rebuilder86

Something must be said about the roadside head gasket changeability of the 4k tho haha. Such an awesome engine,

anyway sorry, what carb has it got? what cam has it got what is its intended use I understand that budget is not something any of us enthusiasts consider when starting to think about modifications to personalise our ride. Its more about what we want to achieve with an older vehicle. id be looking at what might be broken before investing in power. Get used to it as a powerless beast and experience its flaws while u haven't spent any money, and include the cost of upgrades to those flaws in your plans for the drivetrain. That is of course, if it is to be ur daily driver. In which case, i second altezza, put that diff in the bin

hahaha, who welds a corolla diff. is this for like, a rally joke car or something??? U want JDM mods???

these engines have a serious mean hard 100 degree turn for air/fuel mixture exiting the carb into the manifold, and it really does cause a lot of fuel condensation and therefore an almost incombustible mixture scenario when very cold. That along with a slightly weak spark due to old high tensions leads is enough to cause missfires that are complete show stoppers at cold idle. When the thing is running, and hot, take it out for a gentle spin, and note the colour of the spark plugs insulators. if they are nice and brown, then id say the idle circuit is supplying enough fuel. if they are white, there is definitely an idle circuit issue. If they are black, and sooty, u have a typical rich k engine setup haha. Also, there are plenty of places there can be vacuum leaks that are not audible or testable form outside the carb, but i usually find a vacuum leak on these motors just makes them idle faster, possibly because they only run when set up ʞ©$ɟing rich to begin with. If u find no leaks, check these places: PCV valve, just replace it now with the OEM replacement and don't ask questions, your engine will thank you for it regardless of weather or not it affects the idle The hot idle compensator valve, which lets air in during hot idle to counter for hot fuel bowl evaporation enrichment through the bowl vents into the airflow the power piston valve circuit, including the breather and cylinder walls, which can be so worn out it affects the circuits ability to pull the piston up and causes an overly rich mixture on the primary throat during off idle operation, with this situation u will have poor idle and black plugs with no way to tell, when this happens u put the carby in the bin. and finally, The rubber diaphragm in the brake booster, which almost always shits itself due to brake fluid leaking from the master cylinder into the brake booster drum and melts the rubber, this happens constantly because people dot realise the importance of flushing their brakes hydraulics properly.

for now can u just try jumping a wire from your battery positive terminal, across to your coil positive, then crank it over for us. This will just confirm that u have a wiring/fuse problem. hah and if it runs, don't just say SWEET, and leave that wire there haha

I'm now suspicious it must be the enrichment circuit sticking open, In corollas, this would be known as the power piston circuit. Works slightly different as it uses a diaphragm on the side of the carb rather than a piston in the cover of the carb. Possibly spraying degreaser through the carb has dried out the rubber diaphragm and cracked it. oops

well, here's the thing, the working temp on the rods is listed as 600 degrees, and the mapp gas torch sais it burns at 1900 degrees. U recon ill need oxy purely coz of the size of the manifold cast iron? As for the mixture thing, yes, i can, but then it doesn't idle at all. I'm totally confused by that, i swear it is a fuel solenoid as when i sprayed degreaser up the idle screw port, it came straight out that idle solenoid thread where the solenoid goes., but according to all internet research, they work by letting in bleed air. Perhaps its letting both air and fuel into the idle circuit, but that wouldn't explain why turning the car off (which shuts the solenoid) doesn't stop it from dieseling. To make it all the more complicated, if that isn't complicated enough, after bypassing the fuel computer and making the solenoid permanently open when ignition is on, the idle speed is still creeping up to about 1000 rpm after hard driving, altho without the surging, and when turning the engine off and letting it come to a complete stop after its dieseling fit, start it back up again and the idle is settled nicely at 600-700 rpm. just without the surging.

thats not a bad idea i ended up puttying the exhaust crack, and thay worked for abut 20 minutes. then the putty lew threw and it started high idle surging again :( can't get a new manifold so I'm going to try to braze it up with silver/nickel fluxed brazing rod and my little MAPP gas torch. also tried just grounding the fuel mixture solenoid thing so that it was just permanently open... that worked without the surging but the idle was too high, with base idle screw all the way out and butterfly fully closed, and the mixture screw completely tight against the seat, which means this solenoid fully open must be controlling something else other than the fuel through the idle and primary circuit. it must be controlling bleed air in the idle circuit. With the idle mixture screw completely up against the seat, it shouldnt idle at all. But its idling high with this "constant open" solenoid so fuel must be getting in through some other system i know nothing about, like an air bleed hole or something. That means nothing will solve the severe dieseling issue, it runs for about 30 seconds after turning it off...

