engine misfires when wet
Thread Starter
Rennlist Member
Joined: May 2004
Posts: 531
Likes: 3
From: Lausanne, Switzerland
engine misfires when wet
Hi guys,
Not long ago I washed my car with a high-pressure cleaner for the first time ever.
After the wash, the engine sounded as if it was not firing on all cylinders (spluttering and reluctant to rev). It also made noises (sort of crack, as if I had a firecracker in the exhaust) every 10-20 seconds.
After letting the engine idle for 5-10 minutes, the problem disappeared. It made me think the problem was related to water getting in somewhere, and that letting the engine heat solved the problem.
Yesterday the car spent the whole day outside in torrential rain. When I left the office, I had the same problem for a minute or two. The engine did not fire properly, throttle response was sluggish and the firecracker noises were back. After 2-3 minutes the engine stabilized and the noises disappeared.
Do any of you know where the problem might be?
It is raining again today.....
Jens
Not long ago I washed my car with a high-pressure cleaner for the first time ever.
After the wash, the engine sounded as if it was not firing on all cylinders (spluttering and reluctant to rev). It also made noises (sort of crack, as if I had a firecracker in the exhaust) every 10-20 seconds.
After letting the engine idle for 5-10 minutes, the problem disappeared. It made me think the problem was related to water getting in somewhere, and that letting the engine heat solved the problem.
Yesterday the car spent the whole day outside in torrential rain. When I left the office, I had the same problem for a minute or two. The engine did not fire properly, throttle response was sluggish and the firecracker noises were back. After 2-3 minutes the engine stabilized and the noises disappeared.
Do any of you know where the problem might be?
It is raining again today.....
Jens
Instructor
Joined: Jul 2005
Posts: 197
Likes: 0
From: London, England
I had this problem last year, and all I did was spray the HT leads, Distributor caps etc... with "Damp Start" which is a silicone based aerosol. The problem was solved there and then.
Cheers
Alex
Cheers
Alex
Rennlist Member
Joined: Feb 2003
Posts: 1,031
Likes: 120
From: Albuquerque, New Mexico, USA
Do you have the stock Oxygen Sensor?
I think Adrian has commented in the past that the generic O2 sensor is not properly waterproof, and will cause all severe misfiring if it gets really soaked.
I had one on my car, and during a heavy rain, had those exact symptoms. I subsequently purchased the actual Porsche sensor, and am happy to say that I have not had the same problem again.
Coincidence? Possibly, but it was a cheap enough, DYI fix.
Brian
I think Adrian has commented in the past that the generic O2 sensor is not properly waterproof, and will cause all severe misfiring if it gets really soaked.
I had one on my car, and during a heavy rain, had those exact symptoms. I subsequently purchased the actual Porsche sensor, and am happy to say that I have not had the same problem again.
Coincidence? Possibly, but it was a cheap enough, DYI fix.
Brian
Race Car
Joined: Nov 2001
Posts: 4,140
Likes: 1
From: Surrey, UK
I doubt it's the oxygen sensor. I thought the same when I saw the title - however the description says :
"Yesterday the car spent the whole day outside in torrential rain. When I left the office, I had the same problem for a minute or two."
From cold, the oxygen sensor isn't used until it warms up - which takes a minute or two. Hence, if it was the oxygen sensor the car should have run fine for a minute or two and then had the problem, not the other way around.
"Yesterday the car spent the whole day outside in torrential rain. When I left the office, I had the same problem for a minute or two."
From cold, the oxygen sensor isn't used until it warms up - which takes a minute or two. Hence, if it was the oxygen sensor the car should have run fine for a minute or two and then had the problem, not the other way around.
Thread Starter
Rennlist Member
Joined: May 2004
Posts: 531
Likes: 3
From: Lausanne, Switzerland
Hi guys,
The problem happens when I fire up the engine, and it goes away as the engine heats up. Therefore, I did not think it could be the O2 sensor.
But, it may be the wiring around the air-flow sensor housing on top of the engine. As far as I can see, it is the only part that gets wet when the car is parked in the rain.
Take care,
Jens
The problem happens when I fire up the engine, and it goes away as the engine heats up. Therefore, I did not think it could be the O2 sensor.
But, it may be the wiring around the air-flow sensor housing on top of the engine. As far as I can see, it is the only part that gets wet when the car is parked in the rain.
Take care,
Jens
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Instructor
Joined: Nov 2004
Posts: 198
Likes: 0
From: Berkshire, England
Originally Posted by Seight
I had this problem last year, and all I did was spray the HT leads, Distributor caps etc... with "Damp Start" which is a silicone based aerosol. The problem was solved there and then.
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Racer
Joined: Jan 2005
Posts: 410
Likes: 0
From: Peterborough, UK
I have had the same probs in the rain.
When its raining hard or surface water I get a lot of problems, car stalls will only rev witht he clutch dipped and will only pull on full throtle - not good in traffic!
I had all ht leads, plugs, caps and rotors replaced and still happens. i also sprayed the whole lot with wd40.
My conclusion is there is a earth or something under the car that is effected by the water spray.
Its imposible to diagnose as it only happens in certain rain and I'm neer carry a spear techie with me when it rains - silly me.
When its raining hard or surface water I get a lot of problems, car stalls will only rev witht he clutch dipped and will only pull on full throtle - not good in traffic!
I had all ht leads, plugs, caps and rotors replaced and still happens. i also sprayed the whole lot with wd40.
My conclusion is there is a earth or something under the car that is effected by the water spray.
Its imposible to diagnose as it only happens in certain rain and I'm neer carry a spear techie with me when it rains - silly me.
Rennlist Member
Joined: Feb 2003
Posts: 1,031
Likes: 120
From: Albuquerque, New Mexico, USA
Originally Posted by C4-JohnO
My conclusion is there is a earth or something under the car that is effected by the water spray.
I would agree that the symptoms that the OP described make it unlikely that it is the O2, but your description matches mine original problem to a "T".
Brian
