When is a hot start a cold start?

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Red
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When is a hot start a cold start?

Postby Red » Mon Oct 14, 2013 2:32 pm

Last year I cleared up a starting problem with some bad wiring between the AFM and the ECU. This year, there's a new mystery. When the car sits overnight, it may be 98F in the day, cooling to 80-85F at night, so it isn't really 'cold' in the morning at all. 75F at the coldest, typically 80+.

But when I start in the morning the engine starts rough, stumbles a little, needs some throttle for less than a minute and then runs just fine all day. Starts, restarts, doesn't care, runs well and has full power.

So something is misbehaving in a "cold start" circuit, except with temps up around 80F, I would have thought all the "cold start" systems, the vacuum switches, the cold start injector, all weren't being used. It would just be...What? That comes up to operating temperature and cuts out in less than one minute, so the engine is running nicely again?

Does that point to anything in particular to anyone? Something that counts as "cold" start not because it is cold out, but because the engine has simply reached "room" temperature?

--Red
-- Original owner, 1985 GT-S

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jondee86
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Re: When is a hot start a cold start?

Postby jondee86 » Mon Oct 14, 2013 4:50 pm

Are you still running the factory thermostatic idle-up valve ?

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ae86xy
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Re: When is a hot start a cold start?

Postby ae86xy » Tue Oct 15, 2013 4:27 am

I got the same issue before but with backfiring turns out my cold start injector was plug with white silicone sealant don't know how it got in there, got it replace and she fires/run so sexy now...hope this helps

LongGrain
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Re: When is a hot start a cold start?

Postby LongGrain » Tue Oct 15, 2013 11:27 am

you cant think of "cold start" as it being actually cold for YOU. When you consider operating temperature for an engine is generally just shy of 200 degrees, You're starting up the engine at 100 degrees less than operating temperature. So yes, starting your car on an 80 degree day is still a cold start.

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Re: When is a hot start a cold start?

Postby Deuce Cam » Tue Oct 15, 2013 1:40 pm

Thread title sounds like riddle lol.

A true cold start is when the engine temp. and outside car temp. are equal.

Your symptoms do sound somewhat iacv related. FWIW my iacv is deleted. Mine fires up like normal on warm starts and the idle fine. Cold starts are a different story... For example, mine fires right up on a cold start in 100*+ heat, but it stumbles and will stall since the idle is so low - idle needs to be manually raised for about 1 minute before it idles solid on its own. Colder outside temps require more cranking before it actually starts up. The evening temps have recently dipped into the 60's where I'm at and I'm already getting the excessive cranking on cold starts.

Regarding the cold start injector. Simply try unplugging it and see if there's any change.

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Red
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Re: When is a hot start a cold start?

Postby Red » Tue Oct 15, 2013 6:47 pm

Boy do I feel like a fool. Or rather, like some damned engineer at Toyota fooled me again.

Not having any other bright ideas but having gotten the last of some tune-up parts for an overdue tuneup, I started putting in the new plugs, wires, cap, rotor...

And that damned "engine valley cover" was the problem. The spark plugs came out with some oil on the outside and peeking under the valley cover, there was some oil, apparently weeping past the valve cover seals. Car sat overnight, oil weeped onto the plugs...car stumbled. And then quickly cooked off the fouling oil and ran just fine afterwards.

Valve cover gaskets, go figure. I'm thinking of doing something incredibly cruel to the car, taking off the valley "cover" and replacing it with clear plexi instead. I remember once years ago getting water in there after a thorough engine wash, and it just seems worth putting that black plastic on the shelf and letting some light in there, so I can peek without using a wrench.

Never had these problems with a big dumb Detroit pig-iron V8! Wouldn't have them, if someone at Toyota had molded the casting to divert fluids away from the plug holes, either. I'd try to find out who designed the engine so poorly and have him spanked, but I suspect that would only be seen as a reward there.<G>

Who knew, 28 years and gaskets would need replacing....Such a high maintenance car! <VBG>
-- Original owner, 1985 GT-S

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jondee86
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Re: When is a hot start a cold start?

Postby jondee86 » Tue Oct 15, 2013 10:15 pm

Image

... but the last I heard oil does not conduct electricity. So how is a bit of oil on
the outside of the plug going to interfere with anything ?? Oh, and I'm pretty sure
those cam cover gaskets are supposed to be replaced every 25 years :mrgreen:

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oldeskewltoy
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Re: When is a hot start a cold start?

Postby oldeskewltoy » Wed Oct 16, 2013 8:54 am

I don't buy it Red......

either you moved something when you pulled it all apart... or you inadvertently fixed it when you replaced the other parts.... some weepage of oil isn't going to toss you into stumble mode... especially if it is so minimal that you cook it off after warm up.

I'm guessing something to do with either the 5th injector... or maybe the cold start sensor in the water neck. It also MIGHT be more wiring issues.... the harness where it crosses the engine deals with substantial heat... it wouldn't be the first harness that had a failure do to age and heat
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Re: When is a hot start a cold start?

Postby Deuce Cam » Wed Oct 16, 2013 10:13 am

Yeah both of my corolla's had bad leaky valve cover gaskets when I got them. The spark plug and wire boot on cylinder 4 was oil soaked on both. One of the cars even had oil pooled up around the plug to the point where it was too much to evaporate. They ran fine.

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Re: When is a hot start a cold start?

Postby allpr0h » Sun Oct 20, 2013 6:40 am

same, seen my bigport running with so much oil between the valve covers where the sparkplugs connect, it was a real joke
ran fine
w00t