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| Hybrid34 |
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Hi guys,
Really need some help here as its driving me nuts. EB Fairmont with a EL motor on LPG, Runs fine on LPG, however when flicked over to petrol she Spits, Sputters, Hesitates ONLY under load. If its in a low gear & low revs (under 2g), she'll pop and backfire Free reving is fine. I've replaced - New Fuel Pump - New Injectors (AU Injector type) - Cleaned Fuel Rail - New Fuel Filter - new dizzy - new coil - new plugs and leads The fact that LPG runs smooth through the rev range and gears, makes me think its fuel related, but I've changed EVERYthing... Could it be timing? even though LPG is fine, and would timing cause those symptoms? Any help appreciated, Cheers, Ash
_________________ Sucessful trades with Schmee, Braidy, Niko, The_Ghost, YBHVE4, Stalker
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| efxr6wagon |
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I seriously feel your pain. What a mission!
The symptoms sound very much like a lean misfire. Have you tested the fuel pressure regulator? Or swapped it for a known working one? Or possibly a vacuum leak, especially in the hose going to the regulator. When you open the throttle under load, you have less vacuum - more absolute pressure - in the intake ports, so less fuel will be "sucked" out of the injectors (technically, less pressure drop). The regulator is supposed to compensate for this by increasing your fuel pressure in parallel with manifold absolute pressure, keeping the pressure drop across the injector constant. If the regulator isn't working properly, you will lean out under load. With everything else being brand new, this is the only possibility I can think of. A real long shot: a blocked cat. But that should be a problem under LPG too.
_________________ 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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| Hybrid34 |
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Wow thanks for that response - that makes so much sense.
not the cat as it doesn't exist (we won't go there) 1. Potentially stuffed fuel reg 2. Vacuum leak - but if it was a vacc leak i thought LPG would be affected? Thinking out loud but LPG mixtures may not rely on vacuum as its done by the converter, where as fuel does rely on vacc? I've got a squeak (like someone with a blocked nose sniffing), from a unit behind the glove box when I first accelerate. Its not really a 'sucking'vacc leak noise, but decreasing squeaky noise upon first initial acceleration. Thanks again, Ash
_________________ Sucessful trades with Schmee, Braidy, Niko, The_Ghost, YBHVE4, Stalker
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| Hybrid34 |
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Wow thanks for that response - that makes so much sense.
not the cat as it doesn't exist (we won't go there) 1. Potentially stuffed fuel reg 2. Vacuum leak - but if it was a vacc leak i thought LPG would be affected? Thinking out loud but LPG mixtures may not rely on vacuum as its done by the converter, where as fuel does rely on vacc? I've got a squeak (like someone with a blocked nose sniffing), from a unit behind the glove box when I first accelerate. Its not really a 'sucking'vacc leak noise, but decreasing squeaky noise upon first initial acceleration. Thanks again, Ash
_________________ Sucessful trades with Schmee, Braidy, Niko, The_Ghost, YBHVE4, Stalker
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| efxr6wagon |
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Yeah, vacuum leak is a bit of a long shot too. But if it's in the vacuum line to the fuel pressure regulator, the regulator will likely not work properly, while it may not produce significant problems elsewhere, so you wouldn't necessarily notice it under either petrol or LPG. I don't know enough about LPG systems to know how a vacuum leak would affect one.
Could also be a blocked vacuum line to the fuel pressure regulator. I may be way off the mark, but you've eliminated pretty much all the other possibilities with new parts. When you first accelerate, the vacuum reduces suddenly to almost nothing, and vacuum is what powers the ventilation controls sitting behind the glove box. So, it may be nothing. My AU makes a slight hissing sound constantly when the temperature control is on full cold, but it doesn't affect the car otherwise, so I ignore it.
_________________ 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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| SWC |
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Have you checked your O2 sensor?
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| efxr6wagon |
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You can eliminate the O2 sensor fairly easily. Disconnect the sensor and reset the ECU to clear the fuel trims (unplug it for a minute). Do not reconnect the sensor. That will force the engine to run off the fuel tables alone, with no O2 input. If it runs fine like that, then the sensor is likely your problem.
_________________ 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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| Gab1 |
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I've seen all sorts of weird problems caused by the ignition coil not getting decent power and ground, but if that was the case, I'd have thought you'd have noticed that on LPG too. I'd be checking things like:
Fuel pressure Ignition timing - it could be WAY too far advanced for petrol MAP sensor - seen these cause no issues WHAT SO EVER when disconnected even, running on LPG, then when it's on petrol it wont even run. Wiring to all your Gas stuff - my mates EL will run fine on Gas, but will only run on 3 cylinders when on petrol if 1 wire comes off 1 relay that's to do with the Gas. What sort of Gas system do you have? BRC? Impco? Gab |
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| Mickford au99 |
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My problem with a 99 au forte was very similar to what you're describing. Mechanic found the harmonic balancer rubber was knackered causing pulley to wear, and belt was hitting the knock sensor wearing it away. Car would run properly for about 15-20 mins before everything was hot. Surging while driving, sputtering and stalling at traffic lights. Running rough as guts after stopping at roundabouts/intersections.
I had checked leads, plugs, and changed fuel filter. |
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