Wiring Question
Discussion
Does the wiring for the speedo go through the ECU?
I have an interesting issue, coughs and splutters some times on wide throttle opening, almost cuts out till I lift off the throttle, does this a few times then a big backfire and all fine for a while. A bit later she starts to feel slightly hesitant I look does and the speedo and tachograph doing weird things and jumping around a bit.
I have an interesting issue, coughs and splutters some times on wide throttle opening, almost cuts out till I lift off the throttle, does this a few times then a big backfire and all fine for a while. A bit later she starts to feel slightly hesitant I look does and the speedo and tachograph doing weird things and jumping around a bit.
Aides app uses GPS for speed. The signal from the speed sensor at the diff goes to a splice joint to tell the door ecu that the car is moving so it will disable the door opening function. The other half of the splice goes to the dash connector through multiway 1 that joins the front and rear wiring looms.
CerbWill said:
Aides app uses GPS for speed. The signal from the speed sensor at the diff goes to a splice joint to tell the door ecu that the car is moving so it will disable the door opening function. The other half of the splice goes to the dash connector through multiway 1 that joins the front and rear wiring looms.
Do you know where this connector is, my first plan of attack it a good spray of contact cleaner on everything, it that doesn't work try a new engine loom, it is 20 years old and could do with a refresh anyway.Not sure where the splice joint is but it'll be soldered anyway. The multiway plugs are behind the helmet holder, the dash connector is around the back of the instrument cluster, accessed by taking the instrument surround off and/or the under-dash trim panel in the drivers footwell.
That won't have any effect on your engine running issues though.Have you had a look at whats going on with the software when it starts acting up? The big fuse is a common cause of rev counter issues so maybe worth checking? I'd also be wary of replacing the engine loom as I'm sure there were differences over the years. I replaced mine with a home-made replica of the one in the car so I knew all the wiring was exactly the same.
That won't have any effect on your engine running issues though.Have you had a look at whats going on with the software when it starts acting up? The big fuse is a common cause of rev counter issues so maybe worth checking? I'd also be wary of replacing the engine loom as I'm sure there were differences over the years. I replaced mine with a home-made replica of the one in the car so I knew all the wiring was exactly the same.
No faults logged in the ECU and non show up when it is misbehaving.
If I do go down the loom replacement I will probably take it to STR8SIX first for proper diagnosis before spending on the loom, I will let them then sort the issue out.
The issue has been coming on since the winter when it spent many months under a tarp while the chassis was away for a refurb, this is what leads me to think it may be damp/corrosion in the connectors some where and it is strange that it affects the speedo so I don't believe it is mechanical or something like fuel pressure but electrical.
Not the big fuse of that I am fairly sure, I have the upgraded one, it was changed recently and that normally makes the Tacho bounce with the indictors but this is it starts spluttering and the speedo and tacho start bouncing around and mis reading.
Also may be over fuelling as some big bangs out of the exhaust last night, injectors are quite new green tops that have done about 14,000 miles, coil packs are new and have a nice clean trace on the software readout, leads are new.
Symptoms worse when you suddenly apply throttle and the car starts doing a kangaroo impersonation.
If I do go down the loom replacement I will probably take it to STR8SIX first for proper diagnosis before spending on the loom, I will let them then sort the issue out.
The issue has been coming on since the winter when it spent many months under a tarp while the chassis was away for a refurb, this is what leads me to think it may be damp/corrosion in the connectors some where and it is strange that it affects the speedo so I don't believe it is mechanical or something like fuel pressure but electrical.
Not the big fuse of that I am fairly sure, I have the upgraded one, it was changed recently and that normally makes the Tacho bounce with the indictors but this is it starts spluttering and the speedo and tacho start bouncing around and mis reading.
Also may be over fuelling as some big bangs out of the exhaust last night, injectors are quite new green tops that have done about 14,000 miles, coil packs are new and have a nice clean trace on the software readout, leads are new.
Symptoms worse when you suddenly apply throttle and the car starts doing a kangaroo impersonation.
Sounds like an ignition problem to me. If you get a temporary lack of spark you'll have a load of unburnt fuel in the exhaust hence the big bangs. Could be the ECU connector, I would give that a good spraying and unplug/plug it a few times. Or could be a loose or damaged driver wire to one of the coils.
The erratic tacho etc, sounds like an ECU earthing issue, your running a 4.7? Is it the standard ECU, in which case there is a large braided cable coming from the ecu for grounding. This goes to a lug underneath the dash on the LHS of the centre console, common for it to be heavily corroded and would cause issues as you describe as all of the major electronics in the car are grounded here. If not this, it could also be the main grounding for the entire fuseboard behind the fuel tank, or alternativly the main grounding for battery on the LHS from suspension. I would bet good money on this being your issues.
Edited by tofts on Thursday 23 June 12:17
tofts said:
The erratic tacho etc, sounds like an ECU earthing issue, your running a 4.7? Is it the standard ECU, in which case there is a large braided cable coming from the ecu for grounding. This goes to a lug underneath the dash on the LHS of the centre console, common for it to be heavily corroded and would cause issues as you describe as all of the major electronics in the car are grounded here. If not this, it could also be the main grounding for the entire fuseboard behind the fuel tank, or alternativly the main grounding for battery on the LHS from suspension. I would bet good money on this being your issues.
