[T3] On a 73 T-3 SB fuel injected aut trans pinging .

William J catnine09 at dslextreme.com
Thu Dec 7 13:45:32 PST 2017

I had the air temp sensor unplugged and drive it about 1/2 mile no ping , 
got home letting it run I checked the ARR and is was partly open. Then I 
drove it one mile round trip no ping and parking it for say 20 minutes drove 
home and still running it seemed the ARR was closed at least if there was 
any vacuum I could not feel it so I will try a vacuum gauge. I didn't think 
to see if the idle dropped back fully letting off the throttle. All this 
tells me is with the air temp sensor unplugged there is an across the board 
10% increase in richness. My understanding has always been any vacuum leak 
will make it run richer because it screws with the vacuum signature which in 
turn affects the MPS which is basic. What I don't know is if this is at all 
RPM ranges or certain RPM's and load . You have idle vacuum which is high , 
heavy load low and steady speed cruise some point in between.

I tend to think I has a few small vacuum leaks . The reason is the ARR is a 
main one yet when it does close even with the air temp sensor plugged in 
sometimes it idles fine , they must be vacuum leaks that are there due to 
vibration or heat or the erratic miss would always be there. I haven't 
changed the runner short hoses in 20 years or the vacuum line to the auto 
trans and the runner to head spacer/gaskets I haven't checked to see it the 
nuts are tight since I installed them . I did clamp the 4 runner hoses in 
2009 when all of this insanity began . I tightened every single FI terminal 
out of the plastic plugs as well as all the FI grounds . Last I did the 
grounds and the erratic miss was 90% gone the doing nothing it returned.

With the air temp sensor unplugged the erratic miss was gone and it had 
better pickup and no matter how hard I pushed it I didn't hear any pinging. 
Also at times the idle was 850 then 900 in drive, once warmed up it was 
steady @ 900 RPM.

Now with that temp sensor plugged in idle set at 950 as it has been before 
the ping and even after if I started it the idle was 950 and within a minute 
it would rise to 1500 then drop back down yet it had the erratic miss and at 
each stop the idle would be at 900 to 1000 RPM until fully warmed up then it 
was steady only i drive with a load at idle . Even though the erratic miss 
was there driving it you would never know.

I can hear ticking and did snug up the right EMPI header to heat EXchanger 
yet could feel exhaust leaking there. I need to deal with this . Thought I'd 
remove the header and wrap some sheet aluminum I have around the exchanger 
pipe so the header fits tight then clamp it with the crappy VW mesh doughnut 
deal . I tried to find 1 1/2 " regular clamps and non one stocks them. The 
exhaust leak allows a popping when I let off the gas after stepping on the 
gas and letting off . for some reason I did not hear this today. Sure did 
with the air temp sensor connected.
----- Original Message ----- 
From: "Jim Adney" <jadney at vwtype3.org>
To: <type3 at vwtype3.org>
Sent: Wednesday, December 06, 2017 7:22 PM
Subject: Re: [T3] On a 73 T-3 SB fuel injected aut trans pinging .

> On 6 Dec 2017 at 16:28, William J wrote:
>> Perhaps I have either a vacuum leak that comes and goes or a head temp
>> sensor that is erratic. Also as you said Jim when I open the throttle and
>> let it close it takes a second to drop to idle speed. At least the timing
>> returns to normal much faster yet why it did ping once bugs me . I did 
>> get
>> some where changing the dist .
> It sounds like you were right about the other dist having a sticky advance
> mechanism, and it sounds like you've fixed that.
> An erratic vacuum leak is certainly a possibility. I would check to see if 
> you
> have the right FI air runner to head gaskets. (Have we been down this road
> before?) The correct gaskets are hard to find and don't come in any gasket
> set.
> Also check to make sure the nuts are tight on those gaskets and that the
> (front) cover bolts on the IAD are tight. The sleeves on the air runners 
> can
> also leak if the parts have been installed skewed.
> See if you can find something to plug the inlet to the AAR, just to take 
> it out
> of the picture. If the idle then settles down, maybe there's something 
> erratic
> about the AAR.
> I don't have any idea why you would have ping, unless this engine had been
> running extremely rich for a long time and had built up a bunch of carbon 
> in
> the heads that could glow and cause pre-ignition. I believe you said this 
> was
> an X engine, which should have the dished pistons giving and even lower
> compression ratio, which should make ping extremely unlikely.
> -- 
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
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