My focus is driving me nuts. Its got somewhat intermittant (or varying severity) stutter or hestitation at the lower end of the rev range, more so when cold. Its mainly noticable with very light throttle, such as when creeping in heavy traffic, i cant really feel it at full throttle. It doesnt seem to do it at low revs if its in a high gear and I boot it.

Ive done the usual, replaced the leads, plugs and coil, there is no water in the plug wells. Ive swapped out the throttle body, MAF sensor and injectors for known good units (thanks to a patient friend) and even had the PCM updated to the latest software and reset the adaptations, but nothing has helped.

There are no error codes in the PCM and most sensor readings seem reasonable, although i have very negative long term fuel trims at idle (around -20 to -25%), this improves after a while at higher revs. Oddly the stort term fuel trims are always within a few % of zero. The lambdas are reading reasonably to, the pre-cats are fluctuating from 0.05 or so to 0.8 every second or so, the post cats are at 0.7-8 constant.

Any ideas? I'm thinking of doing a compression test later in the week, but if thats fine i have no idea where else to look.

Edited by ChrisM41 on 03/05/2016 at 21:04