27 replies to this topic

[craig 1010cc]

It feels like a misfire rather than a hesitation.

When the crank sensor went on my old Si, before it failed totally it caused an intermittent miss (the failure was in the wires from the connector to the sensor)

[xrocketengineer]

If it is running "fine" while cold and starts acting up once it is warmed up, it could be the O2 sensor is sending bad data. Unplug the sensor and see if it runs better without it. There is nothing to lose.

Edited by xrocketengineer, 15 April 2019 - 01:11 AM.

[craig 1010cc]

If it is running "fine" while cold and starts acting up once it is warmed up, it could be the O2 sensor is sending bad data. Unplug the sensor and see if it runs better without it. There is nothing to lose.

If the new crank sensor doesn't do the trick, then I shall give this a go. I had ruled it out as on the diagnostics it wasn't flagged or showing unusual values.

[craig 1010cc]

New crank sensor fitted. The old one did have a lot of smeg on the pickup, but same again. drives great til 75deg, then the miss (mainly on part throttle) comes back. tried unplugging the Lambda, no difference (and it does look quite new).

 

I can't help but think that the cold starting quirk is linked in that from cold it won't catch on the 1st or 2nd turn of the key.

[Wiggy]

Bit of a guessing game, but it still could quite easily be Coil Pack.

If you ignore the mystique surrounding the MEMS system, and treat it like any other car; the coil pack would be a strong shout.




But don't shout at me if it's not.

[xrocketengineer]

Bit of a guessing game, but it still could quite easily be Coil Pack.

If you ignore the mystique surrounding the MEMS system, and treat it like any other car; the coil pack would be a strong shout.




But don't shout at me if it's not.

At this point, I second the motion.....

[craig 1010cc]

New coil pack fitted the other week (not that new doesn’t mean dud)

[Steve220]

How are you measuring water temp?

[craig 1010cc]

How are you measuring water temp?

On a smiths gauge hooked into the original dial wiring. But we did check it’s readings against the values on the diagnostic kit and it was pretty accurate

[xrocketengineer]

Since the issue seems to be associated with temperature, is there an air temp sensor like in the SPI?

[craig 1010cc]

Since the issue seems to be associated with temperature, is there an air temp sensor like in the SPI?

On the MPI's they have air temp, MAP, TPS, Cam Position, crank position, Lambda, water temp and oil temp (but apparently the ECU doesn't use oil temp).

 

When we had it running on the diagnostics (all that follows are the opinions of my mate that has the kit and used it on many minis over the years), air temp looked fine, water temp looked fine (but has since been replaced as I thought I had broken it as the connector rotated), the Lambda figure looked in range (and looking recently it does look to be pretty new), MAP figures looked happy, TPS gave a full range of values.

[xrocketengineer]

My question about the air temp sensor is if the reading is fixed. Like if it is reading relatively warm (above ambient) with the engine cold possibly causing hard cold starting but and relatively warm when the engine is hot causing the other condition. If that does not pan out, then a check of the fuel pressure would be prudent. 

[craig 1010cc]

So, finally cracked it. New fuel pump and been out for a few runs now and no sign f the miss or the power loss