Spark plug fouling

[twobjshelbys]

Originally Posted by 169mph

I’m not replacing the EFI until I’ve ruled out all potential causes. When these issues originally started. I thought I could plug my laptop into the ECU and I would be able to run diagnostics to see if a sensor was faulty or a fuel injector was stuck open. Is this not possible. I’ve downloaded what I believe to be the latest FAST software for my ECU. I’m trying to find the correct USB to CAN connector so can I connect my computer to the ECU. Is this a waste of time? Again, I appreciate y’alls help. Thanks, Mike

So you've confirmed it's the FAST and not the Accel EFI system? If so that is good.

I would suspect you can get whatever tools you need to confirm the tune from them (FAST). If they have a standard tune that has evolved I'd say it probably won't hurt - treat it like any other software update. But if the tune was modified by Roush I wouldn't put a different tune in it. The reason is that the faux 8-stack injection is not linear with throttle position and air flow. I've gone into the details in other posts (don't ask me where) but the air flow over the throttle body vane varies by the position relative to the injector, with the net effect being that in the case of at least the Accel, at idle it was running extremely rich because the air/fuel didn't get a chance to mix until the throttle blade was open to about 1/2. I don't know how FAST deals with this characteristic. I never figured out who made the Roush 8-stack so if it is Borla you could perhaps turn to them for some advice on how the off the shelf FAST tunes work.

[169mph]

Originally Posted by twobjshelbys

So you've confirmed it's the FAST and not the Accel EFI system? If so that is good.

I would suspect you can get whatever tools you need to confirm the tune from them (FAST). If they have a standard tune that has evolved I'd say it probably won't hurt - treat it like any other software update. But if the tune was modified by Roush I wouldn't put a different tune in it. The reason is that the faux 8-stack injection is not linear with throttle position and air flow. I've gone into the details in other posts (don't ask me where) but the air flow over the throttle body vane varies by the position relative to the injector, with the net effect being that in the case of at least the Accel, at idle it was running extremely rich because the air/fuel didn't get a chance to mix until the throttle blade was open to about 1/2. I don't know how FAST deals with this characteristic. I never figured out who made the Roush 8-stack so if it is Borla you could perhaps turn to them for some advice on how the off the shelf FAST tunes work.

It's a Borla 8 stack with a FAST XFI Sportsman ECU. I was told that FAST no longer sells my ECU and there's very few people who can tune them or at least not willing to tune them. I believe Roush tune the engine. If so, they should have a copy of the tune or I'm I being too optimistic??

Thanks, Mike

[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...

[twobjshelbys]

Originally Posted by 169mph

It's a Borla 8 stack with a FAST XFI Sportsman ECU. I was told that FAST no longer sells my ECU and there's very few people who can tune them or at least not willing to tune them. I believe Roush tune the engine. If so, they should have a copy of the tune or I'm I being too optimistic??

Thanks, Mike

I don't know how Roush does this any more but when I was having the problem with mine Roush was fairly cooperative. But often that is more related to the individuals involved than corporate policy and my contact was with a direct engineer.

That said, your tune is most likely intact. You can try to get it from Roush but I doubt it will be different than what you have currently since you have no evidence that it was subsequently tuned by someone else (do you?)

However, I don't know how much self-learning this system does. It's possible its learned itself into a corner that it can't get itself out from. If you can get the FAST software maybe you can simply reset the adaptives and let it start over again.

I still assert there is something besides the ECU that is causing this problem. Something is leading the fuel system to over-fuel since I sincerely doubt Roush would ship an engine that behaves so badly by design. You need to find that first.