[V8] Do bad/dirty sensors always throw codes?

[urq]

Since you have parts to swap ... one of the first things I'd recommend is
the MAF ... this thing is the heart of the engine management system, and I
know I haven't seen much discussion about failure modes and replacements.
It so happens that #344 has not been in for its smog test because I'm pretty
sure it will fail.  This car gets the same service as #2, but it has always
gotten worse fuel mileage in comparison.  I have looked at the engine temp
reported by the ECU, and it seems to be right.  

To be honest, I would be a bit surprised to hear about TPS issues impacting
5-speeds ... as it is just a couple switches that the ECU reads.  

Steve B
San Jose, CA (USA)

-----Original Message-----

My engine has loped noticeably since I bought it in 1999.  It has never run
right.  

Before I bought it, the timing belt broke and the engine was repaired.  The
caliber of workmanship I have found throughout the engine compartment is
horrendous.  This led me to believe that the timing belt repair was equally
poor and I might still have a nicked valve or valve seat or who knows what.


Now I'm starting to rethink this.  The symptoms that Sam is reporting are
very similar.  I have thought about doing some parts swapping, one by one
with my 90 V8q, but have never done so.  It runs very well.  I think I may
make a day of it and start swapping things to see if I find anything.  

I have a cheap code reader and got a code on the 5spd for hall sender or
something.  I guess I could start there...swap the distributor out.  I think
I can use one from a 4.2 car too, right?

Ed



> -----Original Message-----
> From: v8-bounces at audifans.com 
> [mailto:v8-bounces at audifans.com] On Behalf Of Karl Middlebrooks
> Sent: Wednesday, February 18, 2009 1:22 PM
> To: Audi V8Q Mailing list
> Subject: [V8] Do bad/dirty sensors always throw codes?
> 
> 
> On V8 #2, my starting point was a car that got 10mpg, was as 
> loud as a Harley, little power on acceleration, and it just 
> feels like the engine is missing.
> 
> After working on the exhaust (replaced clogged cats and rusty 
> exhaust pipe), swapping out the FPR, and disconnecting the 
> OXS, among other things, the car now gets 14.3mpg in town and 
> has more power, but it's still not right. Still lopes a 
> little and feels like it's missing on acceleration, though 
> appears to run smoothly once up to speed.
> 
> Only code I've ever gotten is 2341. After disconnecting the 
> OXS, I get 2342 (which sounds like what I should expect with 
> the OXS disconnected).
> 
> Other folks with similar performance problems have 
> replaced/cleaned the MAF and coolant temp sensors, according 
> to the archives. However, I'm not getting codes for either of 
> these. Is it possible that the sensors are contributing to 
> the problem, but not enough to result in a code? 
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