TVR Chimaera 500 idle problem & cuts out
Discussion
Hi folks.
Little help please.....
My Tvr Chimaera 500 sometimes idles eraticly and when it get to a set of lights or aN island its rev's will go up and down then cut out like its struggling to idle.
After Doing a complete service with new leads,air filter,cap,rota,plugs,oil,Air flow meter & stepper motor The problem is still there!?
Any ideas people!!!??? HELP.....
Little help please.....
My Tvr Chimaera 500 sometimes idles eraticly and when it get to a set of lights or aN island its rev's will go up and down then cut out like its struggling to idle.
After Doing a complete service with new leads,air filter,cap,rota,plugs,oil,Air flow meter & stepper motor The problem is still there!?
Any ideas people!!!??? HELP.....
DHUDD said:
Hi folks.
Little help please.....
My Tvr Chimaera 500 sometimes idles eraticly and when it get to a set of lights or aN island its rev's will go up and down then cut out like its struggling to idle.
After Doing a complete service with new leads,air filter,cap,rota,plugs,oil,Air flow meter & stepper motor The problem is still there!?
Any ideas people!!!??? HELP.....
Only bit you didn't replace was the ignition amp, and when mine was playing up those were the symptoms I got.Little help please.....
My Tvr Chimaera 500 sometimes idles eraticly and when it get to a set of lights or aN island its rev's will go up and down then cut out like its struggling to idle.
After Doing a complete service with new leads,air filter,cap,rota,plugs,oil,Air flow meter & stepper motor The problem is still there!?
Any ideas people!!!??? HELP.....
I had a similar problem with my chim. I cleaned the stepper motor and the throttle butterfly, then re-set the base idle speed. This is done by squashing the bypass hose flat to prevent air getting through to the stepper motor and adjusting the throttle screw at about 400-500rpm. When you release the hose, it should idle at about 900rpm, (clear instructions can be found in the bible). This worked for me and I have had no problems since.
Good luck
Good luck
DHUDD said:
Any ideas people!!!??? HELP.....
Something is wrong either with the engine management system , or the intake/exhaust.You can either try replacing every thing that could conceivably go wrong until you fix it, or take it to an expert and have them find and fix the problem. Your call.
GreenV8S said:
DHUDD said:
Any ideas people!!!??? HELP.....
Something is wrong either with the engine management system , or the intake/exhaust.You can either try replacing every thing that could conceivably go wrong until you fix it, or take it to an expert and have them find and fix the problem. Your call.
I think the speed sensor has 2 functions. On 4x4's it limits the top speed, and it prevents the stepper motor from trying to control the idle if the car is still moving. The problem here is no signal (like a failed sensor) means the ECU thinks the car is stationary, so the idle should be controlled. I would suggest an easy test would be to disconnect the speed sensor and see if the problem changes. More generally to try and isolate idle problems, wait until the car is warm and idling nicely and then unplug the stepper with the engine still running. This will prevent it from controlling the idle any more, so try taking the car for a drive, and see if the idle then still fluctuates/ stalls. If it does its likely to be mixture (air leak or like) or possibly ignition (a misfire). Another option is to wind the base idle screw up a turn or two so the stepper cant shut so much air off, but if you go to far the idle may become too high, and the ECU will generate a fault code. Not that this does any harm.
The overall problem with the idle control system is it expects the engine to behave in a certain way (within set parameters) when it pulses the stepper motor, and if it does not the whole system becomes unstable and overshoots, so the rpm sticks high or goes too low. It may not be a brilliant design, but it normally indicates something else is not spot on else where.
The overall problem with the idle control system is it expects the engine to behave in a certain way (within set parameters) when it pulses the stepper motor, and if it does not the whole system becomes unstable and overshoots, so the rpm sticks high or goes too low. It may not be a brilliant design, but it normally indicates something else is not spot on else where.
There is a converter (under the dash) which takes the speed input from the speedo sensor and converts it two states as follows:-
State 1 - When road speed >3mph it outputs a constant 5V square wave which equates to around 30mph
State 2 - When roadspeed is less than 3mph - Zero volts.
I found that the sensor on mine was periodically outputting a square wave when I was stationary. As I have an electronics background I investigated the simple circuit and found that it has been poorly designed. i.e there is no allowance in the circuit for elecrical noise which is common on any car let alone TVRs which don't have the advantage of a metal body. I've made a minor mod which resolved this.
The point of all this is that if the ECU always sees a square wave indicating speed it will never set the idle speed (by use of the stepper), because it needs to see no speed and minimum throttle position before it does so.
This badlty designed unit could be the reason why all Chimaeras and Griffs seem to go through this idle speed problem and Range Rovers don't !
I would need to think about the simplest way of testing this for someone without electronics experience. Fixing it is another problem because buying a new converter doesn't solve the problem. The circuit either needs the mod that I've carried out or the power supply into the unit needs smoothing.
I noticed the problem when I was using a Lucas Laser? ECU diagnostic analyser which continued to show >3mph when I was stationary. After the mod it showed <3mph when stationary.
If anyone discovers that they have this problem then I will be happy to work with them to resolve it. Please contact me direct.
Mike
State 1 - When road speed >3mph it outputs a constant 5V square wave which equates to around 30mph
State 2 - When roadspeed is less than 3mph - Zero volts.
I found that the sensor on mine was periodically outputting a square wave when I was stationary. As I have an electronics background I investigated the simple circuit and found that it has been poorly designed. i.e there is no allowance in the circuit for elecrical noise which is common on any car let alone TVRs which don't have the advantage of a metal body. I've made a minor mod which resolved this.
The point of all this is that if the ECU always sees a square wave indicating speed it will never set the idle speed (by use of the stepper), because it needs to see no speed and minimum throttle position before it does so.
This badlty designed unit could be the reason why all Chimaeras and Griffs seem to go through this idle speed problem and Range Rovers don't !
I would need to think about the simplest way of testing this for someone without electronics experience. Fixing it is another problem because buying a new converter doesn't solve the problem. The circuit either needs the mod that I've carried out or the power supply into the unit needs smoothing.
I noticed the problem when I was using a Lucas Laser? ECU diagnostic analyser which continued to show >3mph when I was stationary. After the mod it showed <3mph when stationary.
If anyone discovers that they have this problem then I will be happy to work with them to resolve it. Please contact me direct.
Mike
Gassing Station | Chimaera | Top of Page | What's New | My Stuff