Having a weird issue

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muddybumper
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My tercel:: 1987 SR5
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Having a weird issue

Post by muddybumper »

Recently when I've been starting my 87 tercel it's been idling high and the exhaust manifold will start glowing orange. Does anyone have any ideas what I should be looking for? The car has mostly just been sitting since July but before that it was my daily driver. Thanks in advance.
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NWMO
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Re: Having a weird issue

Post by NWMO »

MB,

How does it drive once warmed up? Glowing exhaust is typically "un-burned" fuel leaving the piston and burning in the exhaust manifold. Can be related to timing or carb issues running very rich. If it drives ok once warmed up, the CAT is likely ok and I would proceed to check timing (if you have a light) and go through the carb adjustment procedure from the FSM.

Chris
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dlb
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Re: Having a weird issue

Post by dlb »

Chris, I've never heard that about glowing exhaust. Neat. You learn something new every day.

I would check the AAP diaphragm. If it is ruptured, the intake manifold will suck fuel through the ruptured diaphragm to the first cylinder. Not likely enough to make the exhaust manifold glow but the AAP is such a common cause of running rich that it's the first thing I think of.
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muddybumper
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Re: Having a weird issue

Post by muddybumper »

I haven't tried to drive it since noticing this issue, I didn't want to cause any unnecessary damage. The timing does need to be adjusted though, so I will get a light and check it next time I have it running.
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Petros
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Re: Having a weird issue

Post by Petros »

timing retarded too far will cause hot exhaust (fuel is still burning when the exhaust valve opens). best timing is at about 10 or 12 deg BTDC (vs. the factory 5 degrees, for emissions, causes hot exhaust and burnt exhaust valves). I do not think it being too rich would get it that hot, but too lean a mixture can result in hotter exhaust (the lean mixture burns slower, and can still be burning hot when the exhaust valve opens).

Either way, too lean or too rich a mixture is bad for the engine. Check the AAP vac line for wet with fuel, if so you can cap off both ends as a temp fix (it will run fine after warm up, the only time the AAP is needed when it is cold). Also look for vac leaks that might cause a run lean condition.

A very hot exhaust can cause damage to the exhaust valves, so best find the cause and get it fixed.

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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muddybumper
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Re: Having a weird issue

Post by muddybumper »

Update:

I replaced the spark plugs and wires and adjusted the timing. I'm still getting a glowing catalytic converter (not exhaust manifold like I previously said). Any suggestions? My next idea is to clean out the carb, replace the vacuum lines, maybe replace the distributor. I'm not losing power or lugging when I step on the accelerator so I don't think it's a timing issue any more.
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NWMO
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Re: Having a weird issue

Post by NWMO »

mb,

Start with the AAP "check the AAP vac line for wet with fuel". If it's running well (besides the glowing cc), I wouldn't jump into the carb, vac lines (besides AAP) or distributor just yet. Then I might pull the cc and have a look. They are suppose to run very hot, but it shouldn't be glowing. Do you still have the shields around it?

Chris
Psalm 37:4 "Delight yourself in the Lord and he will give you the desires of your heart"

In remembrance of my friend ARCHINSTL:

T4WD augury?
"Oh, do not ask, 'What is it?' Let us go and make our visit."
T.S. Eliot - "The Love Song of J. Alfred Prufrock"

"Now and then we had a hope that, if we lived and were good, God would permit us to be pirates."
Mark Twain
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muddybumper
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My tercel:: 1987 SR5
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Re: Having a weird issue

Post by muddybumper »

Thank you for the info. I do not know what or where the AAP vac line is, I'm fact I am still generally a newbie when it comes to the Toyota tercel. I have a fsm on the way in the mail, once I get that hopefully it will show me exactly where all of my vac lines are.

As for the cc, yes it still has shields around it
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Petros
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Re: Having a weird issue

Post by Petros »

do not just randomly replace parts, it is a waste of time and will only add to your costs and frustrations, and not fix it.

Always diagnose the problem BEFORE you try to fix it!!!

there is a factory service manual available for free down load in PDF format on this site I think in the repair guides section. the FSM has a good section on trouble shooting, where it lists symptoms, and sends you to different parts of the manual for tests and checks of the different system.

The AAP is the "auxiliary acceleration pump", it is vacuum operated and is located on the front side of the float bowl on the carb, it has a black vac line that goes from it to the TVSV (toyota vacuum switching valve), that is on the coolant outlet on the front of the head on the engine. that black plastic thing with live 5 vacuum ports on it on the coolant outlet. You just pull the vac line, if it is wet with fuel, it means the AAP is leaking fuel into the intake manifold. if so, just cap off both ends, it is only needed on cold start up, after it warms up it, it does nothing (when it works property, if not, it leaks raw fuel into the engine). Too much fuel is bad for the engine, and for fuel economy.

the cat may also be all plugged up, not allowing gasses to pass though, not unusual on an old car. there is a way to test for cat flow, not sure how it is done. if your cat is bad, most states do not require testing on cars over 25 years old. and most will just remove a bad cat and install a straight pipe in the exhaust. This is just another idea to investigate, not necessarily the cause.

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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muddybumper
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My tercel:: 1987 SR5
Location: Idaho

Re: Having a weird issue

Post by muddybumper »

I pulled the vac line from the AAP and capped it off. I didn't notice any fuel in the vac line itself but so far I haven't noticed a red hot cat so that may have been my issue. I bought a fsm and there isn't anything in there I could find about the AAP, but luckily the Chilton manual had a helpful diagram. Hopefully this helps out with my fuel economy too because I have been getting 12-14 mpg lately which really sucks.
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dlb
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Re: Having a weird issue

Post by dlb »

muddybumper wrote: Sat Jun 04, 2022 1:54 pm Hopefully this helps out with my fuel economy too because I have been getting 12-14 mpg lately which really sucks.
12-14 mpg is abysmal. In a t4 with the 4.11 gearing, you should be getting high 20's for mpg. (the 3.73's got better fuel economy, low to mid 30 mpgs). Anyway, fuel economy like that is a sign that the car is not running properly but if you methodically work through all the basics and you will surely find the cause(s).
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