NF engine running too lean

[Eyvind E. Spangen]

Thanks a lot! Now I went to the junkyard and pulled a DPR from a car there.
I was thinking about pulling the whole metering head/air flow plate thing,
but it was just too messed up with connectors left open etc, so I left it
alone, only got the DPR, which was not messed with like the one I had on my
car.

I installed this, and now the car feels a lot better and has got almost
perfect CO content. But when driving, it's too lean. The car lacks a lot of
power and feels like it's slightly missing. If I try going up a hill in 5th
at about 60 mph, it almost won't keep the speed.. I tried richening the
mixture almost 1/4 turn, but that was far too much. Tried 1/8 turn and did
not feel very much difference at all. I have the Bentley manual and will try
all the measurements there, but it is kinda weird that the car is running so
lean, but richening the mixture makes no difference until it gets to 1/4
turn and far too rich.. With the old DPR, the car was running far too rich,
CO content over 10%, but it had the correct power. Now it's slower than a
school bus.. :P

I tried measuring the DPR current using some cables I made. I'm sure they
are working and connected the right way, I set my multimeter to 200 mA, but
I got nothing except 0.00 anyway. Will the current stay at 0.00 all the time
if the car stays in open loop?

-- 
E. Spangen



-----Original Message-----
From: quattro-bounces at audifans.com [mailto:quattro-bounces at audifans.com] On
Behalf Of syljay at optonline.net
Sent: 20. september 2007 05:59
To: quattro at audifans.com
Cc: magliocc at rocketmail.com
Subject: Re: adjusting engine rich/lean

>>From: William Magliocco <magliocc at rocketmail.com>>
>>Does the engine have a good O2 sensor (if it has one>at all, I am not
familiar with the Euro specimens)?
>>If so, you should be able to rough it in with a
>>digital volt meter on the output of the O2 sensor. 
>>You are looking for 0.4 to 0.5 VDC if you are at>stochiometric (14.7:1)
ratio.>
>>You could also disconnect the black lead of the 02
>>sensor; this would put approx. 0.5 VDC on the computer
>>input.  Hook the meter up to the O2 lead you just>disconnected and adjust
the flow plate for the 0.5VDC level.

>***** I also set up the basic idle mixture this way.I disconnect the O2
sensor wire from the harness and attach the voltmeter to the O2 sensor.
>I pull the plug on the DPR also as I do not want the computer messing with
the mixture. You are basically in limp-home mode at this point. But what the
hell, it cant hurt to pull the DPR plug.
>Then I set the mixture using the voltmeter. It takes a bit of doing as the
adjustment is pretty touchy and the O2 sensor is REAL sensitive at
stoichiometric.
>You don't have to be dead-nuts accurate here as long as you get the reading
in "the window" . . the range within which the computer can make adjustments
with the DPR.
>I've had a situation where the idle mix setting was just at the edge of the
operating window. From a cold start, the system never went into closed loop
mode . . .the mix was just too lean and the DPR could not drag it into
Stoich. 
>However, after a good warmup, the system went into closed loop mode. But,
more often than not, the system would go into open loop during idle. At
RPM's over 1500, the system would go closed loop.
>The fix for the problem was to richen up the mixture just a wee bit.

>After the adjustment, you can confirm the setting by measuring DPR current,
which should swing around 0 ma as Huw mentioned.
>Also test from a cold start. Time how long it takes for the DPR current to
start swinging. I think the time was about 3 minutes for the O2 sensor to
get hot enough to start working.
 

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