Club G40 Forum
Technical => Engine and Transmission => Topic started by: LeonL on July 19, 2009, 11:24:25 am
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Hi there,
I bought a G40 the other day and on the way home i realised it has a serious lack of power. The acceleration from standstill was pretty slow and i only mananged a top speed of around 85mph-90mph.
The car is on 89k miles, tottally standard apart from jabba sport induction kit. I have taken of a few of the boost pipes to check for cracks aleady but have been unable to find any.
I am a total noob when it comes to a problem like this so any advice, ideas, experience etc... would be greatly appricated.
What should i check/test and how should i go about it? Could it be something very serious?
Thanks
Leon
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howdy
erm, your best bet is to check to see if you do have boost, if you look at the throttlebody there is a little plastic control arm (looks like something off a remote control car)
prize that off the ball joint it connects to, turn the car on, now if you clasp the boost pipe that comes away from the radiator, squeeze it, now shut the valve that you have released from the control arm, and you are now pressurizing the system, doing this will cause the pipe you are squeezing to expand.
WARNING Do not close that valve for more than 2 or 3 seconds, as it will try and pop a seal somewhere
if the pipe expands then you have boost, if it doesnt, it has a leak and you will be able to now source the leak
im 99% sure it will be a leak
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if its not a boost leak (probably) or the BRV not closing properly, or then its looking at the charger!
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Well i done the above and the pipe expanded...Meaning i dont have a boost leak, right?
So what now? :(
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well if there is no leak, then it might be best to plumb a boost gauge in to see what pressure you are getting out of the charger.
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It an easy enough task putting a boost gauge on?
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i would also have a quick check to see how tight the charger belts are
how does it sound when driving? maybe a loss of power through a cylinder not firing or a lead not linked up correctly. i done this the other day when i was fiddling. took the car for a spin and it was pants to drive. sounded ok ish but no power. pulled over and realised that i hadnt pushed one of the leads all the way back on the spark plug. maybe it could be something simple like that. hope its simple for you anyway
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Car drives fine, sounds fine also. Just not G40 power...
Tried different plugs from another G40 today, took for a drive and it was still the same. Played about with the timing a fair bit taking it for a test drive each time it was changed, didnt affect it at all.
Could it be the actual leads?
Any other ideas?
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are you getting a spark through each lead
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How would i check?
**Complete noob to cars really**
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if its idling ok and driving without hesitation, then it would suggest that the ignitiion/fueling is ok, but you have a boost leak or lack of charger pressue.
1. check for boost leaks in pipes/joins
2. check the brv on the throttle properly closes to build up pressure.
3. check the charger belts are tight and its actually spinning
4. hook a boost gauge up (t in to the fuel pressure regulator vacuum hose line)
if all these are good - its time to get your charger looked at I would suggest. - Has it ever been serviced? what size pulley are you using?
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To state the obvious it has to be a problem with one of the following - Fuel (pumps, filter, fuel lines, regulator or injectors), Air (filter, air box, supercharger, intercooler or throttle body ) or Spark (coil, distributor, leads or spark plugs).
-The more accurate a desciption of exactly how the car is behaving often makes it easier to narrow down the problem!!
How is it driving across the board? Is it a complete lack of power or intermitent.
Have you got a lack of power throughout the whole rev range or just some of it?
Does it struggle to get up to the higher revs when stationary?
How does it sound under load and revving freely?
Etc etc..
Some suggestions,,
Is there air leaking from any of the pipes including the intercooler, exhaust and manifold?
Is there enough fuel to the engine, any fuel leaks at the back of the car (ie smell of fuel by the pumps) or blocked lines maybe?
Do the HT leads or ditributor look worn?
Are all the connectors plugged in around the engine bay and bulk head...
Before concentrating on any one component just stop and try and go through the car logically, fuel air spark, part by part to see if there is anything that might be easily missed and is actually quite obvious. It might not be some thing that you need to be an expert mechanic to spot. Hope this helps a little - good luck
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sorry to thread hi-jack, but what would cause a seal to pop when pressurising at idle and not when under load?
i.e. what changes to make it ok at high revs?
