Cold Start / Fast Idle Problem

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Hteverow
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Posts: 48
Joined: Sun Jun 03, 2018 3:35 pm
My tercel:: 1986 SR5
Location: Maine

Cold Start / Fast Idle Problem

Post by Hteverow »

I'm wondering if anyone can help me diagnose a minor issue in my Tercel.

Winter mornings here in Maine are typically frigid, so I typically perform the cold start procedure in my Tercel by pressing twice on the gas, for one-Mississippi per pump. The car will always immediately start, but if it hasn't been running in the past few hours, it will take about 45 seconds to a minute for it to actually set into a smooth fast idle. In that period, though, it runs quite choppily; I'm not sure how to describe it better than that. After a bit, though, it's as though the cam manages to pop its way into proper position for the fast idle. I let it run at around 2K RPMs for a few seconds, and then blip the throttle to return it to its normal 800 RPM idle.

What should I do to get it to immediately set into fast idle mode on a cold start? I'm an impatient, immediate-gratification millenial, and I'm tired of having to wait for my car to get its shit together in the AM.
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Petros
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My tercel:: '84 Tercel4wd w/extensive mods
Location: Arlington WA USA

Re: Cold Start / Fast Idle Problem

Post by Petros »

I use three pedal pumps to the floor, than start it. once running, I blip the throttle up and down for about ten seconds, than rev it to perhaps 4000 rpm and hold it there for about 5 seconds. It will still be up on the high idle speed, but I can drive off with it that way. if I do not give it that high rev it likely will stall out unless I let it warm up longer.

In the FSM is a procedure to check/adjust the carb linkage and idle speed from a cold start, make sure everything is adjusted correctly. Check you have no vacuum leaks (very important), and there is no water in your fuel/carb.

in prolonged subfreezing weather any moisture will cause ice crystals to grow in the fuel system, that may be causing your issues until it warms up enough to make it run smooth. Once you get it all adjusted properly, and verify all vac lines are in their correct place and there are no vac leaks, you might try adding those fuel additives that are supposed to absorb the moisture out of the fuel system.

It might help is you can find and run it on ethanol free fuel too.

Good luck.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
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rer233
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Re: Cold Start / Fast Idle Problem

Post by rer233 »

Think you'll find your problem is with the choke break- either a ruptured diaphragm or bad (or improperly routed) vacuum line. Best way to diagnose is with a cold engine, take the air cleaner top off, have someone start the engine, and see if the choke flap opens slightly (it should.) If it doesn't, open the choke flap slightly and see if the engine smooths out. If it does, you've got your answer. Even with everything operating 100% properly, our cars will never be as smooth when cold as the fuel injection you millenials are used to (yeah, I'm an out fart.)
if it aint there, there's a good chance it won't break!
83 SR5 Silver/Blue (Snowmobile/work beater)-totaled but drivable
85 SR5 Blue
88 SR5 White (the 'good' one)-not anymore-totaled
87 fwd silver wagon a/t
87 4wd dx Cream (a/t- not anymore- now m/t)
Hteverow
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Posts: 48
Joined: Sun Jun 03, 2018 3:35 pm
My tercel:: 1986 SR5
Location: Maine

Re: Cold Start / Fast Idle Problem

Post by Hteverow »

I will check out all of your suggestions this weekend, thank you very much!
The Professor
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My tercel:: 1987 Tercel SR5 4WD wagon
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Re: Cold Start / Fast Idle Problem

Post by The Professor »

Petros wrote: Thu Jan 24, 2019 7:11 pm I use three pedal pumps to the floor, than start it. once running, I blip the throttle up and down for about ten seconds, than rev it to perhaps 4000 rpm and hold it there for about 5 seconds. It will still be up on the high idle speed, but I can drive off with it that way. if I do not give it that high rev it likely will stall out unless I let it warm up longer.
I'm going to have to try this, our T4 can be hard to start, hot or cold. I'm almost certain the choke breaker is borked on my carb, but I need to catch up on maintenance on the rest of the fleet before I put the T4 down for service.
1975 Subaru SuperStar wagon
1984 Subaru Turbo-Traction wagon & hardtop
1987 Subaru RX 3-door
1987 Subaru RX Type-RA 3-door
1987 Toyota Tercel SR5 wagon
1999 Subaru Forester S
2002 Subaru WRX sedan
2019 Subaru Outback 2.5i Limited
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