Overcounting rev counter diagnosis

[MPx]

On my way up to Curborough on Sat I was sitting for long periods on the motorway at 4000rpm. After about 90mins, I noticed that I was doing 4500 but still at the same original speed. Stopped for breaky soon after and when I got going again, it wasn't long before the rev counter had climbed from the "correct"? 4000 to 4500 then 5k and eventually 6k without ever changing speed significantly. Sometimes it did drop back down to about the right reading.

I've done a search on here and come across threads that suggest 1) a bad earth or 2) a duff Alternator.
Problem is I'm a numpty at this sort of thing. What exactly do I need to check where to find out which if either of these things is the problem. Any other ideas welcome too.

[bobbrown]

Not sure why alternator as the circuit diagram show the signal is from the ignition coil, could be a faulty connection some where
There are only three wires a green which is +12 volts ignition feed common to all instruments, black earth and a white and slate signal feed.
Could be a faulty tacho but I would be inclined to check the wiring first.

Bob

[GeoffSmith]

May also be the onset of an ignition related fault - if it continues, I can put a 'scope on it to see if there is anything obvious.

[MPx]

Thanks Bob/Geoff. The alternator thing came from Stevo and M100TWO here
forum.lotuselancentral.com/viewtopic.php?f=37&t=5758&p=64377&hilit=rev+counter#p64377

I'll try to put a meter on the grey wire and rev it to see the voltage change. I'm pretty sure it will, cos the thing functions, it just doesn't necessarily show the right result! Maybe me pfaffing about with it will improve or disconnect a dodgey connection if there is one. Not sure how I'm going to test it anytime soon. Dont really fancy another trip to Curborough just to see!

[saska]

If you have elanscan and you can capture the RPM creep and approx when during the scan the RPMs creep up, then if ES is showing RPMs correctly then it would suggest a fault in the gauge as both the ECM and the gauge get their signal via the same ECMHC (harness connector). So looking at the scan plot X as Time, Y-left as RPM and Y-Right (second curve) as Speed then it should be pretty obvious if it is creeping in ES. If both ES and gauge show the creep then I'd be thinking the gauge is OK and cleaning connectors to the coilpack base plate and the earth lead that goes to the front baseplate mounting bolt.

[MPx]

I managed to capture (or more accurately NOT capture) a rev creep on Elanscan. Having recorded 90 mins of nothing going down, I got a hit very soon after setting off from the SWLC open day last week. Just after I joined the private road back towards Exeter, I noticed the rev needle rise - but no corresponding rise in speed, noise or feel. Elanscan shows what it felt like - say 4000-4200rpm. From about 400secs in until I stopped about 10 mins later, the rev counter guage was hovering around 5500, but Elanscan doesn't show any movement like that at all.

That certainly puts paid to the idea that I'll only see it on a long journey, but not to the fact that its extremely intermittent (no issues again this weekend). So as Tony suggests, its most likely just the guage, which I guess I can live with. Its just a bit off putting when you glance down and it looks like you're reving the nuts off it. Grateful if anyone who understands these things would have a quick look at the Elanscan and let me know if there's anything else I need to know or indicates any other issue. Many thanks.

[Brit-Car-Nut]

Aftersales still have tachs for 15 pounds + VAT. Shipped to your nearest dealer.

[saska]

Grateful if anyone who understands these things would have a quick look at the Elanscan and let me know if there's anything else I need to know or indicates any other issue.

The scan shows a PromID of 699 which I've only seen with a switcher chip. Also shows 10K faults of Prom Error which also seems to occur with switchers.
Do you have a switcher and which program was selected -- looks like maybe Everest or Kili closed loop since max boost was 0.83Bar and it went closed loop @ about 55secs ?
There are some weird things going on here so I'll tell you what I see and maybe others can help with ideas.
1. There are 5 knock events all of which are associated with boost over 0.5 Bar except one -- the last which occurs with 0 boost.
2. There is knock retard applied on 4 occasions between 680-720secs but only one of the retards is applied in direct conjunction with a knock event -- the others don't associate with a knock event.
3. Spark advance at idle is pretty good on startup but in the final 15 secs before you switched off it looks very low 3-8°BTDC
The rest of the scan looks fine: temps good, EGR, secondary throttle, etc. all working.
I'd tend to agree with Geoff that maybe there is something ignition related going on but as to what is the 64K question.
Were it my car I'd consider the following:
1. Base timing (always a good plan)
2. Check earths to coil pack baseplate and engine manifold -- bad earths are common on older cars and can cause weird & wonderful things.
3. If you do have a switcher, I'd consider removing it and fitting a std 1499 Everest as a diagnostic measure to see if the behaviour changed. Think I've a 1499 Everest somewhere if you want to borrow it.
4. Clean up or swap out the coil packs for known good ones to see if behaviour changes
I doubt any of this is related to the RPM climbing (looks like the gauge) but you never know.
Good luck

[MPx]

Thanks very much Tony, very kind of you to take that much trouble with your reply.

