Club G40 Forum

Technical => Engine and Transmission => Topic started by: dan182 on June 05, 2016, 05:18:58 pm

Title: Revs dropping
Post by: dan182 on June 05, 2016, 05:18:58 pm
Hi there recently fitted piper cam lighten fly wheel when driving and its a warm day the revs keep dropping and picking back up again if you floor it perfect but if your driving alone ,at 2000rpm it stutters and gets worse the more you drive is there anyway to check fault codes?
Title: Re: Revs dropping
Post by: kwijibo_coupe on June 05, 2016, 09:56:42 pm
Does the rev counter play up too?
Sounds to me like it could be the coil starting to fail.
Title: Re: Revs dropping
Post by: dan182 on June 06, 2016, 09:26:11 pm
No rev counter seems fine its almost a juder
Title: Re: Revs dropping
Post by: GR40 on June 07, 2016, 11:05:37 am
Did you remap the ecu or are you running on stock map?
Title: Re: Revs dropping
Post by: dan182 on June 07, 2016, 09:14:40 pm
It had a chip in the ecu but that was for the r1 charger but thats it
Title: Re: Revs dropping
Post by: GR40 on June 08, 2016, 02:04:43 am
What are the specs of the cam? If you have gone too aggressive with the duration of the cam then this is to be expected, especially with a lighter flywheel! You may need to remap the ecu to match your cam.
Title: Re: Revs dropping
Post by: dan182 on June 08, 2016, 09:29:41 pm
Its a schrick 275 but at idle engine perfect and it dosent do it every journey
Title: Re: Revs dropping
Post by: GR40 on June 09, 2016, 08:51:48 am
I am starting to suspect the blue temperature valve that connects to the ecu. When was the last time you changed that? They are known to go bad over time. If its faulty your mixture at idle will change drastically. Its worth replacing, they are dirt cheap. Also, did you time the car after you replaced the cam? Did you time it with the blue temperature valve disconnected? If not timed that way it may be throwing the ignition too far out.
Title: Re: Revs dropping
Post by: dan182 on June 10, 2016, 10:20:20 pm
Didnt time it at all but surly it would run like a pig all the time?
Title: Re: Revs dropping
Post by: GR40 on June 11, 2016, 06:22:49 am
Actually no it wouldn't. Since the cam is designed to work with this engine it would need some adjustment but would work even if it's a bit off. In General when you are changing a cam you have to adjust timing and fuel for the simple fact you have changed the duration that the valves stay open and as a result the amount of mixture that goes in and out the cylinders. So what I am thinking is that the car is fine as long as the engine is cold but when it reaches operating temperature the ecu changes its timing and fueling according to the new chip and that is when you start bogging and rev haunting. That being said it could be 100 other things that the car bogs down I am just throwing some information out there that might help.
Title: Re: Revs dropping
Post by: dan182 on June 11, 2016, 06:46:14 pm
Where do you plug a g40 see if there any faukt codes?
Title: Re: Revs dropping
Post by: GR40 on June 12, 2016, 11:35:02 pm
I think there are 2 cables under the dash at the driver side. There are supposed to blink the code if you connect a light to them but I have never done it so I am not sure of it! You may find the correct info in here somewhere if you are willing to spend some time searching!
Title: Re: Revs dropping
Post by: hayesey on June 13, 2016, 09:41:35 am
check the FAQ sections, there's info on this in there and a free tool that'll read the codes off a g40 from a laptop if you have a vagcom type lead.  however, the diagnostic system on a g40 is not like a modern car, it's very basic and pretty limited in it's usefulness, more than likely there will be no codes.
Title: Re: Revs dropping
Post by: dan182 on June 19, 2016, 04:22:03 pm
Just checked fault codes only one is 00521 co potentiometer g74 no signal any ideas ?
Title: Re: Revs dropping
Post by: GR40 on June 19, 2016, 05:15:52 pm
that is the cubic sensor right before the throttle body
looks like this
http://www.bar-tek-tuning.com/cosmoshop/pix/a/n/1290785646-24110.jpg