rain causing miss fire
 

Hi. Really need help now. Whenever it rains my car ( 95 wrx import ) runs terrible, it idles at virtually 0 rpm it splutters and miss fires and just bunny hops down the road. Iv tried changing the usual things like coil packs etc and even moved my ecu to the glove box just in case it is getting damp but nothing is working, the problem sometimes stops when the engine is hot but not all the time. Has anyone had the same problem or know how to solve it, its driving me well nowhere fast and mental at the same time.

This happens with mine, too (but too a lesser extent, another MY95 WRX).
Have you got any cracks in your coil packs? I know that this might make the problem worse, but there's loads of potential areas that damp can affect. If you find a solution for it, I'd definitely be interested to know!

Ht leads

Have you got the covers under your bonnet vents?

Have the above two posters got an open cone air filter? Could be that?

I had this issue when I first got my MY99 STi 5 mapped (inc. OEM MAF + open cone to clear the FMIC hard pipe)... I reckon the water on the cone altered the airflow ('less' air) and therefore 'fooled' the MAF into overfuelling for the actual amount of air going in ?!?!

Since I went to Simtek and MAFless (but still keeping the cone air filter) I've had no probs whatsoever - roars through the rev range like a well oiled sewing machine. Even in monsoon-like conditions.

Just a thought.


But before you investigate any of that, liberally spray the coilpacks with WD40 -- it usually works wonders if the rain is causing electrical shorts....

when i had the exact same problem it was the knock sensor it was badly cracked and when damp water got in and caused the problem so new one from ebay about £40 solved the problem, but its not easy to do you have to take off the intercooler and its at the back of the engine down low and you need a thin long extension bar socket to reach it and itll be tight and hard to undo then clean the surface before the new one goes on.

Goujon's suggestion is 'winning' so far, IMO... :D ;)

Don't want to hijack, but hopefully my setup is similar to the OPs....
I still have the covers under the bonnet vents, and I'm running a panel filter.
goujon's suggestion is very interesting. I'll whip the cooler off over the weekend and try refitting the knock sensor.

Coil pack/leads would be my guess.
The moisture in the air (not the actual raindrops, but the damp feeling in the air)
can provide the coilpack with an easier path to ground then through the cables.

Yeah, I'd get the WD40 out first... before going further.

remove coil packs . insert 28mm heatshrink over black rubber boot cut to size and av it with a hot air gun , problem solved on mine. make sure you leave the end open for the plugs :thumb:

Thanks guys. Iv changed coil pack and still have a panel filter on but I will have a look at some of your ideas. Hopefully 1 will work

Over the years I've had a few cars do this to me, and *usually* emptying a can of WD40 under the bonnet works! ;)

:thumb:

same problem here, same year as well, 95 wrx

bonnet vent covers on, stock air filter 9well,panel filter but housing) and if mine sits for a day or 2 when its raining, i get a car that drives but is missing and its only until about 4 miles down the bypass it will just "burp" and you can feel it purring again LOL

i like the heat shrink appraoch, might try this and see if it works, i thought it was water dripping onto the block/coil packs and this method of fizxing it sounds ideal LOL