Yet another carb question...

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MrWrench
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Re: Yet another carb question...

Post by MrWrench »

34ish F° in my garage today.

I pumped the gas petal twice and it instantly started and idled consistently at 1,200 RPM. choke is nearly fully closed.
2 min in, the RPMS climbed to 2000
3 min in the choke is halfway-ish opened.
exhaust started popping and it fluctuates from 2100-1900 kinda like a misfire sound?

4 min in I revved up to 3,000 and it idled down to 1000/950ish

Idling rough between 900-1050

6 min in I revved again. Idle fluctuation from 800-1100 really rough and nearly stalling at 800-850ish
7min turned on blower motor

Lights flickering on dash like it's about to stall at 800rpm-1100 with blower motor on

8 minutes in I turned blower motor off. No change in idle fluctuation
Nearly stalling - choke is fully opened at this point. Like 99 percent of the way pointing vertically

At low RPMs it's adding fuel in left fuel bowl. Idle smooths out when fuel added

10 min in I turned it off and restarted by just turning it off and back on. Smooth idle around 1100.
I revved it to 3000-3,500 and it went back to fluctuating between 800-1100

11 min in after revving again it starts fluctuating between 1100-800 and occasionally stalling around 750rpm

New plugs and wires as of yesterday. Haven't checked cap/rotor yet.

Timing not set with vacuum advance off/plugged. I set my timing light on it when I got home and bumped it forward from 5 degrees to 10 degrees because I remember seeing that the 5 can cause exhaust valves to burn up. I suppose the upper outer most line was likely disconnected since I discovered that was leaking later on.

I will look at the fu-6 page in a few and see if I can't pull it out and clean it. Likely tomorrow since it's 12 degrees outside and I don't have any wood for my wood stove yet.

Thank you everyone for your help so far!
1984 SR5. Lifted offroader with a snorkel. Aka "Thunderbucket"
1985 SR5. Daily driver. Aka "Spud"
1986 SR5. Dakar Rally clone build.
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dlb
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Re: Yet another carb question...

Post by dlb »

MrWrench wrote: Mon Feb 14, 2022 2:44 pm Timing not set with vacuum advance off/plugged. I set my timing light on it when I got home and bumped it forward from 5 degrees to 10 degrees because I remember seeing that the 5 can cause exhaust valves to burn up.
This is crucial -- the manifold vacuum advance hose that goes to the distributor vac advance must be disconnected and plugged, otherwise your timing will end up about 8 degree retarded. Which is way off.

Also make sure the vac hoses going to the distributor are connected to the proper ports. The upper port with the big hole should be connected to manifold vac, the upper vac port with the small hole (if your car has it) should be connected to the high altitude (HAC) system, and the lower port should be connected to the carb so it gets vacuum at part throttle.

advanceunit_zpsb84f2f73.jpg
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Nordical25
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Re: Yet another carb question...

Post by Nordical25 »

For it me it sounds like your high idle is fine (first minute with 1200 RPM). Then the problems begin when moving to low idle. It sounds to me like it is getting too much air occasionally. But it is still worth of checking timing and distributor parts as previously mentioned.

At which RPM you set your timing? According to my manual you should adjust timing at 750 RPM. Otherwise there could be already some added timing degrees due to behavior of distributors spring system and vacuum at higher RPMs. So 800RPM is ideal at your case I guess if your car stalls at 750RPM. If your can can manage 750 RPM idle, even better.

And yes, it is worth of checking distributor cap and rotor. I guess that they won't cause entirely that fluctuating idle, but worn ones won't improve your idle either.

If you remove carb for cleaning, it is also worth of checking condition of intake manifold to see that it looks intact (no visible cracks). In that case it is worth of installing all new gaskets between intake manifold, steel plate, "bakelite"-looking gasket and carburetor and to clean all gasket surfaces before installing new gaskets. What can happen: there is e.g. a leak of a cracked intake manifold, bent steel plate around gasket surface or "bakelite"-gasket can be damaged (bubble lookalike) or a leak in paper gaskets. So even they could also cause that high occasional idle RPM.

And new gaskets must be installed in a right way since there e.g. a small hole in steel plate and some mixture lines in bakelite gasket after the cleanup.
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MrWrench
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Re: Yet another carb question...

Post by MrWrench »

dlb wrote: Mon Feb 14, 2022 7:48 pm
MrWrench wrote: Mon Feb 14, 2022 2:44 pm Timing not set with vacuum advance off/plugged. I set my timing light on it when I got home and bumped it forward from 5 degrees to 10 degrees because I remember seeing that the 5 can cause exhaust valves to burn up.
This is crucial -- the manifold vacuum advance hose that goes to the distributor vac advance must be disconnected and plugged, otherwise your timing will end up about 8 degree retarded. Which is way off.

advanceunit_zpsb84f2f73.jpg

I was definitely unaware of this! I have a vacuum plug/cap kit coming in the mail today and I will re-time it.

