Help Request: P0507 and possibly P1128/1130

2001 986 Box S, stock. Rarely Driven History: June time frame: Went through vehicle and did many things since had oil pressure issue. So decided to go through vehicle at same time. a) on June 16th at 92139 miles, Upgraded the oil pressure spring and cylinder due to chronic flashing oil pressure light at stop light after coming off highway. c) on July 18th cleaned MAF ( Bosch ), Throttle Body (per my notes, lower left bolt of the 4 bolts on body may not be fully tightened, was very difficult to access). d) On Aug 1, I did a smog check...(was a mistake, I smogged the boxster when it was a differeny vehicle needing the inspection..oh well, getting old) 1st attempt, I think there were multiple MIL not ready..duh..forgot to check prior going to smog station, rarely driven, so had to perform formal drive cycle. After such, it passed smog. (No record of any codes in my notes, but no explicit statement there were no code. There were likely no codes as I would probably have check before the second attempt. There MAY have been 1 MIL not ready, secondary air, but Im not sure, bad memory. But I think I may have also resolved this prior to testing as well. e) on Oct 18,at 92258 miles, did an engine oil flush and filled back with 10w40 Mobile and replaced filter with Mahle . I was concerned had a bad filter causing the low pressure issue. f) on Oct 24, the real smog was coming up in Jan, so went in and checked codes and had 1128/1130 (possible P0507 but not sure). So I recleaned MAF and cleared codes, but codes came back. I was suspecting MAF issue, even though I used MAF cleaner . Order a new aftermarket MAF. g) On 12/15/24 at 92301, Replaced MAF with aftermart band (A-Premium), checked codes (which were now definitely P1128/1130 and 0507) and cleared them out. h) On 12/16/24 Went for drive cycle. After, checked codes, 2 codes present P1128/1130, but only 1 MIL incomplete, Secondary Air. Cleared Codes, drove back home 15 miles from drive cycle. Checked Codes again. Now only 1 code P0507, but now 3 MIL incomplete. But I do see a very subtle fluctuation of RPM at idle and I think RPM may be a little high I do have an aftermarket IAC on order as a backup. So, my basic questions are: 1) I do hear what MAY be a hiss in the engine compartment and am wonder what is the best way (location/access) to do a smoke test on this vehicle? I do have a tester, but havent used it on this car yet and figuring I might as well do it as a leak check. 2) Where would be best placed to just build in a smoke test port? 3) Any suggestions on what would be best path forward? I tend to think that its never a good idea to clean these MAF sensors as I think thats probably what kicked off the problem in the first place. As far as I know, there was no issue prior to cleaning, but don’t know for sure.

So just tried to do drive cycle yet again. Got check engine light, P1128/1130, but not P0507. I have a foxwell 510 elite with the porche package, this allows me to either use the generic OBD2 portion or the Porsche portion to access data. Use the Generic: P1128/1130 with two MIL Incomplate: Evap and 2nd Air Use the Porsche : DME Control Systen P1128/P1130 with readiness errors of Cat Conv Efficiency, O2 Sensors and O2 Sensor Heater as Not OK. I'm still suspecting bad MAF in light of previous cleaning attempt, as it seems unlikely that both bank sensors crapped out at same time, but I suppose its possible. Anyone have suggestions?

Just did a smoke test using the MAF port after removal the aftermarket MAF. No evidence of any leak seen.

I also did an external propane exposure within the engine bay, no evidence of idle effect either.

Reset Codes and then turned over engine and waited to get fuel system A/B closed loop to do live data at Idle. I graphed all the responses, and all valves are reasonable stable, (oxygen sensors do not seems to be switching). STFT B1 6.4%, and STFT B2 31% LTFT B1 -0.8%, LTFT B2 -0.8% MAF 3.75 g/s Sonda Lambda OV B1/S1 0.065V, B1/S2 0.04V, B2/S1 0.72V, B2/S2 0.695V STFT B1/S1 25%, B1/S2 99.2%, B2/S1 3.1 %, B2/S2 99.2% I am not noticing any real performance issues in general except for maybe a slight idle roughness. And of course the error codes and inability so far to get the MIL readiness resolved.

this was with the original Bosch MAF reinstalled.

well, swapped out all 4 O2 sensors and threw the scanner back on. Looks like the Sonda Lambda S1 is now switching on both banks. So that's a good sign. Will review more scanner data tomorrow and try to get a drive cycle. Right now, 5 MIL are not ready, no codes at moment.

