Need help diagnosing carb problem.

[WheelDrummerManiac]

Hey hope you are all doing well. My carb is not acting right. I rebuilt it about three months ago and that fixed the problem I was having at the time and it ran fine if not a little rough after the rebuild. Now though only sometimes it runs fine. Sometimes it idles too high, and sometimes it struggles to idle at all. When cruising it decelerates much too quickly like its getting bogged down or not getting enough fuel, and everytime I touch the throttle the whole car jerks. I'm mostly worried about the idle right now because its annoying as hell and I dont want to stall at an intersection. I dont want to rebuit the carb again, but if I have to I will. Here are a couple of google drive links that are videos so you can see and hear whats happening. Second one you can see the jet thats keeping it running. The carb is the aisin #15340 btw.

https://drive.google.com/file/d/1FAx3w3 ... drive_link

https://drive.google.com/file/d/1A_5Zsy ... drive_link

If anyone could help with this, I would super appreciate it.

[dlb]

There are so many possibilities with such an array of inconsistent symptoms like that. Did you have a carb kit and replace all the parts that came in it? Could be a vacuum leak, could be a leaking AAP diaphragm, might not be related to the carb at all, especcially since the carb was working (mostly) fine after you rebuilt it. Have you done all the other routine tune up stuff recently, like plugs, wires, cap, rotor, fuel filter? If any of those are suspect or due for replacement I would start with them. I would also check the timing and confirm it's correct.

Also, easy thing to check: remove the cap and make sure the rotor twists counterclockwise slightly and then snaps back when you let go of it. If it doesn't snap back, the mechanical advance is stuck due to dirty old grease in there and that is causing the engine to run with incorrect timing. That can make the car run poorly but also inconsistently because the rotor might move slightly this way or that and alter the symptoms. I've run into that two or three times on Tercels over the years.

Let us know what you find.

[Paul]

I was able to see the first video. These carbs behave best when all the emission controls are hooked up and functioning properly... not trying to be critical, but I see several vacuum lines missing and the TVSV is broken off. I would use the vacuum diagram as a guide to put things back in order and verify routing of lines.
When the carb starts surging like that, a functioning AAP delivers pump shots - compounding the problem. If the diaphragm leaks, fuel is sucked into the vacuum line and causes other troubles, like cylinder 1 fouled. Since the AAP is for cold weather warmup, I would disconnect and plug this line for now. Temporarily raising the idle speed may help until you have it all sorted out. Going back over the service manual tuneup adjustments might reveal something out of order. Frustrating problem... good luck.

[dlb]

I wasn't able to watch the videos last night but just did now and I agree with Paul. The cycling shown in the video is likely due to a vacuum leak, and the missing vacuum lines also point to a vacuum leak.

Also agreed re: the carb and emissions systems are designed to all work together so when you remove or disable components from the system, it usually ends up having some quirks in how it runs.

[WheelDrummerManiac]

Very frustrating yeah. When I rebuilt the carb I replaced everything I could. There were some washers and I think a diaphram that didn't come in the kit though. It might have been the aap diaphram. Thats when we noticed the TVSV was broken and it was busted busted. We disconnected the emmisions and jerry rigged something up so I could up the throttle with a switch to warm it up. It was winter at the time. We checked the service manual and connected everthing that was necessary. Again kinda jerry rigged. The thing that really confuses me is that it only does it sometimes, like today it ran fine. Anyway like you said all the emissions are supposed to be connected so I think ill try and get that TVSV. If yall know where I could get one that'd be great. I'm gonna make a new post asking about that. Wish such a fragile little thing wasnt so vital to the operation. Thanks to both of you.

[dlb]

Easy way to check the AAP is suck on the hose that goes to it. If you get gas in your mouth, it's busted. Or you can use a vacuum gauge if you're not fond of the taste of gas.

TVSV's are occasionally available new on Alibaba, ebay, etc but for the most part you will have to find a used one. Should be plenty to be had, I suggest joining the fb group for finding used parts like that. I prefer the forum for a lot of things but the fb group is far more active so it's good for finding parts, and quick responses to simple questions.

[WheelDrummerManiac]

Cool didnt know that trick. No gas from the AAP atm. Will check it when it acts up again. To facebook I go!