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Old 10-06-2018, 10:43 PM
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Dan Martinic
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Default AFM Help

To help diagnose a looong running issue, I've taken AFM off with the purpose of cleaning it up.

1. I got the adjustment port cap off and boy it looks suspect in there: does this look right? Is there not supposed to be an adjustment screw down this hole?







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Old 10-07-2018, 12:27 AM
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darek_u
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This is the adjustment screw.

Last edited by darek_u; 10-08-2018 at 03:48 PM. Reason: typo
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Old 10-07-2018, 11:13 AM
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Dan Martinic
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Hmm.. to me, I'm looking at a solid hole with an Allen-shaped hole at the bottom?

It looks like something is missing!

In any case, if this is the screw, I would imagine it will no longer be adjustable (seized / corroded)? I've been told not to touch this anyway... but I have reason to believe it may have been tampered with in the past. Too bad I can't find anyone with a CO measuring device.....

Q: What can I use to clean the inside (where the air flows)? On hand, I have brake cleaner. Could that damage the temp sensor?

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Old 10-07-2018, 03:06 PM
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Tom M'Guinn
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That is the adjustment screw. Porsche says there's a special tool (9230) to turn it but if you google you'll see people come up with their own hex or similar tools. However, if you are having a running problem and if it is actually related to the AFM, it's more likely a dirty/worn wiper inside. See clarks for a detailed write up of how to get in there to see/test and (maybe) fix that issue. Cleaning the outer aluminum will make it look better but unlikely to make it function any different unless the barn door is sticking (in which case maybe oil the pivot points). I'd just be careful not to drench it and maybe use CRC MAF cleaner.
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Old 10-10-2018, 12:00 AM
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Dan Martinic
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Well... I adjusted that wiper, and other than a slightly nicer throttle response at low speed (very slight), no change.

Admitably, it's not a big thing; but since most everything at present is running well, it's bugging the heck outta me: cold start first 2 mins hesitation (from none to heavy, depending on the day, though I can't quite find a pattern, but usually worse on hot/warmer days) and occasional pop in exhaust at throttle-off moment during shift up.

Have had the hesitation issue for couple of years... exhaust pop after recent big work. But you know that

Perhaps it's just "tired engine" syndrone.....
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Old 10-10-2018, 12:29 AM
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Dan, your description sounds like a vacuum leak somewhere.
See if you can check the j-boot hoses, and the J-boot itself, but be careful removing it if you do.

I've seen cracks at the base of the rubber nipples, and where the J-boot attaches on the turbo. Also, there's a 3/4' (or so) plastic fitting that serves as a hose to J-boot coupler and they crack. Some of the cracks are hard to see and only leak under temperature or vibration.
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Old 10-10-2018, 07:57 AM
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I have always thought the same Paul, and over the past year, while doing some big jobs, I've tried to test for vacuum leaks, changed a bunch of lines, and inspected the boot.

However, I've never been 100% confident in my inspections, so I'll give the vacuum leak search another go. Will give me a chance to use my homemade j-boot adapter again...

Car always feels better after an afternoon under the hood lol
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Old 10-10-2018, 01:15 PM
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"Car always feels better after an afternoon under the hood lol"

Clearly, it feels neglected and you're obviously not spending enough time with it!
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Old 10-10-2018, 02:36 PM
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Temp sensors, fuel pressure, fuel pump check valve, dirty/leaking injectors, head gasket coolant in cylinders, DME grounds, vacuum leaks, AFM out of whack, weak ignition, KLR blink codes, TPS, cracked solder joints in DME/KLR, leaky valves/seals -- so much to check, so little time, though I'm guessing you've been over a lot of that already? A wideband O2 sensor -- even a temporary one -- might help quite a bit.
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Old 10-10-2018, 04:39 PM
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Originally Posted by PaulD_944S2 View Post
"Car always feels better after an afternoon under the hood lol"

Clearly, it feels neglected and you're obviously not spending enough time with it!
I'll just buy it some fresh oil then
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Old 10-10-2018, 04:41 PM
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Originally Posted by Tom M'Guinn View Post
Temp sensors, fuel pressure, fuel pump check valve, dirty/leaking injectors, head gasket coolant in cylinders, DME grounds, vacuum leaks, AFM out of whack, weak ignition, KLR blink codes, TPS, cracked solder joints in DME/KLR, leaky valves/seals -- so much to check, so little time, though I'm guessing you've been over a lot of that already? A wideband O2 sensor -- even a temporary one -- might help quite a bit.
Pleaee explain: temporary wideband?

I am confident in many of those, but have not checked:

Fuel pressure
pump check valve
weak ignition (how to test?)
KLR blink coded

Nice to have a list! I'll start going at it
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Old 10-10-2018, 06:07 PM
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Originally Posted by Dan Martinic View Post


Pleaee explain: temporary wideband?

I am confident in many of those, but have not checked:

Fuel pressure
pump check valve
weak ignition (how to test?)
KLR blink coded

Nice to have a list! I'll start going at it
I just meant a wideband that you installed temporarily for diagnostic purposes, if you aren't into having it all the time.

Tough to test for weak ignition -- and symptoms usually first appear under heavy throttle, so your symptoms don't really line up. You can look at the condition of the cap, rotor, plugs and wires, but sometimes they can all look fine and still causes missing, etc., so I tend to change them every 2 or 3 years for good orders sake. It's often the wires that go overlooked.
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Old 10-10-2018, 07:25 PM
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Dan Martinic
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Yes, I thought the same, and recently I installed new cap, rotor (Bosch), plugs, and just last week, wires.

No difference. Plugs are carbon fouling pretty quickly though!! Dry black crud covered already.

What's holding me back from the wideband is removing a freshly installed exhaust to get the bung. Can wideband be temp installed in stock O2 location, for diagnosis purposes? I think I know the answer.......
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Old 10-11-2018, 12:24 AM
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The wideband sensor can't take the heat from the stock o2 location (and you'd loose your closed loop, which would change your AFR). Sounds like you are running rich based on the plugs. Sure the O2 system is working as intended? For kicks, you might see if the hesitation goes away if you pull a little fuel via the FQS. It's not a proper fix, but may be a helpful piece of diagnostic info.
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Old 10-11-2018, 09:01 AM
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Hmmm.. my idea is that the O2 (which is new last year) kicks into closed loop and "fixes" the issue after the 2 mins driving; I did try running with it unplugged once and honestly didn't see much difference other than slightly worse mileage.

Perhaps I can use my 'scope (the new mini Chinese one) to test O2 system? I've seen videos... but can't figure out how to back-probe that connector
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