Puff of black smoke when throttle pressed

blackbox · 01-11-2015 6:17pm #1

I've installed a replacement (used) engine in Kermit, my green MR2, and mostly he is running fine.

However, when I gun the throttle, there is a slight hesitation followed by a puff of black smoke when it picks up.

There are no fault codes showing.

The car definitely needs to have the plugs replaced, but could there be something else causing this?

Hal1 · 01-11-2015 6:32pm

It's carbon build up. Might be worth getting it terracleaned. http://www.terracleanireland.ie/
I would get a service done in the mean time.

blackbox · 01-11-2015 7:30pm

That Terraclean is a bit pricey - I know people who had it done and saw no improvement (maybe they didn't have carbon to start with!).

I'll change the plugs and I might try Redex.

Another fact - the petrol in the car could be more than a year old - could this be a factor?

Hal1 · 01-11-2015 7:39pm

Yeah I'd drain the tank and put in a new fuel filter. The terraclean was about €120 when I got it done. I think it's cheaper for petrol cars.

Waterson · 02-11-2015 9:52am

hi OP, is it the normally aspirated engine or the turbo charged one? Black smoke is usually indicative of an over fuelling issue. Does she idle steadily or do the revs fluctuate. coupled with the hesitation, it might be an idea to check the fuel system for correct operation...air mass meter and lambda sensor readings might shed some light.

blackbox · 02-11-2015 4:59pm

It's normally aspirated. It was idling fast and irregularly, but that stopped after some serious gunning of throttle. Now idling perfectly. Mixture seems fine except when blipping throttle. No OBD faults logged. Lambda voltages look to be oscillating in normal ranges.

Waterson · 02-11-2015 7:15pm

ok, if you have access to a scantool rthat can log live data, try checking fuel trim percentages. roughly + or - 10 % when idling and at say 3000 RPM is what you would want to see. If these are fine, try checking the plugs are gapped correctly and are the right colour. heavy black carbon deposts would again indicate a rich mix

blackbox · 04-11-2015 3:16pm

Thanks Waterson. I'll try the high idle trim voltage test at the weekend. I should have new plugs by then.

blackbox · 16-11-2015 1:27pm

Changed the plugs and no improvement.
Didn't get to check trim voltages yet.
Added Redex injector cleaner, but as car is not taxed I can only drive it on private lane so probably not enough use to make any difference.
Going to try cleaning throttle body and maybe exchange MAF next weekend.

Puff of black smoke when throttle pressed

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