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Posted by: porschefile2010 Jan 18 2014, 02:07 PM

Just pulled the plugs after 1500 miles on a rebuild and they are all evenly black. Can I adjust the screw on the control unit to lean it up a bit and if so which way and by how much? Thanks once again. Richard

Posted by: dlee6204 Jan 18 2014, 02:59 PM

The knob on the ECU will only adjust your mixture at idle.

Posted by: SLITS Jan 18 2014, 03:35 PM

Check your fuel pressure and ignition system.

Posted by: porschefile2010 Jan 18 2014, 03:49 PM

Thanks. So I have the idle adjustment on the throttle body screwed right in and it is still revving at 1100. Should I adjust the ECU to bring the idle down to, say 900 ? The idle at 1100 is very smooth and the engine is pulling well but I suspect is rich and using too much fuel.

Posted by: SLITS Jan 18 2014, 06:22 PM

You have a vacuum leak ..........

Leaking AAR... plug it off and see what happens

Cracked hoses

Cracked elbows that mount lines to plenum

Crack in the plenum

There are 22 clicks on the ECU from full lean to full rich. The cars I have set up are generally 11 - 13 clicks from full lean.

That otta keep you busy for a bit.

Posted by: porschefile2010 Jan 18 2014, 08:56 PM

Thanks for that. That will be really helpful. I went over all vacuum hoses earlier in the week and replaced a couple and added hose clips to them all where they were missing. So I might have a careful play with the ecu even if it's just to find out where it's set at the moment. Appreciate the help.

Posted by: boxsterfan Jan 20 2014, 11:26 AM

Have you looked at your Air Flow Sensor? Timing, dwell and spark plug gap?

How about your fuel injectors? Are they spraying a fine mist?

Here is a link to troubleshooting L-Jet systems from Bowlsby's site. Note: this is for a 912E (same motor...type IV 2.0L.)

https://bowlsby.net/914/Classic/zTN_Man08.pdf

Posted by: r_towle Jan 20 2014, 11:31 AM

1500 miles on a rebuild.
Have you done a leakdown test to see if your rings are seated properly?
How many times have you adjusted your valves in the past 1500 miles?

Rich

Posted by: Cap'n Krusty Jan 20 2014, 11:50 AM

Not gonna help a D-jet owner all that much ..................

The Cap'n

Posted by: boxsterfan Jan 20 2014, 12:00 PM

Doh!!

Posted by: porschefile2010 Jan 20 2014, 05:35 PM

Have you done a leakdown test to see if your rings are seated properly?
How many times have you adjusted your valves in the past 1500 miles?

Rich
[/quote]
Hi Rich.
Thanks for that. We did the valve adjustment after 500 miles along with an oil and filter change.
We will do another valve adjust in 1500 miles.
But I am thinking I will fix my electrical issues next as there seems to be a body of opinion that poor functioning battery/alternator issues may affect the D Jet?
The little car has a bad earth leak. So battery is in good nick but is dead after about three days sitting but ok if used every day.
Weird thing is when I shut down after a drive there sound like there is something running behind the radio somewhere. Like a whirring sound of a very small fan or similar. So I have a really good sparky looking at it tomorrow.
Also did a rough check on my mpg and in US numbers seems like about 22mpg. Not good.
Thanks for the help . Richard

Posted by: stugray Jan 20 2014, 05:40 PM

I thought that a vacuum leak would make it run lean because there is more air entering the system than is being measured so too little fuel is being added.
Just curious.

porschefile2010 - Do you have any friends with an Air Fuel Ratio meter?
You can get the kind that you just stick up the tailpipe.
That would tell you right away if you are running rich.

Posted by: porschefile2010 Jan 20 2014, 05:46 PM

Interesting. I thought than when you had a vacuum leak the sytem thought there was too much air so threw in more fuel than was needed. So I am sure someone will put us straight on that one.

I can get hold of an AFR when we do the next valve set but I can't see any other reason for the plugs to be black, exactly the same on all four. Unless it was oil coming through but it's not a heavy deposit. Also with the mpg it just seemed there was too much fuel going in.