87 911 carrera plugs

[ghnat]

I know it may be a long shot but I just removed my plugs (engine idle erratic and some hesitation) and would like some expert opnions. My engine has 200+k on it. What do they tell?

[ghnat]

Hmmm why didn't the pics show

[jpachard]

Greg, What kind of plugs are you using??

Cheers, james

[ghnat]

bosch super
trying to insert a pic and I must be doing something wrong

[jpachard]

Greg, You need to attach it. Scroll to the bottom of the post page and you will see the button. The .img button needs to be directed to a web host, not your d drive.

As far as the plugs go, I run the cheapo Bosch copper plugs in my '87. Mind you, this is a race car so it sees alot of maintenance etc.

Cheers, James

[ghnat]

Ahh, got it
Here they are. There is some lint from a rag, please ignore the red lint...

[2.7RACER]

Greg,
I'm not an expert at reading plugs, but things look a little lean to me.
That said, let me say this. I have a '85 Carrera that had the same symptoms you described, erratic idle, some hesitation. When I went for an emissions test it flunked big time. Bottom line, the mass air flow output to the computer was all over the place. With the miles on your car that is the first place I would look.
Heres the deal, as air flows into the motor, a little spring loaded door opens. The more air, the more it opens. Attached to the door is a wiper potentiometer. As the door opens the voltage to the computer rises. The computer responds by increasing the duty cycle to the injectors adding more fuel.
After 15 or so years this little pot wears down and instead of a steady increase in voltage to the computer, it sees gaps where the voltage may drop from say 3 volts to 1 volt. This when the door is open asking for more fuel.
It is reasonably easy to trouble shoot off the motor. With a ohm meter across the connector gradually open the door. The resistance should increase slowly and smoothly as you open the door. A defective unit will be erratic. The resistance may move up and then drop or not move and then jump up suddenly. This is a common failure with old mass air flow units.
I've replaced the one on my carrera and earlier on my wifes 944.
I opened up the little sealed plastic box and tried unsuccessfully to clean and reset the wiper arm to no avail.
Rebuilt units are available for around $200, new ones for around $400.
Usually people try everything else before they look here. Me, I look there first with older Porsches.
Replace the O2 sensor if it is more than a couple years old.
Thats my 2 cents for what its worth.

[ghnat]

Thanks for the advice. I got an o2 sensor because I bet the one in there is old. Have not replaced it yet. I also tightened up some hoses around the Idle Control Valve and cleaned the ICV which helped the idle a little. It would almost stall if I tapped the accelerator. It is a little better now.

I got the car 1.5 years ago and want to put a lot of work into getting it to purr. After that paint and other cosmetics.

The engine is leaking so I figure I will take it out and tear it down. I have not done that before but with lots of reading from Wayne's books and the bently manual I have a good place to start. Whew, a lot of work ahead.

[jpahemi]

Hello,
These look a tad on the rich side??
J.P.

[2.7RACER]

Greg,
I forgot to mention very nice pics, exceptional.
jpahemi,
I was looking at the insulator, not the carbon on the plug body. Could be a hot plug. But like I said, I'm no expert...

[jpahemi]

Doug,
I just changed my chip and have been monitoring my plus. II've gat a nice tan ceramic with very little carbon on the metal area. Pre chip days, the ceramic was darker and the electrode had a darker color. It's hard reading plugs on DME cars.
Regards,
J.P.

[ghnat]

I think I will change the plugs and monitor the new ones and see how they do.

How long should I leave the plugs in before inspecting them?

Thanks for all the help...

Doug - my camera is a canon digital elph s400 with 4M Pixels.