Hey guys

My '04 turbo is stock except for FVD ECU installed by the dealer back in the day. Noticed around Christmas last year a few dead spots in the low rev range (1500 and 2000rpm), especially at low throttle load, that make the car jerky in traffic. Car also seems to bog down before it goes when making sudden throttle inputs. Very annoying as I commute at peak hour every night.

Tried several things:
- New MAF
- New coil packs
- New plugs
- New fuel filter
- New air filter (back to the paper one as we suspected the K&N was throwing in oil)
- Frequent resets of throttle body

It's still doing it, still showing nothing on the diagnostic. I'm super aware of it now that I've been chasing the issue for so long. At the point where I'm thinking of selling it. Driving me mad.

Any idea before I throw in the towel?

Thanks in advance
Longi

 

Reflash the ECU?

 

02 sensors ?

 

+1 go back to stock if you can to remove this as a point of problem... Or contact them/datalog to verify.

 

Oh and do a boost pressure test from the turbos... May just be a leak or hose off...

 

maybe its the FVD flash... I have one also.. and I dont think the car runs right with it... it could be some other component at fault, but it just doesnt seem to be smooth power... it's like all or nothing..

 

Get a new tune.

 

Everyone else is right on, but where are you located? Might be easier if you happen to be next to a good shop.

Henry

 

Sounds like a pre turbo after (non pressure side) leak...

 

+1 on the ECU. When I did the Softronic flash, the car was just like that for the first few days. It seems to have learned over the fist week and smoothed out much better than before the flash. If yours isn't smoothing out and you have already fixed everything else, I vote ECU with the others.

 

O2 sensors are a great suggestion. Take a look at those. If they test good, then it could be clogged cats, or the tune. It could even be something with fuel supply. Boost leak seems very likely at this point. I doubt the flashed ECU is the whole problem, if anything it would just be exacerbating another problem.

-Matt

 

Long shot but worth checking:There's a switch on the clutch pedal mechanism that limits the engine output, in order to not have the driver accidently fry the clutch if you were to give too much gas w/o clutch pedal fully released. If the switch is not adjusted good and it gets activated too easy by for instance resting the foot on the clutch pedal, which is common to be "prepared" in stop go traffic, the engine does runs seemingly normal but it can make the engine have these hickups and bogs in the low rpm ranges when you change the throttle angle.

If not that, look for a intake leak somewhere.

 

Check your hose clamps, I had one fail on me, and it acted just like that. Boost leaks will drive you nuts and many times won't throw a code.

 

engine mounts/ trans mount? have you checked them, also for free play in axles. If the play/ slop is enough it will cause this jerking.

 

Many thanks for the suggestions. This is so much more useful than my dealer's "diagnostic says it's ok" and "let's try and change this thousand dollar part" approach.

By the sound of it, I should test out possible causes in order of increasing cost/complexity. Here's what I take from the suggestions:
1. See whether the clutch switch is interfering (MrWhite's suggestion)
2. Leak test, upstream and downstream of turbos
3. O2 sensors. Not sure what they are and how that's different from MAF. Is it easy to check?
4. Engine mounts
5. Axles. Also a good suggestion, I can imagine how some play can induce jitter/shudder at certain frequencies. Is that easy to spot?
6. ECU re-flash. Would have to track down the original software etc.

Again, thanks for this. Gives me a way forward.