friggin puzzled. 8v gti lump spluttering and misfiring....

[deanpompey]

ok so took my donor out of a 95 8v gti. ady code. ran beautifully, didnt miss a beat or splutter.

put it into a mk2 5days later and now it misfires like a b!tch an splutters like hell when you put your foot down. also wont idle correctly, sometimes just far too high, sometimes too low, others will hunt like a b!tch.

timing has not been touched.
ecu etc all from same car.
new plugs, leads,cap,rotor arm.
tried 4 ecu relays all from working vehicles.
compression results: 120 130 120 120 psi respectively
no apparent air leaks.

no vagcom fault codes.

Garage's scanners wont give real time data (could this be cos diag port is wired to ign live instead of perm live?)

very friggin confused!

any ideas people?

[deanpompey]

oh and TB clean as a whistle

[snifferdog]

Maybe the coil pack?!

[javalin]

sounds like electrical / sensor issue.  What did you do with temperature sensors (oil, water), pressure (oil), air flow, air temp and o2 sensors?  Also worth checking that the throttle position sensor is wired ok.

Also need to investigate why the diagnostic port doesn't work.  Get vag-com on it too.

J

[deanpompey]

got vagcom on it today just had a blast at measuring blocks as was only there for 5mins

throttle angle is sitting at 10.00 degrees, should be between 2.5 and 6.5

throttle regl should be 6 - 21% mine is around 38% and varies

intake air temp 15-55 deg, mine is 149?! doesnt change at all, but then i dont have the switch in atm as the induction kit i have on it is for vr, switch is currently sat in the cold air feed hiole in wing, so shouldnt be that high? need to get it incorporated somehow.. but pretty sure sensor is dead anyway with reading being that high.

group 1 box 3 02 sensor should be between 0.0 1.1 mine is 1.56 aand adjust conditions should be 00000000 mine is 10000011 dead lambda?? brand new fitted 2 days ago, although wire could have been broken as it was fitted dodgily.


reckon these are my problems then?

[Khare]

those comp test figures looks pretty low....
I had 160 on 3 cylinders and 150 on 1.

Does sound electrical though dude, try a new coil.

[deanpompey]

it was a basic hand held gauge, engine turned 3 times only. if id have cranked it 5 times it would have been 150's and 160's.

and going off the vagcom readings i dont think its the coil, more like sensor issues

[deanpompey]

iv just read a REALLY old thread found in the deepest darkest depths of google, says that you can get an 8v to re align the throttle itself by simply turning ignition on and leaving it for 5mins and car will realign itself? does that actually work??

[FlySpeck]

I have done the same mate, after battery disconnection it makes a reset of sensor readings as far as I know. Lots of clicking and whirring - when stopped, start the car and drive (if it works lol)

You can do a TB alignment from vagcom as well. I would perform an ECU reset and TB align, then see if any readings are still way out...

Im feeling that the IAT reading at 149 may be the cause, or the MAF is reading nonsense, mine started acting up tonight in a similar way but after switch off and restart, it was ok....weird. I'm suspecting the MAF on mine, not sure yet if the VR has an IAT too as only had gti's before.

[deanpompey]

ok so i had 5 or 6 fault codes on vagcom this morning, and TB alignment was doing nothing. cleared the codes, now only one coming back is hall sensor. which is strange seeing as its come up with 2 known working dizzy's?

then after all the days of swapping bits over and messing around, i decided to try the leads anyways... put my mates leads on, and BINGO! runs lovely, well, until it hits the 5000rpm limiter

can anyone provide me with a list of things that could cause this?

i know timing is one, and i think crank timing is out a tooth, so thinking that could be my problem, but just want to check any other options first as i dont particularly want to do a cam belt change, and i dont wanna pay a garage to do it either! it is running fine apart from the limiter, so it will serve the purpose of getting it through the MOT retest.