Rough idle need help - Toyota Nation Forum : Toyota Car and Truck Forums

NZAE92 · 08-14-2011, 03:23 AM

It's been ages since i've been on here but i need help.

My 4AF is running rough seems like it has a lumpy cam but it doesn't lol.

It runs right when its cold but when it gets warmer the idle drops and increases constantly, i've replace the gaskets between the carb and the insulator and between the insulator and the intake manifold has made a little change but is still doing the same thing,
I presumed it had an air leak somewhere or a vacuum leak, i have checked the vacuum lines on the carb and none are cracked or worn. should i just buy the genuine gaskets and replace the insulator also? I'm not sure what else it could be, i have asked the guys at my work and they say it's the gaskets still as they aren't genuine?

cheers for any feedback
Greg

Flashmn · 08-14-2011, 04:41 AM

Did you check the distributor vacuum advancer, it has a diaphragm that which tears as it ages. Non genuine gaskets work fine, never had an issue if the mating surfaces were smooth.

90 GP · 08-14-2011, 05:04 AM

Sounds typical of vac leaks in vac lines to the throttle positioner (on right side of carb). It has two idle speed set points ( idle up with loads and deceleration). It has a diaphragm with two cams and separate adjustments. If any of vac line leaks it will alternate between those two settings which is what you are describing.

NZAE92 · 08-14-2011, 05:32 AM

Another thing that was strange,
was when i sprayed carby cleaner round the base of the carb, it seemed to correct itself and the RPM increased when the cleaner reached the surface of the base.

I still think it's leaking from that area due to the increase in rpm, but will check out what you guys have suggested.
It's been like this for about a month now and happened suddenly, I was confused to what was wrong but hopefully have it sorted soon.

90 GP · 08-14-2011, 05:42 AM

If idle changes with the carb cleaner it is getting sucked in somewhere. Gaskets or through a vac port/vac line in that same region. Did you clean base of carb and intake manifold to remove any remains of any old gasket when you replaced them?

BeatupRolla · 08-15-2011, 03:03 AM

let us know if you solved the problem and how... i also have a rough idle just like you described

NZAE92 · 08-15-2011, 04:02 AM

i have cleaned everywhere all the old gasket off of all bases and no change.

All my vac lines are fine i have clamped them all off and no change so i think it's the gaskets as spraying anything around that region changes the rpm.

Will let you know BeatUprolla if i get it fixed.

I work for toyota so there are other people around me that know alot more than what i do but i trust this site the same i do as my colleagues. one of my colleagues still says it's the gaskets that i've made.

90 GP · 08-15-2011, 04:40 AM

If your work for Toy ( assume you get a slight price break if the gaskets can be ordered), get the Toy gaskets and that should solve your problem. Must be a slight variance in the ones you made versus the original that is causing your problem. It's hard to beat Toy for part quality. If I put one of their parts it's a done deal. May pay more but worth it in my book .

Flashmn · 08-16-2011, 09:51 AM

remove and re-install with gasketmaker.

NZAE92 · 08-17-2011, 03:29 AM

i have ordered the gaskets thankfully they had them at our main headquarters, they were only 5 bucks NZD each so like 15 bucks for both of them.
Will have them tomorrow hopefully get them on tomorrow aswell, will get back to you if it fixes it

NZAE92 · 08-18-2011, 01:36 AM

No change what so ever, it is slightly better with the new gaskets but not entirely fixed.

I got the foreman at work today to have a look and he said there might be something blocked within the carburettor that could be cause the rough idle.

Will be pulling it off early, when i get into work and blowing it out with a dust gun to see if that relieves any blockages, other wise i will have to open it up and see what is inside. Otherwise there is nothing else i can do, i am selling it soon when i get a new car, I am looking at bigger and better cars now

http://www.trademe.co.nz/Browse/List...x?id=399051434

I am moving away from Toyota sadly, they have done me well but i want something faster than what i have.

NZAE92 · 08-24-2011, 04:23 AM

Ok. So after endless thoughts on what could be wrong, i decided to swap out the carb with a second hand piece.
It has fixed the idle problem with a few teething issues but that will surpass.

What i thought was it would give me better power due to how clean it was, after spraying half a tin of carby clean through it and using a dust gun to blow it all out, oh was i wrong.
I have lost power through all the gears and it feels restricted i don't know if that's due to less fuel supplied by the jets, that can be remedied by the fuel screws at the rear of the carb, or my secondary butterfly isn't opening at all.

Hopefully someone can help me with this because it is starting to become a problem and i can't sell up until it is fixed.

Cheers Greg

90 GP · 08-24-2011, 04:39 AM

Did you check the clear sight glass for the float on side of carb? Fuel level should be in the middle range when car is running. Other than that possibly clogged passages inside. Any chance you missed hooking up/ or incorrect connection of one of the numerous vac lines? Any chance you could fullfill your requirements for your next purchase within the choices Toy has to offer? I strayed away on my 2nd vehicle purchase and will never do it again. Big mistake. Nobody builds em to last like Toy.

SuperRA · 08-24-2011, 02:38 PM

Quote:

Originally Posted by NZAE92

It's been ages since i've been on here but i need help.

My 4AF is running rough seems like it has a lumpy cam but it doesn't lol.

It runs right when its cold but when it gets warmer the idle drops and increases constantly, i've replace the gaskets between the carb and the insulator and between the insulator and the intake manifold has made a little change but is still doing the same thing,
I presumed it had an air leak somewhere or a vacuum leak, i have checked the vacuum lines on the carb and none are cracked or worn. should i just buy the genuine gaskets and replace the insulator also? I'm not sure what else it could be, i have asked the guys at my work and they say it's the gaskets still as they aren't genuine?

cheers for any feedback
Greg

I had this exact same problem on my 77 celica which probably used the same or similar carb. The problem (on mines) was an internal vacuum leak inside the carb. I ended up getting another used carb and rebuiding that one crossing my fingers in hopes that it also didn't have the problem. It didn't have the same problem so it did indeed fix it. I'm driving it to work now.

I think I figured out what was happening though. Kinda hard to explain.
1. Engine is rich when cold so vacuum leak is not apparent, (cancels out)
2. Engine warms up and is no longer rich but is now lean because of the leak
3. Engine starts to die because it's lean
4. AAC (Aux Accel Pump) squirts gas into carb because of lost vacuum (from engine dying)
5. Engine revives and runs until gas squirted in runs out. AAC is recharged
6. Repeat 3,4,5&6

Oddly enough, I looked at this thread because I'm having a similar problem on my 4AFE, but I've been holding out fixing it hoping that I'd swap the 4AGE in soon...