Strobe timing error

[Chas54]

My Elan has been running pretty well for a couple of years now but has started playing up and is now unuseable

I have been trying to get my ignition timed right but have a problem with the strobe light being all over the place when i press the button. Its impossible to tell where it is in relation to the timing marks as its intermitent as well. This is in service mode of course . Ive tried the strobe and its perfect on another car i have .
Its just been MOTd and on the way home started missing and coughing a lot. The vacuum when starting hot is also poor but if i use a vacuum tester to draw 35mbar on the MAP its OK.

Ive been trying the smoke test with all the vacuum take offs blanked and cant find a leak anywhere , the individual vac lines are all testing good as well. Checked the servo as well.

I suspect i have an ignition fault somewhere and have been checking and cleaning earths but am a bit confused on their placement.
There is a broken earth on the nearside horizontal chassis section bellow the windscreen adjacent to the coils . There was a phillips screw in a round terminal connector that had two stubs of black insulated wire. I am wondering if the shrouding of the ignition coil cables cable plugs was originally attached to this as well as the coils.

The alloy plate behind the igntion coil mounting plate, has an earth that is insulated from the plate by one of the three nylon bushes , but touches the upright chassis ? . Should this be on the alloy plate instead?.

Ive got to clean the manifold plennum earth and the engine earth at the other end , i always dread the manifold earth as it awkward to get hold of.

Also Why are the bonnet hinges earthed ? .

Any advice welcomed

[dapinky]

Well, I can't help at all with your running issues, as you seem to have tried everything I could suggest.....

..... but....

.... the bonnet hinges are earthed as they connect to the foil liner (under the black insulation) to help electrical shielding and allow the radio to not get quite so much interference.

[KenS]

The Engine Management Manual gives details on the coil baseplate earth tag:

coil earth.JPG

[Chas54]

Thanks . Ive got the base plate earth the right way round now.

I cant see why the plate isnt earthed to the longeron and is actively insulated from it . Maybe another interference issue .

But the one i'm not sure of now is the black wire on the coil pack ABC plug . It looks like its from the injector loom but has a crimp terminal on it that has broken off at some point. I think its connected to the braided cable shrouding and probably should be earthed somewhere.

I know some cables can suffer with induced currents due to fluctuating currents in nearby wires and possibly the injector supply cable would be a culprit and perhaps deserves an earth shroud.

Im going to spend the ebvening trawling through the wiring drawings in the manual. My answer must lay in there somewhere.

[Tuga2112]

check the play on the camshaft sensor unit that controls the timing.

if the computer doesnt get a good reading form there. its bound to make your timing go all over the place.

[Chas54]

Tuga

There is a little bit of play but im not sure how much is acceptable. I might take it to bits and see if its in the drive pin. replacing the whole units an expensive proposition.

I may have to bite the bullet though. I havent found anything else thats a convincing fault , just the ropey connection of the screened cables on the ABC plug of the direct ignition module. Ive found a drawing showing the screening shroud of the A & C cable go to the B terminal and not a missing earth.

Thanks for advice

[Tuga2112]

you can replace just the hall effect sensor. theres "repair kits" from the usual suspects.

i wonder if elanScan can tell you the "raw reading" of that sensor. which could be a valuable piece of information in the diagnosis process

[Chas54]

I did replace the hall effect device with a repair kit about 5 years ago . I am going to check it today but as i understand it, its the injector timing that uses the hall effect.
The reluctor wheel had a clearance to the sensor of around 20 thou but ive reduced this now to 12 thou. the recommende figure i found was "less than 20thou"

The movement of the reluctor wheel at its circumference is around 1mm and the recomended max i think is 2mm. I believe its in the drive dog as the movement is not in the splined end.

After reassembling the coil packs and earth cleaning i do have a more stable spark , but still an intermitent loss whilst strobing. But using no4 cylinder gives a steadier flash . I still have a problem with a poor vacuum on start up . At some point it improves to 35mbar but i cant figure out why . I have tried blanking all the vacuum points , boost gauge . EGR , under wing reservoir, engine top breather , map , brake servo. fuel pressure reg vacuum tested with no leak, secondary throttle reserwoir tested,

Ive smoke tested the plenum chamber with a rubber glove over the air inlet at the throttle and have no leaks , not even from the oil filler ( i suspected possibly a secondary throttle stuck open ).
I am using elan scan but im not sure where the raw data is. I generally look at the graphic traces to spot trends and events and read the live data whilst running. I have a dapinky switch in my cable and can switch to service mode whilst running .

Thanks again for any suggestions

[Tuga2112]

is it irregular sparks, or missed sparks ?

from what you said. if cylinder 4 has good spark timing (i mean the timing gun flashes regularly) i would check every one

if i recall correctly. 1 and 3 are on the same coil pack. and 2 and 4 on the other. if both 1-3 are problematic, swap the coils around, to confirm the issue follows the coil.

are your leads original from factory ? i never heard of anyone having problems with leads, most people replace them as part of diagnosing other issues or just general "restoration" work but many car has newer leads, so its possible the originals are on the way out as well.