Yes its got a switcher, normally set on 6 (everest), as it was for this run.

When I first used Elanscan and posted a file, Ian or Geoff commented on the three (I think) knock events seen that time and the fact that there was no associated retard with two of them. Odd innit!? I know they aren't good, but as there's so few I'd hoped it wasn't too bad an issue.

I suspect you are right that checking out the earths would be a good move - almost inevitably bad by now, and indeed it still may be a dodgey earth causing the tacho creep.

I know that base timing is both basic and vital, but I'm still very hesitant to do it - frightened of making it worse! But I cant do any harm in trying to see what its currently set like so I'll give that a go. I may get the SWLC boys to specifically check it out next time I'm down there if I think it needs changing or cant see where it is for some reason.

Thanks for the offer of the chip. I've probably still got the original standard one somewhere. Would that be as good a test or do you think it would need the extra stress of Everest to manifest the problem?

Haven't got any spare coil packs. But on John's advice I probably need to contact Aiden to see if he'll sell me a Tacho so I may ask if he can do coil packs too!

Appreciate the help

[Brit-Car-Nut]

Aftersales don't list the coils but if you search the forum there are several links for very reasonably priced replacements or more expensive performance coils to be found.

Although the Everest chip is making more power, the stock coil is pretty robust. You might want to get a set of the "affordable" ones for testing and then, if you really need to put red coils in to match the colour scheme, you can order them from the best source and resell the others.

The coils make a difference in everything, so after grounds, I would consider coils to be the next area of research.

[saska]

When I first used Elanscan and posted a file, Ian or Geoff commented on the three (I think) knock events seen that time and the fact that there was no associated retard with two of them. Odd innit!?

It isn't unusual to see knock events with no retard applied -- the ECU only applies retard when the knock is severe enough. It is the reverse that's unusal; retard with no associated knock event.

Thanks for the offer of the chip. I've probably still got the original standard one somewhere. Would that be as good a test or do you think it would need the extra stress of Everest to manifest the problem?

The std chip ought to work as 4 of the knocks occurred at just over 0.5Bar boost -- but I can send the 1499 Everest as I found it last night.

Haven't got any spare coil packs. But on John's advice I probably need to contact Aiden to see if he'll sell me a Tacho so I may ask if he can do coil packs too!

I wouldn't do the tacho yet in case it isn't faulty. I'd do earths, base time, coil packs & chip first. As JohnC suggests you can get reasonable coil packs HERE at £30ea. If you're feeling flush they also do ign leads at £29
As a matter of interest, would be good if you could do all except the chip and then do Elanscan. Then change chip and rescan a similar run.

[MPx]

It isn't unusual to see knock events with no retard applied -- the ECU only applies retard when the knock is severe enough. It is the reverse that's unusal; retard with no associated knock event.

My bad - I obviously didn't quite understand what I was told last time Thanks for clearing that up....but what could cause a retard if not a knock?

As JohnC suggests you can get reasonable coil packs HERE at £30ea. If you're feeling flush they also do ign leads at £29

A pair of coil packs are now on order. I thought it would be useful to swap them round anyway cos it'll assist me to clean up the earths etc. I decided if I was going to replace the leads I'd rather splash and get some yellow ones so have got on to Kingsborne and ordered some of theirs @ £42:50 delivered, but I guess I might also get hit for some extra taxes somewhere before they turn up.

As a matter of interest, would be good if you could do all except the chip and then do Elanscan. Then change chip and rescan a similar run.

Will do....

Thanks again for your help

[dapinky]

Mike,

I've got a spare set of coils (taken off the car when i fitted the MSD ones, but working fine at that time) - they are with Aaron (Kennich) in Wiltshire at the moment, but he finished with them and then never made it to Castle Combe to give them back.

I'd be happy for him to post them down to you instead of over to me if you want to see if it helps.

If it sorts you out, then hang on to them until you can get a new set for yourself and then they can go on to the next needy person (or back to me if i see you before that!).

It may help you to either confirm or elliminate a cause for the problem without unnecessary expense.

That said, i know that they are the same as esprit parts (but don't know if all esprits had the same system) - so maybe you could canibalise the other car????