Well, attempted a drive cycle today and it crapped out. P1128/P1130 were then as soon as I finished the cycle and then when returning home, the CEL came on with a freeze frame captures for 1128 showing 10% STFT and -7% on the LTFT (similar for both banks). So far swapped out O2 sensors, but concerned the connector might be reversed?? Swapped out MAF from old one to aftermarket, with new one on order. Did a smoke test through MAF opening, but concerned throttle body made have made it ineffective. Didnt see any leak. Going to do a gasket check via the coolant reservoir tomorrow, but Im at a loss. The only relevant maintenance Ive really done to the vehicle since it last passed smog was cleaned the MAF. Could someone help me out? Inspection is coming up and Im at a loss here as to what to do..

Cleaned the MAF? How? Generally they can't be cleaned properly, from what I've seen. You can try those sprays and such, but in my experience they have never worked. You may need to replace it. I know on my 987.2 it needed to be replaced soon after I got it from Carvana. They covered it, but the point is, they can fail after some time... I'm guessing that may have happened to yours as well. Unfortunately, it's not a cheap thing to "try" but you may consider doing that with an Amazon -returnable unit or something, so if it doesn't fix it, at least you can return it?

I used MAF specific spray cleaner, actually, did it twice, but it didnt resolve issue. I had done work a few months ago, went through entire vehicle, fluids, filters etc. I dont think I did anything related to these codes. Now that I think of it, I actually didnt clean the MAP initially. I specifically avoided cleaning it because my experience was the same,..it never works. It was only after I got codes that I tried cleaning and that didnt resolve. So I swapped it to an aftermarket MAF, that didnt resolve it either. I have a new Bosch MAF on order and will try that. In the mean time, I picked up O2 sensors and tried those, but it didnt resolve it. I tried smoke test, no leak seen, but I question how well it was done since I did it through the MAF port and so the the throttle body was mostly close, but still, I think it should have worked. As I said above, going to see if any exhaust gas in the coolant to see if its something internal to engine causing issue. Hopefully the new MAF will actually solve it. If it doesnt, not sure what to do.

New OEM MAF is a good idea. Aftermarket can work on more "regular" cars (I've used them there) but on this car, non-OEM things sometimes cause problems, so that's certainly a possibility. Let us know how it goes... and when you make the change, capture the data soon after, and then again if you get another error. It would be good to see how it's trying to adjust the trims, etc... EDIT: Also, since I didn't see it mentioned, how old is your battery? I know the later models are VERY sensitive to low voltages and will throw all kinds of random errors. Do you have a good volt meter and can you measure the voltage after an overnight without starting or charging for a good 4+ hours?

Battery Date 09/21, Everstart Maxx, I often have to charge it because I rarely drive the auto. Electrical/Engine Off (battery still hooked up) overnight 12.2 Volts, Currently charging 10:45AM, will update this evening. I am planning to do 3 tests of idle air flow with the 3 MAFs once the new one comes in (eta Thursday) just to compare and record values and then will try the drive cycle again. All those above fuel trim and voltages confuses me a bit. Im using Bosch 15182/83. and the ones I pulled appear to be OEM also as they were proper part number stamped. Do you know if those pin outs on the sensors are symmetric? Im trying to confirm I put the connectors on properly. Full charge 9:30 PM 12.9 volts

I put the new MAF and started the engine. I did have a CEL and 2 codes, P1128/1130. I'm not sure if they were from before or not, but I dont think so. Maybe it was a result of the MAF swap itself. I noticed the STFT at 10.2% each side. I cleared the codes. I idled the vehicle to close loop, no codes. I then did a live monitor of the MAF. What I noticed is that about every 4-5 seconds, the MAF would spike to anywhere between 4-7 g/s, you could hear it in the engine response also, and then return to some nominal value (< 4g/s)!!! The question is WHY?? Any thoughts ?? What can I do to try to narrow this down? ( I am now suspecting nothing was wrong with any of the MAFs, I think Im going to try the smoke test again, I dont think any point of trying a drive cycle again until this code issue and the MAF spike is resolved) I also did a block check for the hell of it just to make sure no issue there. I saw absolutely no sign of combustion gas through the coolant. I did notice my oil level was slightly high, so I am going to remove some of it tomorrow.

