Knock Knock

Moderators: theelanman, DaveT, GeoffSmith, Elanlover, Nige, muley, Enright, Sy V, algirdas, Specky, nitroman, clemo, dapinky, Dave Eds

Knock Knock

Postby Readit » Sun 30.07.2017, 11:17

Is there anyone here who could tell me what a "normal" reading from a knock sensor might look like?

I have attached an Elanscan with my old car (black graph) overlaid with the new car (blue graph)

Old car was running fine and graph for about a 950 second run 0 - 100+ mph, hard acceleration. Knock counter between 10 - 20
New car hesitating and popping on hard acceleration, and stalling. Graph for about 400 seconds (3 stalls) 0-60 mph Knock counter 0 - 58 but no knock retard
You do not have the required permissions to view the files attached to this post.
All the best plans are flexible, Lotus use Sicaflex.
User avatar
Readit
Enthusiast
 
Posts: 105
Joined: Sun 22.05.2005, 20:06
Location: UK

Re: Knock Knock

Postby Giniw » Mon 31.07.2017, 15:42

I am surprised you get any knocks, I haven't had any on my car — I mean when elanscan is pluged in, which is obviously not the case very often.
Well to be more precise I have had one or two knocks when stopping the engine but I suppose it's just that it shakes a bit when it is stopping.
User avatar
Giniw
God
 
Posts: 1040
Joined: Sat 21.04.2012, 20:46
Location: France

Re: Knock Knock

Postby Brit-Car-Nut » Mon 31.07.2017, 15:58

Most common causes of engine knocking is poor fuel or improper ignition timing adjustment.

Less common is piston damage, carbon buildup or similar things.

If the petrol is old, drain and refill with some decent grade fuel. Make sure the ignition timing is checked/set while the ECM is in diagnostic mode.

Of course, your knock sensor might have died and is now giving odd results.
HD Replacement Shift Cables and Short Shift Kits still available
HD Replacement Shift Cable and Short-Shift Kit prices
Please contact me via eMail, not by PM
Download Manuals Here
Brit-Car-Nut
God
 
Posts: 3844
Joined: Tue 03.07.2007, 17:07
Location: Charlotte, NC USA

Re: Knock Knock

Postby Readit » Mon 31.07.2017, 16:19

Thanks guys for your replies.

Our considered opinion, having had 24hrs to think about it, is that there are no knocks, but the knock sensor is picking up the misfire as a knock and transmitting it to the ECU, which is retarding the spark advance, causing more mis-firing and knocks. We believe the valve timing may be out by one tooth, when the timing belt was replaced. Will keep you posted if we find this is the problem.
All the best plans are flexible, Lotus use Sicaflex.
User avatar
Readit
Enthusiast
 
Posts: 105
Joined: Sun 22.05.2005, 20:06
Location: UK

Re: Knock Knock

Postby lotusflasherman » Mon 31.07.2017, 19:20

Readit wrote:Thanks guys for your replies.

Our considered opinion, having had 24hrs to think about it, is that there are no knocks, but the knock sensor is picking up the misfire as a knock and transmitting it to the ECU, which is retarding the spark advance, causing more mis-firing and knocks. We believe the valve timing may be out by one tooth, when the timing belt was replaced. Will keep you posted if we find this is the problem.


To answer your question in the first posting - been through all my Elanscan data files and haven't found a knock anywhere.. and one of my logs is a 20 minute blast...
I run on an Everest chip so never use 95 Octane fuel unless I'm empty and can't find 98 or 99 and then will only fill with enough to get to me some 'proper juice'..

Not sure I'd concur with your 'considered opinion'.. in fact I'd be surprised that somebody could screw up like that ... have you checked the base ignition timing? Much easier to check that first than get cambelt cover off ...

