1600rpm idle, kangarooing after 20mins driving = ???
Discussion
Pupp said:
SonicHedgeHog said:
Pupp said:
Advance unit vac line from plenum?
Would someone be kind enough to translate that into English?
sphs2 said:
get yourself a 14cux fault code reader from steve heath, could save you hours of chasing you backside all the way round the car, it won't tell you exactly what is wrong but it will point you in the right direction and is only around £50.
Mmmm, just found it on Steve Heath's website. Could be worth a punt. Thanks.I would suspect AFM too, I disconnected mine last weekend just to see the effect and it made it Kangaroo'd like a barsteward at small throttle openings but went ok when giving it beans..
Does your exhaust stink of petrol, that is usually a sign that the AFM is faulty or maybe the connector to it. May be worth cleaning the connector contacts while your at it.
Paul.
Does your exhaust stink of petrol, that is usually a sign that the AFM is faulty or maybe the connector to it. May be worth cleaning the connector contacts while your at it.
Paul.
Where do you want to start?
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Its not as simple as change this it will go away in all cases. A bit more fuel might help, a better spark, a softer cam (less overlap), improved intake breathing. Its basically due to a combination of poor low speed breathing on a high performance cam and exhaust contamination during valve overlap, plus the 14CUX does not cope well with this situation in metering the fuel accurately. You can also add anything that causes poor ignition to the mix as well.
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Its not as simple as change this it will go away in all cases. A bit more fuel might help, a better spark, a softer cam (less overlap), improved intake breathing. Its basically due to a combination of poor low speed breathing on a high performance cam and exhaust contamination during valve overlap, plus the 14CUX does not cope well with this situation in metering the fuel accurately. You can also add anything that causes poor ignition to the mix as well.
Edited by blitzracing on Sunday 28th March 18:12
I had a look at the airflow meter and it was pristine. It was however, one of the things suggested by Steve Heath in The Bible. Need to think about it. It's going in for a service shortly and it might be best to let the pros sort it out rather than me buy loads of new bits as part of a big trial and error exercise. I appreciate the commments though.
paulathome said:
I would suspect AFM too, I disconnected mine last weekend just to see the effect and it made it Kangaroo'd like a barsteward at small throttle openings but went ok when giving it beans..
Does your exhaust stink of petrol, that is usually a sign that the AFM is faulty or maybe the connector to it. May be worth cleaning the connector contacts while your at it.
Paul.
There is a fairly strong petrol smell although I dismisses that as a 'Griff feature'. I'm going to have a search for a new AFM. Even a total dipstick like me can fit one of those. I will check all the connections first though. Thanks.Does your exhaust stink of petrol, that is usually a sign that the AFM is faulty or maybe the connector to it. May be worth cleaning the connector contacts while your at it.
Paul.
If you do just want to get another AFM there are some cheap ones out there (as in Chinese), but one chap who bought one found it not to give a stable voltage output in the heat of the TVR engine bay.
Mark Adams did this bit a while ago for testing an AFM, just needs a test meter.
Here's a quick fault finding guide.
Note that you can drive without an airflow meter in case of emergency (i.e. airflow meter disconnected), because the system will drop into a default (limp-home) mode based on throttle opening.
Most airflow meter faults will cause the engine to run excessively rich. However if the airflow meter remains connected whilst defective then the vehicle will probably not run. In most cases the output from a defective airflow meter will be in the range 2.0-2.5 Volts, which is a viable value. This represents a moderate load and will cause heavy over-fuelling without setting a fault code.
Testing is performed in the following manner. Peel back the rubber boot on the airflow meter connector and leave it plugged in to the airflow meter. Set up the digital multimeter to read voltage. Insert the negative probe into the Red/Black wire (sensor ground), and the positive into the Blue/Green wire (Airflow signal).
Turn on the ignition, but do not start the engine. The meter should immediately indicate a reading of approximately 0.3-0.34 Volts. Most defective airflow meters will overshoot to 0.8 Volts or higher, and take at least 2 seconds to come down to the correct voltage.
Now start the engine, and the reading should rise to 1.6 Volts (3.5 Litre engine) to 1.75 Volts (5.0 Litre engine).
The next test is full load, and as with the fuel pressure test it will require use of a rolling road or a steep hill in the same manner. Under full load the voltage should rise to 4.45 Volts (3.5 Litre engine) to 4.95 Volts (5.0 Litre engine).
On this injection system, the idle CO mixture adjuster is provided on the airflow meter. It is located in a boss on the top of the airflow meter, pointing towards the engine. Leaving the multimeter negative probe in the Red/Black wire, move the positive probe to the Blue/Red wire.
