Inherited an 89 Corolla (automatic). It won't idle well at all, it bucks up and down quickly. I've adjusted the idle speed screw (at the back near the firewall) so it idles faster than normal, so at least it doesn't stall out. It runs fine on the road, has lots of power,and runs smoothly, but of course idles too fast now at stop lights, and will diesel and sputter for a while after I shut it off. I usually have to leave it in drive with the brake on to shut it off.
I've replaced the cap, rotor, plugs, air filter, oil change, sprayed two cans of carb cleaner through the carb, adjusted every screw in/out on the carb to no avail. There seems to be no obvious vaccuum line leaks or electrical sparking (watched the engine run in the dark for arcing), no warning lights on the dash.I removed and checked the EGR valve and to the best of my limited knowledge it's functioning normally. The engine runs very smoothly at higher RPM's, no missing at all.
My fear is that I have to remove the carb and give it an overhaul, looks like a lot of wires and hoses to get mixed up. I also may have completely screwed up the idle/mixture/fast idle screws in my frustration, and would like to know where the adjustment screws should be normally set. Does anyone have a link to an exploded view of the carb and proper screw adjustments, before I resort to rebuilding the carb? My Haynes manual is of little help to me.
Thanks in advance, any help would be much appreciated.
I had the same problem with my car....all the tweaking will do you no good. THe problem for me was 2 things, power sterring belt and carb. Just get them replaced and you should be fine.
REN69, I think the reason it's dieseling is because I have set the idle speed very high so it doesn't stall on me when I come to a stop sign. Not to say it can't be a timing problem though. I've thought about changing the timing belt, it's still got the original one I believe.
Liter, are you saying the power steering belt was too tight? I'll check mine.
Trigger, I'll look into the air flow sensor as well. I assume it's an electric doo-dad of some kind situated inside the air breather snorkel? I don't recall seeing something like that on my engine (4A-F) but I'll double check.
A couple things I tried this morning helped a bit. I removed the plugs to check their condition, and they were in very good shape, but after checking the gap on them I realized I had gapped them to the 4A-FE specs when I originally replaced them (0.032 I believe) instead of the 0.043 intended for that engine. So I cleaned and regapped them and rerouted the wires a bit. I also found a small crack on the (new) distributor cap, which might have been caused by me overtightening the mounting screws, so I'll have to replace that soon. I started the car and it seemed to run a bit better, but only a bit.
Hmm this sounds much like what my 88 did when I bought it. I have a question, is it a miss at idle speed? Pull #1 spark out and compare it to the others. Is #1 very black? Ever found gas in the vac lines to the EGR valve or choke pull-off?
Long story short your car has an Aisan 2a series carb. on it, and they employ what is call an AAP (Aux. Accellerator Pump) which is intended to help richen the fuel mixture during initial start. When the engine warms up, there is a thermal vacuum swith mounted on the passenger side of the intake manifold (above the water pump area, small black thing that sticks out with a bunch of vac lines going to it) that closes the vacuum to the AAP once the engine coolant is warm to prevent over richening. What happens a lot (happened to me) is that the AAP diaphragm gets a pinhole in it, and the vac lines start sucking gas into the vacuum lines that go to it. The vac line that goes to the AAP ends up connecting to the vacuum source that is on top of the intake runner that goes to #1 cylinder (that black round thing on the intake manifold that goes to #1 with 2 vac lines going to it). When idling the vacuum is pulling gas from the carb into the #1 cylinder and flooding it out, thus a well timed "put put put put" at idle and fine after about 1500rpm or so. So check the #1 spark plug, if it is nastier than the rest, then you've got a ruptured AAP diaphragm. Chances are if this is dead, a lot of rubber on the carb is shot, but in the meantime, you can cap the AAP. The AAP is located (when facing the car) on the left rear corner of the carb, it's near the top. plug it and the connection to the Themal switch in the intake manifold, and put new spark plugs in it and be amazed. This piece also comes with a carb kit when you buy it. Any further questions you can E-mail me at macboy91si@gmail.com and I may be able to get you a few pictures of what I'm talking about.
I know it has been 2 years since this thread started, but I had to reply to the last post.
Plugging the AAP fixed my issues totally.
I have a 4A-F Carburettor fed engine which over the past month or two developed a lumpy idle (which slightly sounded tough) and some severe backfiring on idle, decelerating engine revs and off throttle coasting.
I had checked all that I felt was neccesary to my knowledge and was about to resort to a new Dist Cap.
I took some time and read this thread.
I followed "macboy91si's" instructions by un-plugging the Vac hose from the AAP Diaphragm and blocking both the hose and the AAP outlet.
I Fired up the engine and bingo, I couldn't have expected a better result. Not a single backfire at any time.
So, just to make sure, I replaced the existing black Vac hose with clear tube. I fired up the engine once again to see fuel flowing freely through the tube just as "macboy91si" wrote.
After this I plugged the hoses more permanantly and put the car back together and was very impressed.
I know is puzzled me to no end when it happened to me originally, it's an odd system the way it works, I'm just glad this helped someone. I love this generation of Corolla, especially the carbed 4-AF engine. It's simple AND reliable, but the only problem is there isn't much diagnostic info on the 88 & 89 models that have the carb system. It's a very good system when it works correctly and can yield 28mpg city and 33 on the highway with 220k and a 3-speed auto. Let me know if I can be of any other help.
I just aquired an 89 corolla 4af last week that has been severely neglected, 198k, so i did plugs, wires, cap, rotor, VC gasket, cleaned the inside of the carb, air filter, oil change, and trans service. So I go to crank the car up and its spitting and sputtering, backfiring, and if i press the gas down enough to get past it it sounds great, but if i let off it sputters and dies, hard to crank back up. Sounds like ill try this solution tomorrow. Thank goodness for forums. I'm a toyota trained master tech, but have zero experience with this carb motor, and it was 530, and i didnt feel like jacking with it.
__________________
Toyota Factory Trained Mechanic - 2002 Toyota Tacoma Double Cab V6 - Super White - Deckplate Mod - 06 Aluminum Tacoma Wheels
By what you are describing here, it could quite possibly be the same fault as what I had.
Your case sounds quite severe compared to mine. Maybe you have a slightly bigger hole. Therefore flooding #1 cylinder majorly.
Good Luck
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.
ToyotaNation.com is an independent Toyota/Lexus enthusiast website. ToyotaNation.com is not sponsored by or in any way affiliated with Toyota Motor Sales, USA, Inc. The Toyota, Lexus and Scion names and logos are trademarks owned by Toyota Motor Sales, USA, Inc.
Bazooka Joe
Linear Mode
