Undriveable due to massive flat spot below 5000rpm
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Thanks for suggestions so far guys,
Car now in Hayling Island, will pull all plugs and replace as a set, got 12 plugs with the car.
Had a good look at all the inlet and hoses all seems fine, VAF moves easily by hand with no feeling of tightness anywhere in its travel. Will give it anther try tomorrow evening after work
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Don't wanna sound like how to suck eggs, As DJ suggested take one lead off at a time but with engine running, if no change in running/revs, then it will highlight fault with lead/cylinder/plug etc
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Sounds like spark trouble a bit to me. I'd borrow DJs disty and see if the coils on it's way out.
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Thanks again for suggestions.
One query - if it were problems with sparks wouldnt that cause problems at any speed?
This idles fine. Over 3k or more it is smooth.
If very gently accelerated from idle to 3 k it is smooth
When accelerated like normal it has a horrendous flat spot - possibly more like air/fuel mix?
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For the sake of 30 mins of fiddling i'd find someone local and borrow their TB inc TPS and IAC, induction pipe and VAF that would rule out the whole lot in one go.
Find someone willing and start swapping bits out.So many things can cause this you just have to rule them out one at a time so start with the easy and free stuff before you go buying stuff that does not need replacing.
Do the basics remove induction pipe and check for cracks, check all vac lines breather pipes and fuel pipes for kinks or leaks, smell injector area for leaks, ground test the plugs, check the fuel pump is working.
Is it worse when cold or hot or the same?
Does it idle ok if left? is it stable or hunting?
is there any misfire? listen next to the sxhaust for one at idle.
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@4a56a0479e:
Is it worse when cold or hot or the same?
Seems to be the same hot or cold
@4a56a0479e:
Does it idle ok if left? is it stable or hunting?
Idles fine, initially at 1500 when cold, dropping down to 800 warm
@4a56a0479e:
is there any misfire? listen next to the sxhaust for one at idle.
No misfire ate idle, no misfire once above 5000. No misfire if very gently accelerated in neutral, misfires really badly or doesn't pick up at all when accelerated normally in neutral.
Car is parked in layby on busy road so can't test for acceleration when driving in any safety.
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@9efc1501d5:
Is it worse when cold or hot or the same?
Seems to be the same hot or cold
@9efc1501d5:
Does it idle ok if left? is it stable or hunting?
Idles fine, initially at 1500 when cold, dropping down to 800 warm
@9efc1501d5:
is there any misfire? listen next to the sxhaust for one at idle.
No misfire ate idle, no misfire once above 5000. No misfire if very gently accelerated in neutral, misfires really badly or doesn't pick up at all when accelerated normally in neutral.
Car is parked in layby on busy road so can't test for acceleration when driving in any safety.
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hi mate think i have seen your car parked outside the church ?! I am on creek road but i don't have any vsix parts I'm afraid but if you need any tools or a hand gimme a yell
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Great, thanks for the offer! And, yes, it is the one outside the church :P
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Do all the basic checks to rule them out, then….
Could be the VAF or TPS.
If it was crank sensor I wouldn't expect it to still work ok at higher revs, same for the fuel pump.
Is there anyone near enough to pop down and swap some parts over?
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Might be worth checking for leaks around the variable resonance induction system (vris), those should open at idle but then close after about 1500 then open again at 4000, cant remember the exact values but not far off, its odd to have something effect such a large range of the revs, but the vris does effect a large range of the revs and with v6 engines its very common to have a flatspot thats due in part to the way a v6 works and its need for a variable induction system.
At idle itd make minimal noticeable difference as theres no load on the engine, but once load is applied and the vris is in the wrong state for the rpm/demand then the fuel to air ratios would be squiffy and bogging your car down ie flatspot.
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This is now fixed and currently relisted on fleabay
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Sorry for late replies to you all but have been busy with other things. Car is now fixed and on eBay, 20 watchers but no bids at yet :(
I checked out the induction system, changed the fuel filter and went to the diag box after making up a test lamp. Unfortunately the box was unmarked and it took me a while to find a pin out for it.
Plugs were changed and I have been driving it daily for the past week to see if any problems recur. Take the long route along Southwood Road Hayling just to check on the MX-3 parked there.
I have updated the ebsy ad to point out that if no bids received by Thursdasy it is being withdrawn, I am very impressed with the car now it runs well and will put an MoT onit and keep it.
thanks to you all dor your helpful suggestions, guided me in the right direction and taught me a bit about modern electronics.
My other car is a 1954 Daimler Ferret
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Do we know what the fix was?
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First off tried to find any air leaks in induction area - no leaks and nothing different when put back together.
Battery then needed charging - all the while the car was in the layby outside Hayling Church, about 3 miles from home so there were brief visits each time I was passing.
Tried it with newly charged battery, started ok but hideously flat before about 5k when accelerated hard, would run ok with very gentle acceleration.
Found it impossible to try and hold multimeter probes on TPS while playing with it on the car so that came bake home to be tested, next the VAF - both tested out ok.
Ordered a fuel filter from Japarts though filter on car seem clean and shiny on outside, slight improvement but still hesitant.
Pulled all six plugs, a couple of tubes had oil in them. Replaced plugs and it seemed a lot better. Been driving around the island and brief bursts on the M27 and seems fine.
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So it was a misfire?
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Originally it was far more than a misfire.
I picked the car up and it seemed fine. Got on the M27 at junction 1 and came off at the base of the A3 to go the back way to Tesco to put some fuel in. At that point, pulling away from the traffic lights, it failed to respond to the throttle. It was just driveable by accelerating to 3000 in neutral, putting it in gear and dropping the clutch.
After filling to see if fresh fuel would help it was just as bad and became worse when trying to get onto Hayling. Eventually stopped to call the AA who were unable to do anything except drive behind as I kangarooed the rest of the way home.
I think it could be a combination of low fuel/ bits blocking the filter (though it was fairly new), tired plugs and removing, cleaning, replacing components making the electrical contacts more secure.
No one fault as such but just a combination of things which together made the car sick. As each cause was investigated and eliminated the car got progressively better.
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You never mentioned the misfire before, just a flatspot
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No you called it a misfire - to me not responding to the throttle at all above idle and then coming in with a bang at 3000 or more revs is a massive flat spot.
One thing I forgot - VRIS was operating, gave the linkages a good does of WD-40 and anything else that looked like it could do with some got a squirt too. That may have helped.
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@24751c52fd=macspite:
misfires really badly or doesn't pick up at all when accelerated normally in neutral.
