Problems With Gti6 On Sudden Throttle Opening.

[felix2566 2]

I have been having a problem for the last few weeks, when I open the throttle suddenly from idle the engine splutters and almost cuts out. The revs will rise slowly and then pick up normally. If I open it slowly it will go all the way to the limiter fine.

 

I have replaced the coolent temp sender, idle control valve, tps, map sensor, tried 2 different lambdas.

I know that these can all cause problems and so changed them all, but the problem still persists!

 

A possible problem could be that the fuel pump is not delivering enough fuel, the fuel pipes that I have fitted are AN8 which could be a bit on the large size and maybe stop the fuel pump delivering the correct pressure.

 

I was also thinking that maybe the fuel pump is on the way out, it makes quite a loud wineing noise while its working, is this normal. My car is completely stripped out inside so maybe it is just more audiable? Will a 306 gti6 fuel pump fit in my tank?

 

Does any one have any suggestions as to what the problem could be?

[C_W 3 1 Cars]

Sounds more like TOO much fuel than lack of it. Can't help with the reason why it's doing it although I find my Mi16 engine splutters if you jab the throttle (always has done) in neutral.

[KRISKARRERA 2 1 Cars]

Sounds more like TOO much fuel than lack of it. Can't help with the reason why it's doing it although I find my Mi16 engine splutters if you jab the throttle (always has done) in neutral.

Ahh so mine's not the only one then!

[taylorspug 7]

Sounds more like TOO much fuel than lack of it. Can't help with the reason why it's doing it although I find my Mi16 engine splutters if you jab the throttle (always has done) in neutral.

 

Mine did this aswell! Changed absolutely everything and could never get it to go away. Bloody Motronic...

[pug_ham 242 3 Cars]

Have you got the VSS wired in?

 

IIRC the CTi-6 Mark (dead 205) has had a similiar hesitation if you floored it but ws fien on gradual throttle openings.

 

Graham.

[felix2566 2]

Yes I have got it connected, I dont know if it is working though, not sure how to test it?

I will try running it with out the VSS connected and see what happens.

[CaptainK 11]

My first incarnation of my GTi6 was the same - floor throttle and it'd splutter then slowly recovery. But if you slowly pressed the throttle down, to match acceleration, then it'd go fine.

 

Never knew what the problem was with mine as the thing killed itself after only a few weeks. Its being fixed, but I haven't driven it in over 3 months, haven't seen it for about 1 1/2 months.

[felix2566 2]

mmmm, I will ask around. Have posted it on the 306 gti6 forum with no luck either. Will have to keep on at it, will sort it eventually!

[felix2566 2]

Tried running it with out the VSS connected an dit didnt make any difference.

 

I also tried running it with out the VSS and the lamda, the idle speed would get progressively lower untill it spluttered and died!? No idea why, I thought that the engine would run with out the lambda??

[Toddy 7]

Yes I have got it connected, I dont know if it is working though, not sure how to test it?

I will try running it with out the VSS connected and see what happens.

 

 

Without the VSS connected you will feel some lag when first setting off up to ~1300rpm then it will drive normal further up the rev range without hesitation.

 

It will run without the Lambda as it reverts to a base map.

 

Sounds like a dodgy ICV but you have replaced this.

 

Have you altered the cam timing or anything else since it has started to play up?

 

Has the diagnostic socket been wired in when the engine conversion was done?

[felix2566 2]

I have replaced the cambelt myself ( the first one I have ever done,I did it before I had the engine running). But I followed the guid off the 306 gti6 forum, I was very careful to make sure that all the pins line up. It seems to run fine so long as one moves through the rev range slowly. I will back fire on the over run sometimes, if one is using engine breaking.

 

Could this problem be due to the cam timing being a bit out?

 

I do have the diagnostic socket still wired in and a friend of mine is coming over on tuesday to plug in a reader to see if we can see some problems that way.

[Toddy 7]

I have replaced the cambelt myself ( the first one I have ever done,I did it before I had the engine running). But I followed the guid off the 306 gti6 forum, I was very careful to make sure that all the pins line up. It seems to run fine so long as one moves through the rev range slowly. I will back fire on the over run sometimes, if one is using engine breaking.

 

Could this problem be due to the cam timing being a bit out?

 

I do have the diagnostic socket still wired in and a friend of mine is coming over on tuesday to plug in a reader to see if we can see some problems that way.

 

Cam timing can cause this type of problem

 

recheck your cam timing and remember the bottom pulley can be out due to the two pieces being bonded together and sometimes slips and becomes misaligned, best to check that both pistons are at the exact same height with a zip tie down the bores and that the cam pulleys are aligned with the holes.

 

Has it always been like this?