Yes standard ECU obviously different map.Edited by tofts on Thursday 23 June 12:17
I have just been out for a spin over lunch and thinking about it while driving and come to the same conclusion, will check the earths inside the car and the battery earths first, the car was better just now but not 100%, wipers decided to stop so killed the ignition and restated while driving up the M40 and the wipers came back to life.
It has to be an earth and I think the one under the dash will be my first point of call and then the battery earth point.
You have to loosen the main centre tunnel cover, so you can remove the under radio tray.
There is a hidden screw either side about where the front of the seat ends, feel at the bottom of the leather/vinyl for a break in the glass fibre move this upwards and there will be a screw there, I generally use a piece of hollow steel to pass my screwdriver through so it does not mark the cover as your undoing the fastener. Remove the rear cubby hole, there may or may not be fasteners there depending on how they were feeling at the factory.
This "may" be enough to lift it up to facilitate the removal of the under radio tray without actually having to disturb anything more. There is a further screw on the tray about where your knee would be (drivers side), and There is also a nut and bolt on the left hand side, remove the vent to gain access.
That should be about it. If there is still not enough room to remove the tray, then there are wing nuts on the back of the dashboard to unfasten, but I don;t think you will have to bother.
From there, you will see the binding post. its part of the "upper" framework on the LHS, so not only check this for corrosion, but check the two bolts that bolt the top and bottom of the car together, big M12 allen headed buggers as it relies on these also being in an un-corroded condition.
Also, in answer to your first question, no the speedo does not go through the ECU, the pickup goes through the car on the rear LHS, where it goes across to near the fuseboard, there is a splice there to go in to the window control unit and then down the car to the speedo.
J
There is a hidden screw either side about where the front of the seat ends, feel at the bottom of the leather/vinyl for a break in the glass fibre move this upwards and there will be a screw there, I generally use a piece of hollow steel to pass my screwdriver through so it does not mark the cover as your undoing the fastener. Remove the rear cubby hole, there may or may not be fasteners there depending on how they were feeling at the factory.
This "may" be enough to lift it up to facilitate the removal of the under radio tray without actually having to disturb anything more. There is a further screw on the tray about where your knee would be (drivers side), and There is also a nut and bolt on the left hand side, remove the vent to gain access.
That should be about it. If there is still not enough room to remove the tray, then there are wing nuts on the back of the dashboard to unfasten, but I don;t think you will have to bother.
From there, you will see the binding post. its part of the "upper" framework on the LHS, so not only check this for corrosion, but check the two bolts that bolt the top and bottom of the car together, big M12 allen headed buggers as it relies on these also being in an un-corroded condition.
Also, in answer to your first question, no the speedo does not go through the ECU, the pickup goes through the car on the rear LHS, where it goes across to near the fuseboard, there is a splice there to go in to the window control unit and then down the car to the speedo.
J
Edited by tofts on Thursday 23 June 19:44
Edited by tofts on Thursday 23 June 19:45
Oh, forgot to say, depending on how high you can get your handbrake, you may need to remove this. 2x 10mm nuts. Fiddly, but possible, be careful with the handbrake wire, I have broken one getting it off, forgetting its still attached.
furthermore, note EXACTLY where the wiring loom is if you have to disturb it, its a very tight fit under the console and has to be in the one place it is right now to fit!
J
furthermore, note EXACTLY where the wiring loom is if you have to disturb it, its a very tight fit under the console and has to be in the one place it is right now to fit!
J
Edited by tofts on Thursday 23 June 19:57
For the speedo - if you've had a chassis refurb, check the sensor location and distance to the rotating disk. It could be it's not bene put back at an optimal clearance, dirty etc.
And if you need wiring diagrams
http://www.thetvrsite.com/cerbera/wiring-diagrams
And if you need wiring diagrams
http://www.thetvrsite.com/cerbera/wiring-diagrams
Also there's a rear earthing point, either on the chassis behind the rear seats or in the boot above the tank.
I can throughly recommend one of the sealy probes when doing wiring work
https://www.amazon.co.uk/Sealey-PPX-Auto-Probe-Plu...
Instant indication of live or neutral, plus the opportunity to put either live or neutral through the probe tip for testing circuits
I can throughly recommend one of the sealy probes when doing wiring work
https://www.amazon.co.uk/Sealey-PPX-Auto-Probe-Plu...
Instant indication of live or neutral, plus the opportunity to put either live or neutral through the probe tip for testing circuits
Issue found, the nice shinny new powder coat is doing what powder coat does and is contracting slightly.
The bolts holding the top part on the chassis were not very tight at all even though they were nice and tight 2 months ago.
Going over the car with some spanners last night has resolved the issues.
Tofts you are a star, thank you.
The bolts holding the top part on the chassis were not very tight at all even though they were nice and tight 2 months ago.
Going over the car with some spanners last night has resolved the issues.
Tofts you are a star, thank you.
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