Help!?

[Laird Scooby]

Originally Posted by Lolvo 940

Hi it seems to always idle around 20 on afr gauge.
Will cruise at 14.7 and 10/11 ish at wot.
So driving it seems fine its why its leaning on idle.?
Also has a brand new bosch lambda sensor with genuine plug .

Originally Posted by Laird Scooby

Where is your wideband sensor for the AFR meter located?

If your sensor is post cat, you'll get false readings, especially on idle.

[B10B]

Is your motor chipped or got an Ostrich?
Could be a bad map or something out of scope on the idle fuel/warm up fuel tables once its reached operating temp, however a redblock will not idle at an AFR of 20, even at 16 you WILL get a lean misfire.
Going over the basics may pinpoint the problem, an ARF gauge can highlight a problem so long as the sensor is not at fault which seems likely or as said wrong placement.
Lean at idle everything else ok = a vac leak after the MAF would be the next thing I'd be hunting for.

[B10B]

After my initial thoughts something else came to mind.
An exhaust leak before the sensor can give a false reading too at idle, while being masked under normal driving.
Check your manifold for any leaks or cracks and the turbo to downpipe join.

[Lolvo 940]

Hi thanks . I will check . My downpipe definitely has a couple of small leaks .
Spec for enhine as follows.
16t turbo with 3" exhaust
Kl racing intercooler.
Blue me7 injectors obvs with injector resistor mod
Gold ezk with tlao chips
Do88 hard pipes

[Laird Scooby]

Originally Posted by Lolvo 940

Hi thanks . I will check . My downpipe definitely has a couple of small leaks .

That will definitely cause a problem! As the exhaust gases go past these holes at idle, they will draw air in as well. You can prove the point using self-adhesive aluminium tape, wrap it round the holes to remove the blow and test the AFR at idle. The tape won't last long though so it is only for testing but will prove the point.

Also worth noting, if this is the case then at higher rpm the holes will still feed an apparently weaker mixture to the AFR sensor although that error will drop with load and engine speed.

[Lolvo 940]

Thanks guys.
I'm glad its just a leak in exhaust gasses now. Easy fix.
That resistor thingy was for the headlights
And I've since pulled the relay for the auto headlights and now that doesn't get hot anymore .
So now I just have side markers on until I turn the headlights on. Perfect!
Wonder if its because I'm running led h4s? (Novsight)
Either way I'm happy now. 😊

[Laird Scooby]

Originally Posted by Lolvo 940

Thanks guys.
I'm glad its just a leak in exhaust gasses now. Easy fix.
That resistor thingy was for the headlights
And I've since pulled the relay for the auto headlights and now that doesn't get hot anymore .
So now I just have side markers on until I turn the headlights on. Perfect!
Wonder if its because I'm running led h4s? (Novsight)
Either way I'm happy now. 😊

The resistor thingy was the dim-dip resistor then. They do get hot!

If you're running good LED H4s, they should only take about 2A per filament unlike their halogen counterparts which would run about 5A, if you have cheap Chinese LEDs, who knows and also they would stand a fair chance of failing the MoT on beam pattern.

Good news the lean mix was an easy fix!

[Dirty Rooster]

I'll just butt-in incase it's not solved as this symptom mirrors something I had from years ago ;

Originally Posted by Lolvo 940

Just to be clear if I disconnected the battery so it resets itself when I reconnect and start the car it will have good idle afrs until it warms up a bit then goes straight to 19/20. And from that point there after will always have chappy idle afrs. Just can't work out why ..

Now independent of injectors, mods, turbos etc
I thought it was the MAF, swapped for one I already had, didn't fix it.
Turned out to be the O2 sensor.
Bought the right looking one off evilbay for £13, fixed the problem.
Funny thing for that particular problem the Lambda light didn't come (most times) on to indicate a problem, the "codes" were useless, it was a mystery.

My downpipe was the original at that time, no holes.
I cannot imagine having a better turbo and holes in my downpipe!!

[Laird Scooby]

Originally Posted by Dirty Rooster

I'll just butt-in incase it's not solved as this symptom mirrors something I had from years ago ;

Now independent of injectors, mods, turbos etc
I thought it was the MAF, swapped for one I already had, didn't fix it.
Turned out to be the O2 sensor.
Bought the right looking one off evilbay for £13, fixed the problem.
Funny thing for that particular problem the Lambda light didn't come (most times) on to indicate a problem, the "codes" were useless, it was a mystery.

My downpipe was the original at that time, no holes.
I cannot imagine having a better turbo and holes in my downpipe!!

It seems he's found the source of the problem, holes in the downpipe pulling air in. Simple instrumentation fault, nothing wrong with how the car was running!

[B10B]

Originally Posted by Lolvo 940

Hi thanks . I will check . My downpipe definitely has a couple of small leaks .
Spec for enhine as follows.
16t turbo with 3" exhaust
Kl racing intercooler.
Blue me7 injectors obvs with injector resistor mod
Gold ezk with tlao chips
Do88 hard pipes

Happy to hear you've found the cause and are enjoying tuning it.

I'm running a similar setup but with a 19T turbo, IPD cam and custom tuning I've done myself using an Ostrich and Tuner Pro RT.
All the bins are available on Jetronic Wiki and I've had great fun and a few headaches setting everything up right, these engines are worth the relatively small outlay and are very rewarding to tune.