Possibly AFM Defective
Discussion
I have a ‘92 Griffith 4.3 Precat where I am getting very low mpg (120 miles from a tank and the fumes are terrible when reversing the car into the garage)so have tested all the ECU components. Fuel and coolant probes were good (3600 ohms) at around 12 degrees ambient. TPS was at .39v at idle so set to .32v. AFM though when the car was turned on spiked then dropped to 0.5v then slowly moved to 0.4v. I took it apart and cleaned the hot wire with AFM cleaner but there was no difference. The CO was set to 0.8 so have set that to 1.25v. Today I warmed the car to running temperatures and tested it again and with ignition on voltage went straight to 0.32v but continued to drop to around 0.2v. At idle it was 1.2v. I switched off for 5 minutes then it was back to 0.4v and running it was 1.7v at idle which is what I was expecting. It is the original 1992 Hitachi 3AM unit. I am waiting on Rover Gauge and will check. The exhaust smelt much improved now when I put it back in the garage. Any thoughts please?
Steve, I actually am in Fareham - Stubbington to be exact. I will see what Rover Gauge shows and maybe take you up on your offer of a loan as it would be great to get some confidence before paying almost £200 for a new one. Having spent I was aware of your garage so you will probably see me in the future.
Scott
Scott
Im not sure of the current supplies of AFMs- Rimmer do one for around £90, that are aftermarket and I hope would be better quality than some of the Chinese tat for £40 on Ebay. Id of thought the big suppliers like Rimmer would know by now if the parts are sub standard as the Range Rover / Landrover market place is far bigger than the TVR one. The issue of course with the TVR is the stupid placement of the AFM next to a hot exhaust without a heat shield. I did mess around with some very low cost Chinese Bosch equivalents on my car, but they where not heat stable once the car stopped in traffic and the output would change.
scottliv said:
The connectors looks good but I will swing through from the ecu connector to plug. I don’t think the earth is great as it is 1.5 ohms.
Where were you measuring that earth resistance?May be worth doing the same test on one or more of the other sensors sharing the same earth, TPS, water temp, fuel temp. All 4 common ground back to pin 25 on the ECU. However, they all route back to the blue 'loopback connector' down in the footwell. I have experience corrosion/bad contacts in this connector.
It may be that you are actually reading something in the ECU or the grounding of the ECU itself which is at the front of the timing cover. again these earths go via the loopback.
Steve
Steve I was measuring from the pin on the AFM plug to various earth points in the engine bay. I will try and locate that loop back. There has been a weep from the coolant hose in that footwell that I have now
fixed. I plan to get a list of the earths and ensure they are all good. Thanks for the continued support. I spent a long time in the Royal Navy maintaining the propulsion control systems and most of the problems were relating to poor wiring and connections.
fixed. I plan to get a list of the earths and ensure they are all good. Thanks for the continued support. I spent a long time in the Royal Navy maintaining the propulsion control systems and most of the problems were relating to poor wiring and connections.
scottliv said:
There has been a weep from the coolant hose in that footwell that I have now fixed.
Might not be related but.........I had the same and If like me you have some relays in the footwell on the ends of wires, then have a look what happens when coolant migrates down the wiring.
Might pay you to remove em, open them up and make sure they are dry inside.
https://www.pistonheads.com/gassing/topic.asp?h=0&...
Fourth message from the end.
scottliv said:
Cheers Lancepar, it is always good to find sound evidence of a defect. I need to get in that footwell but I only have a single garage and that side is tight against the wall.
No chance of that then. the blue loopback strap connector is right up at the top of the loom.
Steve
Had a look in the footwell tonight. Everything seems in order but could not see the blue loop back connector. The ECU is tucked down the side of the battery so will need a bit of time to get that out. Checked everything again on the temperature sensors and they seems good. The AFM is still suspect I think. Dropped to 0.5v then very slowly (20 seconds) continued then steadied at 0.4v. Will wait and see what Rover Gauge says.
Steve I rechecked the earth for the AFM last night and it is good. Less than 1ohm. I think the AFM is not working as it should and is causing the car to run rich. This has been controlled by turning the CO trim down to 0.8v.
I have ordered Rover Gauge so once that arrives I will be able to get a better understanding of the system dynamically. It is a precat so will not show the closed loop control.
I have ordered Rover Gauge so once that arrives I will be able to get a better understanding of the system dynamically. It is a precat so will not show the closed loop control.
Rover Gauge arrived today - thanks Mark@Blitzracing. Great instructions and had connected to the car no time. All looks good to me with the exception that idle mode is not recognised. I will need to investigate this further with the throttle. I bought the car in June and the plenum had been recently painted. I need to check that the throttle has been put back properly and that the plate is shut properly and will try and adjust the TPS to get the idle mode to register.
I keep plugging this...........so you might have already seen it........hope peeps have found it as useful as I did.
Help with TPS setting...
http://www.v8engines.com/carbs-2.htm#setting-up
Help with TPS setting...
http://www.v8engines.com/carbs-2.htm#setting-up
lancepar said:
I keep plugging this...........so you might have already seen it........hope peeps have found it as useful as I did.
Help with TPS setting...
http://www.v8engines.com/carbs-2.htm#setting-up
Thanks very much. I set it to 0.32v so it may be a little low. Unfortunately work is getting in the way of a tinker.Help with TPS setting...
http://www.v8engines.com/carbs-2.htm#setting-up
That bit on V8 engines is not really correct for the 14CUX, its for the earlier 14CU ECU that wont self adapt the throttle pot setting. You will find your TPS screws are not elongated to allow for an adjustment accordingly.
The 14CUX has a much wider range of voltage:
Throttle closed .085 - .545 volts
Throttle wide open 4.2- 4.9 volts
At its most basic the TPS needs to be less than 10% on RoverGauge to reach idle mode.
The 14CUX has a much wider range of voltage:
Throttle closed .085 - .545 volts
Throttle wide open 4.2- 4.9 volts
At its most basic the TPS needs to be less than 10% on RoverGauge to reach idle mode.
blitzracing said:
That bit on V8 engines is not really correct for the 14CUX, its for the earlier 14CU ECU that wont self adapt the throttle pot setting. You will find your TPS screws are not elongated to allow for an adjustment accordingly.
The 14CUX has a much wider range of voltage:
Throttle closed .085 - .545 volts
Throttle wide open 4.2- 4.9 volts
At its most basic the TPS needs to be less than 10% on RoverGauge to reach idle mode.
Blitz - many thanks - so it must therefore be getting a random road speed signal to stop it achieving idle mode. Full throttle is 4.78v. Hopefully get a chance to play on Friday / Saturday.The 14CUX has a much wider range of voltage:
Throttle closed .085 - .545 volts
Throttle wide open 4.2- 4.9 volts
At its most basic the TPS needs to be less than 10% on RoverGauge to reach idle mode.
You could try simply unplugging the speedo unit to kill the false signal. It think it may generate an error code if you leave it like tis though when you drive the car. Mind you if you have the top of the dash off, take the unit to bits and check for poor solder joints on the main connector on the circuit board. One I looked up had solder over the top of the pins through the circuit board, but the solder had not flowed onto the pins, so worth re soldering anyway if you can.
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