5kcstq low boost, sputtering-bad temp sensor?

[barry at moonbeast.com]

Thanks for the responses-
It sounds like a good idea to start looking at the pressurized intake 
components then.  My 'michelin man' hose is new, as is the thermostat, so I 
don't think those are the culprits.  Guess I'll start by looking for intake air 
leaks.

My radiator fan also comes on after every time I drive the car.  It might be 
lead-melting hot outside or so cold it's raining nitrogen, and that stupid fan 
will kick on every time it sits and idles for more than 15 or 20 seconds.  I 
take it that's NOT normal.  Would a bad multifunction temp sensor cause this?  
I keep thinking that I need to be prepared to put an engine fire out at any 
moment, 'cause that fan is gonna seize and melt my wiring.  I've GOT to get a 
fuse wired into that thing before it does just that.

Looks like an under-the-hood weekend...
-Barry


Quoting Ben Swann <benswann at comcast.net>:

> More plausible is that you have a simple intake tract leak - most likely an
> opening at the bottom of the Intercooler to Throttle body hose aka.
> "Michelin Man hose".  You often can't see these without removing the hose
> and throuroughly examining as the opening oft. occurs under a metal ring.
> 
> Don't get all complicated about the diagnosis - I always hear about clogged
> cats, but have never really seen one and I have looked at a lot of them -
> not saying it doesn't happen.  I have on the other hand seen/diagnosed these
> symptoms.  You have an intake leak which is messing with the Idle
> stabilization as well as throwing off your mixture and causing boost(metered
> air) to be bled off.
> 
> Ben
> 
> [Date: Thu, 28 Apr 2005 14:29:48 -0600
> From: barry at moonbeast.com
> Subject: 5kcstq low boost, sputtering-bad temp sensor?
> To: quattro at audifans.com
> Message-ID: <1114720188.427147bce6d90 at sec.moonbeast.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> Hey gang-
> It's been awhile since I've posted, hope everyone's doing well.  I seek your
> wisdom once more.
> 
> My '87 5k is almost sorted out now, but I've still got some gremlins that
> I'm
> trying to exorcise.  Here's the major issues:
> 
> 1. I'm consistently seeing low boost - in normal driving, not usually more
> than
> 0.9bar, and not more than 1.2bar at WOT.
> 
> 2. Sputtering at idle.  By messing with the idle adjust screw at the front
> of
> the intake manifold, I can balance it between wanting to stall and going
> into
> the infamous "idle bounce" mode where the engine speed rises, cuts out,
> falls
> then rises again (ISV and its hoses have been replaced).  The exhaust is
> sputtering at idle, even though the car is smooth on acceleration and at any
> road speed.
> 
> 3. The water temp gauge shows full cold pretty much all the time.  It has
> risen
> to half scale on occasion, but unpredictably.  Most of the time it stays
> pegged
> on full cold, even after more than an hour at highway speeds.
> 
> 4. Fuel economy is crappy- I get about 19mpg consistently, on rare occasions
> topping 20.
> 
> 
> My (admittedly inexpert) guess at this point is that the water temperature
> sensor has gone bad, and the system never gets out of "cold start" mode.
> It's
> constantly running that intake manifold injector, which makes the system
> consistently run rich, which in turn is plugging my cat.  The plugged cat is
> restricting the turbocharger spool-up and making the engine sputter at
> idle 'cause of the low exhaust airflow and rich mixture.
> 
> Does that sound plausible, or am I off my rocker?  Any insight/BTDT would be
> greatly appreciated.
> 
> Cheers!
> -Barry]
> 




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