Twin spark miss fire/fuel starvation - Alfa Romeo Forum
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Twin spark miss fire/fuel starvation

Good evening,

I was wondering if anyone else had experienced an issue my car has recently developed. I have a ph2 145 qv and believe its what's known as a plastic top cf2 engine. Anyway it's a dec 2000 car. My issue is that the car pull very well and idles absolutely fine but when driving at say 40 in 3rd or 4th and only lightly touching the accelerator there's a definite miss fire but feels more like a fuel starvation. As soon as you push hard down on the pedal it clears and takes off, equally if you were to dip the clutch and let it idle again it will clear. It only ever happen when coasting. It feel like the throttle can only be on full or off, it's like a light switch. For a brief 60 seconds yesterday a red light appeared on the dash, it looked like the shape of an injector but has not been on since.

Any suggestions would be well received so thank you in advanced.

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I'd guess it's sensor related, since the beast idles and accelerates under load okay.

A shonky MAF sensor could cause hiccups.. and you could have interference from a stroppy Idle Control Valve if it's getting confused at light loading.

For the first one, take the MAF out and make sure it's all clean. There's a little wire that hangs out there in the intake air stream.. If it's caked in oily goo (panel or cone filter?) then give is a squirt of carb' cleaner.. to remove the contaminants. Be veeeeeery gingerly with it when you clean it.

The ICV can get moody if it's covered in crud too. It tells the engine when to shut off fuel flow when you're coasting with no throttle... all based on the vaccum in the inlet. The beast sits on top of the throttle body. If the MAF clean up doesn't work, take the ICV off and clean up the little rotary valve inside. It should be metal coloured, not black.

While you're there.. use the poking around to check for air leaks, and to make sure the rubber inlet trumpet (with the "bellows" section) just before the throttle body isn't split.

The throttle cable should not be under tension when the throttle is off, so check that it's not holding slightly open (to mask some other symptom?). You can adjust it by moving the position of the little G-washer on the cable end.

Ralf S.

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fire or fuel , miss , spark , starvation , twin

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