[16v] DPR/mixture/timing questions

[davidwinchell2 at sprynet.com (David L Winchell, II)]

Nate,

I just went through this and the list had the correct result for my problem.
Mine ran great when cold (Charleston, SC cold for less than 2 minutes after
start up.) Once up to temp, the car ran like crap.  Bogging, no power, felt
like it had lost a cylinder or two, limp mode, just ran like crap. Someone
suggested that I check the temp switch on the side of the head (I am sure I
just mislabeled that part.) Got in there and pulled the switch off the spare
head in the garage and started to pull the one off the car when I realized
the wire connecting it was just barely hanging there. I put a jumper wire in
and the problem was gone. That was the problem that Al and I had been
chasing since the 2.0L swap. It took a couple years to get the right
symptoms together to find the problem. It was that simple. 

Just something else to check that matched the symptoms you described. 

HTH,

Dave

David Winchell, II
87 2.0L 16V Scirocco
84 BBS Scirocco Turbo G60
80 Scirocco S
04 GTI R32
00 Silverado

-----Original Message-----
From: scirocco-l-bounces+davidwinchell2=sprynet.com@scirocco.org
[mailto:scirocco-l-bounces+davidwinchell2=sprynet.com@scirocco.org] On
Behalf Of Allyn
Sent: Sunday, March 05, 2006 2:51 AM
To: 'Nate Mellom'
Cc: 'Scirocco list'
Subject: RE: [16v] DPR/mixture/timing questions

Nate,
My hunch is that your current o2 is telling the ECM it's way rich, resulting
in
the computer making  the mixture as lean as possible (0mA). The spikes on
revs
are due to the enrichment that takes place during high rates of change of
air
flow sensor plate position, and happen independently of the o2 sensor input.
An
alternative to consider is that the o2 is fine, and it is actually running
way
rich (adjustment screw on air flow sensor plate is way off). As the screw is
adjusted to lean the mix, the o2 sensor voltage should lower to ~0.5v, along
with DPR current climbing above 0mA once the o2 hits the control band. If
all of
this happens (assuming o2 sensor is accurate), but the engine runs like
crap,
you will have to re-tune the other stuff (timing, etc), to correct what was
misadjusted to originally get it running with the misadjusted mixture (by
the
original dummies at the shop).
HTH
Al

 

> -----Original Message-----
> From: Nate Mellom [mailto:doubt@inwave.com] 
> Sent: Sunday, March 05, 2006 2:25 AM
> To: Allyn
> Cc: 'Scirocco list'
> Subject: Re: [16v] DPR/mixture/timing questions
> 
> Al, thanks for the tips.
> I did some more checking today, and came up with these results:
> 
> I checked the voltage coming from the O2 sensor, and as it 
> warmed up, it ramped up to 1v, and stayed there, fluctuating 
> only .1v in either direction (.9-1.1v)
> 
> I checked the O2 sensor control unit values based on Bentley, 
> which stated that between terminal 2 and 8, I should have no 
> continuity when the O2 sensor is connected to the sensor 
> lead, but I should have continuity when the O2 sensor was 
> grounded.  In both tests, I got no continuity.  I checked all 
> 3 wires on the sensor lead (it was a splice job), and all my 
> connections were tight and dry.
> 
> I reconnected my DPR harness, and again, I got no reading 
> unless I throttled the engine, where it would spike and 
> return to 0.  Even testing the O2 sensor limp-home mode per 
> Bentley (engine off, ignition on, checking for specific mAs), 
> I got no reading.
> 
> The O2 sensor I used was a new NGK (yeah, I know, I should 
> have used Bosch, but I am on a strict budget and got it for 
> $6 shipped) with a vehicle-specific connector.  I don't know 
> what vehicle it was for, but it is a 3 wire, 2 white and one 
> black, so the connections were the same.
> 
> So now, I'm thinking I have a defective O2 sensor, or at 
> least one that isn't working correctly.
> 
> I'll do some more checking, I did check the DPR and it tested 
> okay per the ohm test.
> 
> Nate
> 
> 
> Allyn wrote:
> > Nate,
> > 
> > 
> >>throw in, but what would cause a sudden loss of signal from the DPR?
> > 
> > 
> > I believe if you intermittently open the circuit, the computer goes 
> > into a failure mode where it maintains 0 mA.
> > Another alternative is that I think one of the limp-home 
> failure modes 
> > results in a constant 0mA DPR.
> > Third (not fun) alternative is that the DPR has an 
> intermittent open 
> > in the coil. It would kinda make sense, espeicially if it 
> was heat sensitive.
> > Then there was the crazy crap with Dave Winchells red 16v, 
> where the 
> > DPR had been wired BACKWARDS by someone (positive feedback in a 
> > negative feedback system is a nono).
> > 
> > 
> >>run, poorly, but run.  I don't have an adjustable advance timing 
> >>light, but a friend does, but is it necessary to get timing 
> set on a 
> >>16v?
> > 
> > 
> > I believe there is a 0 mark, as well as a 6 mark on the flywheel 
> > (opening in tranny bellhousing) - meaning you can use a 
> normal light on it.
> > 
> > 
> >>I'm going to install the new DPR and check the mixture 
> again, I've had 
> >>a sneaking suspicion that it's been bad or failing since I got the 
> >>car.
> > 
> > 
> > When I first got the rieger it was doing some funky stuff 
> like yours 
> > was. I ended up troubleshooting by swapping major 
> components (entire 
> > fuel / air handler assembly, ecu, etc). Result was that the fuel 
> > distributor was crap (uneven distribution at idle speeds).
> > 
> > HTH
> > Al
> > 
> > 
> > 


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