dirty fuel = stuttering?

The message from "dave F" contains these words:

Eh - that doesn't sound right.

Blocked fuel filter?

Lambda sensor.

Are they easy to replace? Does replacing a Lambda sensor require a special tool?

As the problem comes and goes plus the fact the engine sounds fine a blocked fuel filter could be a possibility.

What an earth would you discover in the filter , surely the fuel should be crystal clean? I guess debris from the fuel nozzle could fall into the fuel tank.

About £35, if you get it from a local motor factor rather than the main dealer.

Tools needed to change - 1 spanner of the right size. ISTR the last one I did was 24mm, but I could be wrong.

Takes about 20 minutes.

Fairly easy,unless it's truly rusted in, the proper lamda socket makes it easier but it's not vital.

thanks Steve for your help

Of course, if the old one's rusted in, then it could take significantly longer.

The message from "dave F" contains these words:

You can get special sockets for 'em (they have leads hanging out which make ordinary sockets unsuitable) but a ring-spanner usually does the trick. You can get universal sensors - but might need to be OK with a smouldering iron to fit one.

It'll be the knocking sensor. That means no shagging in the motor.

After your posts Steve I've been doing a bit of research and found this website

It's on the exhaust downpipe, after the 4-branch 'manifold' bit - usually just before it disappears under the engine.

Before you go ripping it out and replacing it, find somewhere quiet and see if you can replicate the effect at the same engine rpm in several gears on a consistant basis (the engine needs to be warmed up fully to do this, as there's a bypass for the lambda sensor when the engine's cold) - just as a double check that's what's causing it.

I'd hate someone to go out and get themselves a new part on the strength of an amateur's remote diagnosis!

Also just found this

"It had a lambda sensor replaced at 70,000 miles as the car was running unsteady at constant throttle positions. It has now started to run unsteady again and will probably require another sensor."

Yeap done that and it was a bit funny when consantly running at the 3500rpm mark (the point where you could up a gear) - I'll give it another go tomorrow

Cheers for your help!

Why is that? Maybe its called an ECU?

Could it be an intermittent/dodgy spark plug lead?

I had something like this years ago on a Vauxhall as well. The garage never found anything wrong but over time it got bad enough to get the AA out and they fixed it. The cause: at service time, mechanics would extract the plug leads from the hot engine by pulling on the cool leads rather than grabbing the hot heat shields. The leads only last so long before they break internally with this kind of abuse.

How about it's just been very pigging wet for the last month?

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I can vouch for this as I had exactly the same problem with a Cavalier.

Before getting stuck into fuelling issues, I'd get a replacement set of plug leads.