4ac is doing weird things

[bahnugget]

Hey guys

basically i have a 4ac in an AE86, its getting funky on me..

two main problems:

firstly, and this one COMES AND GOES its really annoying. basically sitting at traffic lights or whatever, the car will have a very rough idle, when you accelerate it hesitates and splutters as the revs rise, and you cant take off easily.. but heres where it gets funky.. after about 2500rpm its all good..

and the second problem happens on track, sliding... basically after a little throwing around (i have to do huge weight shift entries to get slides), the car dies.. it FEELS like engine braking, really smooth but slowing down, the more accelerator you apply the worse it gets. BUT once u back off for maybe.. 10-15 seconds, you can jump back on the throttle and its fine, mostly until the next time it happens. i thought perhaps it might be fuel surge but i havent heard anyone with a 4ac having fuel surge issues before.

[AE86_4life]

i actually have the same problem with the iddles if i place the iddle 1500 or higher its fine but on 900 it from time to time turns off. Well my mechanic told me that the throttle shaft is worn so it doesnt go back to whwere it set to be hence the ups and downs with revs. im taking mine to a carby speclist to replace/ or repair the shaft if it is possible. I dont know exactly what the shaft is but thats what i was told by my mechanic. if u solve it first let us know thanx

[James86]

yea welcomre to the 4AC idle.
i have the EXACT same problem
no idea how to fix it sorry.

my way of fixing it is to save up and change to a 4age

[driftism]

the second problem sounds like the carby... my escort did it on every left hand corner, had something to do with the carby design... apparently they all do it. fitting a twin barrel carb may fix the second problem. As for the first... fitting a 4age should fix things pretty well!

[« R²» Blinky]

Same problem

Fuel filter lol


No joke, did ya try that?

[bahnugget]

it HAS a twin barrel carby.. its a 4ac. it idles fine alot of the time, and by rough i dont mean extremely rough, it just wont rev up from idle without spluttering.

[kravit]

Just problem with idle sticking, my old done it after a while.
Need to replace it, something inside gets worn out.

[Hen is a total nutcase]

Prob 2 - I've heard of this a few times. The carby is the culprit apparently. If turing hard/sliding one way the fuel cuts out. Heard it happens to some carbies and not others.

Prob 1 - Fuel filter is a good suggestion. Also check all vacuum hoses under the airfilter and carby are attached.

Hen

[Mr Freeky]

i had the same problem witth it idling and it always happen in the worse situation like in sydney traffic. and i up'd the idle to about 1500rpm. and every now and again it just at traffic lights it just turns it self off and takes a little bit to start again.

[Course_Out]

I had a similar problem with my 4ac. When doing a bit of sliding around (particularly if I was bouncing around with my foot flat) the secondary on the carb would jam open, the thing would stutter and pop flames, then hit 4000rpm and clear out.

How are all your vaccum lines to the carb? that could be a possible culprit?