Crank sensor symptoms

[Matt82]

Ive got a bit of a puzzler going on with the Golf (1.8t)

Some morning (particularly when cold) when you start and drive away it will have a pronounced stutter when you might light throttle inputs, it feels like the car has plain stalled for a second.

The other day i could feel it doing it in the evening (rare, normally only when cold)

No fault codes, ive monitored ignition timing, afr, throttle position, everything, no obvious signs

For it to cut so abruptly im thinking crank sensor, but the tacho doesnt show any signs

If voltage dropped at the fuel pump, do you think it could cause such an abrupt stutter?

There are similar posts on mk4 boards but no one ever seems to cure it

 

[Matt82]

unfortunately no, never used one

im only able to watch afr etc by obd and i dont think its fast enough tbh.

thinking about it, is fuel pump voltage or the fuel pump itself something that could be intermitent only when cold and only on light throttle applications?

crank sensors normally only go duff when hot (in my experience)_

 

[Matt82]

Well, I had a look under the bonnet on Saturday, first targets were air leaks between maf and turbo and the pcv. That was all fine. Checked vac hoses for FPR and DV, everything intact. The vac hose at the secondary air intake valve wasn’t the best, so changed that. I have disabled the N249 on mine but the pipework was still in place, so I junked that because it just confuses everything.

I went to reassemble everything but decided to put a drop of oil IN the FPR as ive come across these being sticky (on NA cars, not turbo one) though.

The car drives really nice again now. Transitioning between off to light throttle is smooth as a babys bum. The car is smoother/nicer to drive and ive not had to compensate for any poor running since.