running rough at high revs

lincolnGSX

lincolnGSX

I'm having problems with my k10 :( it starts first time & idles perfectly.Even runs nice up to around 40-50.Anything higher & it stutters,misses,pulls back etc.
It's just come out of the blue no warning signs.
I've since changed the plugs,leads,dizzy cap,rotor arm,fuel filter & today i tried a new fuel pump.I've also given the carb a good spray inside with cleaner but to be honest the carb looks very clean & the car has only done 27k.
I got a neighbour who used to be a mechanic to have a listen.I don't have a tacho but it's probably when it gets to about 3500 rpm.He says it definitely sounds like fuel starvation.
Just wondering if anyone else has ever had a similar problem or has any idea's? I've scoured the web & saw somewhere the coil mentioned.So i have a new one on order.I would of expected though if it were the coil the problem would be throughout the range?
Simon.
 
Coils are usually a problem at higher rpm due to heat stress. Once they get hot they progressively get worse. Despite mileage parts unfortunately do still deteriorate with age. So maybe its time has come.
Also have you set the spark plug gap at all or they put in straight out the box?
A larger gap requires a larger amount of energy to create the spark over a larger gap. A poor coil would struggle here too

Your carb may also want 'resetting'.
Where you alter the fuel and idle rpm.
Simply adjust the fuel screw until rpm is at its highest.
Once you've done that simply turn the idle rpm screw down to around 7-800 rpm
 
Hi Andy,thanks for that.I fitted new bosch super four plugs for a micra so gaps fine.Fitted new Bosch coil & leads today.No change :( Has to be the carb...well hoping! It does remind me of the problems i used to get on webers when 2nd choke wouldn't come in..butterflies sticking?
I found a second hand carb on ebay for £20 so will try that when it gets here.
Praps i should give that 'resetting' a try first though.
Looking at my carb Andy,i can't see where it's removed from the inlet?
 
The bolts are underneath the mani fold to remove the carb.
Another idea popped into my head today. Our auto chokes tend to give in from time to time. It may be that the choke is staying on restricting air flow?
Yup try resetting the carb. Good dose of carb cleaner and hopefully that cures it
 
h701micra said:
The bolts are underneath the mani fold to remove the carb.
Another idea popped into my head today. Our auto chokes tend to give in from time to time. It may be that the choke is staying on restricting air flow?
Yup try resetting the carb. Good dose of carb cleaner and hopefully that cures it
Click to expand...
Are micra standard chokes actually a choke? on SU's its done by lowering the needle perch to up fueling, doesn't affect air flow
 
They are a genuine flappy choke :) as they came in a manual pull choke too
The bi-metallic workings on the auto choke produce a rotation motion which can only be the turning of the flap similar to a manual
Plus I always remember forcing it open to spray carb cleaner down it :p
 
Right,changed the carb for one i ordered through ebay.Cleaned,fitted & doing the same.So it wasn't/isn't the carb :(
I've noticed while letting it idle that revving it becomes worse the longer it's been running.Say down from 3000 to 2000 revs & starts missing & spluttering.
There's no smoke from the exhaust & on idle..low revs sounds fine.
Running out of idea's :( Could it be the distributor? The vacuum advance on it seems to work fine.
HELP!!! :eek:
 
Idle should be sub 1000 rpm. Though I think you said you had bo tacho to check?
It appears to be a heat related issue with it getting worse as its warms up. Is it the later magnetic distributor?
 
Hi Andy,yeah it's idling fine at around 800.I just meant when i open the throttle it's starts spluttering at around 2000 revs.
Magnetic distributor? Not sure how do i tell?
 
Tap the dizzy cap off and see what's behind the rotor arm.
Usually the newer K10s had the magnetic type. My magnetic pickup jjst stopped with no warning. I've an older points distributor if you'd like to try it?
 
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Can't see any points so i guess it must be a magnetic one Andy.
Can you just swap them over? No way i can get up to Louth at the mo with it off the road other wise i'd give it a go.Running out of ideas fast.:(
 
That's the magnetic one :)
Yup they're easily swapped over. Just a case of one bolt and shuffling some wires. Simple enough :)
I can probably bring the dizzy up to you at some point
 
Still not getting anywhere with this :( Does anyone know if a fuel pump relay could cause this sort of problem?
CAn't get my head round it at all.Starts first time everytime & idles lovely but as soon as hard revs are applied it starts spluttering & has no power at all???
 
Timing belt changed about 1000 miles ago other than that timing not been touched.i guess belt may have slipped but seems unlikely.praps i should get a timing light & try.:(
 
Not sure Andy.It was done just before i bought the car.i'll take the cover off and have a look.
Mate of mine used to adjust timing by ear,just moving distributer.Is that worth a try or should i wait till i can get a light?
 
drove it this evening about a mile to get petrol.took it slowly getting to 30mph with low revving & it was fine.got back in it & thought i'd take it a few more miles.Not long & it started spluttering,losing power,hesitating etc.One almighty backfire through the exhaust.limped home.
Could it be the engine coolant temp sensor? do k10's even have them?
 
The very late k10s had ecc. Identifiable by an egr pipe coming off the exhaust
If you have could be more options as to why its playing up
 
Ah right.No,no egr on mine Andy.
Similar kind of problem though.Had one go on a corsa sport once.

Looks like i'm going to have to admit defeat & take it to a garage.It's finding an 'old car' friendly one though :(
 
yeah i think it could well be frank.I will have a look at those scrappy sites see if i can get hold of one.

Andy,yes mate.I shall try a dizzy if i can get hold of one.
 
Well,along with all the other new parts i've tried it's now had another dizzy & coolant temp sensor & still no difference.took the rocker off to check all valves doing what they should..and they are.It looked mint inside!

don't think there's much left to try.The only thing i can think off is the idle cut off valve.the replacement carb i tried didn't have one on it so i had to use the one on my original carb.
Has anyone got one they can flog me?
 
Try wiping the inside with wd40, my spitfire used to bog down at high revs and my tacho would noticeably fluctuate, turns out moisture in the dizzy was the culprit, quick spray of wd40 inside the cap and she's run like a champ for about 50 miles before I'd have to repeat. A thin smear of vaseline around the gap between the body and cap finalky cured it for good.
 
thanks for that Enuo.It's still doing it after trying 2 distributors both cleaned with electrical spray & left to dry.
I was sure it was electrical/ignition but beginning to think it's fuel starvation somewhere :(
 
If you're about Sunday that would be great Andy thanks.
Really love this car & it's in such good condition & 'was' lovely to drive.Don't want to part with it if i can help it.
 
Not majorly. Its a radio condensor. Stops interference with radios and phone signals etc iirc.
Though it should be earthed to the engine :)
 
It's not that then :(
The only things left are the two parts i had to swap from my original carb as the second hand one i bought didnt have them on.That's the Vacuum that goes to the accelerator linkage that only auto's have & the idle valve???
 

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