fouling only one plug
 

I having a problem fouling only the #2 plug. I changed the plugs and it did the same thing. All the other plugs looks ok. All parts are new including the wires, cap, rotor. The car stumbles for a few 100 RPM upon accelerating. Then seems to run fine. The car is a 77 911S with a euro 3.0 Any ideas? Thanks Jerry

You could have a leaky injector on #2.

My car started to foul plugs around the 120K mile mark.

At first I assumed the worse such as cylinder damage or extremely bad valve guide wear.

After my engine break down I discovered that the problem was that the oil control rings on the pistons were completely coked up and had lost most of their tension. It was quite a reminder of how important those oil squeegees are on a piston when big oil squirters spraying the hell out of them.

You could be looking at anything as minor as this or something as serious as a broken piston and/or gouged cylinder or a really bad intake valve guide or seal.

Start with a compression and leakdown test. It will at least give you an idea of what kind of condition the cylinder is in.

Does the car have Webers?

No, the car has standard CIS with SSI's

Check the plug wires....could not be firing right due to resistance problems......

Mike is making a good point; just because the ignition parts are new doesn't really resolve whether they are functioning properly or not.

It wouldn't hurt to check the resistance of the wires, swap plugs, etc. to eliminate the possibility of ignition problems before delving into the more sinister culprits.

I checked the resistance today on 3 of the plug wires, the #2 wire was 3.99 ohms, the other 2 were 3.94 ohms. THey should be 3 ohms per the wire sheathing and the bentley manual. Are these out of spec or are they OK> I am going to test the other Tues. By the way, the plug in question is black and dry, not wet or oily, Thanks Jerry

Also, what is a good method for testing a fuel injector. i am thinking maybe it has a cloggeg fuel injector. Thought maybe I try a can of techron.

Black and dry or sooty would indicate that you are getting to much gas in that cylinder. An oily plug would indicate a broken ring or bad valve guide. Have you pull the injector to test the spray pattern and to see if it is leaking?

I'd vote for the oil control ring. Have you dropped 20oz of Techron in the car and taken it for a spirited min. 1 hour drive to REALLY heat up the engine and drive out the buildup?

Be sure to dump your oil after doing this. I typically do the 20oz twice before an oil dump at 2,000 miles if I am really picky about things. The stuff is pretty amazing.

John

In a well ventilated area pull the "bad" injector and put it in a tall clear glass container (gas will melt some plastics bottles).
1. Turn key on, is injector leaking?
2. Lift air plate in airbox with your finger briefly (*), does injector spray nicely?
You may want to replace injector O-ring when you have injector out.

-Chris

* While you are spraying fuel in the bottle, they other cylinders are filling up with fuel also, hence do this briefly.

Good suggestions here. I yawn at resistance specs for ignition wires. Somewhat meaningless in a way. For example, our cars would run fine with NO resistance in those wires. Our radios would cackle, but the engine would run just fine. Even if a wire had infinite resistance (not conducting low voltage electricity at all), it might perform just fine when passing high voltage sparks.

Again, there are good suggestions here. Pull injectors and put them in jars, turn on ignition and raise the sensor plate. Look at the spray pattern. Measure the volume. Play with the ignition system a little. Do the Techron dance. You're likely to solve the problem and even if you don't, you'll have better information.

Check injector first like Chris says. That's my vote. Little plastic and steel parts with fuel forced through it after a few million hours are suspect. Kinda like after several days of bad food, coffee, and pizza...things at the back end eventually lose seal and start heading south...

I've got a 72 T with MFI that fouls #1 consistantly and also stumbles a little between 2200-2700 RPM. With lots of fine tuning, air flow balancing between stacks, CO adjustments on the pump, and new injectors it is much better than where I started. Once I hit 3k and up, she sounds and works well. I've also gone through the entire ignition system and replaced anything questionable.
I still need to do a leak down test because I suspect a leaky valve guide.
I always use Chevron, but I think I'll try the "techron dance" just prior to oil change too.

One question I did not see asked is when was your last valve adjustment?

The injectors on my Euro 3.0 are EXTREMELY difficult to remove. I've pulled a couple of them by prying them out, but then had to tap them back in with a soft mallet. It looks like there's a small piece of metal in the intake which locks them in place. Is there a good method of easy removal/installation of injectors?

Quick question... Why change oil after a Techron run? I just changed my oil and happened to treat my baby with a bottle of this juice. Do I now need to change my oil again?

