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EP3 Misfire when wet - Help needed please.

R

Rob-EP3

Messages
51
Hi Guys,

My 2004 EP3 has developed a fault where in heavy rain the car starts to misfire badly. In dry weather I have no issues at all.

The issue started around November last year when it felt like a had a blow out on the rear driver side tyre but soon realised it was a misfire. Lucky I was on a clear B road so managed to turn the engine off, restart and all was good again.

All was good for the rest of the year until it happened again another 3 times between February - March, again heavy rain conditions. I rang my local Honda dealer who basically told me if it’s only occasional leave it for the time being and monitor it!

All seemed good again until Monday evening while I was on my way to cinema and a huge downpour started and shortly after the car started to misfire. I managed to pull over and switch off, left the car for a few moments and restarted again. The engine stated without a misfire and I continue for a few meters in the almost monsoon condition and it started misfire again! I managed to crawl to my destination and the car was left for around 2 hours and on return the rain had stopped. I got in the car, started and all was good again, it was almost like nothing had ever happened!

That was the last straw, so I rang Honda have will be dropping the car off tonight for them to determine the fault. I’m due to go to France next week so I’m praying it’s something they can fix quickly!

Have any of you guys experienced this type of fault or could have a guess of what it could be? I can relay this on to Honda later as it might speed up the process and save on the £85 an hour labour lol

Thanks,

Rob.

Ps I have owned the car since 2010 and have never had this issue. Service was done in jan this year, including ngk iridium laser plugs.
 
Possible electrical issues: damaged spark leads/cable sheath splits allowing arcing or capacitance or increased resistance, poor earth, etc. Water/moisture gets into the cabling or other locations it shouldn't be and causes the system (or a sensor) to act differently.

Check all the cabling for splits in the coatings, check and re-seal the various sockets (use something like a silicone grease when reconnecting things to prevent water ingress), etc.

Water is insidious :(
 
Thanks for the swift reply Mike.

I’ll pass this on them tonight. Sounds like it could take a while to find the culprit :eek:
 
I had it changed from the original OEM exhaust to a custom stainless steel made to OEM spec last year as it was corroded. Maybe around the same time the misfire started!

I’ve had stainless exhausts before on 2 previous car and never had the misfire before?

Can you explain more about this potential issue please?

Thanks
 
It's entirely up to you what you do mate. If it gives you peace of mind then get it looked at.

Like you said "had it changed from the original OEM exhaust to a custom stainless steel made to OEM spec last year as it was corroded. Maybe around the same time the misfire started!"

If you are sure it's a misfire get it investigated. Or monitor the issue and see if it happens again in a heavy downpour or heavy rain.
 
Sounds like the exhaust to me. My Fujitsubo Legalis R rattles on the floor in heavy rain or standing water.
 
klashinikov said:
It's entirely up to you what you do mate. If it gives you peace of mind then get it looked at.

Like you said "had it changed from the original OEM exhaust to a custom stainless steel made to OEM spec last year as it was corroded. Maybe around the same time the misfire started!"

If you are sure it's a misfire get it investigated. Or monitor the issue and see if it happens again in a heavy downpour or heavy rain.
Click to expand...

It like a misfire rather than a rattle but I might see if I can replicate the fault by getting the engine up to temp and spraying the exhaust before I drop the car off tonight. If it is the exhaust I might have go back to OEM....
 
Last edited by a moderator:
Rob-EP3 said:
It does like a misfire than a rattle but I might see if I can replicate the fault by getting the engine up to temp and spraying the exhaust before I drop the car off tonight. If it is the exhaust I might have go back to OEM....
Click to expand...

My Skunk 2 exhaust used to this from time to time in wet conditions but I heat wrapped the front b section and it no longer does this.
 
Have you checked the O2 sensors?
I had a custom made exhaust on my EP3 and noticed a misfire in the rain, you will definitely know the difference if it misfires or the exhaust rattle in the wet.

Turns out the company who made my custom exhaust, I will name and shame, (Longlife) nicked the O2 sensor wiring when cutting off the old exhaust (They didn't admit it) but I did manage to get a new O2 sensor from them and no more misfire.

I now have a Fujitsubo and get the rattle in the rain but it is a difference between the two so check the O2 sensors, at least you can rule that out then.
 
Shoonk said:
Have you checked the O2 sensors?
I had a custom made exhaust on my EP3 and noticed a misfire in the rain, you will definitely know the difference if it misfires or the exhaust rattle in the wet.

Turns out the company who made my custom exhaust, I will name and shame, (Longlife) nicked the O2 sensor wiring when cutting off the old exhaust (They didn't admit it) but I did manage to get a new O2 sensor from them and no more misfire.

I now have a Fujitsubo and get the rattle in the rain but it is a difference between the two so check the O2 sensors, at least you can rule that out then.
Click to expand...


Thanks, I’ll mention that to Honda so they can check...
 
Quick update...

I got home from work and thoroughly hosed the exhaust from the top of the mid pipe down with the engine running. No misfire / popping etc! I thought this would of worked considering it only happens in the very wet.

I have now left the car with the Honda dealer, so fingers crossed they might find something tomorrow. I wouldn’t normally worry too much but I’m meant to be driving to France on Tuesday :eek:
 
Krzys said:
Moving away from the exhaust then, does it have the standard airbox and filter?
Click to expand...

Standard Air box and an ITG drop in pro filter. I have recently cleaned and oilled it but it didn’t make any difference. I have bought a genuine Honda filter and told Honda it’s in the boot if they want to fit it.

Could it be as simple as the filter? It has been on the car for years, so possible degradation...
 
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