Well, these symptoms indicate that it has an effect at idle also, unless perhaps there is another issue and it doesnt know that its at idle.... All it has is an O2 sensor, there is no throttle position sensor, or MAF or MAP or anything like that. perhaps it looks at RPM thorough a crankshaft position sensor or something. I'll see if i can see any sensors on the front of the engine when i putty up this manifold crack.....

just checking the rotor against the terminal in the dizzy isnt good enough. that for me, has been the difference between the thing starting, or not starting at all. Test for spark, by turnign ignition on, , loosen the distributor timing nut and spin the dizzy housing with a spark plug connected directly to the coil HV outlet, and firmly grounded against the chassis first, and then if u see spark then test it grounded against the engine. If you see spark, say EUREKA, and then set the timing by putting cylinder 1 at 10 degrees before TDC ( as seen on the pulley marking), and make sure its after the intake stroke, by visually checking the valve rockers then slowly turn the dizzy until it sparks and stop right there and tighten the nut. u may need to do it twice. If u see a god spark then it means there isnt enough power when the car is cranking, as others have suggested. If u don't see a spark, check that u are getting 12 V at the coil. if not, fix that. its possible. If u saw spark when grounded to the chassis but not when grounded to the engine or viseversa, check the earth straps from engine to chassis. Copper Electrical contacts can go from 100% working to 0% just from one heat cycle. all this is based on your suggestion that there is NO or very LITTLE spark

Dave, its the end of carburetors, the last generation i believe. its called a feedback carburetor. It uses a piss-ass half ECM computer thing and takes oxygen readings from the exhaust and adjusts the primary jet in the carb accordingly using an electronic valve thingo. I'm not sure but i believe it may just d this by pulsing this solenoid type thing rather than actually setting an opening size. Doing so really quickly opening and shutting to sort of simulate a restriction, or smaller jet size. I'm becoming convinced that its this cracked header/ manifold.

also, forgot, and htis could be the killer, there is a crack in the exhaust manifold, just where 2 sets of 2 cylinders come to one set of 4. This is upstream or (before) the O2 sensor

hey yall I have left my 4k machine in perfect running order back overseas, and come back to oz to land a new job in renovations so i quickly went out bought the cheapest van i could get that seems to run. I ended up getting a 1993 mitsubishi express also known as L300, which has a 4G63 2L SOHC carby for 1300 bucks. Got it and it was ok, but noticed black spark plugs on my first service, so had a good look at the carby and removed it n found the secondary throat diaphragm was stuff, so i got a new one for 90 bucks n stuck it back on and the power at high rpm was about 1.5 times better. Anyway, after doing that, which involved removing the carby, i now have this problem, where after the van has been runing for a while, like 5-10 minutes and the engine is hot, and i have been accelerating and driving normally, as son as i come to a stop the idle is surging between about 700 - 1200 at a guess (i have no tacho) in cylces of one second. i.e. in one second it has gone between 700 and 1200 rpm. If i shut the engine off and start er up again, it is immediately resolved, but after some more hard driving, it is back again so end up turning the engine of at the lights to reset the engine to a god 700 rpm idle. Its quite dangerous as it really affects engine braking. Some points and history.. I bought the van last weekend. It wasn't surging until i removed the carby and reinstalled it with new secondary diaphragm After i noticed this surging, I immediately assumed i had introduced a vacuum leak where the carby joins on to the manifold because the gasket was stuffed, so i made a new one, but the problem remains, i am adamant there is no vacuum leak there. In order to remove carby, i had to pull out of it, what i assume is the idle solenoid, has 2 wires coming out of it, and i don't think its functioning properly, i think its stuck open, as the damn thing diesels 90 percent of the time i try to turn it off, and i have to put it in gear and clutch out to stop the engine haha... (could be related to the issue perhaps?) When i had the carby out, i cleaned out the visible muck in the throat with supershit 2 dollar degreaser, and also sprayed a bit around the passages and idle circuit to give it a clean, I saw a good steady flow of liquid exiting the idle solenoid hole. How can turning the engine off stop this idle surging, i can't get my head around it. Also, why is there an O2 sensor in my carby engine, what does it control? is there some sort of fuel computer which is being fed by O2 sensor info, and is being reset every time i turn the engine off?? Confuzzeld and need assistance from u guys. CHeers