Now turn on the ignition but do not start the engine. Observe the voltage. The normal adjustment range is between 0.0 and 3.6 Volts, with the higher Voltages producing higher idle CO values. There are approximately 20 turns of the adjuster screw to cover the entire range.
Annoyingly, the adjustment may be clockwise or anticlockwise to increase the value, and this varies from meter to meter! For this reason it is always preferable to have the multimeter connected in this manner when adjusting idle CO, so that you see can something is actually happening.
Typical Voltages that would be found at this point are between 0.9 to 1.4 Volts for non-catalyst cars. This Voltage is always factory pre-set to 1.8 Volts for catalyst vehicles. A value near to 3.5 Volts will generally produce an idle CO value of 9-10%. These Voltages may be used as safe initial values particularly if no CO measuring equipment is available.
Mark Adams did this bit a while ago for testing an AFM, just needs a test meter.
Here's a quick fault finding guide.
Note that you can drive without an airflow meter in case of emergency (i.e. airflow meter disconnected), because the system will drop into a default (limp-home) mode based on throttle opening.
Most airflow meter faults will cause the engine to run excessively rich. However if the airflow meter remains connected whilst defective then the vehicle will probably not run. In most cases the output from a defective airflow meter will be in the range 2.0-2.5 Volts, which is a viable value. This represents a moderate load and will cause heavy over-fuelling without setting a fault code.
Testing is performed in the following manner. Peel back the rubber boot on the airflow meter connector and leave it plugged in to the airflow meter. Set up the digital multimeter to read voltage. Insert the negative probe into the Red/Black wire (sensor ground), and the positive into the Blue/Green wire (Airflow signal).
Turn on the ignition, but do not start the engine. The meter should immediately indicate a reading of approximately 0.3-0.34 Volts. Most defective airflow meters will overshoot to 0.8 Volts or higher, and take at least 2 seconds to come down to the correct voltage.
Now start the engine, and the reading should rise to 1.6 Volts (3.5 Litre engine) to 1.75 Volts (5.0 Litre engine).
The next test is full load, and as with the fuel pressure test it will require use of a rolling road or a steep hill in the same manner. Under full load the voltage should rise to 4.45 Volts (3.5 Litre engine) to 4.95 Volts (5.0 Litre engine).
On this injection system, the idle CO mixture adjuster is provided on the airflow meter. It is located in a boss on the top of the airflow meter, pointing towards the engine. Leaving the multimeter negative probe in the Red/Black wire, move the positive probe to the Blue/Red wire.
Now turn on the ignition but do not start the engine. Observe the voltage. The normal adjustment range is between 0.0 and 3.6 Volts, with the higher Voltages producing higher idle CO values. There are approximately 20 turns of the adjuster screw to cover the entire range.
Annoyingly, the adjustment may be clockwise or anticlockwise to increase the value, and this varies from meter to meter! For this reason it is always preferable to have the multimeter connected in this manner when adjusting idle CO, so that you see can something is actually happening.
Typical Voltages that would be found at this point are between 0.9 to 1.4 Volts for non-catalyst cars. This Voltage is always factory pre-set to 1.8 Volts for catalyst vehicles. A value near to 3.5 Volts will generally produce an idle CO value of 9-10%. These Voltages may be used as safe initial values particularly if no CO measuring equipment is available.
blitzracing said:
If you do just want to get another AFM there are some cheap ones out there (as in Chinese), but one chap who bought one found it not to give a stable voltage output in the heat of the TVR engine bay.
Mark Adams did this bit a while ago for testing an AFM, just needs a test meter.
Here's a quick fault finding guide.
Note that you can drive without an airflow meter in case of emergency (i.e. airflow meter disconnected), because the system will drop into a default (limp-home) mode based on throttle opening.
Most airflow meter faults will cause the engine to run excessively rich. However if the airflow meter remains connected whilst defective then the vehicle will probably not run. In most cases the output from a defective airflow meter will be in the range 2.0-2.5 Volts, which is a viable value. This represents a moderate load and will cause heavy over-fuelling without setting a fault code.
Testing is performed in the following manner. Peel back the rubber boot on the airflow meter connector and leave it plugged in to the airflow meter. Set up the digital multimeter to read voltage. Insert the negative probe into the Red/Black wire (sensor ground), and the positive into the Blue/Green wire (Airflow signal).
Turn on the ignition, but do not start the engine. The meter should immediately indicate a reading of approximately 0.3-0.34 Volts. Most defective airflow meters will overshoot to 0.8 Volts or higher, and take at least 2 seconds to come down to the correct voltage.
