Carbon shooting from tailpipes

TPI 85 Blazer · Post by **TPI 85 Blazer** » Sun Aug 13, 2006 3:58 am

While driving yesterday, the engine starting losing power until eventually it would hardly run at all. This was accompanied by an unusual whooshing sound whever the throttle was opened at all. After messing with for a while, I determined that it would run decent with the exhaust unbolted from the headers. After I bolted the exhaust back up, the symptoms were back: starts OK, but the longer it runs, the lower and lower the vacuum gets. Also, the higher the rpm, the lower the vacuum. Obviously my cats are plugged, right?

After going through all this, I noticed that the floor under the truck was covered with black granules. Not a little, like rust from unbolting stuff, but over a large area. It must be carbon and this must be what plugged the cats. The question is, where does it come from?

Do I have a bad injector so that one cylinder runs rich all the time?

Is the WBO2 so far off that it is always running rich?

Has my charcoal canister gone bad allowing the engine to suck in charcoal?

Please help me figure out how to get my truck home.

PSIG · Post by **PSIG** » Sun Aug 13, 2006 8:15 am

Posting a log file would help a lot. Assuming it was running okay before this - did you make any VE table changes? Fuel pressure changes? WB correction changes? If it was okay on the same VE table earlier then I would turn EGO correction off and see if that helps. Shooting in the dark here - need more info.

David

TPI 85 Blazer · Post by **TPI 85 Blazer** » Sun Aug 13, 2006 11:46 am

Here's the last datalog I made while it was running OK.

MarkW · Post by **MarkW** » Sun Aug 13, 2006 12:16 pm

are you sure your cat's not distintergrating or past it?

Had a similar problem but we had superheated the cat and melted part of the matrix

PSIG · Post by **PSIG** » Sun Aug 13, 2006 1:00 pm

TPI 85 Blazer wrote:Here's the last datalog I made while it was running OK.

Okay - do you have one of it running now? The old log looks fairly good but is definitely rich and looks like you may need to recalibrate your TPS.

Does it run now? Can it idle or high idle? If it will run re-cal your TPS, turn off EGO correction (reboot everything) and tune your idle bins for minimum MAP. Then set the VE bins all around the low speed area to the same VE numbers as idle and maybe you can baby it home.

David

TPI 85 Blazer · Post by **TPI 85 Blazer** » Sun Aug 13, 2006 1:33 pm

I cut the cats off and I got like a cup of carbon granules. The internals of both cats looks solid, just plugged.

As for the TPS, I think it is calibrated. When I close the throttle blades all the way with the idle screw, it goes to 1%. I can open it to 100% by hand, but the way the throttle cable is right now, it doesn't open past 80%. I was waiting to get my tuning better before fixing that. The throttle body does need bushings on the throttle shafts, so it is sticky when the engine is running. When it cracks off idle, the vacuum really dips. Maybe this is why the datalog looks like it's going to WOT.

Since the cats are gone, the O2 sensor is too close to free air to read accurately, so I pretty much have to disable EGO correction.

TPI 85 Blazer · Post by **TPI 85 Blazer** » Sun Aug 13, 2006 2:16 pm

Here's a new logfile. It's just starting, idling and me playing with the idle VE values while blipping the throttle. I did move the numbers from like 40% down to about 30%, so it was idling rich. It's still hard for me to believe that it's been this rich all along. Something must have happened yesterday to quickly make it pig rich. If it's been this rich all along, then my LC-1 is just plain wrong. I usually drive with a laptop and I have an AFR gauge on the A-pillar that I calibrated the LC-1 to. It hasn't been any stinkier than with my carb.

S.Bretz · Post by **S.Bretz** » Sun Aug 13, 2006 3:27 pm

Sounds like you need new cats. The new ones will get clogged too...its ounds like the vehicle is running really rich.

TPI 85 Blazer · Post by **TPI 85 Blazer** » Sun Aug 13, 2006 5:02 pm

For the time being, I have installed these new non-clogging type catalytic converters

My AFR readings must be at least close because whenever I get my idle leaner than 15:1 it gets rougher. It's running and I've re-tuned my VE all around idle. I'm going to clean up here and drive it home.

TPI 85 Blazer · Post by **TPI 85 Blazer** » Mon Aug 14, 2006 6:27 pm

I took the throttle body off tonight and there is carbon in the intake. It's not grains of sand like in the exhaust, this is the normal powder kind. This must be coming up from the EGR valve, then. The intake was clean when I assembled everything. I did note that the line coming in from the charcoal canister was clean, so I can stop suspecting that.

While idling, I disconnected each injector, one at a time. In each case, the (already poor) idle got worse, EXCEPT for cylinder #7. It made no difference whether it was plugged in or not. I also traded connectors with #5, and either way, 5 made a difference and 7 did not. So that cylinder is not firing. I noted that spark plug as being "oily" yesterday, but maybe it was actually wet with gas.

After I cleaned the plugs last night, I drove and it seemed to run fine. Unfortunately, after driving 10 miles or so, it started to stumble again. Maybe that spark plug is fouling out. The O2 sensor is mounted on the even cylinder bank (2, 4, 6,

, so I can't measure any change from unplugging this injector. Also, my cobbled up exhaust is leaking just behind the sensor, so it probably doesn't read right anywhere.

I just can't figure out why it is so rich. Whenever I lean it out more, it gets weak and starts missing.

I am thinking about gettting a new set of injectors. The ones I'm using are history unknown.