Topic

Corrosion at the leads was the cause of my miss-fire .

CyprusMGTF wrote: wrote:

.......ODB gives no faults, although the temperature seems to read a bit low (86 to 95 during normal driving, outside temp 25 degrees) which could cause over fueling, I do get the occasional backfire after the bogging down

Those temps are about right but I suppose you could change the coolant temp sensor.

If you only get a misfire under the same conditions everytime, i.e. pulling away at 2000rpm, I'd wonder about a damaged wiring loom.

The Coil packs are new and no corrosion, the wring loom connecting to the Lambda sensor looked like it had been rubbing against the starter motor, so that has been secured away properly the wires were not damaged. the wiring look OK no signs of obvious damage any where, with the exception of the boot hinge which has been rectified.
I had a similar problem with my old beetle, it had twin webers fitted and it also had a flat spot under certain acceleration conditions, this I eventually traced to a damaged jet in one of the carbs and the accelerator pump having a weak diaphragm. the symptom on the TF are similar, if i feather the throttle then she pulls away fine albeit slowly, If I set the gas at 2000 and don't let it drop she takes off like a rocket,(needed in Cyprus, Mediterranean drivers and all,) allow the rev to drop and the bogging starts., I cant decide if it is over fueling or under fueling during this time, potentially over fueling due to the occasional backfire.

I have the ODB connected all the time and use Torque app to monitor live to see what is going on, but nothing seems out of place. I guess another look this week end.

Just an off the wall idea but...
Maybe the spindle of the throttle-body has worn a flat spot on the shaft and the bushes it runs have worn egg shaped in profile, when the most worn area of the spindle shaft lines up with the worn area of the bush it leans out as it can suck more air in though the gap, the area just off idle is usually the most worn. This may account for your flat spot.

I've occasionally found this to be the problem with flat spots on carbie engines.

Gotta be worth a look anyway, init!

I will check it out but suspect that is not the problem the throttle body i brand new only two months old. However it cant be totally discounted could be a manufacturing defect,Thanks for your thoughts.

Yeah, given that the TB is that new, wear is very bloody unlikely.
Have you still got the old one? Did it have the flat spot when it had the old TB? Could you try it with the old one fitted?

Yes I still have the old one, The flat spot was there with that as well it is a 48mm unit.

Righto then we can discount the TB then..........back to the drawing board

Have you a free flow air filter and a snorty exhaust fitted??

Hi Ian, Yes there is free flow air filter, the exhaust is standard for now, I have 421 ordered. The problem was there before I changed out the filter.
Was out driving last night the reluctance to accelerated from below 2000 is still there. getting above 2000rpm it is almost like a turbo kick in effect. I will try and record is and post.

Fitted new throttle cable. Feels fine now. Only drove far enough to take her out of the garage, turn round and back in again. The roads are filthyafter last night's rain.

Been trying to find a serious knock mg tf160 when reversing off the drive when turning the steering right, only thing I can find is, there is a lot of play at the bottom of the o/s/f shock absorber car has 50k new shock or new bushes?