Fixing your stalling 4A-C Engine

[river]

Hi,

I put a thread a while ago about my 4A-C engine (in my AE71) that stalls a short time after it had started. It seems to stall when it's coming off the high idle when it's cold. It doesn't do it when it's hot. Once it stalls you only need to restart the engine - which it starts easily - and then its okay and won't stall again. Well, not until the next cold start.

So, I did some asking about with Toyota and some mechanics who pointed me to a trouble spot with the 4A-C carby. It's a small diaphram that, over time, deteriorates and this deterioration gives the symptons I have been experiencing. So, after fixing the clock in the RA25 I thought I'd have a go at fixing this. As usual, I have some pics here to help you in case you decide to do it yourself.

The required diaphram is a piddly little thing - about 30mm in diameter and is made of rubber and, as per usual for spare parts, costs a silly amount - $95!!!! However, I was sick of it stalling and if it stalled in the middle of a busy road then I could be in trouble and therefore I decided to buy it and get the stalling issue resolved. It's part # 21675-35510 - but this is for the 4A-C in an AE71, so it is wise to check for the proper part number in case you have a 4A-C in an AE86 or other vehicle.... just to be sure.


Here's a pic of your typical, crusty yet trusty old 4A-C engine.

The first thing you need to do is to remove the air-cleaner top by unclipping the clips that hold the lid on, plus the centre screw. You also need to undo the two bolts that attach the cleaner unit to the engine. I have circled these items. Plus, there are two tubes that connect to the cleaner. These are marked with an X. You will need to pull one end of the tubes out.



Now, once you've done the above you will need to remove the hot-air intake pipe. Often this pipe is broken - as per my pic - but if it's not then undo one of the circluar clips - usually the one just under the air-cleaner (not the bottom one). If your pipe isn't broken then be careful as it will be old and easily cracked. I have highlighted the pipe with my lovely red line. I fixed my pipe during re-assembly.




Once this is done you can safely move the air-cleaner to one side out of the way. If you want you can disconnect the air intake pipe - but this isn't necessary, as you only need to move the cleaner unit out of the way - not disconnect it totally.

I have labelled the items that need to be removed or loosened to get to the area where we need to work. 1 - unclip the fuel filter and move it aside. This gives you room to get a spanner on 2 and loosen the throttle-cable-fastener nut. Once loosened pull it free from its restraining cradle. Remove the electrical wires by unscrewing 3. Unbolt 4 from the side of the engine bay. There isn't much room to work and that is why the above items need to be removed or moved out of the way - to get to the next part and to also allow enough room for a screwdriver. The assembly labelled 5 needs to be loosened so you can get into the relevant area (see next pic). The arrow points to the offending component that we need to get too.



The assembly is in two parts. You need to unscrew the bolts 1 & 2 and this part of the assembly can be moved away. It still connects to the engine via a tube, but there is plenty of slack to move the unit aside without disconnecting it. The remainder of the assembly requires you to unbolt nuts 3 & 4. You can't see 3 in the pic because it is obscured by some tubing - but these nuts are accesible and you'll need a 12mm socket (all other bolts are 10mm).This part of the assembly is connected to the carby by numerous tubes. You can remove all the tubes, but I found it uneccessary as you only need to juggle it a little to get enough room for your screwdriver for the next part of the operation.




Here's a close up of the area where we need to work. I took this pic during the re-assembly and that is why the screw holding the wires is in place. Three screws, marked, with X need to be unscrewed. Be careful that you don't drop a screw, and keep pressure on the lid as you undo the screws as there is a spring in there and it may pop out. A small amount of petrol is in the casing, so don't be alarmed - it won't keep dripping or anything like that.




Here's another view of the diaphram housing



After you have CAREFULLY removed the casing you will see the old diaphram. Notice the orientation of the diaphram 'cos you don't want to put the new one in backwards!!!!



If you remove the diaphram you'll see the spring. Be careful not to drop or lose the spring.



Here's a pic of the new and old diaphrams to show you how deteriorated the old one was.




Now, all you need to do is put the new diaphram over the spring and screw the casing to the carby. The three screw holes are not evenly spaced, so you will have to turn the diaphram around until it lines up with the screw holes. Be careful when assembling to keep the diaphram in place, despite the spring trying to push it out. It's a tad fiddly but easily do-able. Once done, you just re-assemble the parts in the reverse order that you dis-assembled them. And then you're all done!!!

I hope this helps you. So far - but it's only been three days - my crusty and trusty old 4A-C hasn't done its normal stall stunt on me.

seeyuzz
river

[Trent-KE30]

Thanks for that River my 4K does exactly the same thing I might have a look at it, is your new diaphram a geniune toyota one if so how much did it cost?

+rep

Cheers Trent

[river]

Hi,

Yes, it's new. It cost $95!!!!!

I went to Pick n Pay or whatever it's called on Friday and had a look at the diaphrams of some old wrecks... but they were in a worse state than my old one. I guess they're quite old now (20+ years) and after such a long time and being soaked in petrol they've perished. I doubt you'd get a good one out of an old 2nd hand car or wreck.

Does the K engine have a similar thing?

seeyuzz
river

[Vios-GT_07]

+ rep for you mate

almost all 4A-Cs have this problem and i was given the solution to this was purely words.. and i tried to disconnect and do everything but to no avail.. basically was told to just disconnect one vacuum line.. but that didn't help.. and didn't know where or what the diaphragm looked like.. this will definitely help..

cheers mate

[rj_darlow]

G'day,
+ rep... If I ever get round to re-connecting the automatic choke then this may come in handy. Until then I'm used to holding my foot on the accelerator a little bit to hold the revs up...

Cheers,
Richard.