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Thread: Stumbling?

  1. 24th August 2017, 04:25 PM #1
    Fourgearsticks's Avatar
    Fourgearsticks
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    Stumbling?

    Hi again, since changing thermostat to an 88c one (old one was stuck open) the V8 Disco 1 is running crook. It goes ok at full throttle (as well as a baby V8 can go pushing around 2 ton) but when you throttle off it "stumbles" and misses.
    The machine has an unknown history, it has done 210k. I have put in new plugs, new dissy (old one vac advance no good), new leads. Looks like somebody has replaced new sensors on the back right of the plenum, 2 at the front of the inlet manifold and the one on the inlet to the plenum. Looks like the previous owner has had trouble and tried to fix by replacing the bits I mentioned.
    There was one injector completely disconnected and one on the other side with a terminal pushed into the plug and not connected.
    Hooked those up but still stumbling and missing as yoo back off and just cruising with minimal throttle. When full throttle no problem.
    What's left besides injectors or ECU? Do injectors normally run passed 210k without trouble? Would some dodgy injectors give the symptoms I mention?
    Thanks
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  2. 24th August 2017, 05:17 PM #2
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    bee utey
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    There are only two sensors on the engine itself that affect the fuel delivery, the throttle position sensor and the ECU temperature sender at the front near cyl #1 injector. Sometimes people manage to swap the injector lead for the temp lead as they use the same style of plug. The other sensor is the MAF which is in the air intake near the air cleaner box. The MAF has an idle mixture adjustment screw that may help, others will chime in on measured voltages that you should see at a particular wire. The temp sender for the ECU is not the same as the one for the dash gauge. It should read approx 280 ohms across its two terminals when at operating temp.

    Around the back of the plenum is the fuel pressure regulator. This may have failed or the vacuum hose has fallen off. Check for signs of fuel in the vacuum hose.
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  3. 25th August 2017, 11:25 AM #3
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    Are the engine ECU and flapper box thingy from a 3.9 (1994) interchangeable with the (1991) 3.5?
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  4. 25th August 2017, 05:12 PM #4
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    Turns out the flapper box is interchangeable, changed it no difference, still stumbling. Put the old one back on again.
    The fuel injection computer has different part number and different mount on 3.9 compared to 3.5 but still same number of terminals. I swapped the fuel injection putor and all good, smooth as a V8 should be. So looks like it wuz putor
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