By convention, bank 1 is normally the LH bank as seen from the driver's seat, so if you mean RH as looking at it from the front, you are correct. If you use your diagnostics to look at the live data from the O2 (lambda) sensors, the only ones you are interested in are the pre-cat ones. With the engine running normally they should flip flop between 0V and 1V. If they hang at either end, then either something is causing them to hang or the sensor is dead. Compare the readings you get from the bank 2 pre-cat sensors and see if there is a difference. If it is something else causing the problem, the ECU will adjust the short term fuel trims to compensate.

I would suspect your engine uses platinum spark plugs which normally have a change interval of something like 40-50,000 miles but if you don't know how long they have been in there, it's worth changing them anyway.

It is primarily inhabited by P38 owners but we do have a few with later models. The difference between this forum and a lot of the others is that most of us have been working on cars for years so the cause of a specific fault with one model of car is going to be much the same with something else.

Does it have the cross bolts on the mains? That is the main difference between the RRC and P38 engines even though they are both 3.9 litre (3950cc for both the RRC 3.9 and 4.0 litre P38).

I don't but as plod didn't specify cruise when they ordered my car, I haven't got it. However, on other cars I've found that it actually makes the economy worse as it will try to maintain the speed when going up an incline rather than keeping the throttle opening the same and allowing the speed to drop a little.

As he is fitting a later cluster to an early car, the engine type will be correct in the BeCM. Changing it from GEMS to Thor may correct the temperature gauge but there's no telling what other things would be changed. I think the main differences are going to be in the cluster pcb, in much the same way that the tacho will read differently if a diesel cluster is fitted to a petrol car or vice versa. The petrol ECU sends 4 pulses per rev while the diesel sends 3 and the correct reading is calculated by the instrument cluster itself.

You'll need to add an extra ground too. The early GEMS had a single wire to the gauge sender with the ground through the body (later GEMS have a different sender with two pins so has a ground wire to it), the Thor one has a 4 pin connection, two signal and two ground wires.

I did 800 miles at a steady 75-80 mph on Saturday and my trip says 22.3mpg......

But I was running on LPG so it's all pretty much irrelevant.

I would have gone about it a different way. Retain your existing main PCB and satellite board with the message centre on it but swap the actual gauges with their faces. That way, any differences between sensor voltages, will still drive the gauges to the same place. GEMS uses two temperature sensors, one for the ECU and one for the gauge but Thor has a single one containing two separate senders so it is quite possible the temperature/resistance outputs are different.

If it was a fuel pressure problem it would affect all cylinders equally so that would seem to rule that out. I'm assuming there is only one MAF sensor on your engine and not one per bank, so again that rules that out. That leaves the lambda sensors as there will be one, or possibly two, per bank. Can your scanner do live data? In which case log, if it can, or watch the outputs from the lambda sensors. They should flip flop between 0 and 1V about once a second. If either hangs at one end or the other, that is likely the problem. In saying that, the sensor gives 0V when lean and 1V when rich, so with a dead sensor giving a permanent 0V, the ECU would interpret that as lean so richen rather than lean off the mixture on that bank.

Does the diesel have a crank position sensor? On a V8 when they start to fail they do it when hot but will start working again once left to cool down. If it does and it is accessible, when it stops, spray it with cold water to cool it down. If it restarts immediately then that is likely the problem.

Is it the hose or the clip? I've found that the constant tension spring clips are fine if they are fitted exactly perpendicular to the stub. If they are on at a slight angle they will leak. Easily done considering what a pain it is to get to them.

I normally use the Diagnostic function and move them from 0 to 100%. You can hear them operating and see what the feedback pot is reporting. It will often go to 105% (which is a good trick if you can do it) but you'll be able to see if you are getting full travel and the correct feedback.

I remember somebody saying on rr.net that one from a Saab of some description fitted and worked. No idea on the part number or how well it worked though.

Pipes not pushed fully home on the valve block?

But if you did read from the beginning, or even from halfway through, you'd see that if he plugs the SAI pipe with his finger it runs normally...... Definitely a problem with the SAI system rather than anything else.

Do you have any diagnostics James? As you've found, the temperature sensor on the Thor is two sensors in one body (rather than 2 separate sensors on the GEMS). One feeds the dashboard temperature gauge while the other feeds the ECM. If you connect OBD diagnostics that can display live data and look at what engine temperature is shown. If it is obviously wrong, that is the problem.

Unless your lower grade fuel is really poor, a P38 doesn't need top grade stuff. Recommended fuel is 95 RON which equates to 90 in the US as a different method of grading is used (AKI or (R+M)/2).

As it appears to be an SAI problem, there is limited knowledge here to help as only NAS cars had it fitted. Reading about it in RAVE, it appears that it should only operate on a cold start and not a hot start so it could be caused by a temperature sensor problem. I understand on later NAS cars, there is an additional one in the radiator, presumably earlier ones just used the engine sensor.

RAVE says:

The engine control module (ECM) checks the engine coolant temperature when the engine is started, and if it is below 55°C (131°F), the SAI pump is started. Secondary air injection will remain operational for a period controlled by the ECM and is dependent on the starting temperature of the engine. This varies from approximately 95 seconds for a start temperature of 8°C (46°F) to 30 seconds for a start temperature of 55°C (131°F). The SAI pump operation can be cut short due to excessive engine speed or load.

As it's operating a solenoid, I would suspect at a pretty low frequency or it wouldn't get chance to operate before it released. Then again, I would expect the SAI to operate for a set time rather than being pulsed.

I've got a spare UK Thor ECU..... You only need the Nanocom to copy and paste the initialisation code from ECU to BeCM.

@LPGC, no it isn't a PWM signal, it is a permanent live directly from the fuse (via a splice) with the ground,either permanent or pulsed supplied from the ECU. So provided he is testing the voltage with respect to ground and not across the pins, it should show full battery voltage.

If the SAI isn't needed to pass emissions in your particular US State, then it can be removed. All you need to find is some blanking plugs to blank the holes in the cylinder heads. Once they are blanked the rest can be taken out and removed. Not sure if that will throw a fault code or not though. If you disconnect it and check for any SAI related codes you may have to put a resistor in place of the solenoid to fool the ECU. The purge valve is a separate system and even on a UK car if that is disconnected you will get a code thrown.

Ground is supplied by the engine ECU. They both share the same supply from fuse 26 which also feeds the MAF, ECU box fan, O2 sensors and cam position sensor on a Brown/Pink wire. See pages A1, page 4 for a description of how it works and A1 pages 8 and 15 in the ETM for the relevant bits.

Dodgy connection somewhere.....