 240sx??

              But other than that its a GREAT write up. at least now we can all be dicks when people ask about their hesitation problem and post this link to them.

              I always wanted to be a **** anyway


              Good Job

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              • #8
                I wasn't sure about the fuel filter. Isn't it 300zx? or is it maxima. Let me know so we can update this. I will for sure add pictures in future but I don't have a camera because I'm ghetto.

                The spark plugs listed are the ones people have been using in their cars without problems. I am using the BCPR6EIX-11 regapped to .8. I don't think there is an inaccuracy there. As for the PCV valve is it the same as 240sx?

                And thank you for the ATF tip I used to run it in my oil to quiet down my lifters in my last car. Worked well. Seafoam is 11 bucks so I'll stick with that and it can go everywhere you want it to lol. Even cooking.. well not cooking, but hey Send me a PM sticky so we can update some inaccuracies in this thread.

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                • #9
                  fuel filter is NOT the 300ZX one (unless you leave the top bolt out) I used the maxima one.

                  The spark plugs you used are fine, But I was saying that when you go to the store to look for plugs, rather than looking for the part # posted on here, you can just look up "91 honda civic DX 1.5" in the book and see what plugs they have in stock. And they will work.

                  I dont know for sure about the PCV valve.

                  Ill snap some pics and post them up here later if nobody else does.

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                  • #10
                    fuel filter is 1996 Infiniti J30. Looks identical to the one I replaced it with. I'm gonna try 300zx next time, I'm sure its higher flowing.

                    oh yea and I think it would be good to add check for boost leaks to the list. I know thats one of the next things i'm going to get at to solve my high rpm stuttering.

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                    • #11
                      Bignate, my rpm stuttering (hesitation) was caused by a bad fuel pump. Perhaps you should look at yours as well. Try going through the list. It's not always what it seems :P With a boost leak you should be losing boost though? Are you losing boost?

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                      • #12
                        well I've only got the stock boost gauge so i cant really be sure. I imagine it would have to be a pretty major leak to show on the gauge. It pulls really hard until i get over 5000rpm or so then it stutters all the way to redline. Pulling the the in tank pump and checking out the sock is one of the next things I'm gonna try. I think I may have found the culprit yesterday though. Yanked out the ECU and found a Kakimoto racing sticker on the side and they had the thing sealed with their lil twisty things with their logo on it (cant think of a good word for these lol). The ecu looks like the stock one (I think) but I'm sure its been tuned.

                        so what ive done so far:
                        changed plugs
                        checked coils (all under 1ohm, would have cleaned them but they looked 2 days old)
                        changed fuel filter, air filter
                        reset ECU
                        Cleaned MAF
                        tryed some octane booster with sunoco 94 with no improvement

                        What I need to do:
                        check in tank pump/filter
                        check IC piping
                        investigate ECU
                        fuel pressure test
                        check\clean TPS
                        test with different ignitor

                        anything else I should give a shot?

                        oh yea should also mention its a GTR. I just realized this is in the GTS-T section

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                        • #13
                          It could very well be your ECU. I was having pretty much the same problem as you. Mine was a broken fuel pump. I was running too much boost for the stocker to keep up haha.

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                          • #14
                            not to jack your thread, but if you replace your fuel pump with an aftermarket one, you should get an adjustable fuel pressure regulator as the walbro flows way more than the stock fuel pump did. stock regulator wont last long and your mileage wont be good....

                            *EDIT* bignate try taping the bottom of your coils up , sounds like you have the same problem i did on my 25det

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                            • #15
                              Any recommendations for the adjustable fuel pump? I hear there are variable ones...I want something that will be pretty much bolt on.

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