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rpm not stable after raining

3K views 12 replies 7 participants last post by  smc4C 
#1 ·
Hi guys

Probably not a new issue as in the subject.
I started engine after a few days of big raining and it has unstable rpm on idle gear. Same situation appears during smooth driving up to 2,5-3k rpm. Sometimes during acceleration on 1st and 2nd gear the car "jumps" as if choking

I suppose something electronic got wet. Any idea what would be the first to check?

Thanks
 
#2 ·
Hi guys

Probably not a new issue as in the subject.
I started engine after a few days of big raining and it has unstable rpm on idle gear. Same situation appears during smooth driving up to 2,5-3k rpm. Sometimes during acceleration on 1st and 2nd gear the car "jumps" as if choking

I suppose some electonic got wet. Any idea what would be the first to check?

Thanks
What year is your car? Do you have the metal bracket over the TCM?


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#4 ·
did problem go away after engine bay area warmed up?
 
#5 ·
No. The worst was when I started cold engine after 3 days of raining. The vibration was terible. After few minutes was much better and after 150km of driving there is still unstable (jerking) acceleration up to 3000 rpm when I want to accelerate slow and smooth.
 
#6 ·
Had the same problem on a Opel speedster turbo. Bad grounds. Had to replace the whole electric loom.
Also tested: coilpack,Maf sensor,plugs, nothing worked.
The speedster was 10 years old...

If i can remeber , a member from this club noticed the grounds on this car were weak? 4C-ophe maybe ????
 
#7 ·
Hi Remik,

If it's not throwing up any Check Engine Light - CEL Codes, then it's less likely to be an electrical fault and more likely to be a fuel fault.

As it is worse after rain, is there any possibility that water is getting into your fuel tank via the filler cap? I would be checking the little rubber seal on the door flap to make sure it is covering the fuel filler hole as a starting point.

Can you drain a sample of fuel / siphon some out and have a look at it? Free water will separate from the fuel and be clearly visible.

If it is water in the fuel, putting an ethanol blended fuel (while maintaining the correct MON/RON rating of the fuel) will absorb the water into the ethanol and that will then get consumed in the engine rather than sloshing around in the fuel tank as free water (due to the different densities between fuel and water).

If the fuel tank is badly contaminated, you will need completely drain the fuel tank and it will need a fuel filter replacement too if you want to be sure you are getting unrestricted fuel flow (water can clog fuel filters leading to reduced max fuel flow).

I would advise you against continuing to drive it if you have a misfire like this as it cannot be good for the engine.

If you can rule out fuel related issues, you can then then chase electric gremlins, which usually begins with the battery itself and cleaning the + & - terminals.

Good luck, and please let us know what you find.

Cheers,

Alf.
 
#8 ·
Hi Remik,

If it's not throwing up any Check Engine Light - CEL Codes, then it's less likely to be an electrical fault and more likely to be a fuel fault.

As it is worse after rain, is there any possibility that water is getting into your fuel tank via the filler cap? I would be checking the little rubber seal on the door flap to make sure it is covering the fuel filler hole as a starting point.

Can you drain a sample of fuel / siphon some out and have a look at it? Free water will separate from the fuel and be clearly visible.

If it is water in the fuel, putting an ethanol blended fuel (while maintaining the correct MON/RON rating of the fuel) will absorb the water into the ethanol and that will then get consumed in the engine rather than sloshing around in the fuel tank as free water (due to the different densities between fuel and water).

If the fuel tank is badly contaminated, you will need completely drain the fuel tank and it will need a fuel filter replacement too if you want to be sure you are getting unrestricted fuel flow (water can clog fuel filters leading to reduced max fuel flow).

I would advise you against continuing to drive it if you have a misfire like this as it cannot be good for the engine.

If you can rule out fuel related issues, you can then then chase electric gremlins, which usually begins with the battery itself and cleaning the + & - terminals.

Good luck, and please let us know what you find.

Cheers,

Alf.

Thanks a lot for all suggestions.
The problem has been already fixed. The first cylinder had an issue as there was bad connection in coil with spark plug.
And moreover the spark plugs were in terrible condition as shown below.

For all of you guys to know my Alfa has only 10k km so I suggest to check and change the spark plugs quite often ;)

107966
 
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