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Discussion Starter · #1 ·
Hoping for some advice as I don't know what to try.

I have an S70 T5 1997 manual. UK Car with ME4.4.
It was smoking quite a lot so I bought the parts and had the PCV renewed by a local volvo mechanic.

There has always been a bit of a flat spot at 1500-1600rpm however it's now stuttering at those revs since having the PCV renewed. The more throttle you give it the smoother it is, however in 4th gear for example with very light throttle it stutters badly.

When I look at the ODB readings for short term fuel trim it seems very strange. (I'm not sure if it was doing this before the PCV renewal or not)

At idle it goes roughly from -4% to +4%
at 1500-1600rpm it goes straight to +25% and stays there
at 2000pm it is around -2% to +6%
at 2500pm it is around -4% to +6%

The long term fuel trim is around -1% and doesn't seem to be changing.

Is it correct to assume the stutter is because it's dumping in loads of extra fuel at those revs?

It's had new (genuine parts) spark plugs, o2 sensors, rotor arm and distributor cap, MAF and all TCV.
I don't think there are any vacuum leaks in the pipes.

The only thing I'm not sure about is the Idle air control valve which is hissing, is it supposed to do that?

Any suggestions please?
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