Marshall8hp
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Here is the a cut from the workshop manual. Mine does this, but then picks up again from the almost stall to keep running.
P38A Air intake temp readings...
- Thread starter MrGorsky
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So, I've had all the spark plugs out this morning. Cylinder 1 was a bit oily and black, but the others were fine.
I've also had the Nanocom on it. I can't seem to be able to make a recording of the live data. It starts and then just stops. Opening the csv file just shows the headings, but no actual data? I can take a live trace of the EAS, but not the GEMS engine data. Any ideas why that is?
The exhaust isn't blowing from anywhere I can find, but the chugging under load is still there. The CATS are very rattly.
Lastly I now have a fault code!
Code 0122 throttle position sensor circuit A low input. Checking that against live data shows it goes from 0.08 volts at idle up to about 0.76 near WOT, but them suddenly drops to 0v at WOT so that'll need fixing too.
Looking at RAVE, I'm waaaay off spec!
I'm starting to think there might be a few things wrong with my car....
I've also had the Nanocom on it. I can't seem to be able to make a recording of the live data. It starts and then just stops. Opening the csv file just shows the headings, but no actual data? I can take a live trace of the EAS, but not the GEMS engine data. Any ideas why that is?
The exhaust isn't blowing from anywhere I can find, but the chugging under load is still there. The CATS are very rattly.
Lastly I now have a fault code!
Code 0122 throttle position sensor circuit A low input. Checking that against live data shows it goes from 0.08 volts at idle up to about 0.76 near WOT, but them suddenly drops to 0v at WOT so that'll need fixing too.
Looking at RAVE, I'm waaaay off spec!
I'm starting to think there might be a few things wrong with my car....
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Marshall8hp
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Seems you might need a tps. Before that though, unplug it and give the connectors a good clean.
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Still not working. I've ordered a new one and we'll see.
RAVE says that it won't rev above about 2000 rpm with a duff TPS, so that might be the reason behind my lack of kickdown too.....
RAVE says that it won't rev above about 2000 rpm with a duff TPS, so that might be the reason behind my lack of kickdown too.....
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Circuit A? That would make sense. Guessing it has 2 tracks and compares the 2 in case one starts acting up. So maybe takes an average but if one is vastly different it goes into some kind of restricted range?
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I doubt it's that sophisticated.
There's probably allowance in the OBD standard for a circuit B if you ever needed one for another TPS.
There's probably allowance in the OBD standard for a circuit B if you ever needed one for another TPS.
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I'd want redundancy on something like a TPS. What does RAVE say? We're talking Solihull's finest here: the top chaps have a range of hammers from toffee to BFH.
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Time to close this out I think.
A replacement Throttle Position Sensor (TPS) has sorted it all out. The rough running is gone, power is back, kick down is back, the running rich smell is gone, the rattle and chuffing from the CATS is also much reduced. So I think it's safe to say it was the TPS all along, although when I replaced the CPS that did help things a bit.
Take note! If you have rough running issues, lack of power, and no kick down, check the TPS for operation. It should read around 0.5 volts at idle, and around 4.5 volts at WOT.
Lastly, the air intake readings well below the ambient temperature of your environment seem to be perfectly normal. I've taken a trace of mine and it rises and falls as you drive along, it's gets lower at speed. I can only assume this is due to the vacuum being produced by the engine induction....?
A replacement Throttle Position Sensor (TPS) has sorted it all out. The rough running is gone, power is back, kick down is back, the running rich smell is gone, the rattle and chuffing from the CATS is also much reduced. So I think it's safe to say it was the TPS all along, although when I replaced the CPS that did help things a bit.
Take note! If you have rough running issues, lack of power, and no kick down, check the TPS for operation. It should read around 0.5 volts at idle, and around 4.5 volts at WOT.
Lastly, the air intake readings well below the ambient temperature of your environment seem to be perfectly normal. I've taken a trace of mine and it rises and falls as you drive along, it's gets lower at speed. I can only assume this is due to the vacuum being produced by the engine induction....?
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Result and one for the betterment keeping the beast on the road
First I got to the bottom of my Nanocom issue, now I've got to the bottom of this. It's a good day at Gorsky Towers. I might buy a lottery ticket.
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Datatek
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Wind chill as airflow increases or decreases.
Marshall8hp
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I had a find the other day, I bought NOS plenum chamber, in original LR packaging and it came complete with stepper motor, TPS, throttle shaft, butterfly, heater plate, and everything else, ready to bolt on and use. Another eBay bargain that sat on the site for a month without a bid, so I messaged the fellow and made a low ball offer, and he said yes as he was happy to see the back of it. Now in stock for spares or to swap if needed. Well pleased.
Re the IAT, see my post at the opening of this thread...personally I draw the line where IAT reads below zero when ambient is +10 to 15. I guess it's also possible that nanocom is under- reporting the IAT temp.
I can't see windchill having much of an impact on the gems IAT, it's just a shrouded thermistor in the side of the air filter. But if Gems can't read the intake temp then it can't accurately convert the MAF voltage to an air flow.
We'll probably never know, unless someone has access to the Gems systems engineering docs or a brand new P38 GEMS. I may take a look at my Defender and see what that shows as it uses the same Gems sensor set-up.
Glad the TPS was an easy fix
I can't see windchill having much of an impact on the gems IAT, it's just a shrouded thermistor in the side of the air filter. But if Gems can't read the intake temp then it can't accurately convert the MAF voltage to an air flow.
We'll probably never know, unless someone has access to the Gems systems engineering docs or a brand new P38 GEMS. I may take a look at my Defender and see what that shows as it uses the same Gems sensor set-up.
Glad the TPS was an easy fix
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Windchill will be related to pressure so as speed changes so will the temperature. I think that is what Data was getting at.
I wouldn't be surprised if -10 is a default when starting to throw more fuel in and then as it warms up it switches to the real values and starts to use the readings from the o2 sensors and whatever to fine tune the mix.
Thanks Grrr. If pressure goes up, and volume is constant, then Temp shd go up, so there shd be more to it than that. I'm not sure how big a speed-related temp fluctuation MrG was observing anyway - in a test on mine it went up, and only by one or two degrees.
The IAT temp doesn't seem to use a default, in the field nanocom is reading at least. MAF and IACV are also delivering live data, so it looks like air calc is live, whereas on the fuel side gems initially uses a default for the o2 sensors, as you say
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