Just did another smoke test. Found a leak in the top of the air box. The air box top frame was cracked and the gasket under the lid not seating well either. 99611012302 Going to try to RTV the top and see what I can do with the gasket/seal for it (Also corrected the oil level, it was only slightly overfilled but now its 1 bar under max on the dash and about 80% between notches on the dipstick. I probably took maybe 200 ml out overall)

Excellent work, and thanks for letting us know the progress as you do it. Agreed on looking for leaks... a jump of air means something may be intermittent and "burping" here and there. Typically rubber seals can do this, but it can be anything if you're "lucky", as you noticed. Certainly, seal up those breaks, and continue working on it... no other tricks or shortcuts to recommend. You're on the right path, it's just tedious!

I could see where it could be 'burping' as the corner of the top frame was basically broken across (my doing a few months back) but I discounted it initially as as the cause of the P1128/P1130 as it was upstream of the MAF and I had taped it thinking it was cosmetic, but apparently not. But I guess the MAF response time cant handle that sort of transient spike. I did not see any other leaks at this time. I did also clean the throttle body as part of my overhaul a few months back, so its conceivable some leak there, but I didnt see any smoke. I think I got lucky with that MAF signal., both watching it live and then graphing it. Clearly, I'm not a car guy. Will let the RTV dry a day, re-smoke it to see if it sealed and then carry on.. Also, the trick I used this time was to use a thin edge right angle small pry bar and slide it between the top frame and the housing below and wiggle it up slightly while holding the clip on one side and slowly work my away across the top towards the other clip, holding the back slip as I approach it. I specifically avoid try to pry up using my hands on the plastic end as thats what caused the plastic break in the first place. Live and learn. Will update tomorrow, hopefully, thks

Well, here is the latest. The air box was in worse shape than I thought. Not only was the top frame broken, but the box itself has a split at the seem. Conceivable, this seem was closed up when the lid was push down sort of clamp is back together, but nevertheless, it needed repair. I broke out the light strip and the plastic welder to tack it. This time I attached some images. The first image shows a side shot with a light inside the box so you can see the split. The 2nd image is how i clamped it closed..and the 3rd image is the plastic welder tackling it from the inside of the box. I also superglued the top piece and added some compressible foam. In any case, I did not smoke it afterward. I reassembled it all, put the MAF back in and broke out the scanner. There were no CEL or codes to start, and none came on after idling for 10 minutes. The STFT on both banks was initially up at 25% but then settled down to 12-13 % on both banks after about 10 minutes. I did see sonda lambda switching on both banks, so it appears the sensors are working. The MAF was reasonably stable at 4 g/s. It still had a little fluctuation. Definitely not rock solid but that periodic fluctuation I saw before was gone. I will pull the MAF tomorrow morning and smoke it again, and if it looks ok, try a drive cycle. But my basic issue now is the STFT being so high. I assume 12% still represents an issue, does it not?? I did order another used airbox for the hell of it as backup, but its a week out still.

Well, smoked it through the MAF opening, didnt really see anything. Not sure how effective this approach is as I assume most of that cavity is open to atmosphere though the side intakes and the throttle body is mostly closed also. Confirmed no codes, went for a test drive, no CEL or codes immediately after, but still had 3 MIL Incomplete immediately after. Then after driving home, checked again had 3 codes now (P1128/P1130 and P0507) and 5 MIL Incomplete. WTF? I guess my next step will be to smoke it through the gas tank? Any suggestions?

well, tried more smoke testing, didnt see anything. Giving up. Porsche For Sale.

