30 replies to this topic

[Kernal H]

Mines a bit lumpy at idle, don't trust the tacho in the car... mines way out! Had a garage do the timing and idle, he set it at 750rpm while the tacho was reading nearer 500rpm. I don't think anything is wrong with the engine, it smooths out at about 1000rpm (according to the tach ) so more like 1250rpm lol

How did your garage know the engine was doing 750rpm? You tacho works in a way that it is extremely unlikely for it to be wrong. The only way it would be out was if it is the wrong tacho for the engine, ie it's designed for a 6 cylinder engine, not a 4.

My tacho is one taken from a mini, a genuine one. The garage was using a snap-on laser gun to do timing, linked to the 1st HT lead. it displays both the timing degrees and the RPM speed. This is HIGHLY unlikely to be wrong, as the timing would then be out as well, as I said engine runs fine at 8 degrees. It's the tacho that's wrong.

[Kernal H]

so should i check that i'm getting spark at all the cylinders and if thats fine go and get my carb checked out. If it is something with the low idle speed is there anything i can do at home to sort it?

Raise it? There's a little screw on the carb, should be simple enough to find. You can always look in Haynes! But be careful, as I said my tacho's out, and was idling pretty high.

[wooly123]

ah ok ill give that ago, where about is the screw on the carb. i dont have the haynes only the restoration one, not the one that actually tells you how to so anything.

[Kernal H]

Do you know what carb you have? Shouldn't be difficult to find, look for the accelerator cable, which should (with all luck) be connected to the throttle thingy. And it's around there. *waits for a better response*

[wooly123]

its just a standard 998cc carb. so with this screw i just turn it a tiny bit and see when runs best?

sorry to be annoying

Edited by wooly123, 10 March 2008 - 09:28 PM.

[Kernal H]

Um... yea. But you obviously don't want it too high, that wastes petrol. Inwards raises it and outwards lowers it. It shouldn't be hard to find. If your engine is idling too low you might be able to see the engine moving slightly. Before you fiddle about with the carb, does revving the engine (but not actually moving the car) help to reduce the shaking? I really think that if it's just the idle you shouldn't mess around with it. Mines correct, and yet still does it.

[wooly123]

yep revving it stops it. but its only started since i hate the carb taken out and put back in.

ill think ill do what you say and just leave it for a bit and see what happens, if it gets worse ill have a little play.

cheers for all your help Kernal

[wooly123]

The excess heat and power loss could well indicate that it is running lean

what can i do to over come this?

[digitalboy0]

have u checked u aint just hit someone and there head in wedged in between ur wheel and shell ?

[Dan]

I really think that if it's just the idle you shouldn't mess around with it. Mines correct, and yet still does it.

750 rpm idle is not correct. The engine should not shudder at idle. It's bad for the engine, the engine mounts and everything bolted to the engine. Raise the idle until it just stops shuddering, you should find that this will be around 900 rpm. You should know that your tacho works in exactly the same way as the Snap-On timing gun, only the tacho has a more reliable connection to the ignition. If the tacho seems to be reading wrong I'd be more inclined to suspect a fault with the ignition than with the tacho, they are generally pretty reliable.

[Kernal H]

I really think that if it's just the idle you shouldn't mess around with it. Mines correct, and yet still does it.

750 rpm idle is not correct. The engine should not shudder at idle. It's bad for the engine, the engine mounts and everything bolted to the engine. Raise the idle until it just stops shuddering, you should find that this will be around 900 rpm. You should know that your tacho works in exactly the same way as the Snap-On timing gun, only the tacho has a more reliable connection to the ignition. If the tacho seems to be reading wrong I'd be more inclined to suspect a fault with the ignition than with the tacho, they are generally pretty reliable.

Why would a digital timing gun connected to the HT lead be less reliable than an analogue tacho that's 20 years old? I don't get how this would be? Surely if the timing gun wasn't correct my whole timing would be messed up, it needs the RPM speed to know when to flash to show the timing mark. It was showing 4 degrees, and now it's 8, the engine is running better now than when it was at 4 degrees, ergo it works. Sorry to go off topic.

[computerdaz74]

dont want to hijack the post but I'm having similiar trouble. Steering wheel shakes like mad when doing about 40mph in 4th.
a bit slower and its fine, a bit faster and its fine.
WEIRD!

This started on Saturday after I fixed a blowing manifold to downpipe link (standard setup).
engine mounts seem fine but did notice some movement in subframe mounts a few weeks back. (long before this problem showed up).

[wooly123]

it would be much easier is i had a tacho but i unfortually ive losst the past 3 times on ebay for a 3clock dial lol ill go out and have a little fiddle. cheers for the help Dan

[Lund]

I really think that if it's just the idle you shouldn't mess around with it. Mines correct, and yet still does it.

750 rpm idle is not correct. The engine should not shudder at idle. It's bad for the engine, the engine mounts and everything bolted to the engine. Raise the idle until it just stops shuddering, you should find that this will be around 900 rpm. You should know that your tacho works in exactly the same way as the Snap-On timing gun, only the tacho has a more reliable connection to the ignition. If the tacho seems to be reading wrong I'd be more inclined to suspect a fault with the ignition than with the tacho, they are generally pretty reliable.

The whole steering column, wing mirrors and heater switch panel vibrate like mad when my 850's idling, the 'shudders' stop when I pick up the rev's. I take it this is not good?

[samwell]

I really think that if it's just the idle you shouldn't mess around with it. Mines correct, and yet still does it.

750 rpm idle is not correct. The engine should not shudder at idle. It's bad for the engine, the engine mounts and everything bolted to the engine. Raise the idle until it just stops shuddering, you should find that this will be around 900 rpm. You should know that your tacho works in exactly the same way as the Snap-On timing gun, only the tacho has a more reliable connection to the ignition. If the tacho seems to be reading wrong I'd be more inclined to suspect a fault with the ignition than with the tacho, they are generally pretty reliable.

Why would a digital timing gun connected to the HT lead be less reliable than an analogue tacho that's 20 years old? I don't get how this would be? Surely if the timing gun wasn't correct my whole timing would be messed up, it needs the RPM speed to know when to flash to show the timing mark. It was showing 4 degrees, and now it's 8, the engine is running better now than when it was at 4 degrees, ergo it works. Sorry to go off topic.

It doesn't "know" the rpm so that it can figure out when to flash, it flashes when there should be a spark at cylinder 1 no? and then an extra feature would be to calculate the rpm from that. I'm not saying either person is right but your arguement is flawed.