[s-cars] ping vs. rattle

Wed Jan 26 09:07:21 PST 2011

 I wouldn't spend any time trying to figure out why the engine isn't getting enough fuel, or trying to modify the ignition timing in any way.  Chances are good that if these parameters were off, you'd have a check engine light.

If this sound really is the engine pinging (detonating) under a no-load situation... in other words, it isn't some other mechanical noise... your headgasket is likely blown between 2 adjacent cylinders.

This is a fairly common failure, and the symptoms are detonation sounds, even under no load.  Keep running it, and you'll burn up the cylinder head between those cylinders.

If I were you, I'd perform a quick compression check ASAP.  If you find 2 adjacent cylinders low, you've got a headgasket problem.  The usual is #4 and #5... BTDT.  If your compression is even across all 5, be happy.

Dave

-----Original Message-----
From: Phil Mische <pmische at att.net>
To: theringmeister <theringmeister at triad.rr.com>; s-car-list-bounces <s-car-list-bounces at audifans.com>; 'james McCarthy' <jjssmccarthy at yahoo.com>; 'S-CAR list' <s-car-list at audifans.com>
Sent: Wed, Jan 26, 2011 9:52 am
Subject: Re: [s-cars] ping vs. rattle

Can get it to occur with the car stationary in neutral (clutch in) but much
> less severe (quieter).

You're right, he never specifically said idle.  Still, if the car is
stationary and in neutral with the clutch pedal down the engine is certainly
not under load. You can rev yourself silly, but if the engine is not under
load the air-fuel mixture can't be detonating.  Maybe you could induce
enough spark lead to induce a ping with no load, or have it happen with
REALLY crappy fuel or a motor that's about to seize, but that's very
unlikely what's going on here.

PJM

From: Wylie Bean [mailto:theringmeister at triad.rr.com] 
Sent: Wednesday, January 26, 2011 10:12 AM
To: Phil Mische; s-car-list-bounces at audifans.com; 'james McCarthy'; S-CAR
list
Subject: Re: [s-cars] ping vs. rattle

I don't think he ever said it happened @ idle... Only that he could make it
happen with the car stationary as well as in motion.  The way I read it, it
happens btwn 2800-3100rpm, not @ idle.

Wylie Bean
TheRingmeister at triad.rr.com
90 cq
91 90q20v
92 UrS4
08 Q7 3.6
via BlackBerryR

-----Original Message-----
From: "Phil Mische" <pmische at att.net>
Sender: s-car-list-bounces at audifans.com
Date: Wed, 26 Jan 2011 09:53:21
To: 'james McCarthy'<jjssmccarthy at yahoo.com>; <s-car-list at audifans.com>
Subject: Re: [s-cars] ping vs. rattle

Detonation only occurs when the air-fuel mixture spontaneously combusts well
in advance of when it's supposed to - it only happens under load.  Therefore
if it's making the noise with no load (at idle) it's a rattle, not pinging.

If there was fuel starvation (kinked hose) it would ping like mad at WOT.

PJM

From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com] On Behalf Of james McCarthy
Sent: Tuesday, January 25, 2011 3:38 PM
To: s-car-list at audifans.com
Subject: [s-cars] ping vs. rattle

Need the wisdom of the group.

So I'm starting to think I'm getting some pinging since replacing my fuel
pump (used a bosch OEM unit)... old pump was replaced as precaution 2 months
ago currently running RS2 turbo, MAF, injectors, EM and IA software. Not
100% convinced it started right after the pump swap but definitely not there
before.

Here are the symptoms -
At approximately 2800-3100 with moderate tip in of the throttle I get a loud
rattle (machine gun/ rattle snake) that I can sustain but starts to fade if
I hold it. Can also get to to occur at higher RPM but with less consistency.
Rarely hear it with WOT...

Can get it to occur with the car stationary in neutral (clutch in) but much
less severe (quieter).

No change in Peak boost smooth throttle with no hesitation even with WOT.

So I feel like I might have have had occasional backfire when letting of the
throttle complete and quickly after WOT (but that would be a symptom of
running rich correct???

No exhaust problems I can see (stroumng unit) BPV is forge unit and holds
vacuum. I actually pulled the cat/ center section off this weekend - no
rattle and the cat is perfect.

So I'm wondering of the "new unit" is a bit anemic??? - consider replacement
- but why would this come up now - running the same setup for 2 years (no
previous pinging).

If I go with the 005 or 044 - is the noise going to make me nuts?

Will dive back into the tank to make sure hose isn't kinked somehow...

No codes.

Any other thoughts?

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