stumped

[Mike Miller]

UPDATE: I replaced the plugs and it made no difference. Put my inductive pick up timing light on each plug wire and watched it fire. # 4 did not fire at all. I replaced that wire and it now fires and the car runs better. It still misses under load though. Kent suggested looking at the engine when running when it gets dark - I'll try that tonight and see what I can (or cannot) see.  

I still don't understand why boost is comng on so early. I used to see 1.7 bar max at this altitude - now I see 1.8 at way less than 1/4 throttle. I still wonder about a clogged Cat. Bypass valve, MAF, WGFV have all been replaced. Chipped ECU removed and replaced with a stock one. None of that made any difference - although I replaced those for a _low_ boost problem that went away when it started to miss under load. 

mike

----- Original Message ----- 
From: Bernie Benz 
To: Mike Miller 
Cc: 200q20V mailing list 
Sent: Wednesday, February 24, 2010 3:50 PM
Subject: Re: stumped


Mike,
  I’ll add to the ignition consensus. BTDT. Unhook one plug wire at a  
time and test. When one unhook makes no difference you‘ve found the  
right line. Move that plug to another cylinder or replace that high  
tension wire, etc.
My problem was one bad plug, no visible problem with it. Replaced the  
one plug and all are going strong at 225K. Those stock Pt plugs are  
great, last for ever. I’ll use them in the A6 2.7T if I ever need to  
replace the cheap original stuff.

Bernie

On Feb 24, 2010, at 12:33 PM, Mike Miller wrote:

> I've been chasing a bad miss problem for a while. I seems to be  
> getting
> worse. Spark plugs  all look good and I've swapped out the wires. I've
> replaced the MAF and ECU (now stock) and have no vacuum leaks. I  
> can make
> full boost according to the dash gauge and I can hit high RPMs.  
> (6000+). The
> car runs smoother above 3k rpm. I am getting 1.6 boost at about 1/8th
> throttle and can make the boost jump in neutral up to 1.1 (.8 is  
> normal for
> my altitude (4800ft) with the engine off/ingntion on).
>
> At slight throttle, there is a steady miss that magnifies as the  
> throttle is
> increased. The miss is worse the higher the gear. There is no miss  
> when the
> throttle is lifted. Initially, as long as I kept boost under 1.0,  
> it ran
> fine but now it is missing even at .8 bar.
>
> I'm wondering if the Cat is clogged - thoughts?? That might explain  
> the
> abnormally high boost with very little throttle. It holds about  
> 1.6/1.7 from
> about 1/8th throttle clear to about 7/8ths (don't feel any  
> acceleration
> change) - WOT will then push it up to 1.8.
>
> mike
>
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