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Smooth idle and power delivery - replace 997.2 Throttle Body
2009 C2S 141 K miles
So.... WTF... check out the pics.....
Issue: Bouncy idle and then choppy, chuggy power delivery up through the 2K and 3K range. No check engine light although my Ford friend said I would get a lean condition if I didn't do something about this issue.
Usual Suspect: Clean throttle body and mass air sensor by spraying the MAF and shooting spray on the butterfly with the throttle body in place. I did.... kinda improved... but not that much.
Recommendation: Just try replacing the gasket first... cheap and easy. And with the throttle body removed, spray the crap out of it and get a ton of juice into the butterfly pivots. If you break it, you will just replace it anyway.. no harm no foul. Then replace whole throttle body if that doesn't work. Still cheap and easy. Or.... just replace the TB.. heck, it is cheap too so why not??
Background: I was getting an uneven idle and then when I was in Atlanta a few months ago, I was seeing outside temps on the highway of 107 F and started to get a pretty serious chugging power delivery. Yikes!!! No CEL. My Ford buddy said high ambient temps always see spikes in Ford parts... they feel temps stress and can warp parts.... so he said.
Pulling the Throttle Body (TB): So I first attempted to do a serious cleaning of the throttle body and removed it. What I found was silt around the gasket which told me I had a vacuum leak. So I cleaned and re-seated the gasket, and then sprayed the F out of the TB, and re-assembled. It ran smoother but not perfect. I took another long trip and felt an ever so small amount of chugging.... so I just ordered a new TB and gasket. When I pulled the TB, I was shocked to see so much silt in there from just two months time.
Effort: Pretty darn easy. 1 - Remove the airbox and hose from the TB. 2- Disconnect the electrical connection from the TB. 3-Remove 4 Torx bolts (you will need a torx socket set). 4-Remove gasket, 5-Clean everything, 6-Replace with new parts (just 20 ft/lbs for bolts or snug). 7-Reset TB by turning key, don't start.. hold for about twenty seconds... return and move key to start (or something like that.. I always get it to work if you dick with the key)... you will hear it click clack.
Result: Silky smooth!!!! Yeah!!! Very very noticeable... so much so that I guess I didn't realize that, over time, my smoothness was eroding.
Check out the pics.... Notice the accumulation of silt around the old gasket! And the grime in the TB throat. What you can't see is the little arcs of grime where the butterfly was closed that I could actually catch my finger nail on. The bolts are corroded and the old TB had corrosion around the bolt holes. I guess this is all from metal mismatch.
Full disclosure: Maybe only the gasket required replacement??? Was the corrosion around the bolts (on the backside of the TB) causing the joint to separate just a tiny bit?
Where to buy: Don't buy the Porsche labeled unit. Rock Auto had the lowest prices but I was a bit worried as they had two line items with the same number and neither denoted a Bosch part. The original is Bosch... so I looked around and purchased a Bosch TB from Vertex Auto $160 for TB - $4.20 for four bolts, $12.23 for the gasket. In the pics, you can see the TB is the exact same. Save your money and get a Bosch unit as the Porsche-labeled unit is $450. Read here: https://rennlist.com/forums/997-foru...xperience.html
Bonus: Note the gook from a tiny power steering leak I have. I think it is coming from where the reservoir inserts into the pump... the reservoir jiggles and should be tight.
Your idle should be dead flat. No bounce at all. Does a moving needle mean replacing the TB? I dunno. Note I have 141K miles on 2009 and cleaning did not fix the issue - it usually does BTW. That is a ten year old car with a bunch of miles. At a minimum, pulling the TB and spraying the F out of it, cleaning and reseating the gasket, and spraying the mass air sensor are all things you can do for a few bucks of MAF spray cleaner and an hour or so of time.
No less vibration... just a nice smooth sounding engine and power delivery.
Peace
Bruce in Philly
Last edited by Bruce In Philly; 09-17-2019 at 11:32 AM.
FYI Regarding this issue. Go and Search HUNTING IDLE by Dartmouth I posted on Dec. 6th 2018 of the same problem. The thread includes in detail my problem and later in the thread my solution meaning Throttle Body replacement.
I cleaned mine before I did engine mounts last week. So I can attest that replacing the TB is incredibly easy.
As a new owner, I've struggled to understand what's normal and what's not. This week I'm gonna meet with my local Porsche Club for the first time so I'm gonna ask some of those guys to drive my car and see what they think. I have a slight hesitation from launch - but I'm not sure if that's just the AWD measuring traction and distributing power? It's almost like the car hunkers down, then launches out. I could see the hesitation coming from an aging TB though. Mine was pretty dirty before I cleaned it.
Things that helped my rough idle in order: 93 octane gas helped a little at first, plugs and coils helped a lot, new engine mounts eliminated so much vibration it scared me at first. But there's still just a little shake, not a vibration, just a shake now. Almost like a muscle car
I would confirm the part numbers in the Porsche PET Katalog and on a website like Pelican as they may.... maybe... different for the S and base. BTW, you really don't need the screws... I got em because mine looked corroded and well... they were less that $5. These are the part numbers from my order form:
FWIW, I've noticed that things like screws and clamps etc can have differing part numbers..... I dunno why.... note the screw starts with 900.... not always.... I have found that some of these common "shop" parts will have two numbers for the same thing.
I did this a few weeks ago and ordered the part from Roc Auto by the Bosch number. I got the identical unit, with the Porsche 997--- part number on it. Cheap and fast too.
Grabbed a gasket from my dealer. Probably could have re-used it, but cheap insurance. My screws all looked fine, low-torque, no reason to trash them.
My idle steadied considerably. I have a 3.8S and there's a little bumpiness in the idle, but it amount to less than half a needle's width on the tach. Drivability greatly improved, smooth gas pedal response and no dipping coming to a fast stop.
The old TB had a bit more "slop" to the butterfly.
Just want to thank @Bruce In Philly for this fantastic write-up. I swapped in a new throttle body over the weekend and both the install and the outcomes were perfectly predicted by this thread!
I wonder how much of the difference before/after is due to just reteaching the throttle body? Meaning did you try the TB reteach procedure with the original TB installed?
09-16-2019, 08:17 PM
Smooth idle and power delivery - replace 997.2 Throttle Body
