getting some engine judder - G40 playing up

goosyganger · October 08, 2010, 07:11:59 PM

Hi all,

Got some running issues on my G40 that i got running recently. Basically because of an issue with a chip I got to run with my 65mm toothed pulley and g60 injectors i am currently running the standard chip with stock injectors (but still on the 65mm pulley). Initially i was running the standard chip with the g60 injectors and was getting this problem (i thought it was flooding it on boost), so I changed to stock ones but the problem is still there.

So, to explain the problem. I can drive it off boost nice and gently all day long and not get this problem, runs fine. Doesnt over heat, doesnt hunt on idle or anything. BUT, as soon as i touch boost the problem begins. Basically after i let off the accelerator its ok but when i start to accelerate again (gently or hard) it starts to judder. its not constant though, it only happens every 4-5 seconds consistently. I noticed the engine stutter on idle, so I dont think its just on acceleration. It does however seem to stop when the engine builds momentum and is in high revs. EG, sitting on the motorway in 5th doing 70 it doesnt do it, but when i slow down to 50 it starts. But its the same in all gears, when pulling away in first it judders, etc.

I find it strange though that its fine all day long until i touch boost, then it starts doing this constantly even if I dont boost anymore. After left to cool and driven again it is back to normal. Also, worth noting that I had this in my mk3 coupe and drove it for a year and didnt have any problems like this, now its in my mk2 saloon and its started doing it. Dont see what could have changed other then the pulley and front mount at this stage. I'm waiting on a new chip to come in the next few days and will fit this with the g60 injectors but dont see it stopping.

Any ideas?

Thanks
Nik

hardchargin40 · October 09, 2010, 10:36:51 AM

define stutter? i.e. missing... ignition. or small misfiring...fuelling.

possible your hall sender on its way?

goosyganger · October 09, 2010, 12:37:44 PM

im not really sure to be honest. I had the g60 injectors in and they have been cleaned so i thought they were working fine but thought maybe it could be misfiring so i swapped them with my standard injectors which i know work for sure but still doing it. Could there be another cause for a misfire other than a dodgy injector?

and could be ignition i guess. its hard to say because i havent felt this before, as your driving the engine almost feels like it stalls for a second because its jolts. like if you put your foot down on the accelerator then let go and put it straight down again.

sorry if this is no help

PeteG40 · October 09, 2010, 12:56:08 PM

well the g60 injectors will have been totally overfuelling on a stock chip all the time!

however that aside, does sound like an electrical issue - the ignition components - leads, coil, plugs, dizzy etc - how new are they all

goosyganger · October 09, 2010, 01:05:38 PM

Yeah that's why I put the stock injectors in to see if my maye that would resolve it but it didn't unfortunatly.

The leads and coil and pretty much exactly a year old so pretty new but have only covered around 5k miles. The dizzy is off my Old gt and I would say is pretty old. Also the plugs I would say could probably do with changing. I am going to get some today. Could something have gone wrong with the hallsender while the engine was stood in my garage for a few months over the summer?

G40 AD · October 09, 2010, 01:09:10 PM

have you done anythingwith the timing recently as I experienced something very similar when my engine builder put both my marks on the dizzy instead of the head and therefore didnt have the right timing the first day i dorve it and got very similar results to this... was generally jolty at some speeds and not at others... so if you have changed it since beforeit started could be well worth a look... (just mark it where it is curently and try advancing and retarding and see if the issue clears up and if not then just set it back as it was on the marker...

Ad

G40 AD · October 09, 2010, 01:11:25 PM

sounds very like it could just be any of the unrenewed ignition parts... always worth doing as you dont lose anything even if it isnt those that are causing the issue!

goosyganger · October 10, 2010, 11:43:29 PM

Well I fitted new plugs and a different dizzy and spent some time playing withthe ignition and have seem to have got it running a fair bit better. Definatly less rich and smoother. I gave it some boost and the problem seems to still be there, however not as bad and after you drive for a while it seems to go away. Until you give it boost again and it does it. But it's nowhere near as bad.

Could the engine temp cause any issues like this? Also I I'm running a 65mm pulley on standard injectors and stock chip at the moment. Could this cause it?
Thanks

hardchargin40 · October 11, 2010, 08:49:10 AM

sounds like the spark is breaking down when on boost.

Have you checked condition of the plugs etc? Could be the coil as mk3 polo ones are shite. Have you run a good earth from it to chassis aswell, always a good recommendation to make sure your earths are strong and healthy. Unfortunately, diagnosing ignition faults tends to be down to replacement or slaving bits in unless its from dizzy onwards where you can break it down into individual tests. Whats the condition of your dizzy cap contacts?

Also if its temp related as in the blue CTS, then it'd more likely be misfiring with the ECU using defaults as soon as it gets to 70+degC.

goosyganger · October 11, 2010, 12:26:20 PM

Hmm, thanks for that mate. I will check out all the earths and stuff and see if I can get to the bottom of it. Just try to elliminate things i guess. Ill try a few things and see if it helps.

So could it be a faulty blue temp? Not sure it can be though because it only does it after boost. And no reason why it wouldnt do it off boost after reaching that temp. mystery.

If anyone has any other thoughts please throw them in.

Thanks

Yoof · October 11, 2010, 06:48:57 PM

If you've run with 250cc/min injectors on a stock map for 192cc/min injectors, your plugs are probably gone- often once the ceramic has been plastered with fuel they won't recover.

Try a new set of plugs

goosyganger · October 11, 2010, 11:22:48 PM

I changed the plugs yesterday. will take them out and have a look at them once ive got the new chip in. But its running nicer now, I just think its over fueling on boost. so im driving it off boost at the moment.

Thanks for the hint mate its good to know. It was running a bit rich for a while before i put it in this shell so the plugs were due a change. should run much better this week i hope.

hardchargin40 · October 12, 2010, 07:51:52 AM

You'll have proper lack lustre performance too with greens fitted and no proper map in there for them. Overfuel - rich - no torque.

Forgot to add, When i had my old red G, I did this, fitted greens, engine was proper lack lustre but I only ran them like that to drive down to jabba for a custom remap with Mike Truelock. He gave me a naughty telling off for running it like that but got away with it as fitted new plugs at same time.

goosyganger · October 13, 2010, 12:47:04 AM

Ok so I put the new chip in today and g60s. Ran so much better. A little high on idle in my opinion but starts nicely and stuff. Over the weekend I fitted new plugs and a different dizzy and adjusted the ignition so it runs a lot better as it was a little rich before.

Took it out for a run and it pulled really nicely but unfortunatly I am still getting the problem. What concerns me is that my mate said his did something similar to this before he melted a piston in his last g40. I have run out of ideas really.

Could it be anything to do with like the temperature of the air? Or fuel pump? Or dodgy knock sensor?

Yoof · October 13, 2010, 08:17:56 AM

How old are your fuel pumps?