Poor running Ongoing

[gmg31]

This problem has been discussed several times both on LEC and Facebook groups in the last year. My problem began almost a year ago when I noticed extremely poor running after I had been on a short journey in my car over the next few weeks it became apparent that upon starting the car she would run perfectly and could be driven pretty much all day as long as I didn’t stop. Once I had stopped for a few minutes the car would then run very very badly not just the odd hiccup but only running on two cylinders, shaking and backfiring.

I posted the issue on LEC last year and there was a broad range of advice over the next few weeks. I did some basics, change the coolant temperature sensor fitted new spark plugs checked all the wiring cleaned everything and simply could not identify the source of the problem so put the car In to bed in Sept.

In Spring 2020 I noticed that there were several other members who started to raise almost exactly the same fault and one of the key bits of advice was to check the injectors by putting the ignition on and turning the accelerator to listen to the clicks of the injectors. I tried this and it was quite clear that there was an issue with my injectors. I have since removed the injectors and had them reconditioned, one of the injectors was evidently faulty and they have since been returned good as new. I put everything back together only to find that not only is the problem not fixed but it is now a permanent problem and there is not a period of time when the car runs smoothly.

If I use plastic pliers to remove the plug leads there is absolutely no difference if I remove number two and number four. As I put them back on I can hear and see the clicking of the spark so it is quite clear that the coil pack is working. If I remove either plug lead 1 or 3 the engine dies so it is very clear that it is injectors 2&4 that are not working.

I pulled all of the connector plugs apart and again based on advice I cleaned all of the terminals and sprayed with WD-40, when I pushed them all back together I added a tie wrap to pull the connectors tighter together but the car is absolutely no better.

I’m running out of options and would welcome any bright ideas.

[david924s]

Really daft point and maybe no use but easy to try, have you removed the battery connections to "reset" the ECU not sure if the Elan responds in the way some other cars do but with all the faults you mention and particularly the injectors or CTS maybe the ECU has become "confused" trying to adapt to poor or incorrect diagnostics/operation so perhaps removing the battery for 10 minutes and then reconnecting may clear the faults and let the ECU learn again what the rectified situation is.


Like I say not sure the Elan ECU is clever enough to adapt to fault situations or will reset and relearn but for the time it takes to disconnect the battery it might be worth a try, you seem to have tried all the obvious reasons for the fault.

Not sure if you have also checked the fuel pressure to the fuel rail, I know in my Porsche 944 days I had poor running issues caused by the fuel pressure regulator.

PS Nice to hear of another Elan in the Teesside area!

[RonR]

With all spark plugs connected, try running the engine with fuel injector 2 disconnected, then with fuel injector 4 disconnected.
Injectors 2 + 4 are both triggered by the same output from the ECM. If one is bad it can hog the current so the other one of the pair doesn't work.
Disconnecting the bad one should allow 3 injectors to work, this is how John-W managed to get home from his European trip last year.

If it won't run on 3 cylinders with either of the above then either:
1. You're incredibly unlucky to have 2 bad injectors at the same time (even after cleaning).
2. There's a bad connection/break at connector IHCBS where the injector loom meets the car loom, or at ECM pin C15.
3. There's a wiring break somewhere in the injector loom - check that there's 12v on all 4 injector's +ve terminals.
4. Last resort - unlikely but possible - you have a blown injector driver in the ECM.

Injector Wiring.gif

[Simon_P]

As RonR says, with the addition that you check the resistance across the injector terminals.

[dapinky]

The only other thing I can think of is to swap the 2 known good injectors for the 2 known bad ones - if the fault goes with the injectors, then the injector(s) is at fault - if it remains on the pair it currently fails on, then the fault is in the wiring (or ECU signal).

[cliff]

Hi,

I have a set of injectors removed when I rebuilt the engine, you are welcome to borrow them to see if it cures the problem. I am back in the UK tomorrow so could pop them in the post.

[RonR]

I was just checking something in the electrical "Course Notes" on BCN's site, when I noticed it had a different set of wiring diagrams to the Closed Loop manual:

Injector Wiring from Course Notes.gif

In this one the C15 and D15 ECM pins are drawn reversed to the diagram in the Closed Loop manual. It has injectors 2 + 4 controlled by pin D15.

So I looked in the electrical manual version 6 which agrees with the course notes - pin C15 controls injectors 1 + 3, D15 controls injectors 2 + 4.

We're on a roll I thought, so I checked the electrical manual version 2 - which has pin D15 controlling injectors 1 + 2, with D16 controlling injectors 3 + 4!

Discounting the EMV2 diagram which is obviously a Friday afternoon job, I would check pins C15 AND D15 and their associated wiring.