Driving in rain, no power below 2000 rpm
10-09-2005, 10:41 PM
#1
Cruisin'
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Driving in rain, no power below 2000 rpm
I recently acquired a 1985 930 with 140,000 KM. I am a newbie to maintaining cars and very much appreciate your advice!
The car is 1985 911 Carrera, Japan model. It has been dealer serviced for the past 20 years and has original / factory parts, except for K&N air filter. (by the way I changed oil / oil filter at a Porsche dealership a few days ago and it cost an equivalent of US$350 dollars! Is this the case elsewhere???)
Anyway, this morning, for the first time driving the 930 in heavy rain, at first idle started be unstable, moving between 500-900 rpm. Usually it is very stable around 700 rpm.
Then the idle got more unstable and the engine stopped. I was able to restart it, but there was almost no power below 2000 rpm. It was difficult to get the rev above 2000 rpm, even without moving the car.
For the next 15 minutes of drive back home, with dozens of traffic lights (I live in Tokyo), at every red light the engine died / almost died. There was no power that simply engaging the clutch would make the engine stop.
At every green signal, I had to rev it above 2000 rpm in order to get the car moving.
But then, during the drive to the next traffic light (a few hundred meters), with engine above 2000 rpm, the EX light would blink. As the manual says I am to turn off engine immediately when I see EX light blinking, it was very scary.
Since this never happened (albeit my short history with this car) I am assuming it is because of rain.
Questions:
1. Is this symptom due to rain?
Symptom 1: at idle, little power.
Symptom 2: at 2000-3000 rpm, EX light blinking.
2. If so, how is rain causing this problem?
3. How can I prevent it from happening? (other than no driving in rain
)
Thank you so much in advance for your advice!
The car is 1985 911 Carrera, Japan model. It has been dealer serviced for the past 20 years and has original / factory parts, except for K&N air filter. (by the way I changed oil / oil filter at a Porsche dealership a few days ago and it cost an equivalent of US$350 dollars! Is this the case elsewhere???)
Anyway, this morning, for the first time driving the 930 in heavy rain, at first idle started be unstable, moving between 500-900 rpm. Usually it is very stable around 700 rpm.
Then the idle got more unstable and the engine stopped. I was able to restart it, but there was almost no power below 2000 rpm. It was difficult to get the rev above 2000 rpm, even without moving the car.
For the next 15 minutes of drive back home, with dozens of traffic lights (I live in Tokyo), at every red light the engine died / almost died. There was no power that simply engaging the clutch would make the engine stop.
At every green signal, I had to rev it above 2000 rpm in order to get the car moving.
But then, during the drive to the next traffic light (a few hundred meters), with engine above 2000 rpm, the EX light would blink. As the manual says I am to turn off engine immediately when I see EX light blinking, it was very scary.
Since this never happened (albeit my short history with this car) I am assuming it is because of rain.
Questions:
1. Is this symptom due to rain?
Symptom 1: at idle, little power.
Symptom 2: at 2000-3000 rpm, EX light blinking.
2. If so, how is rain causing this problem?
3. How can I prevent it from happening? (other than no driving in rain
)Thank you so much in advance for your advice!
10-10-2005, 12:20 AM
#2
RL Technical Advisor
Hi:
How old are your plug wires, distributor cap & rotor?
From your description, I'd venture that you need new plug wires, distributor cap, and rotor.
Thats the most common cause of running problems in wet weather.
You can perform a simple test by spraying the wires and cap with a bottle of water while the engine is running. Its even better at night where you can observe the corona from old plug wires.
Hope this helps,
How old are your plug wires, distributor cap & rotor?
From your description, I'd venture that you need new plug wires, distributor cap, and rotor.
Thats the most common cause of running problems in wet weather.
You can perform a simple test by spraying the wires and cap with a bottle of water while the engine is running. Its even better at night where you can observe the corona from old plug wires.
Hope this helps,
10-10-2005, 04:01 AM
#3
Cruisin'
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Steve,
Thank you for your advice! I looked in the maintenance records, and they have been serviced (opened up and cleaned) every year, and distributor cap was replaced in May 2001 at 105,000 KM, so it is 4.5 years / 35K KM (22 K Miles).
From the ouside, the wires look normal and I didn't know how to check for their correct operation. I took a picture of the rotor and inside of distributor cap.
http://www.geocities.jp/kide_1120/index.html
They do seem to be worn - metal parts that make contact difinitely show wear, although I am not sure if this is normal or excessive.
Anyway, I will try recreating the problem by spraying some water. (It is running fine now, I suppose the moisture has evapolated. )
Thank you.
Thank you for your advice! I looked in the maintenance records, and they have been serviced (opened up and cleaned) every year, and distributor cap was replaced in May 2001 at 105,000 KM, so it is 4.5 years / 35K KM (22 K Miles).
