Spark plug fouling

[jhv48]

Those plugs appear to be covered with fluffy carbon deposits and if so, that’s a rich condition. I wouldn’t run the car too much until you figure out why the injection system is dumping too much fuel into the cylinders.
It’s a good thing the car won’t start now. You don’t want to drive it much running rich, as the excess fuel can wash down the cylinders and cause real problems.

[twobjshelbys]

Originally Posted by jhv48

Those plugs appear to be covered with fluffy carbon deposits and if so, that’s a rich condition. I wouldn’t run the car too much until you figure out why the injection system is dumping too much fuel into the cylinders.
It’s a good thing the car won’t start now. You don’t want to drive it much running rich, as the excess fuel can wash down the cylinders and cause real problems.

I concur. Mine looked like this.

However, I also had another symptom: My rich portion of the DFI tables were beyond 1/2 to 3/4 throttle. Running steady at that speed/rpm/position and then letting off the throttle would result in backfires... I could also get it to backfire by "foot on the pedal" acceleration/shifting like you'd get when merging into highway traffic and then letting off the throttle...

Do you have a backfiring problem?

[169mph]

Originally Posted by twobjshelbys

I concur. Mine looked like this.

However, I also had another symptom: My rich portion of the DFI tables were beyond 1/2 to 3/4 throttle. Running steady at that speed/rpm/position and then letting off the throttle would result in backfires... I could also get it to backfire by "foot on the pedal" acceleration/shifting like you'd get when merging into highway traffic and then letting off the throttle...

Do you have a backfiring problem?

When I first bought the car it had nasty backfire when decelerating. The flanges connecting the header to the side pipes were leaking. The backfiring went away after I replaced gaskets and bolts. The last few times I drove the car it would backfire when accelerating and decelerating That's what led me to check plugs.

Thanks, Mike

[jhv48]

I’m no FI expert but could the problem be a failing/rusted/plugged 02 sensor?
Might be a simple cheap thing to try first.

[twobjshelbys]

Originally Posted by jhv48

I’m no FI expert but could the problem be a failing/rusted/plugged 02 sensor?
Might be a simple cheap thing to try first.

Yes, it could be, but only because it had a primary reason to fail.. O2 sensors rarely fail on their own, especially at this age...

Which does make me wonder. I'd get in touch with FAST support and see if there is an equivalent of a "check engine light" code that can be read. You mentioned it had an OBDII connector - how about getting a bluetooth OBDII reader and seeing if it's throwing codes???

Have you tried to download the documentation for that system??? They usually have some kind of troubleshooting tree.

You mentioned that it did backfire, so it's been running rich probably since the beginning. Instead of post-installation troubleshooting I'd start with verifying that the installation was done correctly.

One more... My very initial problem turned out to be that while the engine ran, the throttle position sensor cable was wired backwards (yes, it was a Roush part, and they told me it was likely mine was and it was.) That causes lots of problems because the DFI system at true idle thinks it's running WOT and at WOT is closed... That's really confusing to the software. Their software should give you real-time readouts of TPS and other sensors...

[FlyingGumby]

Originally Posted by twobjshelbys

Yes, it could be, but only because it had a primary reason to fail.. O2 sensors rarely fail on their own, especially at this age...

Which does make me wonder. I'd get in touch with FAST support and see if there is an equivalent of a "check engine light" code that can be read. You mentioned it had an OBDII connector - how about getting a bluetooth OBDII reader and seeing if it's throwing codes???

Have you tried to download the documentation for that system??? They usually have some kind of troubleshooting tree.

You mentioned that it did backfire, so it's been running rich probably since the beginning. Instead of post-installation troubleshooting I'd start with verifying that the installation was done correctly.

One more... My very initial problem turned out to be that while the engine ran, the throttle position sensor cable was wired backwards (yes, it was a Roush part, and they told me it was likely mine was and it was.) That causes lots of problems because the DFI system at true idle thinks it's running WOT and at WOT is closed... That's really confusing to the software. Their software should give you real-time readouts of TPS and other sensors...

+1 on trying an OBD2 reader (if you have a port). Used on my Roushcharged 4.6 3v to diagnose a few things.

First to troubleshoot CHT code. Lucky it was a loose harness at back of engine and not CHT sensor under the intake and supercharger.

Next... went from running great to running rough (and smelling a little rich) overnight. Saw ST and LT fuel trims off with the reader. Turned out the intake snorkel came loose after the MAF at the throttle body. Think the ECU went rich as engine was getting more air than MAF was measuring. Cleaned the air filter and MAF, and reconnected everything. Back to normal.

Another time car ran rough almost like being in limp mode. Popped on the OBD2 reader and got code for TPS mismatch. Removed and cleaned TPS connections and it ran good as new. Never would have guessed that. Will replace TPS at some point.

I leave the reader connected to have data after each run - RPM, intake air temp, coolant temp, relative and absolute TPS, fuel trims, etc.

Worth a try. Good luck.