Thanks...

I'd say yes. Techron is pretty nasty stuff. It does not burn or boil off. I'd run another bottle through, and change oil. If you just lift the oil filler cap and sniff, you'll be able to smell the stuff.

Thanks to all! I am going to test the # 2 wire with a new spark plug tonite to see if there is spark. I may try to remove the injector also to see if it is clogged, leaking. I will definitely use the techron and see how this works also. Will let you all know how this turns out, Thanks Jerry

A leak down test will indicate if a cylinder is leaking at the valve seats and/or rings but it will not tell you anything about the condition of the valve guides.

350, what test will report on the condition of the valve guides? I've been reading the latest leakdown test threads and learned the same you just said. Can they be checked for "play" while adjusting the valves or do the retainer and seals damper the valve too much to get a useful measure?

Tony

Yes, the valve spring is going to be your biggest enemy when trying to figure out what kind of shape your valve guides are in.

Removing the rocker and spring with the engine in the car is an option, but one that would require a lot of work.

I know one rule of thumb is that if you properly adjust the valves but still have noticible intermittent valvetrain noise that is an indicator of worn valve guides.

Another is that most air cooled engines will be due for a valve job between 80K and 120K even if it is treated well.

My problem after going 27230.
1. with euro 3.0 fuel distributor, couldn't get smooth idle.
2. in order to pass smog, installed 2.7 FD, smooth idle and
passed smog.
3. installed 3.0 FD again, still no good. Took out 2.7 heater
exhaust to put earlier exhausts and found #1 & #5 pitch
black compared to others being brown.
4. sent 3.0 FD for overhaul.
5. runs Very Smooth.

So, I think your FD is pumping too much fuel into that cyl.

Chris

scarebus, where did you have the FD rebuilt. That sounds like mine. The #2 plug is black while the others are light brown. Also I ran a compression test today. The #2 cylinder was 160psi while the others were 165, 160, 160, 160, 155. Seems pretty consistant. Pretty happy with these numbers. Put Techron in yesterday, ran it for about 35 min. Ran so poorly I brought it home. Has this partial trottle hesitation at low RPMs then kicks in at about 2500 RPM like it has a turbo, LOL. Tonite I ran it again for a about 1 hour. Started running better by the end of the ride! How long does it take to clean up the fuel injecters with Techron, if that is the problem? Right now I guess I am leaning toward a clogged or bad #2 fuel injector? Thanks Jerry

Jerry,
1. Make sure your injector on #2 is a good one. Swap fuel lines
to verify #2 cyl is getting excess fuel.
2. In my case, it was just running rough at idle, but everything
was normal at all power settings. Oc coarse this was attained
after playing with mixture controls.
3. If you have problem other than idle, play with fuel mixture and
idle air also. The high fuel flow into #2 will give rough idle, and if
you adjust mixtures to smooth it out, then the response for higher
rpm with load would be affected.
4. If smoke comes out at higher rpm, tweek down fuel mixture,
left turn, and give more air,left turn on air mixtue. Play with it.
5. FD over haul was done at: Fuel Injection Corporation, at
2407
Research Drive, Livermore, CA 94550. they have a
website: www.fuelinjectioncorp.com with e-mail address
injectec@aol.com talk to purchasing manager Daniel Toledo.
Tell him Chris from Chris' Auto in San Jose referred you. Might
get a break in price. Mail him the part, and he'll mail it back to you.
Good luck.
Chris

Take out the injector #1 and put into the place of the injector #2 and put the injector#2 in the place of the injector #1. Is the problem go to the cylinder with the injector one, the problem is a bad injector.:)

hello there

although we have different motors it seems we have similar problems and are getting similar suggestions from this board - FYI my post is here:

my post

does your fouled plug look like the one in my pic?

jevvy,

Follow Noah's step by step method and you should find the fault.

Jevvy, mine had fouled the number 2 spark plug also, and was running very poor on acceration from idle to about 2500 rpm. I did a techron treatment and cured the problem. Now I do a Techron treatment before every oil change. Seems to keep things running good so far. Jerry

Hi Jerry & others

Thanks for looking and making suggestions, sounds like there is pre-rebuild hope yet!

I have 1 question though:

Do you know of a UK equivilent to "Techron" as I cant seem to find that exact product over here? perhaps I should start a new thread to ask this.

I would love to think it is a stuck oil control ring or similar however I dont want to go lobbing (putting in) any old treatment

Thanks again for your help