Boost problems

[Todd Phenneger]

   Ameer Antar <ameer at snet.net> wrote: 

so how do you know what yer mixture is. A great diagnostic tool is a 
air-fuel ratio gauge. It will tell you everything about the fuel system. 

Hmmm,  I think I'll add a note to my Sig File.  I DO have a Mixture Gauge.  Thats how I know.  ANd I know where it should sit under full boost.


That's not true about leaks causing rich running. That's only true above 
1.0 bar. Air will be sucked in to the engine thru the leak which was not 
measured by air flow sensor. Beyond 1.0 bar, there is more pressure in the 
intake system, so rather than outisde or false air entering the engine, it 
actually is escaping into the lower pressure atmosphere. Most people run 
under 1.0 bar, so as long as you're not under boost, leaks before or after 
the turbo cause lean running. Above 1.0 bar leaks after the turbo causes a 
slight rich mixture and low boost pressure.

     Exactly,  and leaning only happens above 3kRPM well into the boost.  Hence my conclusion.  It runs fine off boost.

 Above 1.0 and before the turbo, 
it will again cause lean running. If you had a gauge to look at, you'd know 
exactly what was going on.

    Gauges are NOT tell alls.  I've gone over every system twice.  And it only happens at sea level.  It IS fuel delivery I'm convinced.  I've replaced all sensors, rubber compnents, etc.  

 There are many places for leaks to occur on Audi 
turbos. The only way to know a hose is not leaking is to remove it. Leaks 
can be real hard to spot w/ a flashlight in some awkward angle. Also cracks 
many times occur right where the clamps are, making it even harder to spot. 
Check the whole system.


    No, its not hard to check.  YOu simply pressurize the engien and listen for the air.  If it maintains pressure with no leaks yoru fine.   Its a sure fire way to find vacuum leaks.  


The hard starts, is prolly a bunch of things combined w/ a leak. If yer 
injectors are older than 60k, change em. It's real easy to do, esp. on the 
early 5kT's cuz there is no inj. insert.

   Mine have the insert.  Only the REALY early 5kt's didn't have the insert.  ANd replacing is NOT easy.  They cost $50 each.  Thats a lot of dough.  I plan to and that likely is my starting problem, but not my only problem.  thats not the confusing one.  starting problems are easy to figure out.  

 The best way to diagnose a CIS 
system is w/ a fuel presssure gauge, but 95% chance yer warm-up regulator 
is dead. Check the resistance of it. It should be 17-21 ohms. The real way 
to check the reg. is to watch the control pressure rise to about double the 
cold value. Mine was 55psi the whole time, cold or hot, so the reg. was 
telling the engine it was always warm, leaning the mixture.

That doesnt make sense,  55psi is richer.  Less CP leans engien right.   Anyhow,  my control pressure is fine.  I've checked it.  But its at the lean end of the spectrum when warm.  So I'm thinking that my P&P's head and higher compression make it inadequate.  I've tried 5 others but none are right.      Thanks for the resistance measurement though.  I'll check that tomorrow.  I think the heater is heating to much.

 Probably what 
happened was the control valve inside seized or broke it's connection w/ 
the bimetal coil. There maybe other issues, but hopefully yer plugs, wires, 
filters, etc. are in good shape...


   All brand new.   And the Warm up reg function fine.  It just changes to much.   By a tad.
Thanks for the help.  I'm check resistance tomorrow if I have time.

l8r

 


Todd Phenneger
    83' ur-q (awaiting a 20vt)
    84' 4ktq  fun but I'm sick of CIS.


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