Weird Running on Startup

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#1
I have a Toyota T-100, V6 w/high miles. Rececently upon startup, fully cooled down (during warm up) it runs for ~10 sec. like it's firing on 5 instead of all six cylinders, then as the seconds pass it goes away and runs just dandy.

What in the world could this be? Bad remote coil?

I've replaced the sparkplugs and wires to no avail. My next resort is to take it in, although I'm hesitant as they'd need to keep it overnight or have it sit for a few hours to fully cool down.
 
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#2
My guess would be your timing.
 

gasgasman

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#3
Could be carbon build up on the back of the intake valves.

The carbon soaks up the fuel from the injectors, until they get saturated.Then the fuel makes it to the combustion chamber.

When the engine sits, the fuel evaporates from the carbon deposits-then the cycle starts all over again when you start the engine.

Another possibility is, a leaking injector. As the engine sits it dribbles fuel into the cylinder, then when you start up it has to burn that rich mixture off.
 

ochster

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#4
Not real familiar that model, but your symptoms are close to what a EGR valve will act like in a high mile rig.

Just a stab in the dark...
 
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#5
Thanks guys.

Another clue: this started happening out of the blue - no buildup, all of a sudden; now thus.

If it were timing, wouldn't the computer compensate, or is it doing just that - then it reaches it's goal and the "miss" goes away?

An injector? Maybe - good reasoning and presentation. I do run a cleaner every so often in the tank. Geesh: I'm embarassed to say I do not know if this is a throttle body (a la GM) or multiple-point system; will have ot look under the hood.

That's the thing about having a reliable rig: one often misses out on an education.

EGR? Maybe. I replaced one this summer (check engine light came on - dealer did the plug-in test) but did the installation myself. Could be the other is gone now. But at $150 (!) a pop, I'll take it in, and let it cool down. Then with their computer hooked up, start it up and see what the readout is.
 

OKKX'er

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#6
My Ford V-8 ran rough at start-up, got worse and worse, until it quit running. Turned out to be the ignition coil.
 

wrench

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#8
Do you notice any smoke out of the tailpipe when this happens? If so, what color is it?
I ask because, another possible cause could be a "weeping" head gasket. When you start it up cold, the engine has to "pump" the coolant out of the cylinder before it will run smoothly.
Also, when was the last time you changed the fuel filter?

just my .02
wrench
 
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#9
I agree with wrench, its very common for head gaskets to do that , also partially restricted or lean injectors as well, the sweet smell of antifreeze from the tailpipe is a good indicator and white smoke, black smoke is usually fuel and blue is oil , also start it if it skips ,shut it off quickly and pull the plugs antifreeze wont burn and the plugs will be wet. egr causes black smoke and rough running due to it hanging open and loosing intake vacuum valve seals can get oil on the plugs and cause a skip, lots of ash fouling when you remove the plugs and look at them, how long since its been completely tuned up? plugs and wires can do wonders somtimes.... good luck
 
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#10
Sorry for the late response: turns out it was a leaking head gasket (good call, guys). I had a local guy use some stuff called Thermalweld for a fee of >$200 (vs. $2,000 conventional head gasket replacements.) I was on my way with no more symptoms - it now purrs on startup.
 

wrench

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#11
$2K seems very high. Your "Thermaweld" is only a temporary fix. I have heard of some stuff called "Steelseal" lasting more than 20K miles, but have never used the stuff.

Good Luck