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  • Engine lumpy

    Need some help when i start the car up after its been stood for an hour or more its very lumpy but starts to idle a as normal after a few minuets and also drives normally any thoughts on this would be helpful.

  • #2
    Fault codes?
    Panthero Coupé quattro 20vt
    Indigo ABY coupé
    Imola B6 S4 Avant

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    • #3
      Sounds like a leaky fuel system, air gets into the rail , can take a while to purge at idle.

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      • #4
        Havn't plugged into vcds yet, didn't think it would pick that sort of thing up.

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        • #5
          Well it's certainly a better bet than us guessing
          Panthero Coupé quattro 20vt
          Indigo ABY coupé
          Imola B6 S4 Avant

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          • #6
            doesn't actually take that long but i did have an incline it was a fuel problem just not 100% but thanks for the info.

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            • #7
              Well plugged into vcds at last been so busy and no fault codes even when the engine management light flickering all the time. reckon an air leak around inlet.

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              • #8
                Watching this.

                My car Cq20v is doing same... I've been checking fuel pressure at the rail and it is right but falls away quickly when switched off. I'd have put money on this being the problem but a for swap and rock steady system hold pressure didn't cure it.

                No fault codes and after literally 2 mins of idle or driving the lumpiness clears and the car goes really well. Plugs check shows no oil, the right colour and no smell of petrol from cylinder.

                While investigating further I rigged up my rail in a spare manifold and connected to fuel lines. Injector 1 and 4 were wet around the nozzle while under pressure. Not dripping but wet and I wonder if these injectors are over spraying as a result of whatever fault is causing the leak.

                A new set are on their way so I will find out soon!

                Beyond that I'm stumped. Lambda is not that old, certainly less than 20,000miles and the engine behaves impeccably once hot.

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                • #9
                  steve briance , certainly sounds like a bad injector. Are you still on the original Hitachi injectors?

                  Also could be a sign of a weeping headgasket, wetting the plugs and causing a misfire on initial start.

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                  • #10
                    These are bosch injectors. Prob 7 or 8 years old now, possibly older (they have been on a while anyhow!) i thought they might have lasted longer than that I sincerely hope it isn't head gasket leakage, this engine has only done 350miles since rebuild! New gasket, top of block skimmed, torqued down properly and no sign of water loss. The car flies once it is up to temp so I would be surprised if there were gasket problems. I've not done a compression test yet as was waiting for running in to finish but on checking plugs, they were all the same and none of them had oil in them. This could mean all bores are getting contaminated or none of them are

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                    • #11
                      The other thing I thought I knew and had confirmation today is that lambda probe doesn't get involved in cold starts so that can be ruled out.

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                      • #12
                        Look at the injector wiring harness also, most are about a decade past their best
                        Panthero Coupé quattro 20vt
                        Indigo ABY coupé
                        Imola B6 S4 Avant

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                        • #13
                          Yup, sounds a very sensible idea, I keep meaning to pull mine apart and inspect, just never around to it yet.

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                          • #14
                            Funnily enough, this morning I checked the injector plugs.

                            All loom connectors apart from the injector connectors have been changed as most were crumbling. The injector plugs are actually still o. K which surprised me assuming they were of the same age as the rest of them. This doesn't mean the wiring is up to scratch and I know from handling it recently it did seem quite stiff. Will try the injectors first as they are on their way and did show a visible problem.

                            I've got a spare loom which I might get round to replicating as future mini project. The shape of it is quite controlled, it fits with no slack at all in the cable tidy!

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                            • #15
                              Error404 do you make injector harnesses by any chance?
                              Honda CBR 1100XX Blackbird Turbo....undergoing major changes.....
                              S2 Coupe... bit easier off the line...
                              '03 ZX12-R daily hack.... lots of nice bolt ons...

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