[Chas54]

Thanks Tuga

I see what you mean about swapping the coil packs and im going to give it a go.. The leads were changed a couple of years ago and in good nick.
It's 1 and 4 that share the top coil and 2 and 3 share the bottom.

I think i'll strobe all 4 plugs to check if its an irregular missing spark on any although i do see the timing marks do wander a bit even is service mode .

I have taken the throttle body off and i could see daylight around the throttle butterfly at the spindle position, i'm hoping it will clean up in the sonic bath. It could explain my poor vacuum.

regards

[Tuga2112]

i do see the timing marks do wander a bit even is service mode .

i have a small "wander" of 1-2 degrees in one direction in both cars. i assume its normal. as its something that is also happening in my 4runner.

[Chas54]

Well i tried strobing each plug lead and it appeared 1 & 4 had a missing spark intermitentley. Ive swapped the coils round and now 1 & 4 have a steady spark . 2 & 3 now have an intermitent spark but far less noticibly . I do have two other coils i can try but it seems to run better. Whilst the throttle assembly was off i took the time to rmove the idle air control screw i cleaned the seat and the pintle put on a new O ring and now i can actually stop air passing when fully closed . I still suspect a poor vacuum though . incidentally the pintle screw has a drilling through it just above the threaded part. This has a round section neoprene rubber piece through it and i cant imagine what purpose it serves . it is level with the O ring .

One thing i have noticed whilst strobing is the waste spark is far more obvious on 2 and 3 spark plug leads . its a far more rapid flash than i have on 1 and 4. This was true before the coil pack swap round.

I have had the engine running steady and restarting OK whilst hot but i dont know why . when ii started it this evening it was banging and coughing. I could only keep it running my pulling a vacuum on the MAP with my vacuum test pump . The engine is quite steady then and observing the actual plennum vacuum once running, it appears around the same reading. Its just starting where the vacuum doesnt get achieved.

Whilst i can see the 2ndry throttle linkage operate , i cant help wonder if somethings sticking open.
Im going to swap a coil tomorrow and do a compression test on each cylinder , think i'll syphon the petrol out and get some fresh E5 . But ill try it first to see what the cold starts like.

If all else fails i'm going to have to take the plenuum off for a look at the 2ndry throttle butterflys. Ive done it before so i can litterally do ,it blindfolded. Its cleaning the joint faces I dread.

thanks for suggestions
Chas

[Chas54]

Cmpression test came up good and equal for all four cylinders .

I took the thorttle off again today and fitted a blanking plate in the position. Then using my home made smoke device ( Baxters beetroot jar with old soldering iron glued to the top and some baby oil ), blew smoke into the plennum via the MAP connection . I fould a leak straight away and its happened before. The EGR valve gland was leaking . I changed this valve two years ago almost to the day. My old valve had been held open by the vacuum solenoid valve having its black top glued on with a silicone sealent which blocked the actuator from venting up through the solenoid spindle as intended, This had resulted in the EGR being held open and the seat or valve head damaged via the passing gasses . It resulted in poor vacuum on hot starts an erratic idling. It would be OK on a cold start as the vaccum had gone overnight, But after a run the EGR would be stuck open and the idle would be awfull. I swapped the valve for a new one at great expense ..
I now have a vacuum loss again , clearly from the new valves gland , so i have blanked it off with the very same piece of shim steel i used two years ago to prove the fault was the EGR. This time ill save £80 and leave the blank in forever.

Havent tested on the road yet but the strobing of the HT leads all look good now . Im wondering if its because i disturbed all the wiring , some of mine is a bit ropey at the coil pack end. Ive just bought a second hand top loom on ebay and it looks very good for £45.

Thanks for advice received

Chas

[MPx]

i never heard of anyone having problems with leads....

Well I have. I've changed them twice. Originals were swapped out for aethetics (I wanted yellow ones and there was a group buy for leads from America in colours). As part of the more recent years of misfire the leads were found by SWLC to be badly degraded (one barely making contact) and they swapped them out (for blue ones!) as part of the cure. I'm flying again now.

Probably not relevant to this case however - but something that could be worth checking.

[Chas54]

Mike
I did swap my original leads about 5 years ago and have not done a huge mileage. It's not easy to spot a lead breaking down nowadays. I think I might get a lead that will reach No.1, that I can swap for any lead as a test if my lost spark shows up again .
At the moment it's running really well in the garage. A few bits left to put back then I'm off for a road test.

[Tuga2112]

testing leads is pretty straighforward

you take a multimeter. and check the resistance across the 2 ends.
move the leads a bit. give them a twist, a loop. you should in theory notice no difference in the resistance. (not to mention it should be reading below 1... probably below 0.01 )

[Chas54]

finally got to try out on road and im not convinced it's perfect yet. i did a battery dissconect to clear the faults and did the recomended on off wait ten seconds before start to set the IAV valve to 80 counts , drove at 30mph to reset the learned position . On return home and whilst scratching my head about why the O2 sensor was showing zero volts and the engine running rough, i noticed i have a noisey tappet , the oil was hot and spotless but i think i may need to look for the noisey hydraulic tappet advice section. I have brushed off the sensor and cleaned it in petrol in the sonic bath now works OK .