:agree: with John, BCN, who says ... probably poor fuel or improper (base) ignition timing ...
Phil

Leave me alone, I think I know what I'm doing.
Cars: Subaru Forester 2.5XTN, Eclat Riviera & brace of Pacific Blue SE's.... and now an Elan+2S !
User avatar
lotusflasherman
God
 
Posts: 2149
Joined: Fri 05.09.2008, 00:14
Location: Hadleigh, 15m west of Ipswich or 800 miles south (Cap d'Agde)

Re: Knock Knock

Postby Readit » Mon 31.07.2017, 20:04

Fuel should be OK, the car is running an old 9239 chip at the moment so not the most tuned. The fuel in the tank is about 50% Vpower and 50% normal octane all put in recently. I ran my old elan (9930 chip) on normal octane and it never missed a beat.

Why we suspect the valve timing is, the car was pranged 14 years ago, minor OS damage, but pushed OS front chassis member onto crank pulley so it couldn't run. I rebuilt the whole front and while it was all off, I replaced the timing belt. Never done one before, so I could easily have screwed up. The Elanscan is the first time the car has actually run on the road since.

The ignition timing, however has not been touched, car had a 54K miles dealer service and has only covered 55k miles. So it is me or the dealer, I know who my money is on.
All the best plans are flexible, Lotus use Sicaflex.
User avatar
Readit
Enthusiast
 
Posts: 105
Joined: Sun 22.05.2005, 20:06
Location: UK

Re: Knock Knock

Postby lotusflasherman » Mon 31.07.2017, 22:08

Readit wrote:Fuel should be OK, the car is running an old 9239 chip at the moment so not the most tuned. The fuel in the tank is about 50% Vpower and 50% normal octane all put in recently. I ran my old elan (9930 chip) on normal octane and it never missed a beat.

Why we suspect the valve timing is, the car was pranged 14 years ago, minor OS damage, but pushed OS front chassis member onto crank pulley so it couldn't run. I rebuilt the whole front and while it was all off, I replaced the timing belt. Never done one before, so I could easily have screwed up. The Elanscan is the first time the car has actually run on the road since.

The ignition timing, however has not been touched, car had a 54K miles dealer service and has only covered 55k miles. So it is me or the dealer, I know who my money is on.


:smt017 Ignition timing is driven by Cam Angle Sensor which is a dog drive off the exhaust cam so if exhaust cam is timed wrong the ignition timing will be wrong .... won't it??
Phil

Leave me alone, I think I know what I'm doing.
Cars: Subaru Forester 2.5XTN, Eclat Riviera & brace of Pacific Blue SE's.... and now an Elan+2S !
User avatar
lotusflasherman
God
 
Posts: 2149
Joined: Fri 05.09.2008, 00:14
Location: Hadleigh, 15m west of Ipswich or 800 miles south (Cap d'Agde)

Re: Knock Knock

Postby Readit » Mon 31.07.2017, 22:17

That reminds me, something about a chicken and an egg. Phil. Guess when we check out both, we may find the answer.

Then I'm in the market for an Everest chip. Already the BHP is showing an improvement on my old Elan, but that had 130K on the clock.
All the best plans are flexible, Lotus use Sicaflex.
User avatar
Readit
Enthusiast
 
Posts: 105
Joined: Sun 22.05.2005, 20:06
Location: UK

Re: Knock Knock

Postby Readit » Thu 10.08.2017, 12:09

Just found out our diagnosis from the Elanscan was spot on. The timing belt was 4 teeth retarded on the exhaust cam ( or 2 retarded on exhaust and 2 advanced on inlet). The only explanation seems to be there was a mark on the lower pulley wheel caused by the accident which showed more than the real timing mark. Anyway whatever the reason, the engine now purrs like a kitten on roller skates. :clap: Just got the MOT to go now. (and a wonky wheel :( see wanted)
All the best plans are flexible, Lotus use Sicaflex.
User avatar
Readit
Enthusiast
 
Posts: 105
Joined: Sun 22.05.2005, 20:06
Location: UK

Re: Knock Knock

Postby Giniw » Thu 10.08.2017, 12:29

:-)
User avatar
Giniw
God
 
Posts: 1040
Joined: Sat 21.04.2012, 20:46
Location: France

Re: Knock Knock

Postby Simon_P » Fri 11.08.2017, 22:20

Your valve timing is what you measure it to be. It can't be 4 teeth or 2 + 2. They are driven by the same belt!

