My car seems to "shutter" during light throttle cruise. It is very light but you can feel it enough that my wife asked about it today. Hasn't effected my AFR or MPG but it is concerning. I am also tuning the car and it seems to be down on power.

I am leaning toward the coil packs or wires being bad. I have 71k on the car and they are original. I changed the spark plugs and gapped them to .024 and there is no change.

Thoughts?

Edit: Took a log and posted it below. Looks like my AFR is being effected. I also changed my wires for some old magnacores, Yes they are crap, but I wanted to see if there was a change. Seemed to run better but not enough to get rid of the shutter / surge at cruise.

Edit 2:
History:
- timing belt water pump completed
- Head porting, kelford cam install (No cam gears)
- Intake manifold ported with 65mm TB (Buschur)
- New front O2 sensor

Problem:
- Surging, like a misfire, but no code during cruise. Stronger during low speed, in town cruise
- Power down with power curve really slow in lower RPM
- AC not blowing cool air, checked pressure and lines are reading high psi

Solution:
- Replaced coils, wires and plugs (No change)
- boost leak test to 15 psi (Good)
- ????

 

do you have an aftermarket bov/diverter valve? if the spring pressure is not set right or it is VTA then that could be the cause of your stutter if you have already ruled out plugs. gl

 

Yes, I run a Forge BOV. It has been on the car for about 2 years without issue. This just started a week or 2 ago. I will look into it though.

Any other thoughts?

 

Could just be too much energy going out than in
happens to me too

 

Not sure what that means? ^^^

 

what??????

OP... try another bov maybe stock and see if the shudder happens. Check for boost leaks, and maybe replace the sparkplug wires as well. Does the shudder happen when you go on/off the throttle or on the throttle and cruising??

 

I notice the problem more during in town cruising at 35 MPH. At highway speeds, I beleive it is masked by the crappy IL roads bouncing the car around. When I got WOT the car boosts to 29psi and runs fun, except power is down about 40-50hp.

 

do you have a stock fuel pump? mine was acting the same and i happend to change the pump and its gone.

 

Walbro pump installed. DId it do the same at WOT?

 

Was driving today and I have to change my description a bit, it is more of a slight surge while cruising in town. Normally the car is smooth, but this seems to hesitate then surge quickly. Nothing violent though, just slight.

 

Added more detail and log to the original post.

 

Update: I changed the wires and iginition coils and installed new plugs at .024. Same problem still exists, surging at cruise. power down ~40hp and my power curve on DLL is about a 45 degree angle until it levels at 5k+ rpm. This is on a stock turbo.

ANyone have ideas? I am running out of options!

 

boost leaks anywhere? Clean your MAF.

 

i agree with GRNCT9A do a boost leak test at least to rule that out.

 

^ dido that