Poor Running Issues (misfire and poor acceleration/rough)

[chrishoward]

Hi All,

I'm at the end of my tether and although not technical I spend a lot of time and money on my Lotus Elan M100 (1991). The car is running rough with misfiring under acceleration, even moderate. I have used my local mechanic (who knows the car very well) and also https://www.pjslotus.co.uk - who called and spoke to a Lotus engineer with over 40 years experience. spending collectively over 25 hours!

The following have been discounted:

Fitted new fuel filter
Spark Plugs removed and tested
Passed diagnostic scan
Checked Vacuum Hoses
Checked operation of Turbo Wastegate
Disconnect Turbo - no change
Tested a standard MEMSCAL ECU chip - no change
Turbo Wastgate function ok
Checked oil separator valve
Inserted Engine and Turbo Cleaner through the petrol tank
Fitted new ignition coils
Check and test on Injectors (which are new)
HT Leads  — Visual check - appear ok


Please can anyone offer some more solutions or even another specialist? Issues were around the time the Cobra Immobilizer was partly removed (it will turn over now but the fuel is stopped until the immobilizer fob has done it's thing).

This is my car: https://www.dropbox.com/s/g58dm44manofq30/IMG_0748.JPG?dl=0

All the best

Chris

[GeoffSmith]

Set base timing.
Run ElanScan.
Post results on LEC.

[chrishoward]

I'm afraid I don't have access to Elan Scan so it would need to go back to PJS. I do think they should have tried that so will ask.

[HJ2]

Were the spark plugs changed? If so: are they gapped correctly? (0.8mm)

[chrishoward]

Sorry yes they were tested.

[B_land]

Hi sorry to hear you have these problems, I use Unit 4 in Burton on Trent, so not too far from you. Worth a try. Hope you get it sorted

[chrishoward]

The issue is finally resolved . Turned out to be a a burn through on one of the ignition leads that was causing shorting etc.

[muley]

That's good to hear .