Bad cold running surge/back fire

Hello out there and Merry Christmas! I am new. Here is a problem I have with a 2002 Tacoma V6/auto with TRD Off Road package. This is only at cold start – runs ‘normal’after it warms up:

1) Afterengine catches, minor hesitation at idle that QUICKLY goes away. Idels ok fromthere on.

2) Under normal acceleration, power dies with much back firing out exhaust and up intake.

3) During extremely slow acceleration (little gasgiven to it), it slowly accelerates with no problem.

4) Asit warms up, it improves. When it is upto temp, it appears to run and accelerate fine.

What has been done to date:

1) Ashop cleaned the injectors by using an injector cleaner they hooked up toinjector intakes. – No change.

2) Ireplaced the plugs – when removed, plugs were wet (I believe with gas) in onebank and the other bank was dry. Problemstill existed.

3) Ireplaced the fuel filter. Problem stillexisted.

4) ReplacedPCV valve (pretty clogged). Problem still existed.

5) Tookit to dealer – looked at it and diagnosed it as a bad head gasket and replacedboth head gaskets. Also cleaned throttle body. Said it was fixed. Picked it up and it still had the sameproblem. This did not fix it. Got dealer in truck and showed him. They did further checking of all sensors andcontrols/timing/firing while driving it with portable laptop computer they hookedup (why didn’t they do this initially?). They said everything checked outnormal. They had a confab between shopforeman, technicians, service technician and service manager. They said that it may be a ‘bad engine’ butcould not specifically point to anything. I disagreed. They then decided torefund my money for the work they performed and handed the keys back tome. They washed their hands of the truck– wanted nothing more to do with it. At least got a new set of upper endgaskets on everything.

To note additionally:

1) Gascap hisses when removed.

2) Checkedtwo small evap. System valves on driver side under hood. Worked fine.

3) Nocracks in emission lines.


Does anyone have any suggestions?

 

#1 thing I would do is check the ecu temp sensor for accurate reading.
If the outside temp is 60 on a cold start and it's reading 150 then it's going to run like crap until it warms up. You Need to check cold parameters. Might want to clean the t/body while your at it if it's dirty.

 

Hmm... Wet spark plug says no spark/detonation in that cylinder. Did you check the plug wires?

As for backfiring, check you exhaust for leaks. Always good to replace your O2 sensors and clean your MAF.

 

Dealer cleaned and checked all sensors. Said all were working properly. Dealer cleaned throttle body along with new gaskets during head gasket replacement. Head gasket work done this week 12/17. With that said Where is ECU temp sensor? This then leads to my next question, what is best shop manual and where can I get it and its aprox. cost?

 

Doesn't mean anything if they weren't looking for a cold reading. A hot reading could be ok. Car has to sit till coolant is ambient temp. Sometime 8 hours. I THINK the sensor is by the top rad hose behind the t/belt cover.
As far as a manual someone might chime in because I ever have had to buy a manual.

Can't help to much more than this since it's not in front of me.
Would be nice to get a cold temp reading from the ecu.....

 

Hmmm... I thought the head gaskets were designed not to leak out and not into the combustion chamber. That type of job at the dealer can't be cheap. IAC valve?

 

Head gaskets leak anyway the want to....
It's a long job. Not sure if the head gaskets needed work at this time anyway.

 

I would look for another motor. Sounds like a cracked block or head.

 

Here is the latest and the apparent cause - Got my hands on a code reader. Checked codes - there were none. Reset system with the code reader then drove all sequences and there was still no codes. BUT, before resetting system and doing the driving cycles, got new gas (it was down to less than 1/4 tank after doing all of my checking prior to this). And the symptoms basically disappeared - it was bad gas!

Thank you all for your suggestions. I did appriciate them.