Rovergauge Long Term Trim +100% Poor MPG
Discussion
Hello gentlemen,
Had my new Chim just over a week and she's been running great but getting terrible MPG. 11.4 MPG on first calculation which I know is off for a 400 driving around town and mostly on 30/40 roads. Yes yes don't buy a Chimaera for the fuel economy but as a daily drive I want her to be as good as she can be.
Hooked the car up to Rovergauge and got the following fault codes. Reset them and they didn't come back whilst letting the car idle for a while and gently revving up.
Short term fuel trim seems to be cycling around 0% as you'd expect, long term trim though once warm at idle is fully saturated at +100% on both banks. AFM reading is 3% linear and 30% direct. Everything else seems quite normal. Any suggestions as to where to look next and what could be the possible cause of this long term fuelling issue?
Alex
Had my new Chim just over a week and she's been running great but getting terrible MPG. 11.4 MPG on first calculation which I know is off for a 400 driving around town and mostly on 30/40 roads. Yes yes don't buy a Chimaera for the fuel economy but as a daily drive I want her to be as good as she can be.
Hooked the car up to Rovergauge and got the following fault codes. Reset them and they didn't come back whilst letting the car idle for a while and gently revving up.
Short term fuel trim seems to be cycling around 0% as you'd expect, long term trim though once warm at idle is fully saturated at +100% on both banks. AFM reading is 3% linear and 30% direct. Everything else seems quite normal. Any suggestions as to where to look next and what could be the possible cause of this long term fuelling issue?
Alex
Interesting mix of faults..... Firstly there is no timestamp on error codes, so they could be very old if the ECU has not been reset at any point. An AFM / Throttle pot error will occur if you get a high AFM output reading at the same time as a low throttle pot, and logically this situation cant exist, as the throttle must be open to produce a high AFM reading. So go for a drive and see if new errors are logged.
In terms of adding fuel, this means the lambda outputs are a low or no volts, so the ECU sees the mixture as lean, so it add fuel. Problem is the lambda probes can tell the difference between a lean mixture and un burnt mixture as both are high in oxygen, so a misfire will cause this type of error. Id drop all 8 plugs out and look at the colours and see if they vary significantly. A misfire would account for the terrible MPG.
Have a read here as well:
http://www.g33.co.uk/img/fuel/14cux-fault-finding....
In terms of adding fuel, this means the lambda outputs are a low or no volts, so the ECU sees the mixture as lean, so it add fuel. Problem is the lambda probes can tell the difference between a lean mixture and un burnt mixture as both are high in oxygen, so a misfire will cause this type of error. Id drop all 8 plugs out and look at the colours and see if they vary significantly. A misfire would account for the terrible MPG.
Have a read here as well:
http://www.g33.co.uk/img/fuel/14cux-fault-finding....
Thanks for that Mark, I'll see if I can run Rovergauge this evening when I get in and see if the faults have reappeared after a day's driving.
Had a look at the plug on cylinder 2 and it was a bit wet and sooty looking. I'll check the others for condition later after work. Doesn't feel like she's misfiring.
Surely a faulty AFM could cause those fault codes but it's weird that it looks like it's working correctly in RG.
Had a look at the plug on cylinder 2 and it was a bit wet and sooty looking. I'll check the others for condition later after work. Doesn't feel like she's misfiring.
Surely a faulty AFM could cause those fault codes but it's weird that it looks like it's working correctly in RG.
You are only looking at a tiny part its range at idle, its far harder to take meaningfull readings under load as there are so many other variables, and we dont know the actual cubic foot per minute of air to calibrate against- so we have to make do with 30 -35 % at idle (this in its own right can be anywhere from 750 to 900 rpm) plus the different engine capacities. A good test for the AFM is how long it takes to stablise its output when first powered on with a test meter:
Lucas 5AM Airflow meter testing. With thanks to Mark Adams of Tornado Systems
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 after the initial "warm up" spike. 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.
Mind you your trim is adding fuel- if the AFM output was high it would be removing it as it becomes too rich.
This is the correct waveform for the AFM when it's first powered on, followed by the engine being started. This trace of 1.62 volts is a 3.9 at 800 rpm.
Lucas 5AM Airflow meter testing. With thanks to Mark Adams of Tornado Systems
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 after the initial "warm up" spike. 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.
Mind you your trim is adding fuel- if the AFM output was high it would be removing it as it becomes too rich.
This is the correct waveform for the AFM when it's first powered on, followed by the engine being started. This trace of 1.62 volts is a 3.9 at 800 rpm.
Edited by blitzracing on Monday 11th June 13:41
Haven't probed the AFM yet but should be able to borrow a multimeter tomorrow to take a look.
Drove home from work today, car ran fine until stopped in traffic for a while. Became very hesitant on acceleration at one point and idle became erratic hunting from 500rpm to 1200rpm and dropping to 500rpm when coming to a stop from 30mph. I suspect in the baking sun something wasn't liking the heat.
Smelt very rich but cleared by time I got home. Let her cool off a touch. Plugged in RoverGauge and it dumped out the following faults this time:
Cleared the codes. Ran the car for a while and logged the data, ran beautifully and nothing seemed amiss. Fuel temperature was previously at about 60C and dropped slowly to 40C whilst idling with the bonnet up.
Long term Lambda had dropped this time to roughly +20% on both banks and short term Lambda was fluctuating around -10% to +20%.
Pulled the plugs on the even firing side and they looked all like this:
Cleaned off with a bit of petrol, replugged both AFM and TPS and drove her to get some fuel. Drove beautifully. Will see what she does tomorrow, think I'm going to need to log a drive though to catch it in the act.