Which port should be blocked off in order for me to properly time it?
Thank you!
1984 SR5. Lifted offroader with a snorkel. Aka "Thunderbucket"
1985 SR5. Daily driver. Aka "Spud"
1986 SR5. Dakar Rally clone build.
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MrWrench
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Re: Yet another carb question...

Post by MrWrench »

Nordical25 wrote: Mon Feb 14, 2022 11:43 pm
At which RPM you set your timing? According to my manual you should adjust timing at 750 RPM.
It was probably around 900 or so? I don't know for sure exactly. Since I didn't have the vacuum advance disconnected and plugged, I'm thinking I might just turn it back to it's original place since it's likely a visible spot on the distributor bolt, then properly retime it from there.

Would that make sense to do?

I'm hoping to not have to remove the carb for cleaning, but we'll see what happens. I'm going to try and look into cleaning the idle jet like NWMO had previously mentioned this evening, along with fixing the timing.

I really appreciate everyone helping me out! Fingers crossed I can get this pinpointed soon. I miss driving the car. Haha.
1984 SR5. Lifted offroader with a snorkel. Aka "Thunderbucket"
1985 SR5. Daily driver. Aka "Spud"
1986 SR5. Dakar Rally clone build.
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Re: Yet another carb question...

Post by Nordical25 »

According to service manual (https://tercel4wd.com/fsm/1985T4WD.pdf), max RPM is for adjusting ignition 950RPM. So steady 900RPM should do fine. The service manual also verifies procedure mentioned by dlb. So that would be a good start. You don't need to turn distributor back to original spot just for adjusting.

You are welcome and please let us all know how it goes.
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dlb
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Re: Yet another carb question...

Post by dlb »

MrWrench wrote: Tue Feb 15, 2022 4:18 am I was definitely unaware of this! I have a vacuum plug/cap kit coming in the mail today and I will re-time it.

Which port should be blocked off in order for me to properly time it?
You can just unplug the hose from the upper vac advance port with the big hole and plug the end of the hose with a snug-fitting bolt, then you can set the timing. Make sure the idle is in the 800-900 range when you set it though, like nordical mentioned.

Once you set the timing and reconnect the vac advance hose, the idle should should jump up a bit. Now you can adjust the idle back down to the 800-900 range.
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MrWrench
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Re: Yet another carb question...

Post by MrWrench »

Here's how the vacuum lines to my distributor are currently set.
The big port upper hole is currently ran into the the orange (one way valve?) And follows to the metal loom, which seemingly follows up the line to the "gas filter" (per page EC-38) it's the port that had 2 lines coming from it and the other end connected to the TVSV
The upper port with the smaller opening runs to The metal vacuum piece which splits off and runs into the choke breaker (as far as I can tell, that's what it's called) it's a little diaphragm that is on the driver side of the carb. It has a port shortly past that point that runs directly into the TVSV (Second from the top)
The bottom most line seems to run into the HAC (red/black port in the strut tower)
I will try and get everything adjusted now and see if it runs any better or different.

I will also attempt to set the timing soon.
I'll report back with my findings.

Thanks everyone!
1984 SR5. Lifted offroader with a snorkel. Aka "Thunderbucket"
1985 SR5. Daily driver. Aka "Spud"
1986 SR5. Dakar Rally clone build.
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Re: Yet another carb question...

Post by dlb »

If your car still has the vacuum diagram on the underside of the hood, you can use that the confirm that the hoses are all going to the right place. What you describe sounds incorrect to me but it's also hard to explain these things with just words -- it's a lot easier when you're actually looking at it, of course.
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MrWrench
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Re: Yet another carb question...

Post by MrWrench »

My car does have the sticker but it's barely readable.
Following the FSM and Noridcal25s comment.
I believe I have them routed correctly now.
The bottom most port on the distributor runs to the bottom of the two metal lines on the metal vacuum line piece running along the valve cover. From there it's difficult to trace, but it seemingly runs into that 2 vacuum port that runs into the 3 from the top port in line with all 4 ports of the TSVS. (I hope that makes sense) and the small hole seems to trace to the high altitude compensation unit.
The big hole runs into the orange one way valve that's right behind the cylinder head. I hope that's correct?

I am going to attempt to plug off the vacuum advance and set the timing now.
Thank you dlb and everyone else again for your help. I have yet to clean the idle jet as NWMO mentioned because it's a bit deeper in the carb than what I have parts to repair at the moment. I ordered a rebuild kit.


