[thomash]

Hi,

I need some advice regarding my Sporttronic which has a low and lumpy idle when warm, doesn't pull clean from low rpm. I just doesn't feel right. When the car is started from cold it has a lovely steady idle at around 900 rpm and when giving it the boot it pulls clean without any hesitation all the way through the rpm range. Sometimes it can leave a misfire cylinder 1 error code when pushed really hard (but not in a while).

Things checked so far:
ECU-resetted (a few times)
Timing checked with correct cam locks
Lambdas disconnected (throws an error but doesn't affect idle)
New MAF fitted (runs smoother but not smooth enough)
New NGK sparkplugs fitted
Coils switched without any change
Sprayed for air leaks using start gas to no avail
Changed throttle body

So any pointers to what I should be upsetting the wife by doing next?

 

[ChrisS]

Did you do a compression check when you replaced the spark plugs? Might be a clue in those results.

Crank position sensors can play up when hot. At least check that the area round the sensor is clean - they tend to get pretty messed up down there, particularly if the rear crank oil seal is weeping a bit (like they do).

Sounds like you've done most of the usual checks already though.

 

[thomash]

I changed the crank position sensor... No change at all. So I changed the engine wiring loom... Strangely enough that seemed to have effect. The idle is steady and not lumpy any more, but now I can feel that I have a coil/spark plug that isn't firing 100% of the time. Oh joy...

 

[mgbglasgow]

Maf bud, readings from maf are ignored when engine is cold, ecu in open loop mode, then when warm it uses maf readings, so its the maf,,,,,, check inlet tract etc for good seals and no splits first,,,,

 

[ChrisS]

Not convinced about that notion really, and a new MAF already tried....so, how about lambda? If it's bad or going that way, that would mess up warm idle for sure. A cold lambda is most definitely ignored as they don't output any signal at all until they warm up, although the probes on these do have heaters so they should produce a valid signal pretty quickly. Normal warm up enrichment will tend to mask some issues so it's a tricky one to diagnose.

 

[mgbglasgow]

And it wont be happy wae lambdas disconnected, why are they?

 

[mgbglasgow]

Maybe a scan would show something useful...

 

[mgbglasgow]

Had lumpy idle,, replaced all inlets yesterday for autolusson on the 166, sweet as a nut,,,, from a software point of view it screems maf, but id put system back to original,ie lambdas plugged in, would be good to have another 166 to swap mafs over, seen some **** out the box, especially the 26 quid ebay ones,,,