URGENT! Ignition mystery (solved)

[HJ2]

Hi all,

I am a bit stressed at the moment
I just swapped 2 potential faulty ignition coils for fresh MSD ones like i did a couple of times before. The car ran fine, but at high refs there were some misfires...
After swapping the coils (pretty straight foreward) the car sounds like it is running on 3 cilinders. I swapped ignition leads for known good ones and now put the original coils back. Still the 3 cilinder sound Then i removed the plug leads one by one, but no difference ! Hmmzz. does this point in the direction of an overall weak spark? Now i removed the plugs as well. All 4 appear to spark fine!?
Then i added a seperate grond to the baseplate... No luck again.
I checked for error codes: None. I unplugged an cleaned the connectors on the baseplate... no luck... I cleaned the metal sutface of the baseplate... nope..

Now my next suspect is the coil base plate. Does any one know how to check this? Can it be done with checking te resistance between te connectors? By head is is around the 50 KOhms.

Also there is no petrol smell, which makes me wonder it there is anything wrong with the fuel injection?
My friend needs to drive home, but can't now, so i am hoping somebody recognises this problem and can point me in the right direction here so he can make it home.

As always, all help appreciated!

[Portugal_lotus]

Hi friend ,
If the 4 sparks plugs has fire i bet the problems is fuel injector ,
Could you check which cylinder doesnt work ?

[lotusgirlmarie]

Hi friend ,
If the 4 sparks plugs has fire i bet the problems is fuel injector ,
Could you check which cylinder doesnt work ?

I agree completely. Failed injector.

[HJ2]

Thank you both!

I totally agree, and allready have some spare's at hand now (time for bed for me after bringing the poor chap home in a 2.5 hour drive )
But what are the odds... Coilpacks out, new ones in and.... injector gone?

However the car was allready running rough under heavy load / high rpm, because this was the reason that i wanted to swap the packs tonight and is swapping coilpacks did not correct this problem i wanted to see next if the injectors were fine anyway.

What do you recon... Is it possible that fresh coils killed an allready injector on it's way out? What mechanism would be behind this?

Anyway thanks again! This was really a lousy sunday evening all in all. Missed a great party, missed diner, troubles with the missus because... and a boring bonus highway trip in the Elan. I'll keep you posted and hope i hve some better news to post tomorrow evening

[lotusgirlmarie]

I've now had two injectors fail. Between age, the heat and the car sitting for a length they seized. Sometimes things just happen. I don't ask why. I just fix them and try to understand what I could have done differently/better

[HJ2]

Marie, what would be a good way to determine the odd one out?
I'll replace that first, and if it solves the problems i'll swap the lot so we get a nice and even spray pattern again

[Portugal_lotus]

I had The same problem and it was fuel injector stuck !
Sometimes its possible to repair The injector , add 9 volts in The injector and see if it will works.

[Ian T]

Marie, what would be a good way to determine the odd one out?

To confirm which injector isn't working, start the car and leave it idling, then (one at a time) unplug a spark plug lead. If the revs drop or it stalls, that is NOT the faulty injector. If the revs don't change, you have found the culprit. I don't much like touching spark leads while the engine is running, if your leads are in poor condition you can get a nasty shock. A more fiddly alternative is to unplug the lead and lay it aside, then start the engine, but bear in mind that it will be more difficult to start also.

There are a few reasons why one might not work - it could have failed (broken) or it could simply have a poor connection, broken wire to the connector etc. As it's not running on 2 cylinders, I'd say the ECU is fine.

HTH,

Ian.

[HJ2]

All,

Yesterday (before reading your spot-on post Ian!) I ultrasonically cleaned my old, good working set of injectors so i could swap them with the suspected ones in the car.

However at first i started the car and wiggled the connectors on the injectors. Bingo!
Strangely enough wiggling multiple connecters gave a response in running behavior.
So 10 sec. later i had multiple culprits: Corroded connectors on the injectors and a corroded injector bond strap on the belt side of the block.

I cleaned the lot and used a good contact spray and voila, the car is running on all 4 cylinders again. I also reinstalled the MSD coils again. Perfect!
However... a test drive revealed that some horses are missing, especially on top end. Also when coasting there is an ever so slightly hesitation, almost not noticable.
HT leads are old and worn and who knows how far the corroding on the connectors got internally , so i suspect these and with the current prices i will replace both and hope it runs like it should.

Thanks again for the help on this one!