08 Taco backfires thru intake lacks power when trying to accelerate with cold engine

This problem started about two weeks ago, noticed it when I started it and tried to climb small grade, persisted when I added throttle to accelerate on road, engine was cold had been running only about three minutes, after about two more minuts all was normal? Too it to my mech. scoped it no codes static or road test( warm engine). Plan to take it bact to the shop and leave it there overnight for cold start test. Any Idead? Thanks alpinebob SoCal

 

It sounds like a timing problem with the VVT solenoids ( Camshaft Timing Oil Control Valve Assemblys ) and possibly dirty VVT Solenoid oil filters.

 

I agree. Cold thick(er) oil and dirt screens.
At least, that would be my guess and the “easier” to fix.

 

Thanks, I will change the filter screens ASAP.

 

Will change screens...Thanks

 

Here is a good example of their location.
Thanks to @Fullboogie
https://www.tacomaworld.com/threads/oil-control-valve-location.270960/page-3#post-15729126

 

I'm thinking check fuel pressure as cold engines require more fuel to operate, I would think a VCT issue would set a code. Another possibility would be a dirty MAF sensor.

 

It seems like most with filter/OCV throw p0012.

I didn’t think about fuel? That is a good thought.
Curious to know if it only happens in Open Loop?

 

Would be hard to say, most modern engines will be in Closed Loop 30sec-1min after startup if O2 sensors are working properly. I would want to look at Fuel trim, O2, MAF, and ECT PIDs first and depending what I saw there I'd likely want to put a fuel pressure gauge on it and drive it.

 

Still don’t know why a Toyota hasn’t made a dedicated port/valve to check fuel pressure.

I guess we either use a SST or get creative.

 

If it's backfiring through the intake and lacks power you are running severely lean. Possible causes are MAF, fuel pump, injectors, vacuum leaks, or as mentioned a VVT issue causing timing to be jacked up, potentially a stretched timing chain., Depends on how many miles you have.

 

Most manufacturers aren't putting fuel pressure test ports in anymore unfortunately. You will need a 'quick connect" tee adapter can't remember the size it's either 5/16 or 3/8, something similar to

$31 BETOOLL Fuel Pressure Test Kit 0-100PSI with 9.497.896.30 Fuel Line Fittings

this would work. I apologize, I'm used to working in a shop environment and having access to at least basic "special tools'.

 

There's actually a really easy way to see if you are getting good fuel without a gauge. Disconnect the fuel delivery line, hook up a hose and put it in a big empty water bottle or bucket. You should see a nice solid stream at cranking. If it's anything less than that or if it looks really weak, well then you may want to investigate that further or get a proper fuel testing kit. If you are feeling really hot, just replace the pump based on those facts alone.

 

Wow! Thanks to all for the help. Arthur Itis kept me from getting around the wheel well and under the engine as I would have needd, so I was not able to locate the plugs that cover the VVTs today. So I spent some tome running the engine and observing performance: upon start cold it would barely take fuel when I applied throttle, I had to "creep up" on the gas to get rpms, after it got to about 1500 turns it pulled away from stop slowly. I let it warm up for five minutes testing throttle response every 30 secs. or so, same result, stumple, backfire. after 10 mins. It ran fairly well but lacked "normal" throttle response which was pretty snappy in the past.
After reading the comments offered in the post, I recall that I added about eight gallons of fuel from cans I had stord for emergency about six months ago without stabil due to "old timer's memory". I think that I will drain the tank justfor drill and thengo from there with the other suggestions a s I can.
Thanks very much guys, Happy 2021
,

 

"And now you know...the rest of the story." Are you really Paul Harvey?

Link for the young ones: https://en.wikipedia.org/wiki/The_Rest_of_the_Story


I hope the old gasoline is the root of your problem.

 

Yep. That works on a lot of makes/models.

 

It's an old trick I picked up working on 1990 Honda Accords and Civics.

 

I remember that man quite well.
I used to listen to him all the time at my grandparents house. He was a brilliant man. Makes me miss the 90’s.

 

Me also. I remember one of my first employers as a young 16 year old mechanic apprentice we would listen every day at lunchtime.