"rough" running

[ourchris]

Hello, all

Just had the car serviced & MOT'd, took it out this morning and it appears to be running "rough". It seems to be hesitant when accelerating as if there are a series of flat spots as you go through the rev range. It also seems to be not settling at idle very well. It still pulls well and is rather quick, but it just doesnt feel right, if you know what I mean....

Any ideas, please ? It was running fine before it went in for MOT, and so I am at a loss.....

Thanks

[HRG]

Duff fuel? (It's my stock rough running answer )

[ourchris]

I hope it is, but I filled it up with superplus, so being the pessimist that I am, I am thinking its something worse

[AntonyJ]

AFM unplugged?

[ourchris]

excuse my general thickness, but by afm, I assume you mean airflow meter . I have looked at all the connections that I can see, and I cant see anything obvious ~ any pointers ?? Thanks

[AntonyJ]

ourchris said:

excuse my general thickness, but by afm, I assume you mean airflow meter . I have looked at all the connections that I can see, and I cant see anything obvious ~ any pointers ?? Thanks

Yes the AFM is the air flow meter, just sounds similar to mine when I left the bloody thing unplugged after some work in the engine bay.

[ourchris]

Just had a look at the other post about AFM's that is live at the moment. If I start up and unplug the AFM, the engine stops. Can I assume that this means the AFM is fully fit ? I've just had a look at the price of a new AFM on TVR parts and almost threw up on the keyboard

[HRG]

I'd wait till you have run a tank through before panicking

[crackedfinger]

Can be simple as loose leads, have you checked those?

[sumoone]

i had this sort of problem with my 94 griff 500
it turned out to be the ignition amplifier which was replaced and bingo......
if your car has one of these you may want to spend a tenner (ebay) for a replacement.

mark

Edited by sumoone on Saturday 18th April 19:02

[ourchris]

Running a new tank of fuel through has had no effect, Its a 94 500, so I think I may try this, but any other suggestions would be really appreciated !

Thanks

[crackedfinger]

Try running a jump cable from the engine to the -ve terminal of the battery to rule out the earth strap. Quick check, as a dodgy earth can cause weird behaviour like this, and with the earth point being open to the left front wheel ...

[panic]

Griffith gremlings...

I have had them into my Griffith engine bay for nearly a year making the car drive rough, then they disappeared...and now the car runs happily with its early thunder.

[GreenV8S]

Check all the HT leads are firmly attached at both ends.

[zippy500]

Flat spots can mean a dodgy throttle pot sensor. Easy to change, but not easy to test as the resistance change is very small. So if you can borrow one to try this may be a good thing to check. Think they are about £100 new

[clive f]

if you`ve just paid to have this serviced then why not take it back and get the garage to sort it out?

[Argent]

clive f said:

if you`ve just paid to have this serviced then why not take it back and get the garage to sort it out?

Exactly!

However a set of blue magnecors and new plug extenders sorted out rough running with my 500 when I first bought it and then .

A.

[griffith400]

Ourchris,

I had something like this at the weekend and it seemed to be related to those 2 damn silver fuel pump relays in the footwell beside the ECU. I've had problems with these failing before and always carry a spare set now!

Took the car out to experience the first proper signs of sunshine in Scotland
Midway round the trip I experienced similar issues to you:
- The car would not idle properly and the revs would sit between 1500, 2000rpm.
- The car was initially hesitant when I touched the accelerator but then would pull OK.
- On full throttle, the car would stutter as if it had a mixture issue.

First thing I tried was to remove both relays and put in my new pair. Bingo, fault gone! Now, I'm not sure if the relays were dodgy or if this has just somehow reset the ECU or something (sorry, I'm not really that knowledgeable) but it did sort the fault.

I need to put the old relays back and see if the fault returns or not but does it sound similar to what you had????