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I know there are many threads beating the potential 82mm TB problems to death, but after being 'one of those cars that didn't like it' and then fixing the problem, I just wanted to post a short reason why for anyone else struggling. Not to guarantee this will apply to everyone, but it's my theory this is largely the main problem.
We've all been told to get the 80mm SL Y pipe, and the McMaster orings, and maybe or maybe not invert the rubber gasket. You modify the Y pipe opening/plastic ring. You fit it up, looks stock, and feels like it seals on the TB opening. Maybe it does. Maybe it feels great installed and you can feel the flex of the runner on the inlet making a nice seal.
It is not enough!
I had the same intermittent rough idle, the eventual pending codes and finally a check engine light, the same codes that others mention related to a bad marriage with their new throttle body. I could see living with it as it drove fine most of the time, but was unpleasant and unpredictable.
I think that no matter how nice it might feel sitting still, as the engine torques around (and yes my mounts aren't that old, they will allow movement no matter what) it allows some air to get in at the TB and confuse the ECU. The long highway cruise issues are probably due to things being hot and expanding, causing the same issue. Aftermarket intakes are either very expensive, too hot (metal), or both.
I added a silicone reducer over the top, tightened it down snugly, and the car feels completely different. Smooth, vicious power and a rock solid idle. No more CELs, no more issues, nothing else was changed. The people going back to an 80mm TB and saying the issue was fixed, well that also made the Y pipe fitment factory with the proper large rubber seal that allowed movement but not loss of sealing.
For reference:
1) You need a 4" x 3.5" reducer coupling. Spectre brand is carried by Amazon and Oreilly, part # 9741. Comes with clamps and is $15-$20.
2) Reduce the coupler with a razor or sharp knife, removing about 1/2" from each end to shorten the whole thing but leave enough flat space to seal on each pipe.
3) You'll fight it a little to get it back in the car because of the added space, but it will fit with some effort. The air boxes will sit a little further back, so the snorkel pieces won't reach. You'll want to find two 3.25" silicone couplers (3" length) to take up the gap, install at the airbox-to-snorkel connection.
4) Lastly make sure the metal tabs under the air boxes aren't resting or rubbing on any wires, if they are cover them with rubber or move the wiring away.
Ignore the white 'goop', it's plasti-weld, I got a little carried away porting the y pipe and was concerned how thin it was in that spot!
Last edited by GinDistiller; 01-21-2021 at 11:02 AM.
Could you describe the conditions on the "long highway drives" that you were having issues with the throttle body? I'd be curious if it is similar to what I've been experiencing which is:
Let the car warm up
Get into boost at least one or two times after warm up to engage SC
Cruise for ~20+ min constant in the 80-90mph range
Light tip in on throttle ~18-20%
Verify there is a slight 'hiccup'
Verify that the STFT start creeping up quickly sometimes maxing out at 25%
Pull over when safe to do so
Verify that the car idles rough (like it comes close to stalling) with the STFTs swinging from negative to positive
Verify that there *may* be a pending P0106 code
Yes, I did experience exactly what you describe (plus a handful of other pending codes too). I didn't watch STFT as much, jumping between open and closed loop always makes it look crazy, but it would at times almost feel like it would stall at idle, and had the definite tip-in hiccup/stumble after being at a steady speed for some time. That seems totally gone now.
Ehhhh, may not be related to the TB lean issue while highway driving. If you don't have a wideband to see your super lean wot condition after the event and/or never saw your STFT pegged out your issue is likely not the same as the main(and dangerous) hiccup/lean issue people deal with.
Ehhhh, may not be related to the TB lean issue while highway driving. If you don't have a wideband to see your super lean wot condition after the event and/or never saw your STFT pegged out your issue is likely not the same as the main(and dangerous) hiccup/lean issue people deal with.
Ehhhh, may not be related to the TB lean issue while highway driving. If you don't have a wideband to see your super lean wot condition after the event and/or never saw your STFT pegged out your issue is likely not the same as the main(and dangerous) hiccup/lean issue people deal with.