Drove home from work today, car ran fine until stopped in traffic for a while. Became very hesitant on acceleration at one point and idle became erratic hunting from 500rpm to 1200rpm and dropping to 500rpm when coming to a stop from 30mph. I suspect in the baking sun something wasn't liking the heat.
Smelt very rich but cleared by time I got home. Let her cool off a touch. Plugged in RoverGauge and it dumped out the following faults this time:
Cleared the codes. Ran the car for a while and logged the data, ran beautifully and nothing seemed amiss. Fuel temperature was previously at about 60C and dropped slowly to 40C whilst idling with the bonnet up.
Long term Lambda had dropped this time to roughly +20% on both banks and short term Lambda was fluctuating around -10% to +20%.
Pulled the plugs on the even firing side and they looked all like this:
Cleaned off with a bit of petrol, replugged both AFM and TPS and drove her to get some fuel. Drove beautifully. Will see what she does tomorrow, think I'm going to need to log a drive though to catch it in the act.
Steve_D said:
When you do the log it may be worth restricting the channels you log as the ECU is pretty low tech and can't handle trying to log too much data.
Yeah she idles a lot nicer when on her own, runs a bit more like a bag of bolts when tethered to RoverGauge.If I can install the drivers on my work laptop I'll run a log on the way home tonight but I'm working late so don't expect mega temperatures in traffic.
Plugs are B7ECS. I'm starting to think it's the AFM playing up more than anything. Went to log a drive on the way home and the car stalled with the laptop plugged in when I started up and the laptop crashed and rebooted so I'll try logging fewer things in the morning when I have another go.
Did manage to see the TP move from 5%to 85% smoothly through its range though before stating the engine in Rovergauge. Is that normal?
Did manage to see the TP move from 5%to 85% smoothly through its range though before stating the engine in Rovergauge. Is that normal?
I had the same kind of issues few months ago. Long term was also to 100%, car was running rich with smells and even smokes on big accelerations. I have done the test with a multimeter plugged on the AFM and it was staying at 0.8 without going down as expected.
I have change it and it's night and day now. Long term are good and the car is smooth. I haven't seen the benefit on MPG yet (but the consumption was also higher than usual) because my odometer was stuck then.
I have change it and it's night and day now. Long term are good and the car is smooth. I haven't seen the benefit on MPG yet (but the consumption was also higher than usual) because my odometer was stuck then.
AlexHillTVR said:
Plugs are B7ECS. I'm starting to think it's the AFM playing up more than anything. Went to log a drive on the way home and the car stalled with the laptop plugged in when I started up and the laptop crashed and rebooted so I'll try logging fewer things in the morning when I have another go.
Did manage to see the TP move from 5%to 85% smoothly through its range though before stating the engine in Rovergauge. Is that normal?
Those where the ones TVR fitted to the 5ltr, really the wrong plug as they run too cold and soot up. Plug choice has caused huge debate on here with quite a few commenting on how good iridium plugs are, or you can run bog standard BP6ES that will run cleaner. Not thats your current issue however. As for RoverGauge, try turning off all the sensors apart from RPM, AFM and TPS when you do the logging to mininimise the ECU load. The ECU has a truly horrible bit of software that basically knocks out the serial output to RoverGauge and some sensor inputs, so just the ECU "heartbeat" remains as the processor cant keep up with all thats going on. Not normally an issue unless you are over 4000 rpm or so. Run the PC on batteries if you can, not a car PC adapter as this can cause a grounding problem through the RG cable.Did manage to see the TP move from 5%to 85% smoothly through its range though before stating the engine in Rovergauge. Is that normal?
Ok new, but hopefully related problems on the way home from work today. The car started fine but then immediately wanted to idle at about 400rpm, stalled itself after a few seconds, restarted and wanted to not idle again so tried to coax it with some throttle- felt like it wasn't doing anything, but slowly the car started to perk up then settled after about 15 seconds at her usual 900rpm idle with no apparent problems.
On the way home sat in traffic for about 10-15 minutes once up to temperature just crawling forward in the sun. Pulling away from the lights I'm easing the throttle in in 2nd from 15mph up to 20mph when it feels like I've got no throttle then all of a sudden slam! Throttle response back, the kind of impact you get from fuel starvation.
Car is fine for the rest of the journey.
On the way down my road I boot it in 2nd and it feels like there's just no power. Almost like there's 50% power but with all the noise of WOT. Am I in limp home mode?
Sod's law I left the laptop at work and so missed the opportunity to log when she started misbehaving!
On the way home sat in traffic for about 10-15 minutes once up to temperature just crawling forward in the sun. Pulling away from the lights I'm easing the throttle in in 2nd from 15mph up to 20mph when it feels like I've got no throttle then all of a sudden slam! Throttle response back, the kind of impact you get from fuel starvation.
Car is fine for the rest of the journey.
On the way down my road I boot it in 2nd and it feels like there's just no power. Almost like there's 50% power but with all the noise of WOT. Am I in limp home mode?
Sod's law I left the laptop at work and so missed the opportunity to log when she started misbehaving!
Finally this problem climaxed into the car stalling at cold startup and running like an absolute pig being coaxed home using the clutch to slip into every gear. Shunting like I've never ever seen before but finally caught her in the act!
MAF reading 0% direct and no difference when unplugged. No power over 3,400rpm. I think my AFM is dead
MAF reading 0% direct and no difference when unplugged. No power over 3,400rpm. I think my AFM is dead
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