Will this highlight all boost leaks, even ones that may only present themselves at high pressure (10psi or more)
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when its under load then air goes in the engine and so you get a max of 1bar which the system can handle - the rest goes into the engine. Pressurising it by taking off the brv and closing it will just back up the pressure as it wont be returning by the brv, neither will the engine be using the air.
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but surely providing the system sees no more than 1 bar it should be able to cope?
n.b. i'm probably completely wrong, i was just contemplating pressurising the system with the engine off using an air compressor which would probably have a similar affect, im not trying to be argumentative lol
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I lookd at the car on Sunday and its holdin bk like the chargers not bilding ne boost cud this be a blocked intercooler dosnt sound like its got a boost leak ?
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yeah pressurising the system to 1 bar would work.
Never heard of a blocked intercooler....
When was the charger serviced? what pulley is it on....
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Its got a staderd pulley on it and don't think it was done that long a go
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Car is 100% standard...
Had a stage 2 rebuild by jabbasport in 2001 at around 51k miles, car is now on 88k miles.
However guy i purchased from said he gave it a "mini" charger service last year (1k miles ago). He has reciet for the parts used and also the parts he replaced.
:(
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hmm - sounds like that should be ok....
hope you get it sorted
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Would it be a good idea to open the charger up my self and take a look to see if there is any damage then put it back together? Or would that only be a job for someone with experience?
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they aint too difficult, if you know what yr doing!
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I dont really know what im doing, all i'd want to do is open it up and have a lookie about to see if there is any obvious problems, worth it considering i have no supercharger experience?
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it all depends if you feel confident enough
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Car isnt working either way so nothing to lose, lol
Anyway update:
Checked the pipe that goes from charger to intercooler, its fine
Purchased a boost guage which i'm still trying to work out how i wire up ;)
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t into the vacuum hose which goes from the top of the fuel pressure regulator to the one way valve/pipe that goes from the inlet manifold to the servo
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Is the boost return valve closing properly when you put your foot to the floor on the accelerator? Some people have been known to tinker with the linkage meaning that the BRV won't close fully when you floor it.
Also, if you let the car warm up, there is a blue plug to the right hand side of the exhaust manifold (looking at it from the front). When you remove this, do the revs drop or stay the same?
I'm 90% sure your problems caused by lack of boost, though.
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Hi,
Thanks for all the advice guys.
Major update now:
-Boost guage has been fitted.
-Checked to see if BRV was closing.
Firstly here is the BRV when no pressure is on the accelerator pedal(foot not on pedal)
(http://i4.photobucket.com/albums/y135/flatlanderuk/DSC00138.jpg)
Now here is the BRV when full pressure is placed onto accelerator pedal(pedal right down)
(http://i4.photobucket.com/albums/y135/flatlanderuk/DSC00139.jpg)
Here is a youtube video showing the movement of the BRV from no foot on pedal to foot all the way down
http://www.youtube.com/watch?v=irPagQi64n4
So...What does this show/prove/conclude etc...?
Also here is what the boost gauge shows while the car is in idle
(http://i4.photobucket.com/albums/y135/flatlanderuk/Boost.jpg)
Is this right?
Thanks
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the butterfly should be completely closed when foot is on floor. check to make sure the black plastic clip is not fouling anything. seen this before and it stops it from fully closing. you wont be using all the boost this way. i think that if you sort this you will have g40 power again
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Well first thing i noticed when i drove my G40 is that the accelrator pedal didnt have much travel as compossed to my Polo GT and other cars i have driven in my time...Mentioned it to the guy when i was test driving it and he said every car is different which i know is true but something fishy is going on here :)
Should the butterfly be angled like this "I" or like this "/" to be fully closed?
What black plastic clip are you talking about Chris?
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its a triangle type of clip
also do a quick check where the throttle cable comes through the bulkhead, there is a 'U' shape metal clip that holds the throttle cabel tight, if its moved along then this would mean that its like you have only been driving the car on half throttle. i always use 2 metal clips on mine just incase they slip off. i would deffo check this first
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Had a quike glance and it all looked okay,
What else could cause this problem?
