jerking MK3 GT

[brightorangeGT 1]

Hi - I dont know if anyone can help me with this but my Mk3 2.0ltr jerks like a cuss when driving at 25 - 30 mph in fourth. Its terrible in slow moving traffic and it sounds and feels as if the G/box, prop, and axle are all loose. There is a kind of jerking/clanging sound and it seems to come from transmission. Yet everything has been removed and changed/fixed/ or replaced. All the bushes in the rear have been replaced with poly. ones. Nothing is loose. I also replaced clucth recently. It also happens when slowing down - it gets to 30 and it starts its nonsense. Yet if I am on 30 in fourth and pressing accelerator just slightly to maintain progress then its okay. It was on a rolling road the other day and although it was down on power - leaking valves - the igntion and carb were okay. Please, any ideas? Thanks.

[cortina crazy 0]

my cavalier jerked a lot at about 30 and it was the carb needed cleaning, but as you've already said thats ok, i dunno mate. bound to be several people on here with ideas, one might even be right :beer: , welcome to the site mate

[brightorangeGT 1]

Hi - thanks - for a while I thought it was carb. Ive got five twin chokes and I'm fed up with taking them apart, swaping bits to make one good one - thats why I took it to rolling road and in that respect I was quite pleased when he said carb was okay. This is really spoiling the fun of owning it - having to slip the clucth all the time to make smooth progres is a real pain.

[MK3-MAD 0]

Hi - thanks - for a while I thought it was carb. Ive got five twin chokes and I'm fed up with taking them apart, swaping bits to make one good one - thats why I took it to rolling road and in that respect I was quite pleased when he said carb was okay. This is really spoiling the fun of owning it - having to slip the clucth all the time to make smooth progres is a real pain.

Is it still playing u up then mate :rofl: I am sure u remember me :beer: Welcome aboard :rofl:

[CorKtina 17]

shot in the dark from Billy Nonothing.....worn engine mounts is my guess.....

 

i say this as I have had a couple of Cortinas that felt exactly like the clutch was juddering but it turned out that the engine mounts were weak resulting in the engine twisting in its mountings rather than turning the prop.....

 

could be this, who knows????

[G.O 20]

worn diff or UJs? :beer:

[chimpteaser 2]

I agree with Corky, I'd suspect the engine mounts, especially as you say it happens on decell but not on accell. Is the throttle cable getting pulled as the engine twists? This happened on a mates escort with very similar symptoms.

[AutoFive 0]

had a similar problem on my old sierra pinto when decelerating, turned out to be inlet manifold leaking round the gasket

 

i thought the carb was US but an old man with a flat cap - a couple of doors away pointed me the right direction.

 

is yours thirsty at the moment?

 

my MPG went right down as the problem got worse before it got better

Edited July 6, 2005 by AutoFive

[bortaf 96]

25 is very slow for 4th gear unless you have 1.3 diff my Mk5 wont take 4th till over 30 you may just be dropping the revs to low to get any decent torque?

Failing that have you checked the gearbox mount isn't soaked in oil, the oil turns the rubber to jelly.

My Mk2 transit did the same thing till i changed the engine mount rubbers it still jerks if i selct any gear to early but not as violent/noisy.

[sheffieldcortinacentre 764]

ditto bortaf to slow for 4th

also check the centre prop mount is tightly bolted to floor & that the rubber in the mount is ok.

[escort21 0]

Could be worn distributor bearings, this makes the rotor run in an oval formation causing uneven spark, i fitted electronic ignition which helps.

[CorKtina 17]

I agree with Corky, .

blimey! i am getting good at this old car lark.....

[brightorangeGT 1]

Hi - Thanks to everyone for your help with this. I've replaced the engine mounts and the gearbox mount and I've checked the accelerator cable is adjusted and not sticking. UJ's on prop are okay and centre bearing is bolted to floor tightly and the rubber is fine. I've checked all around inlet manifold and cannot see any fault there. Economy is down but that I think is becuase head needs doing also it seems to depend on which garage I get fuel from as same applies to the other cars in our family. Best I've got on £20 is 170 miles worst 125 miles. Something I have noticed is with the rear jacked up on stands there is quite some movement in wheel as I move it forward and backwards - before I see prop move - could it be because there is too much slack in diff? I did put a 1.6 axle on and the jerking/clanging was still there although not as bad. Absolutely everything has been attended to/looked at/fixed/fiddled with etc etc. Yes I changed distributor for another - but then rolling road chap said igntionwas okay. If 25 in fourth is too low - surely 30 mph is'nt? Ive even swapped gearbox itself around twice! Please keep your help/advice coming - if you can - I do appreciate it.

[Sarkie83 0]

points? that's what caused mine to jerk at low speed and it felt like something was blocked

[the_jonf 0]

Had a problem on both my capri and old mk3 corty, would jerk under moderately hard accell between 1500 and 3K revs, turned out to be condensor both times. On the corty it only happened when I fitted a new condensor, turned out it was faulty.