4ac doing some 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.

+rep if you can help me!!!

[Talasas]

My old AE82 4AC did the same thing, sometimes it didn't want to go and would bog down, other times it was fine. Because I knew SFA about carbies at the time I never got to iron it out (had it for 5 months).

My guess now would be that you need to tune it, fuel was a very likely cause. If you have a Haynes/Gregory's manual for the car now would be a good time to study the carby section.

I don't know much about the 4AC carby but like most carbies it will need to be checked/tuned/rebuilt every once in a while. Check the float level is a good start.

Again, by what you describe when you're out on the track, weight shifting needs some pumping of the accel which jets extra fuel in. If you were to pump the accel say 3 times and release it immediately each time, you'd be a little overfuelled and so that 10-15 seconds would be the time for that fuel to be used up again.

[Talasas]

I should probably add also that while tuning a carby is needed, it's a complete bastard of a job until you've made sure EVERYTHING ELSE on the engine is in perfect running order. If something is even slightly questionable, it will make tuning the carby very very annoyingly diffcult.

- check ignition system, dizzy clearances, coil etc.
- check/replace spark plugs
- check leads
- check timing

- check air cleaner
- check for leaks in ALL vacuum hoses (these are commonplace for tuning issues)
- check/adjust float (may need dismantling of the carby)
- check idle speed and mixture

[H1TMAN]

Check If there is any overheating problems or water leaking from the head, Mine had a very rough idle and did some of the things you said, turns out blown head gasket. But remember if it is do it asap, mine had rust in the 2nd cylender!!!! Pain in the butt!!

[Bahnugget]

definately not a BHG. been putting up with it for weeks/months and no overheating. i'll TRY and find a 4ac manual somewhere and see if i cant tune that carby up

on a related note i dont suppose anyone knows what resistance leads should be and how to test coil?

[oldcorollas]

if the igniter is the wbosch one on the dizzy, they are prone to getting hot and dying (imho)
my mums car had intermittent stalling/idling issues.. got worse and worse until it pretty much just stopped.. new module is about $70 from sparkies.. try to borrow one and see if it is the issue (or pocket one from pickies)

[MWP]

They are both fuel/carb problems.

First problem i would say is from ideling too rich.
Does it blow smoke when accel from the bad idle?

Second problem sounds like simple fuel surge.

[river]

Hi,

Not sure of this is of any help to you, as it depends on exactly what your engine is doing. Anyway...

http://www.toymods.net/forums/showthread.php?t=12658

seeyuzz
river

[hosking1991]

my sisters ae82 woodnt idle so i did a lebo tune up (old mechanic trick) and it worked just had shit in the carbie

[DeftAnesthetik]

I should probably add also that while tuning a carby is needed, it's a complete bastard of a job until you've made sure EVERYTHING ELSE on the engine is in perfect running order. If something is even slightly questionable, it will make tuning the carby very very annoyingly diffcult.

- check ignition system, dizzy clearances, coil etc.
- check/replace spark plugs
- check leads
- check timing

- check air cleaner
- check for leaks in ALL vacuum hoses (these are commonplace for tuning issues)
- check/adjust float (may need dismantling of the carby)
- check idle speed and mixture

I agree here, my old 3A was running the same way you described, i tried starting with the carb but could not get any results that would permanantly fix my problem. I ended up doing a complete refresh on the engine (minus pistons and crank). this may be a little extreme but basically allowed me to start from scratch and check all clearances, tolerances and just to make sure everything was set right. Also did a carbie rebuild and reset. Although I am not entirely sure what was wrong in the first place, I did not have the same problem again. Gasket kit and carbie kit should cost under $200 and the 3AC/4AC's sure are easy to work on. it only took me a friday night and most of a saturday and i was driving again.

Good luck

[.:2DR-FTU:.]

Dont rule out BHG, my engine runs fine temp wise, but cuts out from water in the cylendars... when there is no water in the system, it runs fine, when there is water in there its fine too, until its under strong vacuum and sucks it in... weird.