2.8 hesitaion

B@fink · #1 25th November 2009, 08:08 PM

Anyone else get a slight hesitation from a 2.8? and has anyone cured it? Other forums including the a6 and passat have a range of ideas but no one ever seems to have the answers! It can best be described a small miss or stutter at light throttle at a cruise 40mph (give or take a couple) but there are no codes showing, economy doesn't suffer, anything more than the lightest throttle powers through it easily and using the tip to knock down to 3rd or up to 5th stops it (so it's 4th at 40!) The car has had new plugs, leads, coil, fuel filter, crank vent pipes, fuel system cleaner, higher octane super unleaded, a small vac pipe that disappears under the ns wing reattached and a good long motorway blast and it has made absolutley no difference. It doesn't really affect the usage as i just scoot through the cough but it'd be nice just to definatively say what it was and that i fixed it! So fellow 2.8rs can it be done? (and before anyone jumps in theres a vac suction pump on its way, updates on success to follow) I will fix this wee gremlin, but theres no harm in looking for a shortcut!

Architex_mA8tey · #2 26th November 2009, 12:41 PM

is it definately engine stutter or could it be a slight delay in the gearbox or drive train perhaps?

B@fink · #3 26th November 2009, 03:23 PM

Definately the engine, if you set the cruise to bang on 40 mph it'll stutter whilst steady in gear, tip down to 3rd and gone, tip up to 5th gone, but if you just leave it in 4th it'll keep doing it potentially forever (its not shunt on pick up of gear or me with a wobbly foot going on and off gas spooling up the converter then backing off) but i'm not brave enough to leave the poor thing coughing when she doesn't need to to find out how long it'll miss for! It feels very much like a gentle ignition miss or a tiny vac leak weakening the mix at such gentle throttle but so far it's eluded me.

PsYcHe · #4 27th November 2009, 06:56 AM

Could be a dirty MAF unit... Have you checked it?

Just_Ben · #5 27th November 2009, 02:53 PM

Yeah, have the air mass meter's output checked. You should see about 175+g/s at 4500rpm ish minimum.

Also, make sure the inlet manifold is down tight and that the change over valves have not failed or have air leaks.
Leaky ijectors can cause this issue but so to can incorrectly fitted cam belt! Have it fault read. If there is a camshaft retardation fault present either the belt is on wrong or the valve timing variators have been refitted incorrectly. The cam shaft pulleys must be loose when tensioning the belt and this is often missed by garages and this can adversly affect the cam timing. Many of thes engines had the variators out as when the breather system blocks up (which it will) the engine forces oil out of the cam cover gaskets and the variator solenoid bases. On some engines the chain spacing on the 2 cams in each head for the variator can differ from one bank to another and be missed when re fitting.

Does it miss at idle at all??

B@fink · #6 27th November 2009, 03:14 PM

nope, smooth as silk at idle, and smooth rest of the time bar 40mph. The maf has been cleaned, and then run disconnected to double check (apart from being a bit sluggish on the uptake when disconnected the maf made no difference to the stutter) There are no fault codes on it at the moment (admittedly with a non vag-com reader, just a gendan engine check, vag-com on the way if the old lappytop will talk to it, it's a bit fussy) The belt was changed (according to paper work over a year back and its only at 88thou now) so they could have made a mess of it and a new one is on my to do list possibly summertime, but i will probably delegate that one out i don't fancy it without the locking kit. I'm fitting a new suction pump within the next week (arrived today in the post) so i will check the inlet manifold nuts are tweaked down when i do that and all the breather pipes a new and shiny (though it wouldn't matter if they were blocked because they had fallen to bits, interesting design using hard walled solid plastic piping.......) is there a way to check the change over valves? If i blip the throttle up the arm moves on the over-run as it winds back down (responding to the vac i assume) so i assumed it was doing something and wasn't stuck, not to say it isn't snapped though. Any big air leaks or mechanical maladies i would expect to show up all over the rev range not just at 40...it's not big or violent but you can feel it. If it makes a difference it's an ACK engine and almost everytime i order bits they're wrong!

Ska · #7 18th December 2009, 09:48 PM

Did you sort this at all? If its speed related then wouldn't that point to drive train components. I say this because I had vibration which manifest like engine hesitation on my ACK whichturned out to be a cracked final drive unit! Just checking but have you cleaned out the Throttle body

B@fink · #8 19th December 2009, 07:49 AM

I swapped the suction pump to no effect, still for 18 quid it was worth a squirt. I have cleaned the throttle body but again a big old zero. I intend to have a bit of a crawl underneath during the festive break to make sure everything is ok underneath as i have an occasional small knock at <5mph over a reasonable sized bump (say going up a lowered kerb for time to time) that having swapped all the anti roll bar links/bushes didn't improve. Hopefully these 2 niggles aren't connected, i really don't want anything as serious as a final drive in winter :O

B@fink · #9 23rd December 2009, 07:40 PM

quick update, checked the car on vag-com and it shows no engine issues (not quite true, it showed an immobiliser blocked start, but that was me using a non coded key

) relating to misfire and a load signal intermittent p1857 on the autobox. No other faults. So whatever the hiccough is, the car is oblivious!!!! Joy!