1.4 judder

norsened · Post by **norsened** » Wed Dec 27, 2006 12:05 pm

Those that have been kind enough to reply to my past posts will know that when it comes to fixing cars I am pretty much useless but I have a problem with my BX that I am determined to fix if it is not too hard.

The old 1.4 has had a judder problem for a while now. When excelerating/decelerating or just motoring in gear there is a slight judder or hesitation from the engine. This seems to disappear if I take the car out of gear but this could just be wishful thinking.

The engine pulls well and can take the car to good cruising speeds and beyond if I am feeling reckless.

I have tried all the tricks in my book: oil change, filter, plugs, rotor/distributer and leads but the judder remains.

As my only previous experience of cars is a couple of 2CV's I am a little stumped although it is a similar problem to a 2CV that needs new points.

This last comment may have given me away as a mechanical idiot but I would appreciate any advice on this problem as it's beginning to get annoying.

thanks

Ben

Stewart (oily!) · Post by **Stewart (oily!)** » Wed Dec 27, 2006 12:51 pm

Hi Norsened, first we will have to work out a bit more detail about your juddering BX, we need to know whether the frequency of the judder increases with roadspeed? does it get louder when cornering? does it get worse under hard acceleration? up hill or down? what about under braking? lets see if we can pin down the cause before we go wasting any time and money.
Stewart

jeremy · Post by **jeremy** » Wed Dec 27, 2006 1:10 pm

Ben - there were a number of variations on the 1.4 BX theme - like the 'suitcase' engine and throttle body fuel injection - so it would be helpful to at least know the year.

So you'll have to excuse my ignorance but it may be worth searching under coil pack on this forum and seeing if anything interesting comes up.

norsened · Post by **norsened** » Wed Dec 27, 2006 6:45 pm

the BX is a 1990 TGE 1.4. The judder doesn't seem to be one that is caused by a driveshaft or wheel bearing it is more of a 'hesitation' like an electrical fault, hence the lead and plug change etc. The coil sounds like a probable cause but I'm no expert. I'll have a look though. Thanks.

tom · Post by **tom** » Wed Dec 27, 2006 8:46 pm

Ok, if we rule out ignition for a minute, we have fuel. Could it be carb icing, Is there a winter position on the air cleaner? are you using it?
Could it be condensation in the tank and an occasional bit of water coming through the jets and momentarily freezing? Blocked tank vent?
Blocked/ water contaminated fuel filter?

thanuttiscotsman · Post by **thanuttiscotsman** » Thu Dec 28, 2006 10:33 am

[quote="tom"] Is there a winter position on the air cleaner? are you using it?
quote]

hi there,
i had one of these cars for 5 years and never moved the air filter thingy and the car ran the same all the time. it is prolly a fuel blockage or even more likely an electrical fault.

cheers rossco

thanuttiscotsman · Post by **thanuttiscotsman** » Thu Dec 28, 2006 10:34 am

oh by the way i would take a quick peek in the fuel tank for crap blocking the pipe. also look behind the carb and see how full your fuel filter is as there may be air getting into the fuel line.

rossco

jeremy · Post by **jeremy** » Thu Dec 28, 2006 12:02 pm

I think there are a few things you can safely say its not.

Fuel tank/filter/pump. These will all produce a restricted flow - which means that the thing will run out of fuel when its loaded - so starts and then dies as fuel supply can't keep up, acceleration - runs normally but splutters and dies after a few seconds when the carb bowl empties - level off - all is fine as fuel supply can keep up.

Drive shafts? - should be able to detect noise when running with the wheels at full lock for outer - inner - a bit more difficult but should be some play detectable.

thanuttiscotsman · Post by **thanuttiscotsman** » Fri Dec 29, 2006 1:46 pm

[quote="jeremy"]I think there are a few things you can safely say its not.

