96 Prelude black smoke @ 3500 RPM - Honda Prelude Forum

Denver96lude · 07-31-2011, 01:17 PM

Hey guys been lurking for a few weeks reading up on Preludes....great forum

I just bought this 2.3L gem from a tow yard for $500 - anyway I have read here and on other forums people say "don't worry about black smoke, Hondas always run rich" but nothing about how to fix this problem. In Denver any visible smoke is an AUTOMATIC emission failure. I'd be really sad to have to sell it ...any help is appreciated.

Also I have already done the following which has helped some but not eliminated the problem:

Seafoamed
Oil Change
Changed Plugs/Wires
Changed PCV
Changed Air Fiter

Thanks again

minilogoguy18 · 07-31-2011, 01:45 PM

CEL on? CEL light work? Catalyst in good condition?

Denver96lude · 07-31-2011, 01:54 PM

Quote:

Originally Posted by minilogoguy18

CEL on? CEL light work? Catalyst in good condition?

CEL is not on, haven't looked into checking to see if works? Guess I'll have to search that....Cat is visibly okay and passed the "Pep Boys exhaust inspection" when I took it in for an alignment

Denver96lude · 07-31-2011, 01:56 PM

BTW I forgot to mention that it does very much smell like fuel when I hit 3500 RPM and the plugs when I changed them were soot fouled -- all 4

minilogoguy18 · 07-31-2011, 02:10 PM

^You know they only visually inspect it if even that, how does the exhaust sound?

You can do a light check by just turning on the car, all lights on dash should light up at the turn of the key to the ON position. Just suggested it since I've seen a lot of older cars that had the CEL bulb removed from the dash to get someone to buy it thinking it was in good running order.

Denver96lude · 07-31-2011, 02:17 PM

Quote:

Originally Posted by minilogoguy18

^You know they only visually inspect it if even that, how does the exhaust sound?

You can do a light check by just turning on the car, all lights on dash should light up at the turn of the key to the ON position. Just suggested it since I've seen a lot of older cars that had the CEL bulb removed from the dash to get someone to buy it thinking it was in good running order.

I have to preface my response about the exhaust with I know very little about exhaust systems - It sounds "normal" to me, it has an aftermarket muffler on it that makes it sound louder than a stock muffler and it does have headers but from what I can tell the rest of the exhaust is stock

the CEL does come on then go off in the on position

minilogoguy18 · 07-31-2011, 02:26 PM

The aftermarket exhaust could be the problem, the O2 sensor thinks that the air flow through the engine is increased and could be adding more fuel to try to make up for it even though only the exhaust flow rate has been increased.

Denver96lude · 07-31-2011, 02:53 PM

Quote:

Originally Posted by minilogoguy18

The aftermarket exhaust could be the problem, the O2 sensor thinks that the air flow through the engine is increased and could be adding more fuel to try to make up for it even though only the exhaust flow rate has been increased.

And the only fix is to go back to a stock set up or *could* replacing the O2 sensor fix the problem?

THATGREENLUDE · 07-31-2011, 03:38 PM

Its the o2 sensor...... You can run just the down pipe with that motor if you have a good o2 sensor. Its the most sensitive sensor of all the sensors on you engine and they are cheap enough to replace with out spending time testing them with a high-impedance DC voltmeter measuring the output voltage if they look old enough and its a motor you just purchased.

Denver96lude · 08-01-2011, 03:09 AM

So went over to a friends house who is more of a mechanic than I and found the following...

MAP sensor had a couple of wires clipped and just wrapped back into electricians tape

3 vacuum lines that were disconnected

the Cat is completely shot from running so rich for so long

flex pipe is cracked

good news is that it doesn't smoke until 4500 RPM's now, its still all black

Compression test on all four cylinders is 150 which is in range 135-180

Now I have an intermittent idle bounce from 1000 to 1500

minilogoguy18 · 08-01-2011, 09:14 AM

Well does the idle bounce when the engine is cold and stops after it reaches operating temp or is it all the time?

Denver96lude · 08-02-2011, 01:22 AM

Quote:

Originally Posted by minilogoguy18

Well does the idle bounce when the engine is cold and stops after it reaches operating temp or is it all the time?

Seems to only happen when warm but isn't always present - when it does happen I can usually step on the accelerator a little and "feather" it out at 1100 RPM

Also will replacing the cat further reduce black smoke? I'm wondering if the soot buildup in the tailpipe is some of the black smoke I am seeing...

Denver96lude · 08-02-2011, 02:05 AM

Any ideas on where this vacuum line is supposed to go? I have included 3 pics since the line runs back to a main line and I show both ends of that main line

minilogoguy18 · 08-02-2011, 05:14 AM

It's for your cruise control, there is a vacuum box inside the fender that the hose plugs into, you should be able to see the hole where it passes through the frame next to the CC.

Tyknowlden · 08-10-2011, 11:02 AM

omg!! change that alt and p/s belt! haha

samurhai · 08-11-2011, 02:48 AM

you don't need cruise control. those lines shouldn't be effecting your idle or your black smoke problem. clean your iavc and fitv for the idle bounce problem