E30 Zone

Got my 318iS tested today at the local garage in preparation for the NCT(Irish MOT). The CO level is fine (0.120) but the HC count is through the roof at 2302 ppm. The mechanic recons its due to unburnt fuel and there is a strong whiff of fuel off the exhaust, but he also said it might be oil, which would mean engine wear

He thinks it could be down to spark plugs or leads and its due for a full service next week. Because the CO was fine he thinks the O2 sensor and exhaust is OK.

Has anyone had this issue, or have any ideas on what should cure it?

Thanks,
Kevin.

Assume that the garage chap tweaked the grub screw in the air intake housing? Normally when these guys have your car hooked up to the gas analyzer, you can adjust the hydro carbon percentage by turning the screw to suit, takes them minutes to do with a nicely warmed up engine - that's the other secret - engine must be 8 miles plus running temperature so that everything settles down on idle.
If you want to detect burning oil - check the plugs: black and greasy then oil in the combustion chamber.
Regards,
pm9575

firstly your CO is 0.12, and the HC being high means, to me at least that the mix is lean as hell, not enough fuel to properly combust hence the high HC readings

are you sure you have a cat equipped iS, most were cat ready but never had one fitted

have a look at your airflow meter dude, if it has the trim pot ajusting screw next to the electrical connector, get the idle CO put up to 0.3 and see what the state of the HC is

leads will be fine, not changed any yet, plenty of coil packs though ( missfire)

if your car is due a fresh dose of oil the crankcase breather can push the HC high simply because the oil is contaminated with unburnt fuel from cold starts etc

get the full emission sheet and post up all the readings dude, before you spend a fortune !

Thanks for the tips guys. I just checked a couple of the spark plugs. Compared them with the Champion guide in the back of the Haynes Manual and they are 'Normal', so I guess this can rule out bore wear?

The plugs look reasonably new and the leads look in good shape also, but I'll get the plugs changed along with oil and filters anyway. There is a slight leak of oil on the top of the engine and a trickle has seemed down towards the plugs, but none on the core or electrode. There was also a slight coating on the plug threads. Not sure if this is from the tricke downwards or if whoever changed them before did this to keep them from seizing in the engine head.

I'll get the mechanic to adjust CO settings firstly and see how it goes.

Thanks again. It's level headed info from E30 Zone members that keeps me from pulling out what little hair I have left!
I'm hoping that I'm near the end of jobs required on this car to get it through the NCT.


Kevin.

Did some reading up on high HC levels and some websites point towards misfires. Would the coilpack be the likely culprit here? Is there a way to check if this is the cause? Can vacuum leaks cause misfires also?

My Sport failed it's MOT on Monday due to high a CO count. It was 5.5%

A quick fiddle with the mixture adjustment brought it down to 3% on which it passed.

Just my input...