Tomorrow i shall take some pictures of the set up for you guys to have a lookie at <3
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yeah not closing right - try tightening the cable by moving the U shaped clip on the ridges of the throttle cable outer
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are both the screws in the butterfly? it could have slipped. thats why it isn't closing
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Yes both screws are in it? Or so it seems from the picture...?
Based on problem with the butterfly not closing when pedal is down would it cause ALOT of power to be lost and effect the top speed of the car a great deal?
Just want to assure my self that my problem is defo this!
Also what could cause this to have happened? As i doubt it came out of the factory like this. I dont want to fix the problem only for it to occur again...
Thanks all, greatly appricated :o
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yes it will be low on power - could be the linkage between butterflies not adjusted or throttle cable not tight enough.
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Yep, that's definitely the cause of your problem. Your G40 is making all this boost, but as the flap isn't closing, the boost isn't going into the engine. This not closing will cause a massive loss in power.
The next thing you need to check is when you put your foot to the floor (with the engine off - don't want to go bouncing off the limiter), check that there black curved bit that the throttle cable cable goes through won't close any more by hand. It may have a small bit of movement, but that's fine. But if you can move it to the point that it causes the flap to close, then either the cable is out of adjustment or something is preventing the accelerator pedal from going to the floor. Check that nothing is getting in the way of that.
If the cable needs adjusting, just before the cable goes around the black bit, you will see a ribbed plastic cover over the cable as it passes through a small channel. There should be a little clip on this. Make sure it's actually there and adjust if needed.
If there's no extra movement in the little black bit, check there's nothing obstructing the movement of the little arm that connects to the little flap.
If there's nothing blocking it, someone must have played around with the linkage (that's the slightly bent metal bit with the beige ball joint sockets). Adjust this accordingly on the threaded rod.
Please also note: It is quite normal for the boost return valve (the flap) not to start closing until the accelerator pedal starts passing that half way point.
As for the cause, it depends of which of the above is causing this...
Either way, this should be a very simple and cheap fix.
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Abit late to go fidling with it at the momment but will get on the case tomorrow. However from the investigation today i found that the butterfly can be closed all the way at an angle like this "/" by moving the little lever with the ball joints conected. This can be done no matter which position the accelrator pedal is in.
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Yeah, that's quite normal. It won't quite close completely vertically - it will be at a slight angle when completely closed.
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Okay gdgd ;D
Will try get it closing like that tomorrow then :) Hopefully this sorts the problem! Will be extreamly happy if it does...
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i'd consider replacing the accelerator cable as well. just for peace of mind. then work from there
its defo a throttle body issue tho, replace the cable then set the air gate position (plastic bit with ball joints) then go from there.
Pete, have you ever come across anything like this before?
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9/10 its the accelorator cable isn't pulling enough. Before you fiddle with the linkage on the throttle. Manually press/push the throttle from where the cable connects and you'll see whether the BRV linkage on the throttle is set properly or if its the cable. Otherwise you'll be messing with the BRV to bodge it when the cable needs to be set properly.
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Only touched the cable, and now the BRV is closing fine and the car has G40 power again :)
Woooooooot!
Thanks all, its greatly appricated :-*
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Last question before this topic can be discontinued, while driving at around 4k revs what PSI should my boost gauge be showing?
Thanks again! ;D
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It's amazing the amount of cars there are out there with loose throttle cables.
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the boost will all depend on the pulley size, spec/condition of charger and belt tightness
glad the throttle cable sorted it
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Yeah seems so,
The difference it makes is rather extreme as well, at least in my case it was.
This is how it was before(Wasnt even on the grooves!:
/---------------
This is how it is now:
-------/--------
Spoke to the guy i purchased it from and he said he had changed a gasket in the inlet manifold but everything was put back as it came out. Guess something was missed ;)
Very happy that this wasnt a more serious problem
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the boost will all depend on the pulley size, spec/condition of charger and belt tightness
glad the throttle cable sorted it
Whats the "average" PSI meant to be for a 100% standard G40
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im sure i heard somewhere that a standard g-lader on standard pulley puts out 0.4bar, somebody correct me if im wrong
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So thats around 6 PSI according to this converter...
Just had a quike look to check if haynes manual states the boost and it quotes 0.5 Bar, which is "7.2519" PSI
Mine seems to be running about 8 PSI
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sounds about right then