Mixture Adjustment On 1.9gti With Cat -is This Possible?

[Sy_ 0]

Hi All,

 

My K plate - 1.9 GTi (with cat) is running extremly rich at idle (lots of black sooty smoke) and seems to be running rich throughout the range (some black smoke when backing off). Plugs are also completely black.

 

I'm pretty new to the cat type of engine, so need to know:

 

Is the idle mixture user-adjustable, or is it totally set by the cat/ECU? I notice there's no allen key type adjustment like there is in the non-cat versions, but there is a large slot-headed screw that looks like it needs to be turned - any ideas?

 

And also, how do I find out which injection system I've got, LU-2 Jetronic, or M1.3 Motronic?

 

Cheers for any help,

 

 

Sy

[welshpug 1,657]

its not adjustable on either system, sounds like a duff Engine temp sensor or a duff Lambda sensor seeign as its smokes all the way through the range.

 

The motronic system uses the TDC sensor, though a Jetronic LU 2 equipped car may have one but only for diag purposes. (my LE 2 had one!)

 

and IIRC it says Motronic on the Motronic ECU's!

[Faz85 0]

I ran my 92 K engine which was running M1.3 management, without a lambda probe for quite some time before having it fitted into the downpipe, however I never experienced those symptoms. It did run a little bit rich (a safety precaution to protect the CAT) but didnt seem to smoke any more than it does now.

 

that screw affair is for the idle speed adjustment if i remember rightly. Also, as for adjusting the mixture, i believe this is only possible on the LE2. with the LU2 and M1.3 systems, the mix is determined by the ECU.

 

Faraz

[Sy_ 0]

Thanks for the replies, still I have a couple of questions:

 

1) so does this mean that on the cat cars there's two methods to adjust the idle (the AFM screw and the small throttle stop screw on the throttle body)?

2) the engine temp sensor - is this the one under the distributor (or at least where the distributor usually is?

 

Thanks,

 

 

Sy

[welshpug 1,657]

adjusting the afm screw wont alter the idle, as the lambda sensor will correct any changes you make (if you can alter it, which I thought you couldnt)

 

so the only place to adjust the idle is the air screw on the t/b