Technical Tickover low in MPI

[pachadwick1]

Hi there, have a 2003 MPI Sporting and the tickover runs at around 750, dipping as low as 730, sometimes 780. This seems to low and even the oil pressure warning light comes on when engine is hot and running at 730 rpm.



I think the tickover should be around 850...?


I have checked connections to the throttle body, pulled out the Sonceboz Idle Control Valve and cleaned it. I'v also disconnected the battery lead to "reset" the ECU.



Don't know what else to do...?

 

[pachadwick1]

An update on this problem. I changed the coil packs and it has made a big difference to power and throttle response. It seems that perhaps 1 of the two coil packs was degraded cause poor combustion in 2 cylinders. The idle is now rock solid but somewhat low, still probably 750RPM.

I now see the low oil pressure warning light, if I floor the throttle from idle, its very predictable, a flicker of red everytime I do it.Not sure why but I guess its an engine crankcase pressure change thing...?


In coming days I will change oil for 10W40 semi-synthetic, new filter and new oil pressure sensor then feedback.

Thanks for reading and any feedback.

 

[purf]

I would reset the ecu to let it start fresh? It might have adapted to running with a weak spark and need time to get back to normal?

Leave battery disconnected overnight

 

[pachadwick1]

Thanks for advice, I did not know I had to leave it that long. Will give it a go.

 

[pachadwick1]

I've spent more time on this issue. The idle still settles at 750 rpm. I am starting to think that the low oil pressure warning light might be a true measure. I have other symptoms which I had not connected with this before. There is a definite loud ticking or knocking on startup from cold, it goes away after a couple of minutes. Listening under the bonnet I could not identify the origin, I assumed it was something in the exhaust manifold or heatsheild that was stressing with heat expansion.


However tonight I put the car on ramps with a plan to change the oil sensor and became sure that the knocking is inside the sump. A very worrying sign that this could be rod knock or main beairng knock. That it goes away is reassuring but it could explain a lower tickover due to higher friction and it would explain lower ooil pressure. I will get a stethescope on it tomorrow.