Fuel tank/filter/pump. These will all produce a restricted flow - which means that the thing will run out of fuel when its loaded - so starts and then dies as fuel supply can't keep up, acceleration - runs normally but splutters and dies after a few seconds when the carb bowl empties - level off - all is fine as fuel supply can keep up.quote]

rubbish!

resticted fuel means low pressure! does not mean no pressure and does not mean the car will run out of fuel at all. it does mean the car can struggle and make the engine judder my bx 16v does this when its running low on fuel i.e low pressure! same scenario! just becuase the fuel is restricted and pressure is lower doesnt mean its non existant. if the pressure is just slightly lower than required then these symptoms can pop up. thank you very much mister.

rossco

DavidRutherford · Post by **DavidRutherford** » Fri Dec 29, 2006 2:11 pm

jeremy wrote:Fuel tank/filter/pump. These will all produce a restricted flow - which means that the thing will run out of fuel when its loaded - so starts and then dies as fuel supply can't keep up, acceleration - runs normally but splutters and dies after a few seconds when the carb bowl empties - level off - all is fine as fuel supply can keep up.

thanuttiscotsman wrote:rubbish! resticted fuel means low pressure! does not mean no pressure and does not mean the car will run out of fuel at all. it does mean the car can struggle and make the engine judder my bx 16v does this when its running low on fuel i.e low pressure! same scenario! just becuase the fuel is restricted and pressure is lower doesnt mean its non existant. if the pressure is just slightly lower than required then these symptoms can pop up. thank you very much mister.

Sorry Roscoe, but jeremy is correct here, as we're talking about a carburettor fed engine.

The details and symptoms etc. that you list are correct, but only for a fuel-injected car. With FI, if there is slightly low pressure you will indeed have rough running all the time, as the injection volume is dependent on injector duration and fuel pressure.

However, with a carb-fed engine low fuel flow will indeed mean that you will get smooth running at idle/part throttle, as the pump can keep up with the fuel usage, and hence the float chamber is always at the correct level
At wider throttle openings the car will "run out of fuel" as the pump cannot keep the float chamber to the correct level. I've experienced this a great number of times on various carburettor-fed engines.

norsened · Post by **norsened** » Fri Dec 29, 2006 6:07 pm

Thankyou everyone for your help.
I shall check the fuel lines first just in case it is blocked with genk because the car has only averaged about 4000 miles a year since new, and that was 16 years ago, so I imagine it has sat around doing nothing but shopping trips for most of its life.
If it is an electrical fault then I'm stumped. Could it be the alternator?
As you can see I am not much of a technical wizkid.
I'll let you know how I get on.

Many thanks

Ben

Stewart (oily!) · Post by **Stewart (oily!)** » Fri Dec 29, 2006 6:29 pm

I have had symptoms exactly pointing at a partially blocked fuel filter that turned out to be an ignition fault, took some finding too, though not on a citroen.
Stewart

DavidRutherford · Post by **DavidRutherford** » Fri Dec 29, 2006 6:42 pm

My money's on either a partially blocked carburettor jet causing lean mixture, and hence hesitation, or a duff coil causing random misfiring

The alternator should have nothing to do with this problem.

Are there any times that the engine DOESN'T misfire / splutter?

thanuttiscotsman · Post by **thanuttiscotsman** » Sun Dec 31, 2006 12:53 am

DavidRutherford wrote:My money's on either a partially blocked carburettor jet causing lean mixture, and hence hesitation, or a duff coil causing random misfiring

well guys its pretty easy to see if the jet is blocked, just pop the clip off the back and take out the 10mm nut at the front, pop the lid off and fire her up. if there isnt a good constant spray of fuel or if its spraying at an angle or down the wall then thats why. as for the coil if you dont have a spare to test with you should as they are really handy. i have a few spare 1.4 coils in my garage and 2 spare ign modules you are more than welcome to as i burned my 1.4 bx early this year so dont need the spares anymore.

cheers rossco

Kingswell · Post by **Kingswell** » Mon Jan 08, 2007 11:11 pm

I had a similar problem on my car which is the same model.

It turned out to be lack of fuel to the engine. The problem was the T-piece on the hoses between the fuel pump and the carb that sends some of the fuel to the carb and some back to the tank sort of like an overflow. Mine had been replaced with a plastic one which widened with time and therefore not enough fuel was getting to the carb.

I also thought it was an electrical problem!

P.S. The carb needle and fuel pump were also changed in the process of locating this problem.