Start Up Miss Fire

[Dave G 0]

Dont know if any one can help, tried searching but am abit pushed for time on the computer at the mo so its probably already been covered.

 

Basically on start up I get a missfire, the engine revs well under full throttle but under gentle throttle at 3500 it starts.

 

At first its down to what sounds like 2 cylinders but then it will start to clear untill its completely cleared and hold revs smoothly, then if i raise the revs by even 100 rpm it will come back with the same symptoms and then clear, it take about 15 seconds to clear from when it starts missing to when it clears from about 3500rpm-5000 rpm and will do this from cold and occassionally when warm but when it has been stood fro a while.

 

Recently serviced but am yet to fit fuel filter but it even with the new cap, arl plug etc it hasnt made it better or worse. Did a compression test recently and all was ok.

 

thanks folks

[trialster 0]

Dont know if any one can help, tried searching but am abit pushed for time on the computer at the mo so its probably already been covered.

 

Basically on start up I get a missfire, the engine revs well under full throttle but under gentle throttle at 3500 it starts.

 

At first its down to what sounds like 2 cylinders but then it will start to clear untill its completely cleared and hold revs smoothly, then if i raise the revs by even 100 rpm it will come back with the same symptoms and then clear, it take about 15 seconds to clear from when it starts missing to when it clears from about 3500rpm-5000 rpm and will do this from cold and occassionally when warm but when it has been stood fro a while.

 

Recently serviced but am yet to fit fuel filter but it even with the new cap, arl plug etc it hasnt made it better or worse. Did a compression test recently and all was ok.

 

thanks folks

 

tried cleaning up the plugs or replacing them?

 

maybe it's misfuelling at low temps!

[Dave G 0]

yeah fitted new ones. they were the same as what came out and maybe ive been sent the wrong ones, they were bosch items, will get number tomorrow and see if any one else is using the same.

[trialster 0]

did you gap them correctly?

 

what colour were the ends of the old ones?

[welshpug 1,629]

no need to "gap" plugs, they come pre set and are not usually adjustable nowadays

[trialster 0]

depends what plugs/where you get them from.

 

i had to gap plugs for my 1.9 gti a year ago... unless its all changed since then.

 

anyways, best to give a quick visual check of them to make sure none of them have been damaged atall.

[luggy 13]

When starting does it fire up straight away or does it crank over a few times before finally catching?

[Grim.Badger 15]

Sounds like it could be a problem with the AFM, check the connections on it and if possible try another one.

[Dave G 0]

Right quick up date.

 

Checked plugs with supplier, were right acording to them and also checked with main dealer amd compared them to another local gti which kindly was brought long to compare and gaps and plugs are the same. I dont know if this makes any difference but we swapped cars for a short drive and mine was quite abit qucker in all gears and from all revs(used a section on dual carriageways to compare)

 

It always starts on the button infact it fires up so quickly it catches me out and im left holding the starter for a second.

 

Im goin to see the engineering shop that did the head rebuild as im a good fmaily friend to the mechanic that worked on the car to see if he can shed any light on it etc.

[BusEngineer 7]

From my own experience from two occasions in the three and a half years iv had mine, try plug leads, i had misfires under load between 2K - 4K and tried plugs, cap and arm, then leads and both times it was leads. Dont know if im barking up the wrong tree, or you've already fitted some but it worked for me

[Dave G 0]

going to get a set monday and see

 

it has me stumped as once ive managed to get it to clear then it wont happen again untill a cold start and it will only do it under gentle throttle, i a blip it up past the problem rev range using 100% throttle it dosent miss at all and on the road its fine.

 

maybe im just expecting to much from the engine and its managment from cold.

[Dave G 0]

right sorry for the dealy but its update time.

 

new leads, check

correct plugs and gap, check

new cap and rotor arm, check

air fitler, check

fuel filter, check

fuel preassure, check

 

still there though, its the only fault mechnically with the car an i now i will get haggled down to hell but all the bull$***ers under then sun thats its somthing serious(going to put the car up for sale soon as i have been offers a lazer green gti)

[luggy 13]

it has me stumped as once ive managed to get it to clear then it wont happen again untill a cold start and it will only do it under gentle throttle, i a blip it up past the problem rev range using 100% throttle it dosent miss at all and on the road its fine.

 

maybe im just expecting to much from the engine and its managment from cold.

 

My old 8v used to do the same on startup, running what sounded like 2 cylinders for about the first 20-30 seconds . I used to be paranoid that it was possibly plugs, leads or leaky injectors but it would clear, it just seemed a part of the cars character . If it doesnt do it when the engines warmed up then it isnt a problem.

[Rob_the_Sparky 9]

I've also experienced this to a greater or lesser extent on my GTIs, never found a really good solution but making sure the SAD is clean and functional certainly helps. Made the difference on mine from starting with a little throttle to not needing any. However, 3500 is a LOT of revs on a stone cold engine, I've only ever needed around 1500 or less for around 10-15s after starting.

 

Rob

 

P.S. I did ponder myself if fuel was leaking into the manifold while the engine was off but my injecotrs have all been re-built and it still does it!

[Guest matts206]

might be worth trying another amplifier

[Rob_the_Sparky 9]

If the ignition amp is suffering they will tend to do one of two things:

 

1) Intermittantly not start, slowly getting worse

2) Die when under body temperatures get high (and misfire before death? Mine didn't but I'd expect them to)

 

Rob

[Dave G 0]

hadnt thought of the amp, had this on the cosworth prior to getting the 205.

 

tbh i only noticed it by mistake and im going to love it and live with it for know, the car is getting the strip soon ready for a major concourse overhall with a few trick bits added along the line.

 

will be starting a project thread very soon

 

thank you all for your help

[richsmells 2]

Mine's exactly the same, but I don't have to rev it to clear. It's fine after 30 secs and it only misses when the engine's stone cold. It's done it since the day I bought it and all ignition components have been changed as service items. I think it's probably the fuel setup or just the AFM showing its age.

Edited March 2, 2009 by richsmells

[Grim.Badger 15]

If you want, I have a 1.9 AFM that I could post if you cover the costs; it's got stripped threads where it mounts to the car but that shouldn't be a problem if you are just ruling things out