4g15 surge/hunting.

L

leadfoot

Active Member
ok fellas my little brothers 4g15 has been having some issue lately he's been having a horrible miss that would throw you around inside the car.

this week he did a water pump so me and the old man along with him complaining the whole time swapped out the motor. now this motor had been sitting a while but it's not the issue we had already though about salvaging the carby from this motor for another 4g15 powered vehicle we had. turns out we never used/needed it but in the time since being pulled off/left to sit that carb had seized the large cylindrical slider and as a result starved the motor of air and made the mixture supper rich. we found this and swapped it out with the carby from the motor we had just pulled out.

up until 3k rpm it will be fine just a touch over with constant throttle or load will cause a hunting much like that of a dud tps on the efi cars but in reverse you'll loose 4-500 rpm and return. under load this just present as a massive miss as if you had suddenly switched in to reverse for a split second. was wondering if anyone had any ideas on what could be the issue. all vac hoses have been triple checked and are all well sealed with no holes. the fuel pump works and seems fine. so by process of elimination it has to be something in the carb itself
 
Don't know these carbs at all, so I'm purely guessing here...
Are they a single or twin throat set up? If twin, how is it operated?
-Possible the secondary isn't allowing fuel to pass properly; would be about the right point at 3 grand for it to actuate depending on type.

Have you checked the float level? Needle valve operating correctly?
 
It will utilise an automatic choke on the carby that is mechanically operated,
Most mitsubishi auto chokes from back in the day utilise whats called a "wax pellet" set up that is heated by the engine coolant running through little coolant lines into the carby.
As the car warms up, the wax pellet melts and the choke is slowly deactivated. These little coolant hoses feed into small fittings on the carby that often corrode and block up, or the wax pellet set up fails.
Take it to a mechanic/carby repairer
 
So... chances are you can ignore what my self & EVL20T said...
Had a look at a friends carby fed cc tonight looking at other things. anyway, had a quick look at the carby & couldn't believe what I was looking, bloody things use a constant velocity carby!!!!!

Haven't had much to do with these type of carb sorry. All that I can really think of is, if they use a diaphragm to operate the slide, if it was to get a hole in it, would possibly cause a similar issue.
More or less... Time to get a work shop manual and pull it apart :thumbup:
 
well it appeared to clear itself up after some minor tweaks. the sound of the air rushing in on the one with the stuck slidder was almost tubo esk. old man has a thing for carby's gonna pick up another one from the wrecker he's gona rebuild it with larger jets. he then wants to try and get a cam for it. all the while i'm just sitting there laughing. and make the remark you know you can get efi heads for these! realy but arn't the tanks different external fuel pump! he exclaim oh well that could work.

could you honestly think of a 4g15 carby pulling about 100kw's i can't that's almost twice the original power!.

also found out my freakish 4g93 sohc block is even more freakish over on 4gt a guy posted an image of a sohc and dohc block side by side his sohc block didn't have a threaded part where a tensioner would go. my block is exactly the same as a dohc block so it got saved from the metal skip. the mivec dreams live on!
 
You must log in or register to reply here.
Back
Top