You put the crank at TDC and count the error on each pulley independently.
Simon_P
God
 
Posts: 968
Joined: Fri 06.08.2004, 12:33
Location: Kent UK

Re: Knock Knock

Postby Readit » Sat 12.08.2017, 09:07

I see where you are coming from Simon, but I was not present when the valve timing was re-checked. It was described to me as 4 teeth out on the exhaust (I assume at true TDC). The only plausible explanation for the error was another mark on the pulley wheel which showed up more than true TDC. Therefore, by using the wrong mark, assuming the cam pulleys were set to their correct marks, the difference of the true timing mark and the incorrect (timing) mark would equate to exhaust cam two teeth retarded, inlet cam two teeth advanced. Hope this explains it better?
All the best plans are flexible, Lotus use Sicaflex.
User avatar
Readit
Enthusiast
 
Posts: 105
Joined: Sun 22.05.2005, 20:06
Location: UK

Re: Knock Knock

Postby CalElan » Mon 14.08.2017, 19:55

Aren't you supposed to lock the cam sprockets in-place with a bolt through them once you have them aligned?
If the bolt doesn't line up with the hole - you're looking at the wrong mark.
User avatar
CalElan
Enthusiast
 
Posts: 241
Joined: Sun 14.12.2014, 01:26
Location: Mountain View, CA, USA

Re: Knock Knock

Postby Readit » Mon 14.08.2017, 21:00

That is very true, but as the installation was carried out some time ago and as part of more major works, my memory of the event has faded. All a bit of a mystery but at least we got to the heart of the problem with the help of Elanscan. The car is now fully roadworthy after 14 years storage, MOTed and raring to go. :D
All the best plans are flexible, Lotus use Sicaflex.
User avatar
Readit
Enthusiast
 
Posts: 105
Joined: Sun 22.05.2005, 20:06
Location: UK

Re: Knock Knock

Postby Readit » Mon 14.08.2017, 21:20

Just to show how Elanscan helped to find the problem, I did exactly the same run after the re-timing.The original 60 knocks were reduced to 3. The knock sensor is apparently just a microphone which counts (apparent) knocks and it interprets as pinking. The 3 counted in the final run were a dodgy plug lead on hard acceleration, subsequently replaced.
You do not have the required permissions to view the files attached to this post.
All the best plans are flexible, Lotus use Sicaflex.
User avatar
Readit
Enthusiast
 
Posts: 105
Joined: Sun 22.05.2005, 20:06
Location: UK

Re: Knock Knock

Postby CalElan » Tue 15.08.2017, 01:50

Sorry, that sounded critical, wasn't supposed to be.
More an affirmation that I understood the process of changing the cam belt - I did mine over the winter and it took me 5 times longer than it should as I checked and re-checked - and of course periodic swear breaks too!
Glad you got it sorted!
User avatar
CalElan
Enthusiast
 
Posts: 241
Joined: Sun 14.12.2014, 01:26
Location: Mountain View, CA, USA

Re: Knock Knock

Postby Readit » Tue 15.08.2017, 08:56

Thanks CalElan, no need to apologise, I am still puzzled as to how it happened. It was the first time I had changed an Elan belt but I have been tinkering with engines for years and would not expect to make such an elementary mistake. :bonk: :bonk:
All the best plans are flexible, Lotus use Sicaflex.
User avatar
Readit
Enthusiast
 
Posts: 105
Joined: Sun 22.05.2005, 20:06
Location: UK


Return to Electrical / Electronics / Stereo / Lights etc.

Who is online

Users browsing this forum: No registered users and 3 guests

cron