Elise S2 111S Idle Issues And Dropping Revs

[un1eash]

I get my k series lambda's from a guy on ebay called a5803, £33 delivered for genuine bosch items. The post cat sensor does nothing but tell the ecu if the cat is working. The car will run with the pre cat sensor disconnected, it'll just be a little rich as it wont be trimming the fuel.

[111rdw]

Maybe not helping but I had a K06a (retains the VVC mechs) and the idle was never perfect. Changed the IVAC a couple of times because the first one make no difference at all. With the second one it worked sometimes - stopping and restarting often fixed it. Bit of a pain but I lived with it.

[glitch]

Thanks un1eash. Rimmerbros did a decent price so I ordered 2 there. I'll try your guy next time:)

 

111rdw that's interesting. I have tried two iacv with no difference in idle. Starting to think might actually need a programmable ecu...waiting to see what mechanic says after trying the new lambda.

[Wildspark]

Maybe try disconnecting the iacv when the engine is warm, in case it is hunting around when it shouldn't be? If you pull the plug when the idle is good and it stays good that would suggest the iacv is causing the hunting? Just throwing ideas out here....

[glitch]

Hi Wildspark, already tried that.

 

If I have it running on idle and disconnect IACV the car stalls and won't restart.

If I disconnect while running and give it some throttle the rpms still dip.

[Wildspark]

It does seem like my  S2 111S has a mild version of what yours has.

When cold the idle is fine, but when warmed up the idle is more lumpy. It sits at about 800 but then dips momentarily to about 500 before recovering. That cycle repeats about every 10-20 seconds or so.

I've now got an ODB2 bluetooth sender so I plan to look at what's going on with things like the fuel trim.

 

I'll let you know if I find anything else.

[glitch]

It does seem like my  S2 111S has a mild version of what yours has.

When cold the idle is fine, but when warmed up the idle is more lumpy. It sits at about 800 but then dips momentarily to about 500 before recovering. That cycle repeats about every 10-20 seconds or so.

I've now got an ODB2 bluetooth sender so I plan to look at what's going on with things like the fuel trim.

 

I'll let you know if I find anything else.

 

Yeah that's exactly the behaviour I have on idle. No fault code, but I bet you will see similar trend as me on short term fuel trim with significant spikes.

[Wildspark]

Doesn't seem to do what yours does at higher revs though. Smooth all through the rev range with no dips or hesitation, at least not yet.

 

I had a general search for k series idle problems and an mg owner had similar symptoms where his was cured by a Bosch o2 sensor. Apparently there is a heater that goes wrong and the cheap alternatives are not so good?

I know very little about it, but if there is a separate electrical heater, maybe the wire to that Is faulty?

 

Time for more reading!

[Wildspark]

This site;

http://www.lambdapower.co.uk/diagnosis/diagnostic_index.asp#q2

Suggests a faulty sensor, but then I guess it would.

 

Probably worth checking the output with a scope anyway.

Interesting about the ecu jumping in and out of closed loop control.

[un1eash]

You can simply check the o2 sensor with a obd2 bluetooth adaptor and torque for android. To test the heater circuit of the sensor this can be done with a voltmeter but will throw an error if it's not working.

The engine runs closed loop when the revs are constant and takes readings from the o2 to adjust the fueling. When accelerating the engine runs open loop and the o2 sensor doesn't come into play.

This is why I asked if it plays up at constant revs, eg 3k rpm.

[glitch]

Torque doesn't work with my elise. It can't find the device. But odb doctor worked and this is the reading i got. From what i understood it should oscillate between 0.1 and 0.9. Maybe its a bit low?

[Wildspark]

I've just run my car up and plugged in the OBD2 bluetooth unit. Not really sure how to get the same graph as on OBD Car Doctor when using Torque pro, but I did get a similar graph from the "Tests" area on Torque. The O2 bank 1 sensor 1 seemed to go from 0.1 to 0.9 like it's supposed to. Sorry, didn't get a screen shot this time.

 

It might be my imagination but the idle did seem to improve a bit while it was sitting there warming up.

[un1eash]

Torque doesn't work with my elise. It can't find the device. But odb doctor worked and this is the reading i got. From what i understood it should oscillate between 0.1 and 0.9. Maybe its a bit low?

That looks fine, it's more 0.8 it flicks between. If it was faulty it would be all over the place.

[Wildspark]

Having done some trawling on the subject of k series idle problems, one point that seems to come up is if the battery is on its way out.

I know that if you disconnect the battery the ecu has to-learn some settings, so I guess a dodgy battery can go to such a low voltage when starting that the ecu glitches and has to re-learn. Poor earth bonds can have a similar effect I guess?

 

Is there a description of the k4 ecu for the S2 111s anywhere?

[Martin R]

I have just read your post on SELOC. You say it ran ok till the cam belt was changed? Were both belts changed? Cam and rear VVC timing belt? If that is correct remove the front and BACK belt covers and check the timing marks line up as per the manual.