True, as I said this won't apply to everyone, but from what I gathered a lot of people had issues with the cruising and then tip-in, not WOT (but I could be mistaken).
I think the consensus was that this was either vacuum leak related, or tune related. Obviously we have little control over tune tweaking, and it's painful to see so many posts about people taking the SC back out, resealing everything, and not changing a thing. I think this inlet connection has been overlooked in a lot of cases, but I could be mistaken. It worked great for me though!
My wideband is going in soon (I got a ridiculous deal on a set of headers and have friends that can weld in a bung, so it was a no-brainer).
True, as I said this won't apply to everyone, but from what I gathered a lot of people had issues with the cruising and then tip-in, not WOT (but I could be mistaken).
I think the consensus was that this was either vacuum leak related, or tune related. Obviously we have little control over tune tweaking, and it's painful to see so many posts about people taking the SC back out, resealing everything, and not changing a thing. I think this inlet connection has been overlooked in a lot of cases, but I could be mistaken. It worked great for me though!
My wideband is going in soon (I got a ridiculous deal on a set of headers and have friends that can weld in a bung, so it was a no-brainer).
Yes that's correct as to cruising at highway speeds and having a slight increase in load causing the issue, but one of the effects is that after it occurs if you go WOT you will run very lean. The theory is that when the hic-up issue occurs it is switching fueling MAPs to back up MAPs in the ECU tune since it for some reason sees the MAP reading as implausible, so until you shut off and restart the car you will run very lean WOT (for modified cars). Some folks just kind of see that there is a TB issue occurring or a slight jitter and don't understand that there also may be significant danger that may come with it if they aren't monitoring AFR and drive the car hard afterwards.
You should definitely try to monitor the key symptoms. STFT bounce around while cruising, but it's different when this issue occurs, you will see it start to PEG at 25. Generally it never goes over 20 so it still stands out very clearly once it has happened. I do hope that your fix resolves your issues for you, I'm just skeptical that its the same issue other folks have been fighting for a long time if you didn't observe your STFT or WOT AFR after an occurrence.
Yep, and I think it's more than a theory. I looked up the fault set requirements of the P0105 MAP implausible code in WIS and it states:
1) Lower limit value: needs to be over 30 mbar between 500 and 1300 rpm
2) Upper limit value: At TB angle greater than 60 deg, must be greater than 300 mbar
3) Vacuum of 500 to 1200 mbar; depending on performance map for motor speed and throttle flap angle
1 and 2 are almost impossible to trip without a bad sensor or serious mechanical problem, so it has to be #3. Those are the only reasons it would trip this pending or active code. I agree the lean stuff is very dangerous. So the problem lies in an actual vacuum issue (what I was seeing), and/or a tuning issue related to the mapping on our modified cars.
I wish now I had mapped STFT before making this fix, then could provide a comparison, but now that it's running great I don't want to touch it haha. Maybe someone else will tackle this and can report!
Yep, and I think it's more than a theory. I looked up the fault set requirements of the P0105 MAP implausible code
Are you SURE that is the code you're getting? P0106 is the code associated to the implausible MAP sensor reading that has been reported. The code you have there might be misleading to others with this issue.
P2007 is the one that came up in STAR for me and I've seen in other threads, the 0105 was what WIS referenced to see those parameters I mentioned above, but I definitely got 'MAP Implausible' reported in either STAR or my MBII scanner. Of course my codes are all gone now. Mine is an early 03 if that makes any difference, I doubt it but sometimes software can vary (P2007 is always proceeded by -00X to further delineate the fault, it could be possible there have been changes to that?).
Could you post pictures of what the airboxes look like with the coupler in place?
Ah I completely forgot to post this up, here is a pic of the couplers installed. Everything is sealed up super well (the side over the plastic snorkel tubes doesn't need a hose clamp, it fits very tight and that plastic is thin enough that I wouldn't want to smash it down with a metal clamp). This also allows snorkels to be removed without tools just like stock.
Another week down and zero hiccup issues, pending codes etc. Very pleased.
01-20-2021, 08:05 PM
