Vt commodore rough idle and when revving

[Snowshaddow]

So I started my 98 vt today and noticed it making a weird sound. The exhaust seems louder and lumpy. I popped the bonnet and it sounds fine at the motor but when I rev it at all it makes a funny sound as if it's struggling. I checked the fault codes but it says it's fine. Checked leads and plugs but they seem okay and havent had this problem till today. It's been raining and the car was sitting inclined forward could water have gone up the exhaust and done something maybe? I don't know what else to check.

Oh it sounds as if it wants to die when it comes down off the revs like it just doesn't wanna keep going.

 

[EYY]

Classic dfi module symptoms. Can happen if the dfi module or coils gets wet, or if the dfi module is failing

 

[vyseriesII]

+1 for dropped a coil pack

 

[Snowshaddow]

Any way to test it? Or should I just replace the coil pack

 

[BOOSTER]

You could try soaking it metholated spirits for 5 mins blow it out with an air compressor and leave it in the sun for an hour but i would also check for AIR LEAKS from the air filter back to the plenum and BOTH CABLES are clipped in on the THROTTLE body.

 

[Snowshaddow]

After looking more closely it looks as if the belt tensioner is jerking or moving? Makes a sound when giving it a rev.
Okay on second thought it might be the coil pack. Tensioner seems normal from what I've been told. Exhaust still sounds funny tho.