[felix2566 2]

I will recheck the cam timing. I replaced my bottom pulley with a solid one, I did notice that the old on had slipped round a bit.

 

I do not know how it ran before I changed the cambelt, I bought it as an engine already out a car. In hind sight not a very good idea, but, we live and learn!

[felix2566 2]

Checked the cam timing last night and it is spot on.

Checked and cleaned the crank and cam position sensor, still no different.

I also noticed that the problem seemed to get a bit worse as the engine warmed up.

 

What would be the syptoms of the fuel pump not providing enough pressure or flow?

How can I check that the pressure regulator is working properly?

Edited June 3, 2008 by felix2566

[Toddy 7]

Checked the cam timing last night and it is spot on.

Checked and cleaned the crank and cam position sensor, still no different.

I also noticed that the problem seemed to get a bit worse as the engine warmed up.

 

What would be the syptoms of the fuel pump not providing enough pressure or flow?

How can I check that the pressure regulator is working properly?

 

 

Seems strange that it would not idle with the Lambda unplugged.

 

From cold it runs off a base map until the Lambda has heated up, the ECU then uses the Lambda as an input once upto temperature. This may explain why it gets worse once warmed up.

 

Can lend you a known good Lambda if needed.

[welshpug 1,626]

an iffy fuel pump might cause this kind of symptom, they usually do humm but shouldn't be that loud.

 

a GTi6 one would be external (P2 on) so might be ideal to fit one inline to see if you get an improvement.

 

It should run with the Lambda unplugged, albeit a bit rich.

[felix2566 2]

Toddy, How long is the cable on your lambda, I am using a lambda from a zx gti because it has a longer cable. My probe boss is on the far side of the exhaust relative to the gearbox and plug, so need more cable. I could be interested in borrowing it, would be happy to pay for postage.

 

WP, are you suggesting that I disconnect my current pump and fit a pick up pipe into the tank and then put one of the inline pumps in instead? I was thinking that if the current pump was not supplying enought fuel, that fitting a stronger pump in series after it would not make much difference?

[kyepan 291]

Straightened out coat hanger wire is also good because you can mark it easily.

 

Does it do the same at 30mph if you fully open the throttle in 5th and hold it open?

 

cheers

 

Justin.

[felix2566 2]

Sorry Kyepen, not sure what your on about with the coat hanger wire??!

 

The car is not road worthy yet, ie, no insurance MOT etc so havent been able to to drive it on the road. If the throttle is partially open it will rev up much smoother. it is when it is opened suddenly from closed that it nearly conks out.

[kyepan 291]

coat hanger, to stick down the cylinder with the sparks out, it doesn't bend or flex and is easy to mark with a metal ruler / measure.

 

The reason i mentioned that is under load in high gear at low speed wide open throttle will show up any electrical gremilns, like breaking down HT leads, knackered plugs, dodgy coil/s or ignition components.. but usually its leads or (dizzy/rotor). Its a simple solution thats all.

 

I'm not to hot on GTI-6 management so can't really advise any more, but mine did what you say when the AFM was disconnected... Might be worth checking whatever air metering device you have (although i'm guessing you only have a throttle pot)..

 

anyhow, good luck with it.

 

cheers

 

J

[felix2566 2]

Was running the engine yesterday and it deffinately gets worse when the engine is hot, could it be that one of the coils is not working properly? If it was on its way out could the heat be making it worse?

[Richie-Van-GTi 70 2 Cars]

a broken coil wouldnt give the symptons you describe, it would be more like a constant misfire at low revs.

It definatley sounds fuel related, is the TPS positioned correctly? IIRC the gti6 will run with it unplugged, albeit not very well but may help to show if its getting a bad signal here although I think its unlikely its worth checking.

If you can get your hands on one try getting a fuel pressure guage inline and watch the pressure when your driving. If on opening the throttle it drops too much vaccuum on the FPR vac pipe it could cause a brief fuel issue until the MAP sensor catches up and the ecu adjusts accordingly.

[felix2566 2]

I think that sounds like the next port of call in the quest to 'sort the engine'.

 

What kind of pressure should I be looking for at idle and throughout the rev range, what would be deemed as being too low pressure?

[C_W 3 1 Cars]

I don't think it's fuel presssure if you meant that pressure.

 

The suggestion it's ignition related is a possiblity but it depends what the splutter is like (ie is it like a misfire or bad fuel mixture), only as when I had a rotor arm problem it manifested as a misfire/splutter at low revs but was other wise fine although this was worse under load.

[dcc 855]

I had this issue on my 205 gti 8v!

 

New headgasket for me - my old 1 was Well and Truely forked. had a lovely big hole between piston 3 and 4 hehe