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  • Stumbling...

    Well...That's what it is doing now. I recently had to do a valve replace, and everything went fine for a while...Now it is stumbling. A lot. At idle, it sounds like a minor backfire, at 3000rpm, it drops the revs to about 2100, and feels like the engine is trying to jump out the passenger side (LOL...I'm that good a driver, even the motor wants to get out and walk on the footpath)...I know that I stripped 2 intake manifold bolts, so I am thinking vacuum leak is most likely cause...I have looked everywhere I could on the net, and found no answer, so does anybody have any troubleshoot checklist that I can go through, in case I am wrong? Or better yet, has anybody had anything like this? The car ran fine for about 2 months after I rebuilt it...but sudden vacuum leak?....Thanks in advance...

  • #2
    i would be getting those stripped intake bolts fixed firstly as this could be your problem, leaking at the intake.
    NS 3.2 Diesel, Polor White , Black CSA Rims, HanKook Dynapro AT Tyres, 3 inch custom stainless steel exhaust with free flow Cat & Muffler, 50mm Lift, Old Man Emu Shocks and Springs, TJM Bullbar powder coated White, Custom 7mm Sump Guard & Transmission Guard, 8 inch LED Spotties plus 20 inch LED Light Bar, rear Reverse LED Light, ARB Roof Cage , Tiger11 Awning.

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    • #3
      Seems very strange to be a vacuum leak...It runs fine, then intermittently stumbles, after reaching operating temperature, it gets worse i/e Runs fine when cold, stumbles when warm, and getting worse... I am going to get heliocoils in, but I am thinking that the most likely cause of this would be a brummy O2 sensor...Which brings me to my next question...Where is the O2 sensor? I have the haynes manual, it tells me how to test it, but not how to find it...It is a 6g72 SOHC...I have looked at the exhaust, but can't spot one, so it must be elsewhere...Any chance of a pic?

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      • #4
        I found the O2 sensor...It was on the exhaust lol So I took it off, gave it a clean (there are no spare parts today), and while I had it off, I started the car. It sounded beasty Anyway, same issue with the O2 sensor disconnected...Idles nicely for a while, then an intermittent stumble (rev drop)...SOoooo...It either is or isn't the O2 sensor (I am thinking it might be), but it needs replacing anyway (the surface is as pitted as a 14 year old boys face), so I will throw a part at it, anyway...and heliocoils...

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        • #5
          Ok...Put heliocoils in, checked all around...no intake leak...I can't get past the oxygen sensor/fuel delivery system playing a role...Then I started thinking (MIRACLE)..."Maybe I have an exhaust leak, that is allowing air to mix, prior to the O2 sensor...Will check that once the engine cools...but in the meantime, is this plausible?

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          • #6
            OK...Now I am starting to get cranky. I have troubleshot everything I can think of, and can find nothing. I listened all over the engine, and can't hear any leaks...The PCV valve, does however, make a really interesting sound...I panicked before I realised what it was, ticking away like a cicada under the rocker cover. Here is what I have tried.
            1) Disconnected each spark plug, and ran the engine. It happened throughout, so it isn't an individual cylinder problem.
            2)Replaced threaded bolts on intake manifold AND checked for vacuum leaks with tin of EZ start...No apparent leaks. Definitely not enough of a leak to create this intermittent problem.
            3)Checked PCV valve..It works.
            4)Tried to find EGR system...got confused, gave up, finally found it, realised that I had been using the lines leading to it, to hold my can of coke in place out of the sun...Found that the EGR sucks just fine...
            5)Checked Dizzy cap, and rotor...They are both a bit worn, and there was a bit of corrosion on the wire leading to cylinder 5...but still wouldn't explain the intermittent issue...That would be a more constant problem, but they are on the "to replace list"...two spots down from "car" but three spots above "wife"
            7) I heard an intermittent ticking...I am waiting until after dark to see if something is arcing out. I am thinking that it is likely to be the coil...I actually have my fingers crossed about that.
            8) Pulled the O2 sensor, and cleaned it up a bit. Strangely, when I pulled the oxygen sensor, the car didn't run any differently. I mean it had the same intermittent problem, and was as loud as all buggery, but it wasn't running rough all anything...I should check to see if I get an engine light if I disconnect it...

            Well, That's so far, and all I can think of...I'll be sure to let you know what it is, if I can work it out...Can anyone give me anything else to check, please? I am shnookered...

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            • #7
              have you looked at the ecu? could be having issues

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              • #8
                Yep. Switched out the ECU...forgot to mention that, lol. Also, it is now after dark, and I can see no arcing around the coil, or spark wires It is the damnedest thing, it only does it when hot. I am uploading a video to facebook now (Ignore the whinge...This car breaks down EVERY Christmas. Without fail...Grrr), because I don't know if I have described what it is doing, very well

                So for your viewing pleasure...My tacho...lol
                https://www.facebook.com/photo.php?v...type=2&theater

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                • #9
                  hmm, could be throttle position module, or the maf. have you checked the leads coming into the dizzy (the 4 on the front NOT the spark plug leads, i was having a huge issue with not firing and missing turned out to be wires into the dizzy not contacting properly. Could also be the sensor inside the dizzy

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                  • #10
                    Yep...Checked the tpm (switched it out with a spare I have)...I just decided to do the tried and true method for looking for a short, and hosed down the engine, while it was running...Top of the dizzy got wet, and it died. I took it off, no water inside...but disconnected the spark leads, now it is running like a dog...Missing on a couple of cylinders...It looks like the rotor has cut grooves into the dizzy contacts, and there is a bit of carbon on them...but would this explain an intermittent issue? Also, I just checked the spark from the coil is reddish...Isn't it meant to be blue?
                    I really am not rich enough to be throwing parts at the problem at this time of year...grrr
                    Last edited by Dreegle; 17-12-13, 10:34 AM.

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                    • #11
                      yeah its meant to be blue, and that dizzy cap dont sound to go think i paid about 60 for both rotar and dizzy cap.

                      i just spent about a grand getting mine back on the rd. my ecu blow up and the sensor in the dizzy and had to replace most of the wiring around the sensors and dizzy. as well as the coil, power transitor, leads, plugs, maf.

                      purrs like a kitty now

                      ps need to fix exhaust leaks now

                      cheers

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                      • #12
                        Resolved. I replaced the coil...didn't fix it...It was the dizzy. The guts of it was worn out, and metal had come loose inside it, causing it to slam into the side of the dizzy cap, and grind/misfire etc. I undid a couple of screws and tapped it a few times...metal shavings and a circular bracket looking thing came out. It is running now, 100%...BUT I am replacing the dizzy anyway...

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                        • #13
                          How big was the bracket and did it have holes in it?
                          97' NK 3ltr GLX LWB Manual | 3" lift | Wildcat headers | K&N air filter | 2.8 crawl gears | 4Terrain clutch | 2.25" exhaust | Factory locker rear | TJM 10,000lb winch | TJM snorkel
                          97' NL GLS LWB Auto | 6G75 3.8ltr | Redback Headers

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                          • #14
                            The "bracket" was about 5mm diameter, and one side had worn away...To give an idea of the size, I undid the plate around the dizzy plug (4 wires out the front), and tapped it with a screwdriver, and the metal shavings, and "bracket" came out. I don't know if it had holes in it or not, because it was too small...It came from the inside of the distributor...I'll see if I can find it, and put up a pic. I was just looking at the haynes manual, and it doesn't look like there should be anything in there...

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                            • #15
                              I popped it next to a 5c coin so you can see the size...Looking at the haynes manual, I don't know what it is from...Any guesses?
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