Air Flow Meter - Diagnostic Tool
Discussion
Hi,
I have tried the diagnostic tool (thanks guys).
Static test passed - dynamic failed for the following fault codes:
12 - Vane air meter
21 - Ignition signal erratic
77 - no description for this code.
92 - no description for this code.
My problem is that that I dont seem to have an air flow meter. I should have this:
And instead all I have is this:
I have tried the diagnostic tool (thanks guys).
Static test passed - dynamic failed for the following fault codes:
12 - Vane air meter
21 - Ignition signal erratic
77 - no description for this code.
92 - no description for this code.
My problem is that that I dont seem to have an air flow meter. I should have this:
And instead all I have is this:
Last S4 said:
Hi,
I have tried the diagnostic tool (thanks guys).
Static test passed - dynamic failed for the following fault codes:
12 - Vane air meter
21 - Ignition signal erratic
77 - no description for this code.
92 - no description for this code.
My problem is that that I dont seem to have an air flow meter.
According to the draper fault code reader-manual, the codes could also mean:I have tried the diagnostic tool (thanks guys).
Static test passed - dynamic failed for the following fault codes:
12 - Vane air meter
21 - Ignition signal erratic
77 - no description for this code.
92 - no description for this code.
My problem is that that I dont seem to have an air flow meter.
12 - Idle Speed Control valve
- Vane air flow sensor
21 - Coolant Temperature sensor (CTS)
- Air Charge Temperature Sensor (Short Circuit)
77 - Kick down activated
- Blip throttle not operate or operated too late (you're supposed to blip the throttle at a certain point during the test)
92 - Heated exhaust gas oxygen sensor 2 (cylinder 4-6), rich mixture.
To erase code 12, try cleaning the ISCV, this is a known weak spot of these engines.
For code 21, run the test again with the ACTS unplugged. If this gives you code 22 (Air Charge Temperature Sensor (open Circuit)), you'll know you have a duff sensor.
For code 77, during the test, you're supposed to keep the revs above 3.000rpm for approx. 40 seconds, after the first code has appeared. This will probably erase code 77. Of course, TVR being TVR, it is possible that they have used an ECU meant for an automatic model. In that case you will always have code 77.
Code 92 is probably a result of another duff sensor: If the ECU cannot properly calculate the amount of air going into the engine, the wixture will be too lean or too rich.
Are you sure you're getting 2-digit codes? IIRC, the later engines with cats and MAP sensor instead of vane meters, should have 3-digit codes. In that case you probably have:
122 - Throttle pot sensor, low voltage
177 - Oxygen sensor left, too rich
92 - no description for this code.
In case you need more assistance after today, I'm sure others on here will be able to help to help you out. I will be
the S on a eurohoon to Italy, to follow the Mille Miglia historic rally 
!Steve
Non-cat cars have an air flow meter. ECU measures air flow, engine speed, throttle position, and decides appropriate fuel and ignition map.
Cat cars don't have air flow meters. The ecu uses the lambda sensors to monitor the air mix going OUT of the engine, and also measures engine speed, throttle position etc, as well as engine load using the MAP (Manifold Absolute Pressure) sensor (a matchbox-sized box on the bulkhead behind the distributor, connected to 2 wires and a rubber tube. From those inputs, it calculates the fuel / ignition map to keep the lambda readings within acceptable limits.
That's why you have to keep the lambdas when you change the manifolds, as I said this morning.
Mine (as per your second photo) is how the intakes should be as standard.
Non-cat cars have an air flow meter. ECU measures air flow, engine speed, throttle position, and decides appropriate fuel and ignition map.
Cat cars don't have air flow meters. The ecu uses the lambda sensors to monitor the air mix going OUT of the engine, and also measures engine speed, throttle position etc, as well as engine load using the MAP (Manifold Absolute Pressure) sensor (a matchbox-sized box on the bulkhead behind the distributor, connected to 2 wires and a rubber tube. From those inputs, it calculates the fuel / ignition map to keep the lambda readings within acceptable limits.
That's why you have to keep the lambdas when you change the manifolds, as I said this morning.
Mine (as per your second photo) is how the intakes should be as standard.
Edited by tvrgit on Saturday 9th May 17:34
Hi,
I ran the test a second and third time and both times the codes 12 and 21 did not happen - just 77 and 92. Maybe the engine being warmer helped.
I have just changed the oil and filter and I will try the test again keeping the throttle above 3000 at the right time (that bit was blurred in my photocopied instructions).
What I have noticed since the test is that its running much better - seems more free revving and less hesitation. I know it should not make any difference, but the test does make some reference to the timing being adjusted.
Cheers, Steve.
I ran the test a second and third time and both times the codes 12 and 21 did not happen - just 77 and 92. Maybe the engine being warmer helped.
I have just changed the oil and filter and I will try the test again keeping the throttle above 3000 at the right time (that bit was blurred in my photocopied instructions).
What I have noticed since the test is that its running much better - seems more free revving and less hesitation. I know it should not make any difference, but the test does make some reference to the timing being adjusted.
Cheers, Steve.
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