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| efxr6wagon |
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Last week, my AU2 XR6 VCT suddenly developed a rough idle (fine driving to work, rough as soon as I started the car to head home). It feels like a lumpy cam - NOT like running on five cylinders. There is also mild popping out the exhaust at idle. Fuel economy is unaffected, not running rich, and idle RPM is normal - not hunting. It's especially noticeable when crawling along at idle riding the brakes in heavy traffic - very jerky. It runs perfectly normally at anything other than zero throttle.
So far: - new coilpack - new spark plugs - checked ignition leads (all fine) - cleaned throttle body and ISC valve - checked intake manifold, vacuum hoses & brake booster for leaks using start spray - checked PCV valve Tonight I checked the throttle position sensor. Volts are 0.6V zero throttle, 4.2V WOT; manual says approx 0.7V and 4.5V. Resistance is 7K ohms zero throttle, 3.5K ohms WOT; manual says 3K and 500 (0.5K) ohms, respectively - quite a difference. Could this be the cause of my rough idle? ECU not recognising that the engine is in idle mode? I tried cleaning the TPS with Contact Cleaner, but it made no difference. And I don't have access to a scantool to pull fault codes. Thanks for your help. EDIT: Have bought a used TPS; will install on the weekend and let you know how it goes.
_________________ 95 EF XR6 wagon, 17" FTRs, DBA rotors, KYB/Koni, AU bottom end, ported EF head, backcut valves, SS Inductions, Territory intake, 10.2 CR, Auckland 1258 cam, vernier gear, PH4480 headers, no cat, Tickford 2.5", 2800rpm stall, J3 chip |
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| efxr6wagon |
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Well, it wasn't the TPS. The new (used) one made no difference. I have a spare set of injectors, so will try that next, I think - unless someone has a better idea.
_________________ 95 EF XR6 wagon, 17" FTRs, DBA rotors, KYB/Koni, AU bottom end, ported EF head, backcut valves, SS Inductions, Territory intake, 10.2 CR, Auckland 1258 cam, vernier gear, PH4480 headers, no cat, Tickford 2.5", 2800rpm stall, J3 chip |
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| Stealth6 |
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When its idling and you blip the throttle, the revs will rise (obviously) but then do the revs drop right back to basically nothing? or just go back to normal idle?
_________________ Yep, I don't know what to write here... |
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| efxr6wagon |
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The revs go back to normal idle (750 rpm), but sometimes hang at 1000-1200 rpm for 3-5 seconds. I don't think that's new though.
_________________ 95 EF XR6 wagon, 17" FTRs, DBA rotors, KYB/Koni, AU bottom end, ported EF head, backcut valves, SS Inductions, Territory intake, 10.2 CR, Auckland 1258 cam, vernier gear, PH4480 headers, no cat, Tickford 2.5", 2800rpm stall, J3 chip |
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| efxr6wagon |
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Well, replaced all the injectors with clean used ones, and no change. Tried all the vacuum lines and intake manifold gaskets with start spray, and no leaks that I could find. Unless it's one of the lines inside the dash actuating the ventilation system.
I have disconnected the battery to reset the computer, to see if that helps. Failing that, I have a spare ECU I can swap in. Any other suggestions?
_________________ 95 EF XR6 wagon, 17" FTRs, DBA rotors, KYB/Koni, AU bottom end, ported EF head, backcut valves, SS Inductions, Territory intake, 10.2 CR, Auckland 1258 cam, vernier gear, PH4480 headers, no cat, Tickford 2.5", 2800rpm stall, J3 chip |
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| efxr6wagon |
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Resetting the computer did nothing.
I swapped the ISC valve - it made no difference. Disconnecting the ISC dropped the revs by about 100rpm, but it still idled rough. Next is swapping the ECU. Any other suggestions?
_________________ 95 EF XR6 wagon, 17" FTRs, DBA rotors, KYB/Koni, AU bottom end, ported EF head, backcut valves, SS Inductions, Territory intake, 10.2 CR, Auckland 1258 cam, vernier gear, PH4480 headers, no cat, Tickford 2.5", 2800rpm stall, J3 chip |
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| efxr6wagon |
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Found the problem. Intake manifold gasket was leaking. Could only find it by spraying start spray with the nozzle basically touching the gasket. When I took the gasket out, it was so brittle that it broke into multiple pieces. Replaced it, and it's sweet again.
_________________ 95 EF XR6 wagon, 17" FTRs, DBA rotors, KYB/Koni, AU bottom end, ported EF head, backcut valves, SS Inductions, Territory intake, 10.2 CR, Auckland 1258 cam, vernier gear, PH4480 headers, no cat, Tickford 2.5", 2800rpm stall, J3 chip |
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| tickford_6 |
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Posts: 6449 Joined: 11th Nov 2004 |
efxr6wagon wrote: Found the problem. Intake manifold gasket was leaking. Could only find it by spraying start spray with the nozzle basically touching the gasket. When I took the gasket out, it was so brittle that it broke into multiple pieces. Replaced it, and it's sweet again. That test work better with carby/throttle body cleaner. Just give the manifold gasket area a good soaking. the engine will smooth out when you hit the section of gasket that leaking. It's pretty common on AUs these days. |
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| Shen Long |
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Age: 49 Posts: 391 Joined: 22nd Aug 2008 Ride: 2002 AUII Fairlane Sportsman V8 Location: Roxby Downs |
efxr6wagon wrote: but sometimes hang at 1000-1200 rpm for 3-5 seconds. This should of been a fairly good indicator that the inlet manifold gasket was leaking. my sis's EF was doing the same but sometimes at 2000RPM's |
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