Chasing A Two Year Cold Start Issue - Stumped and Struggling!

2001 Tacoma PreRunner Xtra Cab 2.7 in Minnesota

I've had issues with cold starts the last two years as soon as it starts to cool off. I'm usually able to eventually get it to start if its been on the heater, but not always. When it does start it idles rough and stumbles until it warms up. As soon as it warms up, it runs great! As long as it was warm or kept inside, it would start and run fine.

I never get a light/code. (except for once when I pushed into the accelerator during a stumble....the code was for a misfire on number one)

Last year I took the truck in and the mechanic said they could find nothing wrong and they put injector cleaner in it.

After that I changed the spark plugs and inspected the coils. One coil was cracked so I replaced it. The problem continued and I struggle with it. I used my work truck until the season changed. Once the weather improved, so did the issue.

Two months ago when things started cooling off, I tried to chase the problem again. I lost my job earlier in the year. Money is tight and I need this vehicle to start. I'm probably over my head, but I have no other options. This is what I've done in the last week.

- I checked the ECT and verified it's reporting accurate temperatures with my OBDII reader
- I cleaned the MAF Sensor - no change
- I replaced the MAF Sensor - no change
- I cleaned the TB and replaced the IAC Valve

I started the truck up today for the first time after the TB clean and IAC change and it's idling very rough/I don't know how to describe it but it's surging. It was warm in my garage so it started fine, but it sounds terrible when idling. I took it for a drive and warmed it up. I didn't notice any issues while driving, but it's when I came back it was still idling rough and surging. The tachometer bounces as it idles. It was idling (still surging) at about 1100 in park and when I would put it into reverse it would drop way down near what looked like 500. The lights would dim with the surge/fluctuation in the idle. I tried to adjust the idle a bit, but couldn't improve the surging.

What next? I'm at a complete loss.
I know I forgot to disconnect the battery/fuse when I did the TB clean and IAC replacement. I did do that when I cleaned/changed the MAF. Do I need to do that to reset the computer?
Could it be the TB sensor? on the back of the TB?

Any help would be greatly appreciated!

 

Just got through dealing with this on a buddies truck, it was a lot of little things,

Cracks in vacuum hoses
IAC valve was dirty
Egr valve was slightly stuck open
Power steering idle switch was stuck open
Throttle position sensor was out of adjustment
PCV was froze up

The fact that the idle changes when you put it in reverse tells me it's an air related problem. Check the plenum box for cracks. Check the air pressure regulator with you mouth by sucking on the hose with your mouth. Its the small one on the plenum box. Unplug vacuum hoses one at a time, see if it gets worse or doesn't change. You should also check obdII to make sure ambient air temperature is reading correctly