Just had new exhaust fitted to replace standard original.Nothing exotic, Janspeed Supersport. Car seems to be “holding” revs between gear changes. And a slight flatspot/ misfire has appeared in 2nd and third gear at 4,500rpm.
I was told the revs might settle down after the car’s electronics recognise new exhaust. Not happened yet but not done more than 40/50 miles. Will misfire disappear similarly with a bit more running?
Is it a misfire or a back fire? Are you running a de-cat pipe? You may have a leak in the pipe work that is drawing in O2 and igniting unburned fuel causing a back fire.
On the other hand the motor may be running a bit lean with the new free flow exhaust and needs to be run in a bit for the ecu to compensate. What are the condition of your plugs and leads?
You giving it some when it ‘pops’? Many decat Ks spit flames.
Ian
It had cat by-pass pipe fitted with new exhaust. It is a misfire rather than a backfire. It starts with a slight stutter, a bit like a flat-spot, but with the characteristics of a misfire then seems to clear. It’s not a violent misfire.Plugs and leads shd be ok. Just had C service. Temperatures ok.
As you say, it might just need to be run a bit more for ECU to compensate. No flames as far as I can see, but let’s hope some appear! Thanks for your thoughts guys.
Right,a month has gone by and I’m still suffering slight misfire 4,500/5000 revs after which it clears.
Have checked distributor and it’s ok.(But not checked plugs and leads yet) Mentioned to bloke who did C service and who is abt to do MoT. He suggests that it might be running lean at that point, following fitment of new exhaust.ECU not learned its lessons, perhaps.If it is running lean at that point what’s the likely damage if I continue to run it without attention as I am unable to get it to garage immediately.Do you reckon I could tool along below 4,500 without causing any damage or am I risking major problem?
Thommo
I presume you’re using Optimax (or whatever it’s new name is!)?
Whatever you do, don’t run on normal unleaded, unless you can’t find Optimax, Tesco 99, or BP Ultimate. It’ll take a couple of tankfulls before you’ll feel the benefit over the 95 octane unleaded.
If you keep below 6K revs before it’s fixed, you should be okay if it’s running lean - unless you can hear the engine “pinging”.
Yep, using V-Power (old Optimax) or BP Ultimate but I did have to put a squirt of ordinaire in a couple of fills ago because I cdn’t find a BP/Shell shop.
I’m not really giving it much and certainly not holding at at 4,500/5000 except briefly for test purposes to try to decide what’s going on.
Thanks for your response.
Thommo
Has the ECU had the “5500rpm limit re-flash”? (To check, contact Andy Plant [email protected] quoting the full chassis number).
Reason for asking is that if the re-flash has been done, the engine should not rev above 5500rpm, if the ECU is aware of a misfire.
The car has an ECU re-flash outstanding under a Lotus recall (2002/2RA)that is intended to cut the fuel supply if a misfire is detected to protect the cat.
So, Pesky, that’s probably the re-flash you refer to, although when I spoke to Lotus about it prior to encountering this current misfire problem, they did not refer to it as the 5,500 misfire recall.
The car is booked in to LRV for that reflash on Saturday next so I’ll see what happens. Thanks
If you are not running a cat then there is no real reason to get the re-flash. There is evidence that the re-flash also addressed some other areas of the ECU map but I have not heard anything or seen anything definitive about that.
The re-flash came about as a direct result of a few cars going up in flames following misfires that were not attended to.
I know my car used to sound alot better - if you like crackles and pops with accompanying flames out the back - before the change.
I would check and clean the offside rear wheel sensor and see if that makes any difference.
I must say that the re-flash when no cat is fitted did seem superfluous but Lotus said that any re-flash incorporated all previous updates. Have yet to see flames but do enjoy the pops and bangs for some childish reason.
Heard a lot about the rear wheel sensor. I’ll have to find it first. But thanks
Heard a lot about the rear wheel sensor. I’ll have to find it first. But thanks
I’ll test you on Sunday
Try a silenced cat by-pass-made my 190bhp run much better.
That’s a thought, thanks