Engine Running Badly (popping, etc)

[DavidM777]

Hi

v.long shot........ I have been away for a week and left my car on charge. On returning it has stopped running smoothly. It just cuts out unless I rev it and the exhaust back fires when the revs are very low (i.e. <1000).

Any ideas?

Thanks

David

 

[ChrisW]

This may be a long shot, but I am sure I once read that the ECU can become disrupted and will then re-set itself.

I don't know if the ECU's of the 964 could learn, but I believe that on the later cars in a circumstance where the ECU has returned to it's default settings, the car should over a few gallons of fuel, re-learn the otimum settings.

In fact, I believe that some deliberately disconnect the battery to force a re-set which with high octane fuel, forces the ECU to re-learn the optimum settings for a higher power output ?

 

[DavidM777]

Thanks Chris. I have the Motec system. Does this make any difference?

 

[rs phil]

yea chris w is correct i done this on mine when i fitted new exhaust ,oxegen sensor etc and the car run alot better,i had motec on e30 m3 before i dont think these ecu,s learn could be wrong,better off bringing to your local motec tuner and have it pluged into, i had problems with motec crank sensor done similar thing

 

[Stewart H]

So, if you turn the battery cut-off off when you park it up, is that going to confuse the hell out of the ECU from one weekend to the next?

 

[rs phil]

no i dont think so i used to do that too,i think there is constant supply direct from battery so the cut out doesnt affect that...im newish to these beetles so could be wrong[]

 

[kasbridge]

Post a thread on the 964 forum on www.rennlist.com there are lots of tech guys who read the forum and Colin Belton (9meister) often contributes.

Hope you get sorted,
Cheers,
Kevin.

 

[DavidM777]

Thanks for all of the help guys.

I went for the traditional approach - take the car out for a good old trashing! Then all seemed fine.

However, I then had a look under the lid and something was loose (joint between the big black pipe along the top of the engine between the air box and throtle body - ????) so I pushed it back together again and then took the car for another spin. All working well except will not idle now and just cuts out?

Any more ideas?

 

[rs phil]

vacuum hoses check none have come off

 

[ChrisW]

Unless the engine management system has adjusted itself for the air leak into the induction system and may now have to adjust itself back ?

This is only a guess, I really dont know.

Maybe the time has come to ask a specialist ?

 

[Ninemeister]

I'm pretty sure it's not a 9m conversion because we do not retain the standard airbox, hence I also doubt that you have a MAP sensor fitted which is why your engine is adversely affected by an air leak. If you bring it in we could sort out the airleak and update your Motec conversion to the full 9m specification at the same time, which as a bonus would probably find you a few more hp.

In fact the last 964RS that had a 3rd party Motec conversion arrived with 275hp and left with 330hp.....

 

[oldtimer]

I think the problem lies with the induction system pulling in air after the mass airflow sensor ie bypassing the throttle valve. Check carefully the big jubilee clipped rubber hose connection on air inlet and the rubber pillar bolts holding the airbox on - the bolt joints can shear and allow the airbox to move about which then pulls off the air inlet connection hose. If you do violent 360 spins this can happen . Dont ask how I know [8|]

 

[Ninemeister]

With the Motec system the strategy of the management is changed to Alpha-N and the air flow meter is removed, so there should really be no worries about the engine cutting out unexpectedly due to a minor air leak. Alpha-N refers to using throttle angle (Alpha) and rpm (N) which are used as the x & y axis of the main fuel and ignition tables.

 

[DavidM777]

Thanks for all of your help chaps and you are all correct!

The big jubilee clips did come loose and air was leaking in there. It was caused the a few bif back fires caused I think by the ignition systen getting damp after cleaing the car and then putting it in the garage before running it hot and then going off on holiday for a week.

I took it to Steve Bull in Devizes and he put it back together for me. All sorted now and running like a dream, but I do like the idea of 330bhp from ninemeister. I think a trip up country will be in order. I'll try to give you guys a call in the next few days.

Oldtimer - did Steve fix yours? He did mention a similar incident following a spin on Coombe.

Thanks everyone for all of your help.

David

 

[oldtimer]

Hi David - in answer to your question - I fixed mine 'in the field' armed with the standard spanners with a bit of help from a fellow driver as more than 2 hands needed! It was out at North Weald airfield and precipitated by Andrew Walsh's infamous left turn exercise as later featured in 'Judgement Day'. I was really lucky to find out why the engine wouldn't run at any revs under 2500 - if I had not been able to fix it the 180 mile journey home on the M11 + M1+ M6 to Cheshire would have been impossible....the clutch would have been an early casualty []

 

[kasbridge]

Oldtimer,
Hello again, you may remember we met at the RS day at Oulton in March, you introduced me to Tony Taylor as I was looking for an RS and you felt I should be aware of going down the modified C2 route to gain something similar to the RS..

I have since bought a Ferrari Yellow RS from Tom Schmitz and am doing a day with Andy at North Weeald next week, do I need to be worried? My car is mint both cosmetically and mechanically and I dont want to goose it - should I hire the Elise instead?
THanks,
Kevin.

 

[oldtimer]

Hi Kevin , yes I remember you from Oulton. You have made a brilliant choice with the 964RS , especially in ferrari gelb , and if Des continues to talk the market up you will be able to retire off the proceeds when you sell it []

Now , there's nothing to worry about at the Andrew Walsh day , and you really do need to do it in the RS - its what it was made for . The RS provides a lot of driver feed back once you know how to feel it , especially if its LHD , and try to get as much seat time with AW next to you as you can. He's a quiet sort of bloke so you need to be proactive in asking questions etc , and do give him the opportunity to drive .
If you dont spin you are not being brave enough or you are too good and don't need the instruction ! You wont hit anything , but yes it does feel strange to barrel up to an imaginary corner that you know you have no chance of making []

There wont be much wear on tyres or brakes compared to say a trackday , and it wont matter if its wet or dry. If you have grippy tyres you will do the mini circuit a bit quicker but the main lessons are about understeer / oversteer/ transition between the two / weight transfer........with a bit of an intro to slip angles and threshold braking.

Do report back to this forum - the undisputed place to post which is why so many folk come hear to read stuff and marvel at Des's wisdom []

 

[kasbridge]

Oldtimer,
Thanks for the advice, I am really looking forward to it. I had an unscheduled trip into the infield at Combe the other week just after Folly and I am still not really sure what happened, hopefully the day will give me a good chance to get the car sideways under controlled conditions and learn how to (a) anticipate it, and (b) retrieve it!

Will post back as requested,
Cheers,
Kevin.

 

[Melv]

You will have a great day with Andy -it's a lot to take in, but ask the questions and he will have the answers.....