High Hydrocarbons

[adam quantrill]

So I have too high Hydrocarbons on the 400SX.

I haven't seen the figures yet. Any quick fixes? I was thinking:

1) check all the plugs/leads are working
2) change the oil (it is due soon anyway)
3) take it for a long drive? But I do 40 miles per day anyway.

any other ideas?

[simboy1973]

Mine was the same at MOT time. Also filled tank and put injector cleaner throug and went for a long blast.

Si

[NaCl]

Worn rings / valves?

I'll get me coat.

[adam quantrill]

Good idea - have injector cleaner in buckets full as I spotted it was being discontinued and got it for 99p a bottle.

[carsy]

Try advancing the timing a bit just for the mot. Apparently it can help.

[johntom]

Unburnt fuel would be a cause, try the plugs and leads. I had a 911sc that failed it's mot with the same, when i pulled the plugs 4 were a nice light brown and 2 were like new ! turned out to be faulty HT leads.

[mk2 24v]

just out of interest OP, what was the CO reading for the test?
as if the CO was fine and just the HC was too high, the MOT manual states that the rpm can be raised to 1500rpm and the HC checked there

otherwise, check the plug condition as mentioned already

[adam quantrill]

Not seen the numbers yet, I shall ask if they did this. But over the phone there was no complaint over CO, just HC.

[adam quantrill]

I don't think he ran with high RMP.

CO is very low - around 0.1% (limit 2.5%) HC at 2700 (1200).

The tester recommends riching it up which will burn off the HC I expect. So I'll set it up for 2% or just under.

[carsy]

Richening it a little should give a better burn and reduce the hc`s.

[chj]

adam quantrill said:

riching it up which will burn off the HC I expect. So I'll set it up for 2% or just under.

For future reference, just wondering what the best procedure is for doing that?

Thanks,
Chris

[carsy]

If you are running 14cux, non cat map, there is a co adjustment screw on the side of the air flow meter. This only affects tick over and low rpm mixture.

Have a read.

http://www.g33.co.uk/fuel_injection.htm

[adam quantrill]

4CU flapper - screw in the same - ish place though the flapper is upside down so a pig to get to.

Managed to bring it up to 1.5%CO this evening so fingers crossed for the HC.

Also did the other MOT jobs - loose headlamp, aim and steering rack 'gator so should be all roadworthy now!

[honestjohntoo]

adam quantrill said:

Managed to bring it up to 1.5%CO this evening so fingers crossed for the HC.

Not withstanding that this will be a different engine to what I have experienced, generally the bog standard flapper has never been that high, that's why its a struggle to get there. Mine is always typically in the range 0.2 - 0.4 CO.

Based on my understanding, there has to be another reason for the high HC, and to raise the CO to an unusual level for the flapper is a speculative fudge.

What else then, could create an incomplete burn resulting in high HC?

• Ignition timing would be the first place to look if the spark is coming in too early - particularly with current fuel RON availability - early detonation (not the same as pre-ignition) may be disrupting a complete burn.

• Setting the timing to avoid pinking under full load would be a solution, methinks.

• Another cause of incomplete burn might be duff spark plugs or plug gaps wrong.

• In the same way, one cylinder/spark plug misbehaving will send unburned HC in the exhaust system.

• I doubt it is plug leads, coil, amplifier, dissy, et al, but it's possible that voltage to the ignition system is compromised resulting in a weak spark throughout the system. Check for a full 12 volts when the engine is running after cranking, at coil positive.

• Then there is the possibility of an high fuel pressure upsettin g the optimum A/F mixture.

• Now we are getting into component failure and in that case only a full component check will validate them all.

• Blocked crankcase ventilation system will also upset the burn status

• Finally the possibility of the engine being coked leads to a pre-ignition situation and incomplete burn. To get a good de-coke using a special process may be the solution. See below.

So many possibilities requiring quite a few hours of validation, so perhaps the CO fudge will be quicker?

Special De-coke Process as follows

---

Steam Clean Inside the Engine - Whilst its Running

• Introduce small amounts of water continuously into the engine intake/plenum via a 1/8" dia pipe, under the influence of inlet vacuum whilst the engine is running at 1500 rpm?

• The water turns to steam inside the combustion chamber and under normal compression pressures of about 120 to 160 psi the superheated steam cleans off carbon crud from everything thereabouts.

• Including - Rings and Ring Grooves - Piston Crown - Combustion Chamber - Valve Heads - Exhaust Valve Seat Area - Exhaust Channels in Header/Manifold - Downpipes - Catalytic Converters.

• The expelled carbon residue floods out of the tailpipe into a very large black puddle.

• Keep allowing in water under the influence of vacuum until the tailpipe expels clean water. It can take as much as 20 litres.

• Evidence of how clean this can be is witnessed when removing heads when investigating a water leak into combustion chambers.

---

Shocking? Absolutely Shocking! I know it can seem that way, but there are citations on the internet

http://www.google.co.uk/#pq=internal+steam+clean+&...

One of the anecdotal experiences I have read, introduced the water using a simple pressurised garden spray.

There is even a YouTube demo.

http://www.youtube.com/watch?gl=GB&hl=en-GB&am...

If you google 'Seafoam', there is another process.

Edited by honestjohntoo on Friday 3rd August 21:48

[adam quantrill]

Well my adjustment got it up to 1.2% CO and the HC dropped to 120ppm so a pass.

I need to put together a proper air intake tube as I suspect a bit of a leak so I can't adjust it as rich as I should be able to - but that can wait for another day.