light misfiring - starts at 15 seconds...done by about 90 seconds

It's cold up in Wisconsin now, and, just like the title says, when cold-starting the van the following happens :

- initially everything is smooth (first 15 seconds)...
- then, random light misfire is audible until appx. 90 to 110 seconds after startup...
- then, van completely smooths out until following morning

I apologize, but I cant find where this is addressed in earlier posts

thanks for any help !!

Carbon buildup comes to mind. Carbon soaks up fuel and when he engine is cold it needs a richer mixture. A lot of that fuel is soaked up by carbon deposits and so the fuel mixture is less than ideal for cold starting. Also if your cold start injector is not functioning that exacerbates the fuel mixture condition even more As the engine ages its efficiency decreases greatly with carbon deposits

I would not concern myself with a transient condition that only lasts 1-2 minutes.

Normal driving condition is the engine up to normal operating temp. If the engine performs well under normal driving conditions and temperature then I am happy with that.

okay... the van fires up instantly on cold-start (which is great), but, what is the length of time that the cold start injector would be active ? Would it be in action as long as up to 120 seconds ?/ or, is it only squirting for about 15-30 seconds ?

The cold start injector is managed by the cold start injector time switch (coolant Sensor) I do not believe it is documented anywhere the pulse time of the cold start injector but since its controlled by the coolant sensor I would have to speculate that the cold start injector operates until the coolant temp changes since its control is temperature driven.

Anybody else please correct me if I am mistaken

To add the first 2 minutes after cold start the ECU is in closed loop and so at this time the ecu is essentially ignoring inputs from various sensors until normal operating temp and so really like I said earlier you need to really be concerned with the performance at operating temp.

An oxygen sensor does not really begin to work until it reaches 600 degrees Fahrenheit and so the air/fuel ratio is not optimal.

The 84-87 Vans had a single wire non-heated 02 sensor which took longer to warm up because it relied on the exhaust temperature. The 88-89 Vans had the upstream 02 sensor 4 wire with a heating element which heated the sensor immediately within seconds

Try putting some dry gass in. I do this every year before the winter season. Some water build up can bogg down a cold engine. Stay warm
Keep on vanning

The cold start injector time switch tested cold at 32 ohms which is in the middle of the recommendations in the manual... I think it's good. The fact that the van starts immediately and happily on a 35 degree morning tells me that the cold start injector must be functional. It is an intermittent miss, and, it seems "mild" ...( I have to put my ear down by the tailpipe to notice it )...and, again, it disappears after a minute or two. 299,000 miles and now that's my only complaint... and I'm sure I remember my '86 doing that too.

I can say that now, in the 6 weeks I've owned it, the van has become a MAJOR pleasure to drive !! it has received -new Toyota oil filter, -fresh Mobil 1 10w30, -new differential fluid, -new air filter, -new Toyota thermostat (badly needed), -new aisin fan clutch, -new coolant temperature sensor, -new PCV valve, -new cap-rotor-plug wires, -new Denso iridium plugs...etc. Also, there was no throttle stop screw and set-nut on the van when I got it--thankfully, I was able to get one off the old van...(I set it at about .095 out)
--additionally it has received ...-new complete exhaust, -new KYB monotube shocks, -new front pads ... and,as a bonus, the van came to me with -new rear brakes/drums/wheel cylinders...-4 new ball joints, -new steering rack and hoses ...

I'd like to say that, thanks to the tutorial by llamavan, I have pulled and re-installed my engine cover for the first time in 16 years of owning these vans !! --easy as pie

I also want to mention that this new '87 LE 2wd has the rear coil springs and I can't believe what a shocking improvement it is in ride quality compared to my '86 with leaf springs -- like night and day

Lastly, as I tidy up and perfect the issues leftover from previous owners, I keep thinking "what would Tim do"...I want the van factory-tight.