For about a minute after cold start, van doesn't seem to have much power. After about a minute, as engine begin to heat up power gradually returns to normal. But there are no codes.

I recently changed lower intake gasket and valve cover gasket and a garage changed axle seal. I followed service manual for gasket change, except I didn't use motor RTV on LIM gaskets corner.

Even before gasket change, van had the same problem but now it seems to have gotten worst.

 

Just guessing, maybe the temp sensor or map sensor. But you would need to run a data recording, to find the problem.

 

thanks master tech. Can you please tell me what is data recording and how to do that? Is it dealer only thing ?

 

You look like the right guy to ask. Considering this only happens during the first minute or so while the engine is warming, could this be "open loop" related? Is it the ECT sensor sensing a hot engine or the O2 sensors getting hot that tells the PCM to shift to "closed loop" mode? Have you ever seen this problem come down to reprogramming the PCM, specifically the fixed parameter (my word) catalog used by the engine during open loop mode?

 

If you don't have the scanner to do the data recording, then the dealer would need to do the recording for you.