Engine Mis Match And Warning Light

[mhyphenl 10 1 Cars]

If anyone can that probably would be the final piece of the puzzle, to be more specific:

 

I start the engine, light comes on for 5 seconds then goes off, revs at about 1200. Revs slowly drop towards 950 ish but suddenly increAse to about 1100 when the light comes on. If I Rev the engine the light goes off and revs drop to normal tickover but increase slowly I er a few seconds and light comes back on!

I need to test the valve theory first I know but I'm just trying to rationalise what the ecu is trying to do.

[jackherer 543]

Have you ever read the fault codes?

[mhyphenl 10 1 Cars]

Yes, explained in the first posts, code 52 air fuel mixture! All usual things checked / replaced

[jackherer 543]

Sorry, I missed that.

 

Overfueling or burning oil can damage lambdas so if blocking off the purge valve doesn't cure it I'd try a new lambda.

[mhyphenl 10 1 Cars]

Righto, blocked off the pipe from the valve and no difference. First time I'd starte her in a couple of weeks so sat in the car and listened to the revs carefully. Start car, light goes off, revs start to decrease from 1200 ish towards the 1000 mark over a couple of mins. At which point the revs increase again to 1250 ish over a few seconds and a few seconds after that the light comes on! Rev the car and the revs drop back to 1000 ish and light goes off, revs slowly climb back to 1100 to 1200 and light comes back on!

What kicks in 2 mins after starting that might cause revs to climb? Does the lambda work from start of after a few mins? And would that explain the pattern?

[jackherer 543]

Lambdas only work when the engine has warmed up so a few minutes is about right.

[mhyphenl 10 1 Cars]

So, lambda kicks in, revs go up then light comes on. What signal in the lambda giving for the revs to increase?

[mhyphenl 10 1 Cars]

just found this old thread which has more info than my new post which hasn't had any replies. If anyone is remotely clued in on motronic please have a look. Purge valve replaced and the issue is the same. I'll order a new lambda but as this one is only 1200 miles old can it really be the issue?? Please have a read of the whole thing guys, i really need to try and resolve this, it's driving me mad.