Minor engine hesitation - Help please....

[lig]

Hi Chaps,

I have this minor problem....my Griff engine seems to hesitate and is not running as smooth as i believe it should, the power is there so it is still enjoyable but seems to have hiccups!! It ticks over fine it is just when it is driven that the problem occurs. It happens in every gear but seems more evident in second and third.

The best way to describe it, is that it feels as though the engine is pulling back like engine brake but intermittently (chugging). When I accellarate hard in fifth it feels like a 'turbo' or something is cutting in as the power band is not smooth but slightly jerky.....

I have just had the car serviced (at a specialist) and I then took it in to the main dealer to see if they could rectify the problem (as I suspected a worn cam). They checked the ECU and found no problems. They changed the rotor arm (had to charge for something) and changed the settings on the throttle potentiometer and it felt better for a while (could have been psycological) but now back to its old self, they thought the Cam was fine and the problem would be more noticeable if it was worn.

A colleague has recommended fitting a new potentiometer but i am reluctant as this could be a costly slippery road.....

I know that the real answer is to take it to a rolling road and get it 'analysed' which is my next step, but thought i would try you guys first in case anyone has had a similar problem...

Cheers,
Lig.

[griff430]

I had something similar on mine. It turned out to be the ignition module on the side of the distributor. The new one didn't initially solve the problem though, becuase when I refitted it, there was a bad contact between the module and the distributor body, but once that was sorted out, it was fine. You could also check your engine run relay and fuel pump relay (the loose relays just floating around the passenger's footwell). Mine had bad connections to those too.

Hope this helps,

Dan.

[lig]

Cheers Dan,

Is the 'contact between the module and dist body' easy to find? And how much does a new ignition module cost?

I assume the relays in question are the ones hanging off the main loom to the ECU? I will check these as some of them have corroded!

How did you find out what the problem was with yours? Was it with the aid of a rolling road??

Thanks for your reply.

Lig.

[simon.b]

Obvious I know, but since its just come back from a service have you checked all the HT leads are on properly, not touching etc, also worth checking the plug screw on bits.

Good luck,

Simon.

[griff430]

lig,

The ignition module makes contact with the distributor body through it's base. There is some kind paste that is supplied with the new module to create a good electrical contact. I think this breaks down over time due to all the heat etc. Also, if you don't spread it evenly when you fit the new module, it can cause you problems. Be careful when tightening the securing bolts too. The thread is easy to knacker.

You are correct about the relays. I had the relays changed, and the multi-plug connectors they sit in too.

I changed a couple of other things to they might be worth checking on yours - Plug leads (made it run so much smoother!!) and a couple of the plug shrouds, because they were loose when I changed the leads. I changed the coil too, but that made no difference, so I took it back and got my money back. I changed the distributor cap and rotor arm as a matter of course. Neither of which made a great deal of difference, but I'm sure they helped, rather than hindered the smooth running of the engine.

I found this all out through a combination of trial and error, this web-site, and the help of a TVR specialist.

Hope you can get yours sorted, becuase I know how frustrating it can be.

Dan.

[andy43]

griff430 said:

The ignition module makes contact with the distributor body through it's base. There is some kind of paste that is supplied with the new module to create a good electrical contact. I think this breaks down over time due to all the heat etc. Also, if you don't spread it evenly when you fit the new module, it can cause you problems.

The white stuff is heatsink paste - used in electronics (eg audio) amps - Maplin or RS do it if you need to get hold of some. A little is better than too much

Does the hesitation occur only when hot - if it is, could be the ignition amp/coil/leads/even a dodgy earth. If its at high revs, could be fueling probs eg filter if it feels like a rev limiter, maybe ignition amp, or thr.pot if the throttle position causes it and you can 'drive thru it' to higher revs, if its under heavy load/pulling at lower engine speeds could be fueling again. If its intermittent, likely to be something electrical that's breaking down with the heat. There's a bit in the bible that tells you how to check the basics on the throttle pot, but if there's a dodgy track on it, the only way to find out its faulty is to change it. Same goes for a lot of the other bits. There's also temp sensors and the ecu itsself to take into account - have you rebooted the ecu and still had the prob straight away?

All the above is just my opinion, I'm not an expert, just been thru the mill with a similar (bldy frustrating ) problem