Running Rich, Carbon Build-up?

[Xx91AccordxX]

I have a 91 Lx with 145,000 and MT. I have had the car for a while, but for the last couple months, I have had a rediculous amount of carbon coming out of the exhaust. I mean it really looks like shit, there is this huge black mark the size of a basketball on the bumper and little droplets all over the taillights and trunk lid. I know Honda's always run rich but damn, not like this. My fuel economy isn't bad, about 325-350 per tank, but I literally "spit" carbon out the tailpipe. Can anyone offer any suggestions of any way to correct this problem. I'm tired of people drawing stuff on my bumper...

[DjSpeedy]

Get the timing checked. It may be retarded. Also If you havent done the belt yet now may be a good time.

[myk]

I had the same problem, mine mighta been worse, whole back end was covered in carbon build up. I also leaked oil like no other. My solution was-get a h22. When I was strippin down the f22 trying to fix the oil leak I noticed a lot of carbon build up on the 02 sensor and in the exhaust in general also my rings where bad. Not sure if cleaning that would help but it couldnt hurt and also my rings where bad and I burned oil. idk if this helps but thats my 2 cents.


hehe I always get people writing "smokey" on the back of my car.

[Accord13&BA4]

You are burning oil, more so than the average Accord...


Either opt for the h22 swap, or try to prolong your current motor...

Use Lucas oil, add a bottle to your next oil change. This should slooooow down the oil burning, but it will still burn oil mind you...

after a fresh oil change, examine the dipstick...examine the color of the oil...if it becomes black within say, 2 weeks time, you have blowby, which means your piston rings and/or cylinder walls are worn...

Can someone drive behind you to see if you puff out blue smoke?

Either it's blowby or you are running extremely rich...


good luck!

[NAiL05]

My F22A6 never left black soot. You throwing any CEL? My h22A leaves more black soot since i know its running rich whenever i get on it. (Running P28 with a really rich tune and yes i can see the black smoke). But you might just need to wash your car??? After time it kinda builds up but you never know.

[eludedU95]

My fuel economy isn't bad, about 325-350 per tank, but I literally "spit" carbon out the tailpipe.

Actually that's not that good. I can consistently get at least 475 miles to a tank. Like mentioned, it could be blow-by which would mean fuel is leaking past the rings. This would also mean oil is getting burnt as well. Do you not have any oil issues? It might also be some bad valve seals. I'm not an expert in this area so I'm just throwing some ideas out there.

[Night Wolf]

my car lets out black stuff too. also water sometimes.

[hemlockz]

look into getting a new O2 sensor, and reset your ECU cause it might be just running rich like you said...
i doubt you can fix piston rings with a bottle of anything.
techron treatment, however, is a decent bottle for cleaning carbon buildups.
oh and if its been like this for a while you should get some thread loosener and unbolt the cat to make sure it hasn't gotten clogged.

[DilutedImage]

It's also quite possible that your catalytic converter is now R.I.P.

2¢

[Xx91AccordxX]

Thanks for the suggestions people. I am planning on the h22 but for now need to maintain the f22. I did want to add that I recently did a compression test on the motor and it held 175+ in all 4 cylinders. I don't know if that can narrow it down a little in relation to determining if I have blow-by, but I guess I'll just do a cylinder leakage test. I would appreciate any more suggestions you all might have.

[lucid]

They're not cheap, but the O2 Sensor is what your car uses to decide how much gas to add. My brother's car ('97 Prelude) threw an O2 code and when he hits the gas it throws black smoke. Also when he shifts hard it spits blue smoke from oil. My '90 240 still spits after a new sensor, but not as bad. That car is flat white, which makes this suuuuuck even more, so here's a tip if you can't get that crap off with soaps, etc., try using armor all wheel cleaner, or something similar that removes brake dust- be careful and make sure it doesn't kill your clearcoat.

[hemlockz]

Thanks for the suggestions people. I am planning on the h22 but for now need to maintain the f22. I did want to add that I recently did a compression test on the motor and it held 175+ in all 4 cylinders. I don't know if that can narrow it down a little in relation to determining if I have blow-by, but I guess I'll just do a cylinder leakage test. I would appreciate any more suggestions you all might have.

you seem really set on having blowby. even after you took the compession numbers youself and posted them... you must really wish you had blowby. think about why you just tested by testing the compession then read your post. o2 sensors often need replaced. at least a lot more often than pistons rings on a 91 accord LX with ONLY 145k. but if you really want your F22 to have blowby (maybe this is to justify swapping in a $2000 used engine for a perfectly reliable and fun engine you already have...?) then boost it @14psi for a few months.

[hemlockz]

They're not cheap

\\

...saw a bosch on ebay for $40. stay away from the $20 ones where you have to wire your own harness in, you probably shouldn't try and do it yourself...

[lucid]

Yeah, I know prelude ones are $100-120 for the one with the right clip on it already. There are a lot more Accords out there, parts are likely to be a lot cheaper. I'm swapping to H23 and had to search just to find one for 100 bucks because I didn't have one at all. I bought the entire donor prelude for $500, so it seems expensive when the rest of your project is so cheap. Theory of internal combustion states that good compression and blowby may not simultaneously occupy the same cylinders at the same time lest the fabric of the universe be torn asunder. If you tear the fabric of the universe asunder with your engine I for one will be pissed

[Xx91AccordxX]

you seem really set on having blowby. even after you took the compession numbers youself and posted them... you must really wish you had blowby. think about why you just tested by testing the compession then read your post. o2 sensors often need replaced. at least a lot more often than pistons rings on a 91 accord LX with ONLY 145k. but if you really want your F22 to have blowby (maybe this is to justify swapping in a $2000 used engine for a perfectly reliable and fun engine you already have...?) then boost it @14psi for a few months.

No, I'm not set on finding blow-by as by problem, I just think its logical. And to go back to the mileage I should clarify. The car's odemeter says 140,xxx but when I bought the car the vehicle speed sensor was bad so the odemeter probably only rolled over 1 mile every 10 or 20 miles. I fixed this immediately but have no idea how long the other guy let this go on for. The car could have 200,000 + miles on it for all I know. Anyway, I don't understand the sarcasm in reference to the engine swap. Why would you perceive this as a bad idea. I think that by simply doing a motor swap and gaining almost 75 horsepower is a good thing, don't you???? Sure the f22a1 is fun but a h22a1 or h22a7 would be more fun, right...Anyway back to the problem at hand, as to other people's suggestions, I checked the ignition timing and she's right on the money so I know I'm not running retarded. My best guess is leaking valve seals or piston rings (which by the way isn't that hard for the average person to do if you understand a motor). I don't believe it's an o2 sensor because it would have thrown a CEL. But, I appreciate everyone's input, even the negative so please keep them coming. I have no problem doing whatever it takes to stop this for the time being just to save myself the embarassment of the huge black stain!