speedy88
Club Retro Rides Member
"Nice Cortina mate"
Posts: 2,281
Club RR Member Number: 118
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Hi all,
Sigma is doing something weird. She runs totally fine, I can go full throttle or cruise and she runs fine. That is until I've been on the motorway for more than 10-15 mins. Then suddenly she starts misfiring and stuttering almost like she's run out of fuel. It will do this at about 80mph and as I progress more miles, it does this at 70, 60 and then eventually 55. By this point I'm normally home.
It will be fine and then lose ALL power, not like it's just missing on one. Almost like it's run out of fuel. Then suddenly it will regain again after half a second.
Also, I thought this was isolated to the motorway until I was late for work the other day. I got 3 miles of pretty agressive driving and suddenly on one of the last corners to work, it did the stuttering thing again. Although it was only very short and didn't continue after that once I slowed down.
I really can't think what it is. Points might need doing at some point but they're not awful. Any ideas?
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Could be coil or condensor failing when they get warm - but more likely to be a restriction in the fuel feed to the carb somewhere.
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Rich
Club Retro Rides Member
Posts: 6,262 
Club RR Member Number: 160
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Car runs normally until motorwayRich
@foxmcintyre
Club Retro Rides Member 160
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+1 for what James said, but, when it gets It gets really bad, if you turn it off for a bit and wait, does the fault clear? I'm wondering if there is carb icing happening due to that missing bit of air box..
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speedy88
Club Retro Rides Member
"Nice Cortina mate"
Posts: 2,281
Club RR Member Number: 118
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Ahh bumhats, I wouldn't think it would ice up in this weather but I'll have a look at that, maybe do an experiment with some hoover hose or something. Coil is fairly easy to rule out but the (most likely) fueling problem could be a few things hmm. I really hope it's not that ancient fuel pump, they're truely the hardest thing to get hold of for these. Second hand ones are available from scrappies in australia, that is the only option... We shall see!
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sowen
Club Retro Rides Member
Posts: 2,245
Club RR Member Number: 24
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Sounds very similar to the fuel starvation I've sometimes had on my Rover, drives normally, short bursts of acceleration are fine, but cruising on motorways was near impossible, slowing down helped, and driving round towns wasn't a problem. I fitted a fuel pressure gauge in the end and that showed a fluctuating fuel pressure problem. I have now re-routing the fuel system (low and high pressure pumps) into a swirl pot as it started to do it again recently and has sorted it now for me.
Do you have any air leaks between the pump and tank, blocked fuel filters?
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goldnrust
West Midlands
Minimalist
Posts: 1,872
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I had very similar symptoms with a blocked fuel filter on the rx7. Though it only took 3-4 mins at 80 to show up. Blocked fuel tank breathers can have the same fuel starvation effect and it'll tank a good long run of continuous throttle before theres enough vacuum in the tank to cause problems.... 10-15 mins on the motorway would do it.
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PhoenixCapri
West Midlands
Posts: 2,684
Club RR Member Number: 91
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Like above, but I've also known odd problems like this with engine speed sensors (crank or cam sensor) working fine till they get hot at certain revs then they'll suddenly drop out. If it's got one of those and nothing else is obviously wrong, I'd change that since they're normally fairly cheap.
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Like above, but I've also known odd problems like this with engine speed sensors (crank or cam sensor) working fine till they get hot at certain revs then they'll suddenly drop out. If it's got one of those and nothing else is obviously wrong, I'd change that since they're normally fairly cheap. Nothing so sophisticated here - carb'n'points.  Posh auto choke though.  |
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I really hope it's not that ancient fuel pump, they're truely the hardest thing to get hold of for these. Facet? |
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When it starts to act up take the fuel filler cap off - it sounds like its built a vacuum up.
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speedy88
Club Retro Rides Member
"Nice Cortina mate"
Posts: 2,281
Club RR Member Number: 118
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Thanks for the help all - got a few things to try now I really hope it's not that ancient fuel pump, they're truely the hardest thing to get hold of for these. Facet? Not sure what a Facet pump is, aren't they electric? It's mechanical with the actuator arm that's pumped up and down by a cam lobe. |
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facet make electric fuel pumps and they have a few models that could replace yours if it was broken, which would be much simpler and cheaper than sourcing an original.
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bortaf
Posted a lot
Posts: 4,549
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coil over heating at all when it plays up ?
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R.I.P photobucket
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facet make electric fuel pumps and they have a few models that could replace yours if it was broken, which would be much simpler and cheaper than sourcing an original. ^ That. |
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taurus
Posted a lot
Posts: 1,084
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As others have suggested - I'd check that the tank isn't forming a vacuum first. The symptoms match a problem with the tank breather. Get a temporary fuel cap and drill a hole in it - see if that makes any difference.
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Posh auto choke though. 