Update: timing is set a 10-11 degrees now.
Vacuum lines are hooked up to the distributor properly. Car still doesn't idle great.
I have a carb gasket kit on the way. I'll try and see if I can't get that jet cleaned out. I was thinking about running a bottle of seafoam and gas mixed to the pump and see if maybe they'll clean something out?
1984 SR5. Lifted offroader with a snorkel. Aka "Thunderbucket"
1985 SR5. Daily driver. Aka "Spud"
1986 SR5. Dakar Rally clone build.
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Re: Yet another carb question...

Post by dlb »

An easy way to check that vac hoses are going where they should is to disconnect both ends and simply blow into the one end with your mouth and feel for it coming out the other end. So for example, you would disconnect the hose from the manifold vacuum ports, and the other end from the upper big hole port on the distributor, and you should be able to blow through. If not, something is mixed up.

For reference, here are some good diagrams of the US federal emissions vacuum stuff: viewtopic.php?t=2810
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Re: Yet another carb question...

Post by MrWrench »

Wow! I have never seen that thread before. The color coding makes that extremely easy to read! Thank you so much!

I just ran through that and confirmed at least the disturber vacuum lines are correctly routed. I definitely had two that were not correct beforehand.

Beyond checking the low idle jet, is there anything else I should be checking? I think I'm gonna take a break tomorrow because it's been a few long nights in the cold trying to trace this stuff down.

I thank you all again for your help!
1984 SR5. Lifted offroader with a snorkel. Aka "Thunderbucket"
1985 SR5. Daily driver. Aka "Spud"
1986 SR5. Dakar Rally clone build.
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MrWrench
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Re: Yet another carb question...

Post by MrWrench »

Since I have a few days until my carb rebuild kit comes in. I figured I'd try to run some cleaner through the carb and see if anything changes. I mixed some fuel additives that's designed for carbureted cars at 3 ounces of cleaner to 16 ounces of fuel.
When 12 ounces is designed for 20 gal so I think it's probably a little heavy of a mix. But either way, to likely no surprise it didn't change anything.

Either way, I'll report back after cleaning the idle jet out this weekend. I might swap the carb completely out for another one I have on a spare engine. I went across all the vacuum lines again and didn't find anything out of order or disconnected. Fingers crossed the idle jet will solve my issue because I miss driving this car!

Here's a video as to how it's running right now. At the end is the car stalling by itself.
https://youtu.be/YU5JwzGObpc
1984 SR5. Lifted offroader with a snorkel. Aka "Thunderbucket"
1985 SR5. Daily driver. Aka "Spud"
1986 SR5. Dakar Rally clone build.
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Re: Yet another carb question...

Post by Nordical25 »

Swapping a new carb can work if a new gasket kit cannot fix issues. When you open your current carburetor, it is worth of spraying carburetor cleaner to dirty metal parts. I have positive experiences of carb cleaner made by CRC when I cleaned old Solex carburetor for another vehicle.

If a carburetor is really stuck it can even need an ultrasonic carburetor cleaner because small channels can be blocked by dust particles. And as I mentioned previously, gaskets between intake manifold and carburetor must be tight. Even a small leak between two AISAN barrels can disturb idle a lot. So they are really worth of checking if you swap the carb to another one.
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Re: Yet another carb question...

Post by MrWrench »

My carb rebuild kit came in yesterday. I'm outside today trying to figure out what is going wrong. One thing I noticed is when I was spraying starting fluid near the TSVS, it tended to seemingly run? But it sometimes will maintain running and then die shortly after so it may have been a fluke. Either way, I swapped that out and nothing changed.
Under FU-2 for "ROUGH IDLE OR STALLS"
There's an option for EBCV valve open.
I went to page EC-32 and found
2. check for open circuit. Specified resistance 11-13 ohms at 68F. It's about 75 in my garage and the part can't be warmer than 50 degrees at best. I measured 13.4 ohms. There was no continuity between the EBCV body and the + Terminal
It's a hair out of range? But possibly due to a colder temperature?

I am currently dismantling a junk carb I got that was on an engine left outside for 10+ years under a tarp. I am trying to source the "slow jet" NWMO mentioned. Can anybody help me locate it?
*UPDATE* I found it! It is the flathead brass colored one I wasn't able to get out. Is there an easy way to clean it beyond pulling the top of the carb off? It was quite the task to try and get it off on the spare engine.

The car idles fine cold, but once it warms up it'll idle poorly and stall.

Thanks in advance!
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Last edited by MrWrench on Sun Feb 20, 2022 1:57 pm, edited 4 times in total.
1984 SR5. Lifted offroader with a snorkel. Aka "Thunderbucket"
1985 SR5. Daily driver. Aka "Spud"
1986 SR5. Dakar Rally clone build.
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