1999 gs400 130k.

This happens everytime I will start from a stop around 15-20mph right before it shifts. I just installed my K&N FIPK intake and it became more prevelant but would happen before sometimes.

What is happening is I hear almost like air sucking in while a valve is opening and then you can hear the valve open completely and the car almost jumps/shifts hard.

Any ideas what this could be?

 

I know on my Supercharged Buick 3800 with an open air filter when cold the IAC (Idle Airspeed Control, essentially a PCM controlled bypass of the closed throttle blade to manage idle airflow) is very noisy.

But it sounds like you have an air leak between the MAF and the Throttle Body. Check the connections and ensure no cracks in the plastic tubing.

 

checked everything on the intake andall the vacuum lines. It's not as bad now but still making that valve opening sound and shifting hard.

im stumped wtfff

 

Sounds like a MAF leak, check the MAF itself for leaks. Shifting hard is a sign of MAF leaks too.

 

Im ready to put the stock airbox back on and see if this still happens.


I hope this noise/hard shift isnt actually my tranny on its way out...130k I figured it would last longer, but I have been a shade rough on it lately.

 

hmmm try not to say the word "TRANNY" lol....lets find all other obstacles first you sure it's not any of the sensors

 

I would, easiest way to find out and confirm what is going on.

 

updates: Stock box on and the noise still is happening exactly the same. I took it to a transmission guy and he said it was fine no need to worry. He heard the noise and also did not know what it could be, seems to think it is coming from the back. I had my mechanic drive it and he also does not know what it could be but he also said he isnt worried about it.


My CEL did come on and I have 0446 comig n up...Could all this be related. I was doing some searching on here and a lot of drivers seem to change the VSV and that solves the CEL. I wonder if a malfunctioning VSV could be making a noise like that. where is the charcol canister located on these cars??