9 replies to this topic

[hitbyastick]

About two months ago I got a random misfire code. I get one for every cylinder, so there's 5 codes total. I've replaced all ignition components but it didn't make a difference. I can clear the code but it comes back after a few miles. Usually under acceleration. Not always the case though. All filters are new, I cleaned the MAF and the car has all the crankcase breather stuff replaced. Compression is good across the board. I'm at a loss as to what else would cause this.

Another thing the car does is stutter. But not all the time. Sometimes it does it at idle, sometimes under acceleration, sometimes coasting and sometimes just cruising. At any speed. It feels like the car shuts off for a split second. Like a sneeze or a hiccup.

If anybody has some ideas that would be quite fantastic. If not the car will be for sale soon.

Thanks much,
Chris

[Keaton85]

What exactly did you replace and with what brands?

[Snabb T5M]

how about telling us what kind of car, year, plugs and gap, etc. Hard to help without knowing more details.

[hitbyastick]

The car:
98 V70 XC 2.4 turbo.
Tried two different types of plugs: Champion Copper gapped at .028 and NGK also gapped at .028 ... makes no difference
Replaced the cap and rotor as well as the wires with Bosch stuff.
The car is bone stock and I havent' done any performance type stuff to it.

[Snabb T5M]

Here's what someone else (Fishey) suggested on a similar discussion in the Performance Forum and it solved the misfire problem.


"You got a boost leak... Ohhh yea... its a booost leak.... Time to find it... Go find your leak.... (Think about this in a really odd singing voice)

Seriously though, I think you got a boost leak maybe near the IAC who knows but regardless your maf is saying OMG SO MUCH FLOW! your engine is only seeing about 1/2 that flow... You get on boost and BOOOM way to much fuel for your actual airflow resulting in said misfire."

[Vagabond]

I have the same thing only it's an NA.

I noticed it recently. Only new part is I installed another fuel pump. I haven't done any troubleshooting yet so I'll post up what I find out this weekend.

[hitbyastick]

How would one go about finding a boost leak. Vacuum leak I can do, but this is new to me
I visually checked all the hoses and clamps and everything looks ok. No vacuum leaks to speak of either (smoke test).

[Vagabond]

My misfire was due to worn plugs and old wires (high resistance: 70-90 kilohms.)

Replaced plugs, wires, grounds, cap, rotor and coil.

Runs like a champ.

[Tommy.]

You could try replacing with OEM volvo plugs. Sometimes people have problems with coppers.

[andyb5]

How would one go about finding a boost leak. Vacuum leak I can do, but this is new to me
I visually checked all the hoses and clamps and everything looks ok. No vacuum leaks to speak of either (smoke test).

Here's how to pressure test your intake system: