misfire under light load

[Mike Miller]

Check spark plug wires. Make sure no insulation cracks allowing a short 
to ground. Try revving the engne at night when you can see if any plug 
wires are "leaking".

You might also try an inductive timing light - put it on each wire and 
see which cylinder is not firing - that's likely the easiest way to 
isolate IF you have access to the timing light. I found a totally dead 
wire that way. Make sure the wires are all seated on both ends.

Could also be the coil wire not seated or arcing under load.

--mike

On 11/12/2011 5:34 PM, Bernie Benz wrote:
> If no obvious leakage tracks on cap or rotor I would not expect a 
> problem there. And no problem under heavy throttle. I’d start by 
> looking at injectors, maybe one is sluggish to open.
>
> Bernie
>
> On Nov 12, 2011, at 3:01 PM, 200q 20v wrote:
>
>> Fellow experts,
>>
>> Driving in 4th gear, 2000 rpm, increasing throttle feels like a
>> misfire in several cylinders. E.g. virtually no power.
>> It is not very pronounced when engine is cold.
>> It appeared to start after last track event. Leaving the track I
>> noticed slightly rough idle and above mentioned misfire while driving
>> home.
>> Changed several years old spark plugs (found the cheapest F5DPOR on 
>> Amazon).
>> Virtually no changes. There are no vacuum leaks (cold engine pulls
>> full boost with no problems) no codes in ECU.
>> Strangely enough during recent heavy rain misfires were much less 
>> pronounced.
>>
>> If left on idle a few misfires a minute can be heard.
>>
>> Wires and distributor cap are about 5 years old, much less then
>> average miles per year.
>>
>> I wonder if anyone has any ideas. I plan to look at replacing cap / 
>> rotor next.
>>
>> Eugene.
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