[MPx]

Our posts crossed Dave, but that's a very kind offer included there. As you'll have seen I've taken the plunge to get some new coil packs so hopefully they'll turn up soon. Looks like I may have missed a trick on (not) getting MSD ones. What are they all about?

BTW my Esprit is an old G-car and I dont think coil packs were introduced until the GM days and the S4 ... but I may be wrong...I often am about the oily bits!

[MPx]

OK so time for an update.

I got the new coil packs and HT leads. Spent a happy few hours putting them on, although I expect everyone else would do it in about 20 minutes . It took me a couple of hours to take everything off. Then another couple on another day to clean up the bits and put everything back.

Here's the old still mounted and the new labelled up

Dismantled backplate shows some oxidsation but not much

Cleaned it all up anyway

Then rebuilt with new coil packs

Then threaded the new leads through to the coil packs

And tidied up for the finished look


So that was some of the action points dealt with. New coil packs and leads. Cleaned up earths.
However, still haven't checked base timing
Also still not tried replacing the std chip.

I've not been using the car recently, but had an emergency trip up to Milton Keynes yesterday so plenty of miles to get a trace.
This one covers the first 15-20 mins from startup

ESData012.zip

And this one the next 40mins or so.

ESData013.zip

Not sure if the news is good or bad. I dont think the retard(s) is/are independent of a knock any more, but I do seem to be getting alot more knocks! The tacho still has periods of creep - displaying up to 1000 or so more RPM than its actually doing. Whaddya think?

[saska]

Not sure if the news is good or bad. I dont think the retard(s) is/are independent of a knock any more, but I do seem to be getting alot more knocks!

There are 20 knock events in the 2nd long run and 9 applications of retard. 4 of the retard applications occur without associated knock events. Don't know why this should occur.
Most of the knock events occur at boost levels above 0.5 Bar. 9 of the knock events occur in the first part of the second run during throttle at > 90% and boost of 0.87 Bar.
The timing looks OK at cold start on the first scan but the spark control should increase the advance when cold anyway. At the end of the first scan at idle and warm the timing looks very low.
Think you need to do base timing next. If the knocks/retard persist after that then I'd be curious to see what effect removing the switcher and fitting a std or everest mem-cal had.
Don't have any other bright ideas I'm afraid.

[MPx]

Thanks Tony. Appreciate your time looking through it. Weird about the random retards innit? I will (really!) look at the base timing. Car will be SORN'd from Thursday so not going to get another run out of it now - but can still do timing in the barn. I'll resurect the thread when I've got another update. Ta muchly.

[saska]

Weird about the random retards innit?

Yes. I re-read a lot of the Closed Loop Manual to see what else besides knock events might cause the 'spark retard without knock' but couldn't see anything I'd missed on previous readings.
Don't usually need to re-read too many things but the closed loop manual doesn't tell all about how the ECU operates, it's more to do with technician diagnostics, so a lot of the ECU programming is inferred rather than 'known'.
ESM may know what else besides knock could cause spark retard but I don't.
Anyroadup, over winter do base timing, note what it was before any adjustment, note if there is any fluctuation or a rock solid strobe and do another ES for when you resurrect the thread.
Also note that any fluctuation can be caused by a loose timing belt as well as in the CAS itself.

[MPx]

Just thought I'd resuurect this post to say the tacho issue is the same. I had the base timing checked by SouthWest Lotus and they said it was absolutely spot on - no adjustment necessary. I took it up to Gaydon last Sunday and had several lengthy periods on the motorway with nearly 7000 revs indicated which was a bit scarey, but then it would fall back to 4000 or so without any change of engine note or speed. Of the original list of things to try, I have:

Changed the coil packs
Changed the leads
Cleaned the earths around the coil packs
Checked base timing is correct (by others)


I have not yet:
Replaced the original chip
Measured the voltage to the tacho
Changed the tacho

The car really does go very well so this is more about the worried well than the genuinely sick but I would prefer it to be right. I think my next step will be to try to get a tacho from aftersales - though I dont fancy my chances of fitting it without issue! Any other ideas welcome. Cheers!

[ESM]

It's curious how once you notice something once you start seeing it everywhere... I noticed a lot of noise on the RPM in an ES log elsewhere a few days ago and here... it looks like a factor here too. It seems to me that there is more noise than usual on the RPM and the level of the noise looks related to the level of RPM; the noise looks quite pronounced at 4000RPM but reasonably normal a lower levels. I would look at the CAS and its wiring

If noise on the engine speed wire is the issue then it might cause RPM gauge errors, perhaps the ECU is simply better at rejecting noise than the tacho, and noise on the timing signals might cause knock because of resultant errors in spark timing.