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Posted by: newto914s Sep 22 2004, 08:51 AM

I was wondering if their is anyway to manualy adjust the air/fuel mixture on a 2L with stock d-jet fuel injection. I really feel like my car is running rich and I hear a good sized sucking nose coming from my throtle plate.
It sounds and feels like my car can't breath.
Thanks

Posted by: ArtechnikA Sep 22 2004, 09:00 AM

fix whatever's broken, and the AFR will be magically correct.

likely suspects: Manifold pressure sensor, head temperature sensor, plenum temperature sensor.

Posted by: mike_the_man Sep 22 2004, 09:03 AM

Take a look through Brad Ander's web page. Pretty well everything you need to know about D-jet is explained here.

http://members.rennlist.com/pbanders/

Let us know if you have any questions after that. It should answer most of them, I hope.

Posted by: newto914s Sep 22 2004, 09:15 AM

Thanks Mike, I've seen Brad's site before. I'll take a good look this time.

Posted by: Bleyseng Sep 22 2004, 10:02 AM

Yes, it can be done but only after everything else is checked that it is working properly and in spec. This is a hard wired FI and works very well when its set up just like it was when it left the factory.
Make sure they aren't any vacuum leaks anywhere.
Make sure the FI parts match their specific year. (ECU,MPS,CHT)

Taking apart a MPS and adjusting the A/F mix can be done but its not easy.

Geoff

Posted by: mike_the_man Sep 22 2004, 10:58 AM

You can also adjust the idle mixture using the knob on the ECU. Right = richer, left = leaner. Without the right tools, adjusting the MPS is just guess work. I believe that Geoff (Bleyseng) could adjust your MPS if it comes down to that.

Posted by: newto914s Sep 22 2004, 11:18 AM

Is it possible to confuse the idle mixture knob with the idle adjustment knob(i.e. raise the idle, or appear to do so)?

I left my car at my father house for a couple of weeks and he did some work on it. He's a good mechanic(owned and mantained an old bug and a volvo p1800) and taught me a lot about cars.
I know he raise the ideal while the car was with him, it cured the stalling problem, and the car had been running more iratically before I left it with him, but in a different way(no sucking sound).

I figure he might have been turning the wrong screw to raise the idle and upset the mixture in the process, or maybe that's not possible?

Posted by: Demick Sep 22 2004, 11:21 AM

If it is running to rich or too lean, then there is probably a problem with one or more components in the FI system, or something is mismatched, or something not hooked up right.

So first make sure everything is working properly to start with.

After that - if you want to make across the board changes to the mixture, that is most easily done by altering the fuel pressure slightly. But if you want to customize the mixture at different loads, you can only do that with adjustments to the MPS - and even then you are quite limited in how the profile can be altered.

First step would be to get a wide band O2 sensor so you really know what your engine is doing. Only then can you make educated changes to the F.I. system.

Demick

Posted by: Demick Sep 22 2004, 11:25 AM

Don't be concerned too much with the sucking sound. It is simply the sound of air being sucked through the idle speed bypass port. Sometimes this can be quite noisy.

Demick

Posted by: mike_the_man Sep 22 2004, 11:33 AM

The idle adjustment screw is on the throttle body. Cranking it out will raise the idle, cranking it in will lower the idle. The idle mixture adjustement is on top of the ECU, which is located on the firewall, under the battery. It should be pretty tough to get these two confused.

Adjusting the idle mixture will definitely change the RPMs at idle though. The only way to properly set it is to use an O2 sensor, or some other type of exhaust gas analyzer.

Check all FI components and make sure there are no vaccuum leaks. Then set the idle mixture, and then you should be able to adjust the idle speed properly.

Good luck,

Posted by: Bleyseng Sep 22 2004, 11:47 AM

Posted by: newto914s Sep 22 2004, 12:49 PM

Thanks again Mike! I'm on it. I have been planning on changing all my vacuum hoses. I just haven't had a chance to go out and messure them all. It would be nice if their was a kit that had all the hoses pre-cut to the standard messurements. Right I just need to suck it up and pull out the tape measure.

Posted by: mike_the_man Sep 22 2004, 01:21 PM

I believe they have all the lengths and sizes for hoses on the Pelican site. Ahh, here it is.

http://www.pelicanparts.com/914/technical_specs/914_20FI_diag.htm

Posted by: newto914s Sep 23 2004, 06:11 AM

I've seen that diagram a million times and never noticed it had all the hose lenths under it. Thanks