Back to the drawing board misfiring Chim
Discussion
Hmmm !
Where to start, Chim back in the garage still misfiring despite local garage's best efforts.
They passed it on briefly to another engineer, who diagnosed little ends!!!! hmmm - not convinced but.... especially as original problem came on suddenly and there are no other obvious symptoms....
suggesting OIL PRESSURE IS LOW, but suspect they are working of the gauge and not tested it in other ways, it shows 30 lb on start up and even warm is showing 15lb at tick over, yes needle does fluctuate occasionally at tick over but take her up to 2,000 and we are back into the realms of 30 +. Oil level fine and oil light never come on except prior to firing up as per
Knowing that the gauges /senders are at best hit and miss, suspect the gauge/sender so its time to eliminate that this weekend. Meantime it is bloody horrible above 2/2,500 pop pop etc. So before I begin considering condemning the engine to a rebuild any suggestions?
Where to start, Chim back in the garage still misfiring despite local garage's best efforts.
They passed it on briefly to another engineer, who diagnosed little ends!!!! hmmm - not convinced but.... especially as original problem came on suddenly and there are no other obvious symptoms....
suggesting OIL PRESSURE IS LOW, but suspect they are working of the gauge and not tested it in other ways, it shows 30 lb on start up and even warm is showing 15lb at tick over, yes needle does fluctuate occasionally at tick over but take her up to 2,000 and we are back into the realms of 30 +. Oil level fine and oil light never come on except prior to firing up as per
Knowing that the gauges /senders are at best hit and miss, suspect the gauge/sender so its time to eliminate that this weekend. Meantime it is bloody horrible above 2/2,500 pop pop etc. So before I begin considering condemning the engine to a rebuild any suggestions?
Revchimp said:
Hmmm !
Where to start, Chim back in the garage still misfiring despite local garage's best efforts.
They passed it on briefly to another engineer, who diagnosed little ends!!!! hmmm - not convinced but.... especially as original problem came on suddenly and there are no other obvious symptoms....
suggesting OIL PRESSURE IS LOW, but suspect they are working of the gauge and not tested it in other ways, it shows 30 lb on start up and even warm is showing 15lb at tick over, yes needle does fluctuate occasionally at tick over but take her up to 2,000 and we are back into the realms of 30 +. Oil level fine and oil light never come on except prior to firing up as per
Knowing that the gauges /senders are at best hit and miss, suspect the gauge/sender so its time to eliminate that this weekend. Meantime it is bloody horrible above 2/2,500 pop pop etc. So before I begin considering condemning the engine to a rebuild any suggestions?
More info needed on the miss fire, is it all the time or intermittent?Where to start, Chim back in the garage still misfiring despite local garage's best efforts.
They passed it on briefly to another engineer, who diagnosed little ends!!!! hmmm - not convinced but.... especially as original problem came on suddenly and there are no other obvious symptoms....
suggesting OIL PRESSURE IS LOW, but suspect they are working of the gauge and not tested it in other ways, it shows 30 lb on start up and even warm is showing 15lb at tick over, yes needle does fluctuate occasionally at tick over but take her up to 2,000 and we are back into the realms of 30 +. Oil level fine and oil light never come on except prior to firing up as per
Knowing that the gauges /senders are at best hit and miss, suspect the gauge/sender so its time to eliminate that this weekend. Meantime it is bloody horrible above 2/2,500 pop pop etc. So before I begin considering condemning the engine to a rebuild any suggestions?
I've never heard of low oil pressure causing a miss fire, low compression on the other hand!
How would small ends cause a missfire??? rattle like hell yes? but they don't come on just like that.. and low oil pressure has nothing to do with small ends as they are splash fed! (small ends being the fixed pin in the rod bearing in the piston so not a true small end ).. Have you check your compressions... are the valves closing.. have you holed a piston etc?.. .See what the pots are at 
may be nothing more than a duff coil for example Discopotatoes said:
More info needed on the miss fire, is it all the time or intermittent?
I've never heard of low oil pressure causing a miss fire, low compression on the other hand!
AT around 2,500 sounds like machine gun going of on what inside sounds like nearside bank.I've never heard of low oil pressure causing a miss fire, low compression on the other hand!
Have replaced: Plugs plus all leads rotor arm Distributor cap, ignition module and coil ( Not done extenders but garage claimed they plugged leads on direct briefly and it made no difference.
TVR Beaver suggests getting compression checked too, rather surprised garage did not in their attempt at elimination.......so this may tell us more just need someone or find someone to do it.
TVR Beaver said:
How would small ends cause a missfire??? rattle like hell yes? but they don't come on just like that.. and low oil pressure has nothing to do with small ends as they are splash fed! (small ends being the fixed pin in the rod bearing in the piston so not a true small end ).. Have you check your compressions... are the valves closing.. have you holed a piston etc?.. .See what the pots are at
Quite! the fact that it came on suddenly is also rather pointing towards something else. Holed piston sounds nasty,!!! but she fires up ok on 8 and will rev on 8 with no probs up to 2,500 or under load.Will take Sardonicus' advice above find a more TVR savi garage, anyone know anywhere decent within a reasonable radius of Abingdon Oxon.
...Hi Tim, you say "AT around 2,500 sounds like machine gun going of " I have heard engines do this when they have a weak or broken valve spring or infact any issue with the valve train preventing a valve from closing firm. There may be just enough spring pressure to close the offending valve giving good running at low rpm but at 2500 if it "floats" you could get combustion pressure fired into the intake or exhaust. could be worth checking.
NZ fan said:
Hi Tim, you say "AT around 2,500 sounds like machine gun going of " I have heard engines do this when they have a weak or broken valve spring or infact any issue with the valve train preventing a valve from closing firm. There may be just enough spring pressure to close the offending valve giving good running at low rpm but at 2500 if it "floats" you could get combustion pressure fired into the intake or exhaust. could be worth checking.
Thanks for that, this does indeed sound like what happens. I am inclined think from pondering it most of last night with aid of Steve Heaths Bible that it is valve related in some way. Been through all the obvious ignition items and all replaced ( except extenders - DOH)so moving on down the engine as it were the valve gear is the next item on agenda.What say others?
Gassing Station | Chimaera | Top of Page | What's New | My Stuff