Now start the engine, and the reading should rise to 1.6 Volts (3.5 Litre engine) to 1.75 Volts (5.0 Litre engine).
The next test is full load, and as with the fuel pressure test it will require use of a rolling road or a steep hill in the same manner. Under full load the voltage should rise to 4.45 Volts (3.5 Litre engine) to 4.95 Volts (5.0 Litre engine).
On this injection system, the idle CO mixture adjuster is provided on the airflow meter. It is located in a boss on the top of the airflow meter, pointing towards the engine. Leaving the multimeter negative probe in the Red/Black wire, move the positive probe to the Blue/Red wire.
Now turn on the ignition but do not start the engine. Observe the voltage. The normal adjustment range is between 0.0 and 3.6 Volts, with the higher Voltages producing higher idle CO values. There are approximately 20 turns of the adjuster screw to cover the entire range.
Annoyingly, the adjustment may be clockwise or anticlockwise to increase the value, and this varies from meter to meter! For this reason it is always preferable to have the multimeter connected in this manner when adjusting idle CO, so that you see can something is actually happening.
Typical Voltages that would be found at this point are between 0.9 to 1.4 Volts for non-catalyst cars. This Voltage is always factory pre-set to 1.8 Volts for catalyst vehicles. A value near to 3.5 Volts will generally produce an idle CO value of 9-10%. These Voltages may be used as safe initial values particularly if no CO measuring equipment is available.
Now that is what I call a comprehensive answer. Thank you very much indeed. The potential for me to balls this up is enormous. I'm going to reread this post several times and see if I'm up to the job before I don my threadbare bodging pants and get stick in.Mark Adams did this bit a while ago for testing an AFM, just needs a test meter.
Here's a quick fault finding guide.
Note that you can drive without an airflow meter in case of emergency (i.e. airflow meter disconnected), because the system will drop into a default (limp-home) mode based on throttle opening.
Most airflow meter faults will cause the engine to run excessively rich. However if the airflow meter remains connected whilst defective then the vehicle will probably not run. In most cases the output from a defective airflow meter will be in the range 2.0-2.5 Volts, which is a viable value. This represents a moderate load and will cause heavy over-fuelling without setting a fault code.
Testing is performed in the following manner. Peel back the rubber boot on the airflow meter connector and leave it plugged in to the airflow meter. Set up the digital multimeter to read voltage. Insert the negative probe into the Red/Black wire (sensor ground), and the positive into the Blue/Green wire (Airflow signal).
Turn on the ignition, but do not start the engine. The meter should immediately indicate a reading of approximately 0.3-0.34 Volts. Most defective airflow meters will overshoot to 0.8 Volts or higher, and take at least 2 seconds to come down to the correct voltage.
Now start the engine, and the reading should rise to 1.6 Volts (3.5 Litre engine) to 1.75 Volts (5.0 Litre engine).
The next test is full load, and as with the fuel pressure test it will require use of a rolling road or a steep hill in the same manner. Under full load the voltage should rise to 4.45 Volts (3.5 Litre engine) to 4.95 Volts (5.0 Litre engine).
On this injection system, the idle CO mixture adjuster is provided on the airflow meter. It is located in a boss on the top of the airflow meter, pointing towards the engine. Leaving the multimeter negative probe in the Red/Black wire, move the positive probe to the Blue/Red wire.
Now turn on the ignition but do not start the engine. Observe the voltage. The normal adjustment range is between 0.0 and 3.6 Volts, with the higher Voltages producing higher idle CO values. There are approximately 20 turns of the adjuster screw to cover the entire range.
Annoyingly, the adjustment may be clockwise or anticlockwise to increase the value, and this varies from meter to meter! For this reason it is always preferable to have the multimeter connected in this manner when adjusting idle CO, so that you see can something is actually happening.
Typical Voltages that would be found at this point are between 0.9 to 1.4 Volts for non-catalyst cars. This Voltage is always factory pre-set to 1.8 Volts for catalyst vehicles. A value near to 3.5 Volts will generally produce an idle CO value of 9-10%. These Voltages may be used as safe initial values particularly if no CO measuring equipment is available.
One further update. Went for a test drive to check a different problem and noticed the kangarooing wasn't there. The idle speeds have changed though. On start up the idle was 11-1200rpm. After 10 minutes driving and with no gear engaged the it had risen to 2000rpm. With a gear engaged and the clutch brought up to the biting point the revs dropped to somewhere in between these two figures. Does this confirm the AFM suspicion?
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