u like my upside down rolla? hah yes toyota did, but fuels have changed since then. Even a slight restriction in the fuel hose can nowadays create such resistance that the fuel pump pulls the fuel to its maximum point and it turns into vapour. Its quite common in our old rollas. The pump can be perfectly fine, but the rest of the system is the problem.

mind u, the tank in these things is pretty high isnt it its like as high as the seat back, perhaps the mechanical pump is indeed below the fuel level.

absolutely a mechanical pump is the best, but if his problem is vapour lock, getting the pump as low as possible was my point and you can not move a mechanical fuel pump. that is the reason i was saying to add a pump down low. My electric pump has failed twice in 1 year haha. granted, it is a 20 dollar piece of junk and is all that is available where i live. Also, pardon my ignorance, what is a fuel circuit relay and what does it do to make things safe? At a guess; I'm imagining something which turns on when ignition is turned on for a couple of seconds (to prime) and turns off until supplied a signal that the engine is running?

i did move the electric pump to just next to the tank and that solved my issues. Any restriction in the fuel lines will make the suction on the fuel a lot stronger and this increases vapour lock tendencies a lot. Its not the lack of flow so much that is the problem, its the increase in suction this blockage creates which causes the fuel to turn into air. OP if this happens again, at very least get yourself one of these electric fuel pumps and mount it in the engine bay as low as possible before the mechanical pump and wire it in to a relay activated by the ignition circuit.

how much rubber hose do you have between the tank and the pump? Was the gunk in the filer black? If you have lots of hose and the gunk was black, its likely hose breakdown. It swells up inside the hose and chunks shear off and act like valves that intermittently block the hose. this is really most likely if there is lots of hose, Also, with relation to pusher or puller pumps, the only difference is that 1. an electronic pump has a piston which moves back and forth between to non return valves and has a clearance between the piston and walls and this is why it s considered better at pushing than it is pulling 2. a mechanical pump is completely sealed using a rubber diaphragm, and is therefor able to deal with air better than an electronic pump. Both of these pumps can cause vapour locks if the fuel tank is not vented and the pump is at the front of the car; especially if ethanol fuel is used. Yes the electronic pump should be mounted near the tank, but if the mechanical fuel pump design could be also mounted near the tank, that would be perfect. My point: mechanical fuel pumps are just as prone to vapour lock as electronic plunger types.

i have an electronic pump still located in the engine bay and sometimes have this issue because of ethanol content. What sort of fuel are you running? E85(common over east) will effectively start giving vapour lock issues when the fuel is more than 4 weeks old. Fuel pump may be fine.

I personally have no idea about your engine. I'm just here to ask you how much that cost? haha PICS??

It might take a while for you to get a response, this is the first time ive seen a question about aircon. This is probably very little help but ive got mine idling at 600 rpm at 20 degrees base timing (vacuum advance unplugged) which goes up to about 30 degrees at idle with vacuum plugged in (4K-U engine with dished pistons, no air conditioning). Most people struggle with 600 rpm with the stock 4k carb from what ive heard.

maybe oen big solid piece of carbon up in behind the valves finally broke loose and fell down into the cylinder? hahah just putting it out there? it does all sound pretty horseshit.

sorry hang on, siiiiick.

Mines better :P

lol! if it only happened at a rotation of a full 360 degrees and not 180 then id say theres an oil burning problem in one cylinder which created all that carbon. do a quick compression test and see what that reveals, but remember a good test does not mean good oil rings: then check the valve stem seals If it really is on all cylinders then, consider oil rings on all 4 fried in which case compression tests wont tell you too much. If the carbon is moist and thick its probably oil, if its dry and scrapes off relitively easy then, in this case: better check timing, mixture, idle screw, float level, and jet sizes in this thing before going too much further! Possibly also the backs of the exhaust valves. just check them through the openings to the manifold.