I have a hydra 2.5 and I recently upgraded my fuel pump a few months ago . I re-autotuned properly (or so I thought) but now 6 weeks later, somewhat coincidentally with the warmer weather I've been getting oscillations in my revs.

When I'm in boost or anywhere above -10 vacuum there's no oscillations. I get oscillations throughout the rev range whenever I'm betweeen -25 and -10. It's about 2 oscillations a second and I can hear it, feel it, and watch my boost gauge needle bouncing around.

Anyone have any ideas of what might be causing this?

 

I used to have this as well. Check your vacuum setting. When the car is idling, check your vacuum level (~500 in Hg). Set the value about 50 higher than what your idle setting is. I have to change mine every time the weather changes.

 

Do you mean the ISC setting?

 

That sounds about right. I am going to hook up the laptop tonight as I need to adjust some values after moving.

 

Mine does this between 600 and 1200 rpm (slowly) sometimes when it's cool..and it either takes a minute to go away or a quick tap of throttle. It also happens when the car is warmed up when I turn the A/C on.

 

Could be from being lean, or from trying to advance the VVT before you have sufficient oil pressure. Those are both easy things to check / fix.

 

OK it was caused by being lean. I started over with a fresh base map from Jeremy and it was ok. Then I autotuned and it leaned it way out and now it does it again. I guess my wideband sensor is dying.

 

Interesing. My car does this when I first start it.... and it stops when It's warmed up. I have some settings to change

 

It could be the cold start enrichment? Maybe it's not enriching enough?

BTW it may be worth contacting Jeremy and asking him to update your map. I sent him mine and there's quite a few changes on the new version. I think he has VVT programmed in properly too on the new map.

 

I got new cold start numbers from him. I have yet to load them however.

 

I got an email from Jeremy yesterday stating he had worked through some cold start issues. Sent him my map for updates as well.

 

To update this thread for anyone searching for information--

This was caused by me running lean. My wideband had slowly died. I loaded up the base map which is far richer than my tune and all was well.

I think Long Term Trim might take input from the wideband so if your wideband dies (the hydra wideband dies slowly and reads increasingly inaccurately) it might screw up your table over time.