Misfiring between 2500 and 3000

Hi All,

As you may / may not remember, my S1 190 went in for its remap recall a couple of months ago. The car came out different…a pleasure at idle and low speed and little change across the rest of the rev range…until a few weeks ago…

As soon as I get caught at a constant speed in traffic at around 2,500 - 3,000 rpm, she starts misfiring quite badly. There is no misfire if I am accelerating off a standing start at all, it is only a constant rpm gremlin.

Any thoughts as to why this is happening?

Plugs ??

…if plugs, would it not be across the rev range and also be a problem on acceleration? I’ve wiggled all the plug leads points around etc as I have had loose connections before which a wiggle has cured, but this has made no difference this time.

if the plugs need replaced or gapped then they might be okay at ‘fast’ speeds but not a slow speeds.

should be RC66YCC with 0.9mm gap and in good condition.

its just an outside chance but it is a basic check you should do.

if it is regular as clockwork in the 2500-3000 range, and you just had a new map in the ECU it could well be a corruption at the fuel sites for that rev-range/throttle position, but i’d check my plugs and then go back to the dealer.

Water in the plugs.
Remove caps, dri with a thin rag and a thin screwdriver around the plugs, dry boot and fit again.

Avoid in the future by sealing the edges of the cable cover with weatherproof sponge tape.

Press your spark leads down onto the distributor cap, mine were forever coming adrift and causing a misfire at a certain rev (2500 sounds familiar). You should find one of them clicks.

Proper solution was to get some Magnecor leads

OK, will give the plugs and leads another check.

…might just mention though at 80mph constant speed on the motorway, the engine doesn’t miss a beat?!

…that is, when my wife is driving,of course … …tsk tsk 80mph

Could also be the TPS, can cause some odd behaviour at steady throttle, especially lower reading as it’s bounces around the values telling the ecu to over / underfuel randomly.

If you can get to a Lotus dealer they should be able to plug in their handheld diag kit doodad and see the TPS jumping up and down.