Help My 911 is running like crap....

[89cab]

OK, this is what is going on,a month ago I was driving and my 911 started to sputter with a load on it,but idled fine...I was driving and it suddenly started giving up like there was a governor on it, but when I pushed the clutch in it idled fine and reved up fine,it only happened for a minute,I thought it was my floor mat hanging up the gas pedal, so I removed it. The problem went away for about a month.Keep in mind I believe it was raining,if that helps.So living in sunny Ca.it hasn't ran in a month, well it just started and the car is acting up again...

So it happened all week on my way to work as it was rainy and every time it happened I would try and trouble shoot..When it did happen no dash lights go on, like battery etc

I have a 1989 911...
I am replacing the Cap,Rotor and plugs this weekend...
I just replaced alternator last year..
I just replaced Fuel pump 4 months ago..
I just replaced CHT Sensor and O2 sensor about 1 year ago...

This is the best I could describe what is going on I could really use some suggestions ...

[DRACO A5OG]

What kind of Air Filter do you have, OEM or KNS type?

How does your exhaust look when you drive in the rain?

[aigel]

Sure sounds like ignition. The wet weather reduces the resistance for a spark to jump to ground from your ignition system (cap, wires, boots). Under load the resistance in the combustion chamber goes up across the spark plug gap and now that you have a nice low resistance in your wet engine bay, the current finds it's way to ground there instead of igniting your mixture.

You should report back after replacing the components. I would bet money it will be fixed.

G

[89cab]

Originally Posted by DRACO A5OG

What kind of Air Filter do you have, OEM or KNS type?

How does your exhaust look when you drive in the rain?

K&N air filter..
Exhaust is fine...

[89cab]

Originally Posted by aigel

Sure sounds like ignition. The wet weather reduces the resistance for a spark to jump to ground from your ignition system (cap, wires, boots). Under load the resistance in the combustion chamber goes up across the spark plug gap and now that you have a nice low resistance in your wet engine bay, the current finds it's way to ground there instead of igniting your mixture.

You should report back after replacing the components. I would bet money it will be fixed.

G

I was thinking that it could be my Coil or wires ...I will get back to you when I replace plugs and cap & rotor, but I was not planning on replacing wires but might have to..

[aigel]

Get in a very dark spot with your car and engine running open the lid. Often you can see the sparks. Not kidding.

Unless your wires are less than 5 years old, I'd yank then. SoCal has a lot of Ozone that eats up all the rubber.

G

[89cab]

Originally Posted by aigel

Get in a very dark spot with your car and engine running open the lid. Often you can see the sparks. Not kidding.

Unless your wires are less than 5 years old, I'd yank then. SoCal has a lot of Ozone that eats up all the rubber.

G

I was going to do that,but some threads say that even with new wires you will still see spark,so not to sure,but I will try it.. thanks

[kidrock]

cap, rotor and plugs are a good start. When was the last time the fuel filter was replaced?

[89cab]

Originally Posted by kidrock

cap, rotor and plugs are a good start. When was the last time the fuel filter was replaced?

Replaced about 1000 miles ago...

[hcoles]

I also vote for ignition. George mentions observation in a dark area, this works depending on this issue - if there are insulation defects you may see halos. This happened to me when I ran a sand rail at night below the dew point, things got a bit damp and engine started to misfire. Replaced cap/wires and issue was resolved. I saw halos running around the engine surfaces.

[hcoles]

if you like I'll give you a set of used Magnacor wires, there is one clip broken. I'm sure the Magnacor people will fix it for you at reasonable cost, they are good people. send pm hc.coles@gmail.com for pickup location

[56 nomad]

hello,
if ignition and fuel are the problem you might want to check the cat converter, my 83 would idle and run fine "except" when i pushed it hard , then no power. problem seemed intermittent as well.
i thought the clutch was slipping or going out but it turned out to be a partially plugged converter.
just my 2 cents, ben

[89cab]

Originally Posted by hcoles

if you like I'll give you a set of used Magnacor wires, there is one clip broken. I'm sure the Magnacor people will fix it for you at reasonable cost, they are good people. send pm hc.coles@gmail.com for pickup location

Thanks for the offer hcoles, I will keep you in mind and email you if so. As you no it is cold and rainy in the Bay Area and debating if I should start replacing Cap,Rotor and plugs,supposed to clear up Sunday...

[89cab]

Originally Posted by 56 nomad

hello,
if ignition and fuel are the problem you might want to check the cat converter, my 83 would idle and run fine "except" when i pushed it hard , then no power. problem seemed intermittent as well.
i thought the clutch was slipping or going out but it turned out to be a partially plugged converter.
just my 2 cents, ben

I have a Cat bypass installed so unless my muffler is bad I think I am OK...What do you think.

[Joe Bob]

My vote, fuel filter.....if you don't know how long it's been, it's time. Sharpie comment on the can is a good thing unless you have a maintenance diary.

Injectors is another issue.....a bottle of Techron twice a year is a good thing.

[89cab]

I just wanted to say thanks to everyone for coming together on this one,I have a strong feeling that it could be a ignition problem..But I did want to ask your thoughts about the Impulse (Reference Mark) Sender, could this also create the same problems..

[89cab]

Originally Posted by Joe Bob

My vote, fuel filter.....if you don't know how long it's been, it's time. Sharpie comment on the can is a good thing unless you have a maintenance diary.

Injectors is another issue.....a bottle of Techron twice a year is a good thing.

I just replaced fuel filter 1000 miles ago...

[aigel]

I really think you should change out all wear parts on the ignition system and then report back. The fact that wet weather causes your issues is a giveaway. We can go in circles thinking about what else it is but any rough running issues, I always recommend people to get their ignition system refreshed. That's easy and once it is ruled out you can continue troubleshooting.

Good Luck!

G

[MH911]

I had similar problems with my 87 last year except rain was not involved. It did end up being that the impulse sender's were shorting out. The insulation was crumbling off. Both have been replaced and she's running great once again. My adventures were documented in another thread.

I should also add that part of the problem was who ever ( before I took ownership ) replaced the Cylinder Head Temp Sensor. They didn't run the impulse senders through the grommet correctly.

[89cab]

OK, I just finished replacing all plugs and Cap&Rotor and 2 break light switches and the tail light gaskets....I am tired.
I went for a test drive and it did it again wright off the bat,almost like its running on 5 cylinders,it did stop by the time I got 1/2 way around the block and then ran fine .I did check out all the wiring while I was replacing plugs and they all seem to be fine even took off all the brackets along alternator and no cracks,I also closed the garage and turned off the lights and ran it but did not see any sparks..

FYI my wires are Beru...
So my next step might be replacing the wires...What do you guys think