Crazy indeed. Sounds like this car may have been witness to more issues than you can see (ie, a larger accident?). I agreee, it may be best to give up... especially if you're not interested in preserving it. Sorry it came to this.

I was planning to preserve it, which is why I went through the whole thing and did a ton of stuff right before this. I rarely drive it, probably have only put 500 miles on it this year. I've owned it for many years and have generally been meticulous about things. No large accident while i have owned and none in its history from what I recall. Some dumbass backed into me one time in the parking lot and dented the bumper cover, and took off, but otherwise no accidents. Im just too old at this point and not a trained mechanic. Im probably missing something simple, but its only simple when you know what it is.. in any case, thanks for the help, greatly appreciated. Posting is live on this forum..

Sorry to hear that... but I totally get it. Good luck with the sale!

Another thought occurred to me, that led me to do a little more research and now this post. One thing I noticed when I was adjusting the oil level the other day. My recollection is that I could generally remove the oil cap with the engine idling. But now, what I noticed it that i can not. The vacuum level is high enough that it wont come off. I can pull the dip stick easily enough, and hear the hissing, but not the cap. So this led me to question AOS . I MIGHT have a manometer (never used so far) and I MIGHT have a spare Oil Cap that I can modify. And this also led me to a research and find a post at : AOS Related? - 986 Forum - The Community for Porsche Boxster & Cayman Owners which sounds an awful lot like my issue both with respect to the following: With the engine shield off, I hear a sort of hissing, similar to his quote of "There is a wind like sound coming from the engine. I can not locate it though. tried the carb cleaner trick with no success. " Myself, same observation, I tried the propane approach, no luck. Maybe I will try the carb cleaner approach also. He also states same codes. I also previously cleaned the throttle body, but maybe I didnt do it well enough (but it was purely preventive maintenance, at least as far as I thought at the time) and maybe the intake sleeves and throttle body were not put back on well enough. Both of these seem viable (more towards the leak than the AOS, since I didnt change the AOS), but it is definitely conceivable that I caused a problem with the AOS tubing by accident ( do remember TRYING to disconnect its tubing, unsuccessfully, and left it alone, but maybe i did something to it) or didnt reassemble the intake/throttle body well enough. I am going to redo that, try a vacuum test but my questions are: a) thoughts on the AOS and vacuum level logic? Would this give rise to those codes? b) if I was smoking through the MAF opening, is the throttle sufficiently closed that I would NOT be testing passed it?? I recognize that the side grill intake is wide open and thus the smoke would certainly escape there, but was expecting to be able to check passes the throttle body also towards the intake. c) would smoking through the oil cap capture past the AOS and into the intake?? Because I tried this, but didnt see anything. I suppose conceptually there might be a difference between leak aspect with engine on vs off as the intake vacuum may be required for the leak to be active.\ d) both leak AND AOS issue coincidentally? Explicit answers would be very helpful, thanks..

Well, I went back through and used a chemical spray while idling (as opposed to propane. I vaguely recall going down this same path at some point in the past- trying to use propane and it not being energy dense enough..getting too old. Anyway.. Found the upper AOS tube leaking. Replaced it, and noticed immediately improvement in the STFT from up around 20% to down in the 1-3% range. Next day, cleared all codes, drive cycle (but had to cut it short due to low fuel), no codes, all MIL ready except 2nd air, enough to smog. Will stick 1/2 tank in it and do more exact drive cycle, but I think issues solved. So my poor diagnosis technique led to new O2 sensors, Airbox filter lid, AOS , MAF hours of frustration..when it was just a bad hose. Now I'm good on spare parts until my death..but its resolved. Case fricking Closed with a week to spare before registration due.

Just fyi, one other tip. That upper corrugated AOS to intake tube is way expensive for the 01 boxster . I found you can actually order a similar tube for a different porsche . The tube is longer with difference end styles, but same diameter. You can pop off the ends of your old tube (which has the split Y end) and put those on this replacement tube. I was able to source this other porshe tube for about $8 on Temu and pick up one as a spare for the future.