mx5cartalk.com

I let my cousin drive my car this afternoon so I could hear what it sounded like from outside the car (he didnt go through a fence this time).

It sounded a bit better than I was expecting, but as he booted it past me it seemed to be blowing a lot of unburnt fuel out the exhaust... How do I make it run a bit leaner? Air filter is only a few months old

Steve 818 wrote:If you want to lean out the fuel mixture you will need to install a Jaycar digital fuel adjuster or an aftermarket ECU.

Or fix the problem that is causing it....

At the very least do an ECU self diagnosis test to check that all sensors are functioning correctly. It could be caused by an air leak post afm, faulty water temp sensor, faulty MAP sensor if NA's have these, faulty cold start valve, incorrect timing, poor leads, incorrect plugs etc. The list goes on, and on, and on! Ideally get it on a dyno if you're concerned.

It could even be just a fuel dump scenario the computer uses at WOT at high revs, which if was the case would be perfectly normal - nothing to worry about.

If the car is running poorly, and using a heap of fuel all the time, then have a close look at it, otherwise it's probably fairly normal. It doesn't hurt to run a little rich at WOT - acts as a safety barrier.

maybe catconverter? adjusting the timing would probably let it use fuel more effectively.

mine has some issues with white/light greyish smoke on cold starts if i keep it revving. astro has witnessed mine blowing a heap of black smoke before, has since then replaced the O2 sensor so i dunno if it still happens on a hot engine.

237,000ks so i gather mines probably heading towards the time a rebuild would be nice (might have some other internal work done at that time too)

Steve 818 wrote: Have you diagnosed that there are problems with his car?

No, but I'm not jumping to conclusions like you were Steve. The black smoke he diagnosed could be caused by a number of things. Posting a reply as you did, to go out and spend some money to fiddle with the mixtures is at best a stop gap measure, and that's if it was the ECU programming that was the problem. Using an aftermarket ECU or one of those Jaycar products could fix the mixtures by masking another problem, but where's the solution in that? The cause of the problem will still exist.

There is no point fiddling with mixtures if there are other problems which are causing the rich mixtures to occur in the first place.

Your post had no constructive advice for the original poster. If he was to take your advice, he would have rushed out and spent untold dollars on an aftermarket ECU, only to find that the problem could have been solved by replacing a faulty sensor for a fraction of the cost and hassle. At least by running a self diagnosis of the ECU, sensor problems could have been either ruled out, or diagnosed for no cost at all and minimal time. He could then take whatever action he chose.

I think you're both right (spineless wimp that I am).

The OP did ask how to lean out the mixture, Steve told him.

However, I'm with NMX in targetting the questions the OP should have asked:

1) Is there a problem?
2) If so what is the problem?
3) Then and only then, how do I fix it?

Cheers,
Alf.

Adam_NAclubman wrote:It sounded a bit better than I was expecting, but as he booted it past me it seemed to be blowing a lot of unburnt fuel out the exhaust... How do I make it run a bit leaner?

Is the car using an excessive amount of fuel? Or are you losing power?

I'm just trying to work out what you are concerned about. If it is just a bit of black smoke I wouldn't really worry. Tell us if there are any other symptoms...

Ok, I'll write a longer post then :p

My Clubman has the timing advanced 2 degrees, pod, fairly (well... very) open exhaust and had new leads 8 months ago. Plugs are gapped correctly.

Every tank I get somewhere between 10.7L/100km and 12.7L/100km. This is quite a bit more than everyone else reports getting in their NA8's. I don't think its my driving as I always got 10-12L/100km in my DR30 which was heavier and substantially more powerful.

When Clubmanmc and I both had our cars on the same dyno on the same day (his with twice the kms mine has, pod and timing, mine with advanced timing, stock intake and exhaust) his made 15% more power than mine, graphs were basically the same shape, just mine was lower

My car pops and farts when engine braking which I did think was maybe from an exhaust leak but now I've got a feeling it's just hot exhaust and unburnt fuel. There is a big fuel stain on my rear bumper above the exhaust.

It runs rich.

It wasn't 'just a bit of black smoke', it was a LOT of black smoke

Ok fair enough Steve, I see your point.

What I picked up on was his comment \"as he booted it past me it seemed to be blowing a lot of unburnt fuel out the exhaust\". My response was in relation to that, and the assumption that he then wanted to remedy that situation, which could have been caused by numerous things. As opposed to your take on his specific question of \"how do I lean the mixtures\"

My initial 'rolls eyes' re-action to your post was in part as a result of my experiences with so called tuning and turbo experts these days who just say \"yeah mate, throw an aftermarket ECU on her, that'll sort it\" and then the poor old guy who trusts what these guys say, pays his $2k and drives away in a car which isn't much improved than before he drove it in there. I've seen this happen all too often and frankly, it really pisses me off.

I apologise if you were offended by my post Steve, that wasn't my intention.

Cheers

Gerard

could the TPS position be causing the problems with Adam's clubman?

ive played around with the TPS on our 5 in the past and noticed with the changes came farting on deceleration and higher fuel consumption and vice versa.

This is a difficult one because, like NMX516 said, there are a heap of things that could be causing it. It is most probably a sensor problem telling the ecu to put in more fuel...

I think the first thing to do would be to run an ecu self-test, as stated above. That will let you know if the ecu thinks there is a problem. Then start looking at things like airflow meter, O2 sensor, knock sensor, check the intake carefully for air leaks after the afm. Look at all of the air sense lines coming off the intake manifold and make sure they are still attached and not leaking. Get a timing light and double-check the timing.

Is there anything else unusual that would point to a cause like high idle or difficulty starting?

Anyone else got any other suggestions?

Idle isnt high, starts easily

Timing was set with timing light a couple of months ago

Adam_NAclubman wrote:When Clubmanmc and I both had our cars on the same dyno on the same day (his with twice the kms mine has, pod and timing, mine with advanced timing, stock intake and exhaust) his made 15% more power than mine, graphs were basically the same shape, just mine was lower

Hey Adam, did/ does the graph show the AFR?

Nah, its power and torque

the fact that the original poster has aid that hes not running a Cat and the fact that stock ECU'd Na's run super rich...( under 11:1 at some rev points) is probably the reason its blowing \"smoke\"........ put a cat in it and have a nice clean bumper!

When did I say theres no cat? Theres standard headers, cat, then an open exhaust with no resonator and a muffler that does pretty much nothing.

And it definitely is blowing lots of unburnt fuel out the back, this photo was a couple of days after washing the car