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YOUR RESEARCHEngine Vacuum Leaks - help with analysis
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Replace because i�m not convinced they
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Reported fix
sensors I changed because I�m not convinced they cured the issue.
Leading evidence: 'Replace because i�m not convinced they' (1 discussions report resolution; 0 report an unsuccessful attempt). Across 1 matching discussions, the most frequently mentioned possible cause is 'every little fix was definitely making a progressive different' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Replace because i�m not convinced they' (1 discussions). For that action, 1 discussions report a resolution and 0 report an unsuccessful attempt. The most frequently reported fix is 'Replace because i�m not convinced they', supported by resolution reports in 1 discussions. These are forum reports and suggestions, not a confirmed diagnosis.
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every little fix was definitely making a progressive different
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At first it seemed like nothing worked but then it turned out that every little fix was definitely making a progressive different.
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I tightened the pipe and went for a drive where I reached operating temp and it seemed to be more stable but sometimes it�s stable anyway.
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Suggestion
Good thing is the 996 engine is externally simple as hell , only the sensors needed to run the engine and pass smog are present..
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Generation: 20261027T073501Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
I finally invested in a small smoke tester and I immediately detected 3 sources of leakage. Both joints for the AOS connector to the intake plenum are leaking. The gray spacers/locks have been removed for disassembly prior to taking the pic. I�m guessing that replacement of this elbow assembly is the only fix?
Also, there�s a leak on the forward plenum boot (forward of the throttle body) from this circled area. What is it? Does it look like it�s missing something? It appears to be threaded but I can�t quite tell.
A Dorman 46051 rubber PCV elbow makes a nice fix for this if also use two appropriate spring clamps. (oil resistant and vacuum rated).
The leak at the crossover plenum is where the "resonance flap" shaft extends through the housing. I don't have a good fix for this other than replace it with a non-leaking one...
Brilliant. My Autozone has the Dorman elbow in stock.
As to the resonance tube, would some RTV over the port/threads make for a temporary fix until I have time to dig into it?
Here it is with the Dorman piece and two 13/16� spring clamps.
This pipe lube is some magical stuff and I would have really struggled today without it. It definitely helps when dealing with old cars (and potentially brittle components). It�s saved me quite a few times with the 996 and with my prior 928.
That Dorman 46051 elbow make a nice replacement for the plastic o-ringed factory elbow. Only used on the "early '99" and I include the Dorman piece in the UAOS kit for "99 models.
You da' man Skip.
On a side note, I can't figure out why people keep telling me that my 9/98 build isn't an "early 99" yet I keep finding details about it that only apply to "early" cars?......
Don't pay no mind to what "people say", they always try to split hairs make concrete rules. One thing is for certain when it comes to Porsche, there are no concrete rules and there is always an exception .
By the way, here�s what I came up with for the leak in the resonance pipe. The OD of the nipple appears to be almost exactly 3/4�. I found these vinyl plastic caps at my local hardware store. I had to lower the engine on the mounts in order to have room for my hand to get in there. This cap has an incredibly tight fit on the nipple so I�ll test this for now and see if I can get by without applying any adhesive. Fingers crossed!
EDIT: Smoke test passed with zero leaks on the motor.
I have a suspected vacuum leak too, despite changing out most of the skinny vacuum hoses, as well as the U and I rubber couplings on the various components.
@islaTurbine
what smoke machine did you get? How is your �chair leg cap� fix holding up?
I bought this one and it's been great for my needs:
https://www.ebay.com/itm/282339070632
The chair leg cap fix has been perfect. No issues at all thus far.
While maybe not the direct subject of this thread - would a loose intake pipe cause a sporadic rough idle? This would be the soft rubber pipe that connects the throttle body to the air filter housing. I tightened the pipe and went for a drive where I reached operating temp and it seemed to be more stable but sometimes it�s stable anyway.
My symptoms so far are:
1. Rough idle on startup (sometimes it happens, sometimes it does not)
2. Stable idle during warmup
3. Sporadic idle drop when warm - drops to about 400 and bounces back when clutch in while slowing down.
4. Engine stalled twice in 900 miles, when the idle didn�t bounce back after clutch in coasting to a stop. Engine was at operating temp both times.
5. Had a pending code for O2 Sensor Oxygen Sensing Range 1 Below Limit Value. I changed all 4 O2 sensors, cleared the fault code memory, and it hasn�t come back yet after about 200
miles. The idle problems remain. No other codes.
I�m reluctant to throw parts at this beyond the O2
sensors I changed because I�m not convinced they cured the issue. What other numbers can I read from Durametric (and at what time - cold start, warm, hot, etc.) to help diagnose the issue?
I�d say the first step is to smoke your engine and see if you have any air leaks. I�d also simultaneously take a screen shot of all the Durametric parameters and start a thread with that info posted there. I had a lot of small issues that were culminating into a bigger one, so I had to slowly and methodically fix them one at a time. At first it seemed like nothing worked but then it turned out that every little fix was definitely making a progressive different.
A dirty MAF can be the source of many evil behaviors, I started changing them out as a service item on all my cars at 75K/150 etc.
With the Durametric you can put it in log mode and turn on all the intake measurements...
They all bounce a little but if you can match a cough from the motor to the graph might lead you down the right path.
Just hook it up put the log mode on and , take it for a short drive.
Have you cleaned the throttle body ?
Good thing is the 996 engine is externally simple as hell , only the sensors needed to run the engine and pass smog are present..
what a great little hack. just fixed mine like this. 19mm fits perfectly.
beers on me.
easy job to do. Just remove the throttle body to give you the space to place the plug. no need to lower engine
