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I have a 155 1,8 TS Formula with an 8v AR67102 engine.

My car have problem running smoothly on idling and on city driving (driving slow, stopping in crosses etc). When giving it even throttle it works fine.

I had it on a compression test and the test showed up to 10 bar pressure on the cylinders but not on cylinder number 3. Here it was around 6-6,5 bar.

I was at the test and I could here the air from the pressure pump comming out somewhere down or under the engine, but I could not determine where it came out. The sound was like air flowing free, not any "bubbling" for example when trying to force air trough some fluidium like water or oil. Could it be that I have to change the hole engine or just replace the top parts of it?

regards
Terje
 

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Only 3 ways to lose compression, past the piston rings, valve or head gasket.. Your description sounds like an exhaust valve just going, tickover slower, possibly puffing sound from the exhaust.
If the rings are stuck in (usually due to running too rich or not warming up) then leave some very light oil (redex type) down the bore for as long as you can, several days.
Hope this helps.
 

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Hi and thanks for your reply!
I do not hear any "ticking" from the engine and it runs evenly and smoothly to a certain point and suddenly the rpm drops to almost 0 and nearly stops, and then it goes back to normal idling. This is going on for just a second or two. Puffing from the exhaust only when the rpm drops. Seems that the exhaust has a white color.
 

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Sounds more like piston/ piston ring trouble. Combustion gasses going past the piston, pressurising the crankcase. Can't really tell from here.
 

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Squirt some oil down the plug hole and repeat the test. If he reading goes up then its most likley piston rings, if there is no change then its most likley valves.
 
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