CDTI - laggy when warm (with Synergy 2)

[martynzs]

Ive had my 05' ZT CDTi for around a year now and love it, after a selection of Clio 1*2's and a 400lbft Tdi Golf (that went pop) its been refreshing to have something comfy and reliable...

It started to develop the usual signs of a dodgy MAF 6 months ago (stuttering, dips in power, flat acceleration etc) and ran much better with it disconnected for the last 1k miles. (even though the diagnostics showed the MAF was in spec...)

I fitted a synergy 2 at the weekend and its MUCH better, really does transform the car BUT im still getting some odd symptons when the car is warm (after 15ish miles). It stops being quite so smooth/responsive and the power delivery is much more lumpy (almost like without the S2 fitted)

Could it be the inter-cooler O Rings getting warm and loosening? Fuel pump?

S2 set to 6, MAF off (runs worse on), bosch maf (thats potentially not perfect)

[marinabrian]

Ive had my 05' ZT CDTi for around a year now and love it, after a selection of Clio 1*2's and a 400lbft Tdi Golf (that went pop) its been refreshing to have something comfy and reliable...

It started to develop the usual signs of a dodgy MAF 6 months ago (stuttering, dips in power, flat acceleration etc) and ran much better with it disconnected for the last 1k miles. (even though the diagnostics showed the MAF was in spec...)

I fitted a synergy 2 at the weekend and its MUCH better, really does transform the car BUT im still getting some odd symptons when the car is warm (after 15ish miles). It stops being quite so smooth/responsive and the power delivery is much more lumpy (almost like without the S2 fitted)

Could it be the inter-cooler O Rings getting warm and loosening? Fuel pump?

S2 set to 6, MAF off (runs worse on), bosch maf (thats potentially not perfect)

Intercooler O rings, a service of your EGR valve, and switch off the MAF compensation if you have a Bosch MAF fitted, amplifying the signal from the Bosch MAF is a no no in 99.9% of cases ;)

My money is on a sticking EGR given your symptoms, something that is masked by unplugging the MAF which isn't the panacea some believe :)

HTH

Brian :D

[DMGRS]

Good call on the EGR valve - if it's badly coked up and sticking, it could well cause problems like this.
If you've not changed your Intercooler O Rings, they're very cheap and easy to change:
Intercooler O Rings - 75/ZT CDTi (http://www.dmgrs.co.uk/collections/seals-washers-and-o-rings/products/rover-75-mg-zt-cdti-viton-intercooler-o-rings-kit)