Author Topic: rough runnung mk2 8v (spent lots)  (Read 1958 times)

Offline Bigdunc

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rough runnung mk2 8v (spent lots)
« on: 13 September 2011, 21:50 »
hi guys as title my 8v digi is running really rough and a tad flat.
main symptoms are

flat in 1st gear
slight judder at 2-3k
do get a engine clunk whel pull off quick (poss mount or subframe bushes)

ok the car has done 141k

in the last 2 months it has had the following done/changed

headgasket with head skim, tappetts were squeezed valves lapped and stem seals changed
cambelt
oil change (10W-40)
new water flanges
new plugs /leads
ECU and ignition modual changed
rotor arm / dizzy cap
replaced throttle body for polished one
all vacume hoses replaced
K&N cone filter removed and replaced with standard air filter box and filter and vacume hoses put back in place
replaced injectors and fuel preasure regulator and fuel lines inside engine bay
Fuel filter
Front engine mount

well basicly most parts changed and still running badly :)

timing was done to the guide on here 6 degrees at 2-2.5k (bts unplugged) and it does advance by 30 Degrees.

some days the car drives better than others and some days it struggles to start

i recently cleaned the conectors to the fuel pump with contact cleaner and seams bit better

main thing i found strange is this morning the car wouldnt start unless i pumped the break while cranking which i though was megga strange.

im running out of ideas to get rid of the flat spot in 1st

clutch was done under 10k ago, it does have a kent stage 1 cam but cant see that causing the flat spot

thanks in advance

Offline Chris1276

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Re: rough runnung mk2 8v (spent lots)
« Reply #1 on: 23 September 2011, 01:10 »
Check the fuel metering unit, I've had a problem were I had to lift the plunger up and down and turn it over to make the engine start only for the engine to stall in a matter of seconds. The metering unit plate (circle disk) could be out of position and can be adjusted by loosening the 10mm nut in the centre, adjusting the disk as to what it says in a Haynes manual with feeler gages and tightening the bolt back up. It is only a thought as I am having to adjust mine tomorrow as it's running lumpy now when earlier my engine wasn't running at all. Think it's page 4b8 in the haynes manual 1.8 8v gti. I also have a high lift cam fitted, timing at the cam is sorted, timing at the dizzy needs doing but until I sort out the correct gap on the metering unit plate it will run like crap. Oh check the little clip in the metering unit under plate, that slightly adjusts the height of the plate too (circle disk on plunger).

It's a mechanical fuel system & works on a vacuum on the early models, well my 8v is anyway, no ecu!!!

I'm only going on my experiences of the last few weeks as I have tested/changed fuel relay, fuel pump, fuel pump lifter, metering unit, braided hoses to injectors, injectors and park plugs. Changed/cleaned/ electrically tested ect. Clean/replace spark plugs, check sp leads and dizzy. Sorry for listing so much but I am doing a full restoration lol. Check metering unit if all else has failed and get as much advice off the people on this site as possible, don't just listen to Me!!
Chris Gti Mk2 8v 1986 Restoration :-)

Offline Benrevs

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Re: rough runnung mk2 8v (spent lots)
« Reply #2 on: 23 September 2011, 18:18 »
That won't apply as the OP's car is a later Digifant.  I would say check your timing, and then check it again. Read RJ's tuning guide and follow it closely!!  Edit: I see you followed the guide.  Check all your vacuum hoses, including the one that goes into the brake servo.  Wiggle them all while the engine is running to see if there is any change in idle.
« Last Edit: 23 September 2011, 18:20 by Benrevs »

Offline Bigdunc

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Re: rough runnung mk2 8v (spent lots)
« Reply #3 on: 24 September 2011, 20:37 »
im running a PB with ecu, i got 2 different maf, i have got a really funny feeling its gonna be fuel pump, as its still funny when driving one min she really smooth next she lumpy and sliggish and then the next its like a rocket again.

Offline Chris1276

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Re: rough runnung mk2 8v (spent lots)
« Reply #4 on: 28 September 2011, 22:33 »
im running a PB with ecu, i got 2 different maf, i have got a really funny feeling its gonna be fuel pump, as its still funny when driving one min she really smooth next she lumpy and sliggish and then the next its like a rocket again.

Hmmm can't really help you but my golfs being a b!tch at the minute as it starts but then cuts out after running. Timing is sorted out, tested so many things and the only things that are left are to change the coil pack, the ignition module and check/change the injectors as maybe fuel isn't getting through properly to help it tick over. Runs really well just doesn't tick over.  :sad:
Chris Gti Mk2 8v 1986 Restoration :-)

Offline bodga

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Re: rough runnung mk2 8v (spent lots)
« Reply #5 on: 28 September 2011, 22:39 »
im running a PB with ecu, i got 2 different maf, i have got a really funny feeling its gonna be fuel pump, as its still funny when driving one min she really smooth next she lumpy and sliggish and then the next its like a rocket again.

Hmmm can't really help you but my golfs being a b!tch at the minute as it starts but then cuts out after running. Timing is sorted out, tested so many things and the only things that are left are to change the coil pack, the ignition module and check/change the injectors as maybe fuel isn't getting through properly to help it tick over. Runs really well just doesn't tick over.  :sad:

Chris, Is yours a 8 or 16v kjet? mine is a 16v and it wouldnt tick over a while ago. i found it was one of the temp sensors on the r/h side of the head that controls the ISV