82 FI fouling plugs

[meangreenspider]

Hello all,

I had a rich running conditon last summer. Car would run rich for about 2 minutes and then run really well until next cold start. I went thru the FI tune up steps and found that Aux air valve had an issue. I stored for the winter, I did start it occasionally over the winter letting it run for 5-10 min at a time. At the beginning of this season the car ran fine for about 25 miles and then began fouling plugs one at a time (I found this after some trouble shooting). I pulled the plugs and they were very nasty and only had 2500 miles on them and only one of them was still fireing. I replaced plugs and car started up easily so I attempted to track down the root cause. I have went back over the FI tune up and trouble shooting steps that were given to me by a forum member but can't find problem. I don't have a fuel pressure gauge but I did pull the return line off of the top of the fuel tank and ran the car with the line in a fuel container and there seemed to be a steady flow of fuel that is being returned to the tank. I did replace the injector o rings / seals last year with o rings out of a muli pack that I got from autozone but I don't see that causing the issues I'm having but would love it if it was that simple.

I guess I am hoping for some forum brainstorming. Could it be that my possible rich running condition was due to valve seals leaking oil into the cylinders and it ran fine once the oil was burnt out and that the seals are so bad now that it is leaking enough to completely foul new plugs in approximately 25 miles? Car has 94k on it.


I also had a slight oil leak on one of the header studs that may have been leaking into the inside of the header also. I considered this for the apparent rich running conditon also. I don't think it was enough to cause all of the issues but could contribute due to the burnt oil affecting the o2 sensor.

Any resonse is already appreciated, the vintage gran prix is coming up fast here in Lexington OH and I would hate to miss it.

[rlux4]

Any evidence of poor valve seals coming from the tailpipe?
How does it run before the plugs foul?
What's your RPM at idle?
How old is your O2 sensor?
The ECU controls fuel/air ratio by responding to sensor input. If one or more sensors are bad it can mess up the ECU's calibrations causing lean or rich mixture.
Ron

[meangreenspider]

Any evidence of poor valve seals coming from the tailpipe?
How does it run before the plugs foul?
What's your RPM at idle?
How old is your O2 sensor?
The ECU controls fuel/air ratio by responding to sensor input. If one or more sensors are bad it can mess up the ECU's calibrations causing lean or rich mixture.
Ron

Thanks for the quick response, it's a slow Friday here at work.
There is a little smoke at cold start up but not after.
Car ran like a dream, I took it for a 2 mile test drive then just kept driving until plugs fouled and had to get a short tow to the inlaws of all places.
idle is about 800 rpms, I have played with it throughout this whole process.
I installed a new o2 sensor when I installed the header within the last 2 years but probably should replace again since oil leak is now fixed.
I checked sensors and sending units except o2 sensor last fall and "seemed" to be in good working condition.

It seemed to me that if the o2 sensor was affected by the oil it would cause a lean condition.

[rlux4]

An O2 sensor less than two years old should be fine, unless as you say it's been affected by burning oil fouling. It sounds like you're taking good care of your FI system, so you may have to look elsewhere. If it runs good it shouldn't be the AFM or ECU. I'm wondering if a leak down test would tell you more.
Ron

[narfire]

If the O2 sensor is pooched, the engine runs on an average setting. I ran mine without for a short while without too much of an issue with the plugs or performance.

[TX82FIAT]

Ron, you may be on to something with a leak down test. Running rich we first go to valve issues. With 98K it may be the original rings have worn. Has it been consuming oil? Ray

[meangreenspider]

Ron, you may be on to something with a leak down test. Running rich we first go to valve issues. With 98K it may be the original rings have worn. Has it been consuming oil? Ray

Doesn't use much oil at all. I had the leak at the header but never had to add more than just a little bit over a summer.

[majicwrench]

Wow, it fouled plugs so badly it had to be towed??? And it was running fine?? So did it fould one at a time as you were driving OR all of a sudden??
O2 sensor will not create a massive rich condition. Coolant sensor will.
Plugs are black when fouled?? Car almost has to be smoking from either too much fuel or oil usage to foul plugs that dramaticly.
keith

[meangreenspider]

Wow, it fouled plugs so badly it had to be towed??? And it was running fine?? So did it fould one at a time as you were driving OR all of a sudden??
O2 sensor will not create a massive rich condition. Coolant sensor will.
Plugs are black when fouled?? Car almost has to be smoking from either too much fuel or oil usage to foul plugs that dramaticly.
keith

It fouled 1 at a time but within a mile or 2 of trying to nurse it to my inlaws house. I did end up with a short tow. The plugs are black when fouled but it doesn't smoke much after start up but I will replace plugs and have someone ride with me to watch for smoke and to push me home if required. I may try to shoot a short video also. You are the 2nd to mention coolant sensor, I tested it last season but for the price of a new one I will just replace it to be sure.

I appreciate all of the input!!

[So Cal Mark]

pull the vacuum hose from the pressure regulator and look for signs of wetness. If the regulator leaks, fuel is pulled into the intake plenum. I'd also check to see if the cold start injector is leaking or staying energized

[majicwrench]

The conector at the coolant sensor needs to be in good shape as well. And Mark is right, check vac hose to regulator, should be no fuel in it.

[meangreenspider]

New plugs and car started up fine but runs terrible( sputtering and smoking). I nursed it 5 miles to my house and it seems to run ok at certain throttle positions or rpms. I checked for leakage at the fuel pressure regulator and no fuel in vacuum hose. I am going to pull the fuel rail and cold start valve to check for any leaks and replace the generic injector o rings with bosch. I am getting inconsistent readings from the temp sensor so ordered a new one. Once new parts are installed I will play with the throttle positon switch to make sure it is operating properly. I will do a compression test and a leak down test next weekend. In the mean time I will throw a new caliper on my X 19 so I at least have something fun to drive. I showed the bad plugs to a buddy and he told me they were affected by fuel and not oil. If all else fails I will seek out a professional (mechanic).

Thanks to all who responded!!!

[majicwrench]

In the interest of saving you some work, compressoin/leakdown not causing your problem. TPS not causing your issue. O rings not causing issues. You could, in theory, have CS valve stuck on, not likely.

[meangreenspider]

In the interest of saving you some work, compressoin/leakdown not causing your problem. TPS not causing your issue. O rings not causing issues. You could, in theory, have CS valve stuck on, not likely.

Thanks,

I'm always interested in saving myself some work. I installed new temp sensor and no change. I pulled fuel rail and cs valve and manually switched on fuel pump and no leaks. I did find that a the injector closest to the firewall that had been changed out had 2 leaks. The hose clamps needed tightened at the fuel rail and at the injector. The fuel injectors spray and very good mist but may be a little too good. I will have to buy a fuel pressure gauge tomorrow.

[divace73]

to me it could sound like a dodgy AFM....out of interest what plugs do yo use??
I've had mine run with a (unknown) O2 sensor that was blown to bits, only discovered that when I changed it...