Help with Young Old Astra 1.6L please..

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Dave T Scotland 19 years ago

Hello ,

Sorry this is so long, but I've spent a long time tying down the problem & might as well give the detail to cut down the field a bit....

I have an almost perfect 1986 Astra L 1.6 petrol; OHV 16SV with 2E3 carb & Siemens MZV BY ignition module. 20 years old but only 29,000 miles genuine and almost 100% rust-free. Brilliant - BUT I have one engine problem that's driving me nuts, and I need fresh ideas please from anyone who can still remember cars with carburettors!! As background, the car has been immaculately looked after and serviced according to the book all the way from new, by the now 86 yr-old one owner who's just retired from driving.

PROBLEM:- The engine CAN BE be perfect - starts well, idles perfectly, accelerates sweet as a nut and pulls very eagerly. Then next trip out it starts and idles perfectly but has a bad rough/flat spot - always (and only) just as you begin to put the throttle down. Can be quite a bad kangarooing, or just a smallish rough bit. After you get through the flat spot with the throttle, it accelerates right up beautifully and pulls like the clappers as normal. Same as you go up thro the gears - each time you begin to pull away in the next gear.

A bit worse from cold, and clears a bit as you warm up, but not much....

Then a couple of days later you can drive all day on a long trip without a murmur of a problem; perfect again. The engine is also never randomly rough - just that bad flat spot as you begin to ask the throttle to open.

I've checked the many rubber pipes around the carb in case of perishing, but they all look OK. I also worked over the electrics even though I don't believe they're the culprit (changed leads and plugs, swapped in another coil as a test, and thoroughly polished up the distrib cap - no sign of cracking or tracking). Also had the emission checked - spot on legal. No exhaust leaks.

Any ideas would be much appreciated as I've reached a dead end. Cheers.

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mrcheerful 19 years ago

have you checked the vacuum pipe that goes on to the manifold at the back below the carb, this often used to block and cause problems, it leads from the air filter and sucks excess oil mist back in. the other thing to check is that if it has the metal breather filter in the top cover that it is clean.

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Bear 19 years ago

Sounds the accelerator jet in the carb, is partially blocked. Can't remember off the top of my head if it is the diaphragm type. With the lack of miles and age of the car, it may be full of rubbish in the bowl and worthwhile a good clean out. Vauxhall used to do a service kit, but doubt they still stock it.

Nigel

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Lofty. 19 years ago

Once had an intermittent problem with flat spots on a Wolsley 15/60. Garage changed plugs, condenser, coil, petrol pump etc, etc. Turned out to be water in the petrol (quite a lot too - so much in fact that you would not believe it would run at all). Defective rubber seal in the filler cap (situated below rear window) allowed rain into the tank when parked on a slope.

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Dave T Scotland 19 years ago

Thanks v much, sounded v hopeful,but.... 1) Checked & cleaned the pipe yesterday, but pretty clean (a little dark sticky oil deposit but not enough to block anything), but no joy. 2) No sign of a metal filter under the rocker cover; there's a brown plastic half cylinder thingy just inside the oil cap - could this house a filter? - feels as if it might clip out, but doesn't come easily & I don't want to break something.

Also noticed if I pull off either small pipe that goes into the inlet manifold, the problem is exagerated; running weak? Cheers, Dave

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Dave T Scotland 19 years ago

mrcheerful . wrote: .

Thanks v much, sounded promising, but...

1) checked & cleaned pipe (a little sticky oil condensate, but not enough to block anything), but no joy. 2) can't see metal filter; just inside the oil filler cap is a brown half-cylinder looking plastic cap; filter under this? feels as if it might clip out, but doesn't come easily and I don't want to break anything

..Cheers, Dave

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Dave T Scotland 19 years ago

Thanks v much, sounded promising, but...

1) checked & cleaned pipe (a little sticky oil condensate, but not enough to block anything), but no joy. 2) can't see metal filter; just inside the oil filler cap is a brown half-cylinder looking plastic cap; filter under this? feels as if it might clip out, but doesn't come easily and I don't want to break anything

..Cheers, Dave

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Dave T Scotland 19 years ago

Thanks v much, sounded promising, but...

1) checked & cleaned pipe (a little sticky oil condensate, but not enough to block anything), but no joy. 2) can't see metal filter; just inside the oil filler cap is a brown half-cylinder looking plastic cap; filter under this? feels as if it might clip out, but doesn't come easily and I don't want to break anything

..Cheers, Dave

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mrcheerful 19 years ago

did you check that the stub on the manifold is clear? with the engine running there should be significant vacuum on it (to draw away any oil build up) with it running use a very thin stiff bit of wire to clean it. or a 1mm or less twist drill.

the brown plastic bit is probably the splash guard for the front breather pipe. the filter (when there) is for a top mounted, smaller breather pipe.

mrcheerful

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Help with Young Old Astra 1.6L please..

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