From the ouside, the wires look normal and I didn't know how to check for their correct operation. I took a picture of the rotor and inside of distributor cap.
http://www.geocities.jp/kide_1120/index.html
They do seem to be worn - metal parts that make contact difinitely show wear, although I am not sure if this is normal or excessive.
Anyway, I will try recreating the problem by spraying some water. (It is running fine now, I suppose the moisture has evapolated. )
Thank you.
10-11-2005, 10:11 PM
#5
Instructor
kide - Steve is leading you down the right path. Every time I've encountered this problem its been due to wet electrics. Especially moisture in the distirbuter cap which prevents the rotor from making decent contact (and hence weak or no spark) as it spins around in its never ending and somewhat thankless job.
One caution though! With the engine running, the plug wires carry plenty of current - enough to cause serious damage to you if you touch one with bad insulation and provide a ground that it likes better than the one its getting. DO NOT grab and 'giggle' plug wires on a running engine unless A) your health/life insurance is really good or B) you're a risk taker that's very, VERY lucky!
Barry
One caution though! With the engine running, the plug wires carry plenty of current - enough to cause serious damage to you if you touch one with bad insulation and provide a ground that it likes better than the one its getting. DO NOT grab and 'giggle' plug wires on a running engine unless A) your health/life insurance is really good or B) you're a risk taker that's very, VERY lucky!
Barry
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10-11-2005, 11:00 PM
#8
RL Technical Advisor
Hi Kide:
Looking at your cap & rotor tells me its time for new ones, Sir.
That carbon track between the terminals of the cap is a major source for cross-firing. If you plug wires have more than 22K on them, replace them all.
The insulating jacket breaks down and the infernal Beru plug connectors go bad.
My BEST advice would be to replace the plug wires with Magnecor 8.5mm ones since they are far, far more durable.
Looking at your cap & rotor tells me its time for new ones, Sir.
That carbon track between the terminals of the cap is a major source for cross-firing. If you plug wires have more than 22K on them, replace them all.
The insulating jacket breaks down and the infernal Beru plug connectors go bad.
My BEST advice would be to replace the plug wires with Magnecor 8.5mm ones since they are far, far more durable.
10-12-2005, 12:13 AM
#9
With the engine running, the plug wires carry plenty of current - Barry A. Waters -
Actually, the plug wires carry a very low current potential, i.e. 60 to 80 milliamps.
It's the high coil secondary voltage, i.e. 25,000 to 35,000 volts, which is the problem.
The voltage is the "driving force", if you will, and it's the current which causes the damage.
The line voltage here in the U.S. (120 VAC) is low voltage but it has a huge current
capability (tens of amps) even though its voltage is low compared to the engine's spark.
This is NOT to imply that the 60 to 80 ma of a spark can't be hazardous.
Note: Since the spark current is 60 to 80 ma, using larger diameter
wire provides NO real benefit. Furthermore, the rotor, the wire ends,
and the plug connectors which have resistors determine the final
spark current. The analogy is using "Monster" cables for better sound
on your home audio system, i.e. a waste of money!
Actually, the plug wires carry a very low current potential, i.e. 60 to 80 milliamps.
It's the high coil secondary voltage, i.e. 25,000 to 35,000 volts, which is the problem.
The voltage is the "driving force", if you will, and it's the current which causes the damage.
The line voltage here in the U.S. (120 VAC) is low voltage but it has a huge current
capability (tens of amps) even though its voltage is low compared to the engine's spark.
This is NOT to imply that the 60 to 80 ma of a spark can't be hazardous.
Note: Since the spark current is 60 to 80 ma, using larger diameter
wire provides NO real benefit. Furthermore, the rotor, the wire ends,
and the plug connectors which have resistors determine the final
spark current. The analogy is using "Monster" cables for better sound
on your home audio system, i.e. a waste of money!
Last edited by Lorenfb; 10-12-2005 at 03:00 AM.
10-12-2005, 04:19 AM
#10
RL Technical Advisor
Originally Posted by Lorenfb
Note: Since the spark current is 60 to 80 ma, using larger diameter
wire provides NO real benefit. Furthermore, the rotor, the wire ends,
and the plug connectors which have resistors determine the final
spark current. The analogy is using "Monster" cables for better sound
on your home audio system, i.e. a waste of money!
wire provides NO real benefit. Furthermore, the rotor, the wire ends,
and the plug connectors which have resistors determine the final
spark current. The analogy is using "Monster" cables for better sound
on your home audio system, i.e. a waste of money!
The wire diameter indeed has no benefit, in and of itself.
The issue is replacing the troublesome Beru connectors and their failure-prone internal resistor with a FAR more durable resistor-less connector and placing the RFI suppression into the wire. The thicker, silicone jacket on these 8.5mm wires has proven to be much longer lasting in the hot environment of these engine compartments.
