Misfire/Knocking at Low Revs

[pickigar]

I seem to have a slight misfire/knocking when driving the car sensibly at low revs. I have a tank of Optimax in it at the moment but it seems worse with this than BP Super!!!

Anybody had this before??

Gary

[Kieran]

Does resetting the ECU help at all?

Check with some other posts, but I think you can reset the ECU by disconnecting the negative battery terminal for about 30secs, then reconnecting.
And if you've got an auto, it'll probably shift roughly for a few miles after doing this - so don't panic!

[pickigar]

I have tried this tonight and it worked for about 15 minutes and it is back again! It mainly seems to do it around 1700 and 2600 rpm when driving sensibly. I think it is more predetonation than misfire but nobody seems to know.

What symptoms occur to others after running on normal unleaded as this is what Magnum Motors were running it on. I now use Optimax.

Anybody have any ideas??

[BraindG]

ive never had a problem running on normal unleaded..
reset ecu and its back to normal..

so i dont think its the fuel

[pickigar]

Does anybody run their car on normal unleaded all the time?

[Brind]

Could be an air leak: brake servo hose, inlet manifold.
Manky plugs and/or worn leads, idle speed control valve faulty, fuel pressure regulator, airflow meter..

I've had to run on standard unleaded a couple of times, and the ECU goes into safe mode dropping the boost power tremendously, the car drives fine it just doesn't have the same power and acceleration.

I've fitted extra negative earth leads and the gearbox shifts quicker, it has even made shifting from cold a little better too, genral running is a little smoother.

[pickigar]

It was noticeably quicker after resetting of ECU and then fine for a good 15 minutes. After that it is creeping back. I think it could be a sensor - possible knock sensor???

I guess it is approaching the time to book it in for a mitsy doctor's appt!!!!

I hate it when cars don't run properly, I just get angry with them!!!!!

[Brind]

You may have crap in your fuel filter, or a dirty injector/s try using some fuel cleaner like those from Nitrox or Redex and see what happens.

[haydar]

Originally posted by pickigar
I seem to have a slight misfire/knocking when driving the car sensibly at low revs. I have a tank of Optimax in it at the moment but it seems worse with this than BP Super!!!

Anybody had this before??

Gary


Are you sure it's a misfire? Does the car judder usually in either 4th or 5th gear at low speed? Usually when one is trying to gently accelerate? If this is the case then it's your transmission and not a misfire. The judder is a known problem with these cars and mine had it too. It was also mis-diagnosed as a misfire initially. Be careful that you don't start throwing money at new spark plugs, leads, etc... which won't help at all if it's the transmission problem.

[pickigar]

How was it fixed, cos that sounds exactly like the problem, down to a tee!!

[Pescha]

I run my car on 96 octane 90% of the time without any problems!

Cheers,
Pescha!

[haydar]

Originally posted by pickigar
How was it fixed, cos that sounds exactly like the problem, down to a tee!!

Check out this thread. If you need any more advice just ask.

http://www.clubvr4.co.uk/forum/showthread.php?s=&threadid=534

[pickigar]

Haydar,

Can you give me the phone number/details of the place you used to get this fixed.

How long did it take? Was it a one day job or longer?

I will try all conections but it sounds like I have exactly the same symptoms as the thread above.

Many thanks for all the info

Gary

[haydar]

I'll dig out their number tonight. In the meantime do check things like the gearbox connectors incase it's a 5 minute fix rather than a £1500 fix!

The job only took a couple of days, though it did take about a week for the parts to be shipped in from abroad.

[pickigar]

Cheers mate

I do have the dilemma of whether to get this done or to have a normal rebuild??? Any thoughts?

Thanks

Gary