Since we began using Magnecor wires & connectors in 1990, we never have to replace them frequently anymore. Technology marches on,...
10-12-2005, 07:12 AM
#11
Cruisin'
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Gentlemen,
Thank you so much for your advice. I will go ahead and get the wires, distributor cap, and rotor! I think with this 930 having more than 140K Kilos of Tokyo dirving, I will be asking for a lot more advice in the coming years! Thank you for making my first post such a pleasant experience.
Best regards,
kide
Thank you so much for your advice. I will go ahead and get the wires, distributor cap, and rotor! I think with this 930 having more than 140K Kilos of Tokyo dirving, I will be asking for a lot more advice in the coming years! Thank you for making my first post such a pleasant experience.
Best regards,
kide
10-12-2005, 03:47 PM
#12
Rennlist Member
kide: Regarding your very expensive oil change, here in the states an "oil change" is usually called a "minor service." In Southern California most shops perform two minors between a major service. That means a minor is done at 5K miles, another at 10K and a major at 15K. A minor service, at my shop, included a chassis safety inspection (brake hoses, brake pad wear, set tire pressures, inspect oil lines, check wheel bearing adjustment, tie rods & ball joints), clutch adjustment (pre-'87), alternator/fan belt adjustment, check all lights, battery terminals, power windows, mirrors, etc., test drive and top off the oil to the correct level. That service takes about one hour (today $100/hr is typical), plus the filter (minimal) and oil (usually less than $2.50/qt.). If they sold you Mobil 1, it's not unusual to see it priced at $6.00/qt. You should ask the dealer to justify the charge, just to see what they did. Regarding your plug wires, if you have difficulty finding the wires recommended by Steve, factory replacements are acceptable, and will come complete with connectors used since 1986.
One point to avoid confusion with your posts; in the USA "930" is used to identify Turbos built for the USA from 1976 through 1979. When Porsche re-introduced the Turbo to the USA in '86 Porsche people began to call it the 911 Turbo. To use "930" to describe a 3.2 L Carrera will confuse some, especially me!
Pete
One point to avoid confusion with your posts; in the USA "930" is used to identify Turbos built for the USA from 1976 through 1979. When Porsche re-introduced the Turbo to the USA in '86 Porsche people began to call it the 911 Turbo. To use "930" to describe a 3.2 L Carrera will confuse some, especially me!
Pete
10-12-2005, 11:13 PM
#13
Instructor
Lorenfb - Thanks for the more accurate info on my plug wire current/voltage warning. That's what's so great about the list; there's always a highly informed tech out there that can set you straight! It also helps the list in general get more out of the forum experience.
I understand that there are later cars that have individual coils for each spark plug, located at the wire/plug interface. These systems (if I'm on track here) use a low-voltage signal to the individual coil to generate the 'big bang' voltage right at the plug itself and therefore _should_ make it safe to fiddle with the plug wires while the engine is running.
Would this be a correct (and more importantly SAFE) assumption to make?
Thanks for correcting my flubbed advice!
Barry
Who needs to read up on his electronics!
I understand that there are later cars that have individual coils for each spark plug, located at the wire/plug interface. These systems (if I'm on track here) use a low-voltage signal to the individual coil to generate the 'big bang' voltage right at the plug itself and therefore _should_ make it safe to fiddle with the plug wires while the engine is running.
Would this be a correct (and more importantly SAFE) assumption to make?
Thanks for correcting my flubbed advice!
Barry
Who needs to read up on his electronics!
10-13-2005, 04:32 AM
#14
"These systems (if I'm on track here) use a low-voltage signal to the individual coil to generate the 'big bang' voltage right at the plug itself and therefore _should_ make it safe to fiddle with the plug wires while the engine is running."
Yes, that's correct. As long as the spark is in the DIS (direct ignition system) connector and
the spark plug is grounded to the engine case, the likelihood of getting zapped is less than
with a conventional spark system. One must still be aware, be very careful, and think!
The voltage triggering the primary of the DIS coil can still be a problem as it can
reach 400 volts versus 25KV+ at the plug.
Yes, that's correct. As long as the spark is in the DIS (direct ignition system) connector and
the spark plug is grounded to the engine case, the likelihood of getting zapped is less than
with a conventional spark system. One must still be aware, be very careful, and think!
The voltage triggering the primary of the DIS coil can still be a problem as it can
reach 400 volts versus 25KV+ at the plug.
10-13-2005, 06:21 AM
#15
Cruisin'
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930 being a specific-year Turbo in the U.S., I see. In Japan 930 designates 3.2 Ltr Carerras. I will be careful. Thanks lot about the information on oil change / minor service. Oil was very expensive at the dealership - about 220 dollars for 10 liters. I am sure it was one of those high quality synthetic one.
Kide
Kide